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1
Mesbah, Abdel O., and Stephen D. Miller. "Fertilizer Placement Affects Jointed Goatgrass (Aegilops cylindrica) Competition In Winter Wheat (Triticum aestivum)." Weed Technology 13, no. 2 (June 1999): 374–77. http://dx.doi.org/10.1017/s0890037x00041889.
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A 3-yr study was conducted in eastern Wyoming from 1995 to 1997 to evaluate the effect of fertilizer placement on jointed goatgrass competitiveness with winter wheat. Fertilizer placement methods consisted of applying 45 kg/ha of nitrogen (50% as urea and 50% as ammonium nitrate) in a deep band 5 cm below and 2.5 cm to the side of the wheat row, broadcasting on the soil surface, or injecting fertilizer by spoke wheel 10 cm deep and 5 cm to the side of the wheat row. Neither fertilizer placement nor jointed goatgrass presence affected winter wheat stand. Wheat yield reductions from jointed goatgrass competition were 7 and 10% higher with the broadcast than deep-band or spoke-wheel injection methods, respectively. Wheat spikes/plant, seeds/spike, 200-seed weight, and plant height were not influenced by fertilizer placement; however, the presence of 35 jointed goatgrass plants/m2reduced spikes/plant 21%, seeds/spike 12%, and 200-seed weight 6%. Jointed goatgrass populations were not influenced by fertilizer placement method; however, the number of spikes/plant was reduced 8 and 10%, joints/spike 3%, and biomass 15 and 21% by deep band or spoke wheel fertilizer placement.
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Kalimuthu, R., R. C. Mehta, and E. Rathakrishnan. "Investigation of aerodynamic coefficients at Mach 6 over conical, hemispherical and flat-face spiked body." Aeronautical Journal 121, no. 1245 (October 2, 2017): 1711–32. http://dx.doi.org/10.1017/aer.2017.100.
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ABSTRACTA forward spike attached to a blunt body significantly alters its flow field characteristics and influences aerodynamic characteristics at hypersonic flow due to formation of separated flow and re-circulation region around the spiked body. An experimental investigation was performed to measure aerodynamic forces for spikes blunt bodies with a conical, hemispherical and flat-face spike at Mach 6 and at an angle-of-attack range from 0° to 8° and length-to-diameterL/Dratio of spike varies from 0.5 to 2.0, whereLis the length of the spike andDis diameter of blunt body. The shape of the leading edge of the spiked blunt body reveals different types of flow field features in the formation of a shock wave, shear layer, flow separation, re-circulation region and re-attachment shock. They are analysed with the help of schlieren pictures. The shock distance ahead of the hemisphere and the flat-face spike is compared with the analytical solution and is showing satisfactory agreement with the schlieren pictures. The influence of geometrical parameters of the spike, the shape of the spike tip and angle-of-attack on the aerodynamic coefficients are investigated by measuring aerodynamic forces in a hypersonic wind tunnel. It is found that a maximum reduction of drag of about 77% was found for hemisphere spike ofL/D= 2.0 at zero angle-of-attack. Consideration for compensation of increased pitching moment is required to stabilise the aerodynamic forces.
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Scott, John W., and Lisa Sherrill. "Effects of Odor Stimulation on Antidromic Spikes in Olfactory Sensory Neurons." Journal of Neurophysiology 100, no. 6 (December 2008): 3074–85. http://dx.doi.org/10.1152/jn.90399.2008.
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Spikes were evoked in rat olfactory sensory neuron (OSN) populations by electrical stimulation of the olfactory bulb nerve layer in pentobarbital anesthetized rats. The latencies and recording positions for these compound spikes showed that they originated in olfactory epithelium. Dual simultaneous recordings indicated conduction velocities in the C-fiber range, around 0.5 m/s. These spikes are concluded to arise from antidromically activated olfactory sensory neurons. Electrical stimulation at 5 Hz was used to track changes in the size and latency of the antidromic compound population spike during the odor response. Strong odorant stimuli suppressed the spike size and prolonged its latency. The latency was prolonged throughout long odor stimuli, indicating continued activation of olfactory receptor neuron axons. The amounts of spike suppression and latency change were strongly correlated with the electroolfactogram (EOG) peak size evoked at the same site across odorants and across stimulus intensities. We conclude that the curve of antidromic spike suppression gives a reasonable representation of spiking activity in olfactory sensory neurons driven by odorants and that the correlation of peak spike suppression with the peak EOG shows the accuracy of the EOG as an estimate of intracellular potential in the population of olfactory sensory neurons. In addition, these results have important implications about traffic in olfactory nerve bundles. We did not observe multiple peaks corresponding to stimulated and unstimulated receptor neurons. This suggests synchronization of spikes in olfactory nerve, perhaps by ephaptic interactions. The long-lasting effect on spike latency shows that action potentials continue in the nerve throughout the duration of an odor stimulus in spite of many reports of depolarization block in olfactory receptor neuron cell bodies. Finally, strong odor stimulation caused almost complete block of antidromic spikes. This indicates that a very large proportion of olfactory axons was activated by single strong odor stimuli.
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Raastad, Morten, and Ole Kiehn. "Spike Coding During Locomotor Network Activity in Ventrally Located Neurons in the Isolated Spinal Cord From Neonatal Rat." Journal of Neurophysiology 83, no. 5 (May 1, 2000): 2825–34. http://dx.doi.org/10.1152/jn.2000.83.5.2825.
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To characterize spike coding in spinal neurons during rhythmic locomotor activity, we recorded from individual cells in the lumbar spinal cord of neonatal rats by using the on-cell patch-clamp technique. Locomotor activity was induced by N-methyl-d aspartate (NMDA) and 5-hydroxytryptamine (5-HT) and monitored by ventral root recording. We made an estimator based on the assumption that the number of spikes arriving during two halves of the locomotor cycle could be a code used by the neuronal network to distinguish between the halves. This estimator, termed the spike contrast, was calculated as the difference between the number of spikes in the most and least active half of an average cycle. The root activity defined the individual cycles and the positions of the spikes were calculated relative to these cycles. By comparing the average spike contrast to the spike contrast in noncyclic, randomized spike trains we found that approximately one half the cells (19 of 42) contained a significant spike contrast, averaging 1.25 ± 0.23 (SE) spikes/cycle. The distribution of spike contrasts in the total population of cells was exponential, showing that weak modulation was more typical than strong modulation. To investigate if this low spike contrast was misleading because a higher spike contrast averaged out by occurring at different positions in the individual cycles we compared the spike contrast obtained from the average cycle to its maximal value in the individual cycles. The value was larger (3.13 ± 0.25 spikes) than the spike contrast in the average cycle but not larger than the spike contrast in the individual cycles of a random, noncyclic spike trains (3.21 ± 0.21 spikes). This result suggested that the important distinction between cyclic and noncyclic cells was only the repeated cycle position of the spike contrast and not its magnitude. Low spike frequencies (5.2 ± 0.82 spikes/cycle, that were on average 3.5 s long) and a minimal spike interval of 100–200 ms limited the spike contrast. The standard deviation (SD) of the spike contrast in the individual neurons was similar to the average spike contrasts and was probably stochastic because the SDs of the simulated, noncyclic spike trains were also similar. In conclusion we find a highly distributed and variable locomotor related cyclic signal that is represented in the individual neurons by very few spikes and that becomes significant only because the spike contrast is repeated at a preferred phase of the locomotor cycle.
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Lemon, N., and R. W. Turner. "Conditional Spike Backpropagation Generates Burst Discharge in a Sensory Neuron." Journal of Neurophysiology 84, no. 3 (September 1, 2000): 1519–30. http://dx.doi.org/10.1152/jn.2000.84.3.1519.
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Backpropagating dendritic Na+spikes generate a depolarizing afterpotential (DAP) at the soma of pyramidal cells in the electrosensory lateral line lobe (ELL) of weakly electric fish. Repetitive spike discharge is associated with a progressive depolarizing shift in somatic spike afterpotentials that eventually triggers a high-frequency spike doublet and subsequent burst afterhyperpolarization (bAHP). The rhythmic generation of a spike doublet and bAHP groups spike discharge into an oscillatory burst pattern. This study examined the soma-dendritic mechanisms controlling the depolarizing shift in somatic spike afterpotentials, and the mechanism by which spike doublets terminate spike discharge. Intracellular recordings were obtained from ELL pyramidal somata and apical dendrites in an in vitro slice preparation. The pattern of spike discharge was equivalent in somatic and dendritic regions, reflecting the backpropagation of spikes from soma to dendrites. There was a clear frequency-dependent threshold in the transition from tonic to burst discharge, with bursts initiated when interspike intervals fell between ∼3–7 ms. Removal of all backpropagating spikes by dendritic TTX ejection revealed that the isolated somatic AHPs were entirely stable at the interspike intervals that generated burst discharge. As such, the depolarizing membrane potential shift during repetitive discharge could be attributed to a potentiation of DAP amplitude. Potentiation of the DAP was due to a frequency-dependent broadening and temporal summation of backpropagating dendritic Na+ spikes. Spike doublets were generated with an interspike interval close to, but not within, the somatic spike refractory period. In contrast, the interspike interval of spike doublets always fell within the longer dendritic refractory period, preventing backpropagation of the second spike of the doublet. The dendritic depolarization was thus abruptly removed from one spike to the next, allowing the burst to terminate when the bAHP hyperpolarized the membrane. The transition from tonic to burst discharge was dependent on the number and frequency of spikes invoking dendritic spike summation, indicating that burst threshold depends on the immediate history of cell discharge. Spike frequency thus represents an important condition that determines the success of dendritic spike invasion, establishing an intrinsic mechanism by which backpropagating spikes can be used to generate a rhythmic burst output.
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Saito, Mitsuru, Yoshinaka Murai, Hajime Sato, Yong-Chul Bae, Tadashi Akaike, Masahiko Takada, and Youngnam Kang. "Two Opposing Roles of 4-AP–Sensitive K+ Current in Initiation and Invasion of Spikes in Rat Mesencephalic Trigeminal Neurons." Journal of Neurophysiology 96, no. 4 (October 2006): 1887–901. http://dx.doi.org/10.1152/jn.00176.2006.
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The axon initial segment plays important roles in spike initiation and invasion of axonal spikes into the soma. Among primary sensory neurons, those in the mesencephalic trigeminal nucleus (MTN) are exceptional in their ability to initiate soma spikes (S-spikes) in response to synaptic inputs, consequently displaying two kinds of S-spikes, one caused by invasion of an axonal spike arising from the sensory receptor and the other initiated by somatic inputs. We investigated where spikes are initiated in such MTN neurons and whether there are any differences between the two kinds of S-spikes. Simultaneous patch-clamp recordings from the soma and axon hillock revealed a spike-backpropagation from the spike-initiation site in the stem axon to the soma in response to 1-ms somatic current pulse, which disclosed the delayed emergence of S-spikes after the current-pulse offset. These initiated S-spikes were smaller in amplitude than S-spikes generated by stimulation of the stem axon; however, 4-AP (≤0.5 mM) eliminated the amplitude difference. Furthermore, 4-AP dramatically shortened the delay in spike initiation without affecting the spike-backpropagation time in the stem axon, whereas it substantially prolonged the refractory period of S-spikes arising from axonal-spike invasion without significantly affecting that of presumed axonal spikes. These observations suggest that 4-AP–sensitive K+ currents exert two opposing effects on S-spikes depending on their origins: suppression of spike initiation and facilitation of axonal-spike invasion at higher frequencies. Consistent with these findings, strong immunoreactivities for Kv1.1 and Kv1.6, among 4-AP–sensitive and low-voltage–activated Kv1 family examined, were detected in the soma but not in the stem axon of MTN neurons.
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Snyder, Melissa, Angela Dispenzieri, S. Vincent Rajkumar, Robert Kyle, Joanne Benson, and Jerry A. Katzmann. "The Biologic and Analytic Variability of Serum Protein Electrophoresis M-Spike, Nephelometric Ig Quantitation, Serum FLC Quantitation, and Urine M-Spike in Monoclonal Gammopathies." Blood 114, no. 22 (November 20, 2009): 1803. http://dx.doi.org/10.1182/blood.v114.22.1803.1803.
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Abstract Abstract 1803 Poster Board I-829 Background Plasma cell proliferative disorders are monitored by a variety of methods. Serum protein electrophoresis (SPEP) and/or urine PEP M-spike quantitation are commonly assessed in patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and multiple myeloma (MM) to determine disease progression, response, or relapse. Serum immunoglobin (Ig) concentrations can be quantitated when the M-spike is large or if the migration is obscured within the SPEP beta fraction. Serum FLC quantitation provides a rapid indicator of response, will detect the rare occurrence of FLC escape, and will allow disease monitoring in the absence of a measurable serum or urine M-spike. The International Myeloma Working Group (IMWG) has recommended that the serum and urine M-spike should be used to monitor disease, and that FLC quantitation should be used only if there is no measurable disease by electrophoresis and if the monoclonal FLC concentration is greater than 10 mg/dL in the context of an abnormal FLC K/L ratio. We have studied serial samples in clinically stable patients in order to assess the total variability (analytic and biologic) of these assays and to confirm the IMWG recent recommendations. Methods Serial data from stable MGUS patients (n=35) were identified by the availability of all 3 serum test results (M-spike, Ig, FLC) in at least 4 serial samples that were obtained 9 months to 5 years apart and whose serum M-spikes varied by less than 25%. For MM (n=60) and SMM (n=48) the samples were within 9-15 months and serum M-spikes varied by less than 0.5 g/dL. Among the 60 MM, 48 SMM, and 35 MGUS patients, there were 23, 41, and 18 patients with measurable disease by serum M-spike (i.e. M-spike >1 g/dL); 19, 10, and 10 patients with an evaluable FLC (i.e. monoclonal FLC > 10 mg/dL and an abnormal FLC ratio); and 5, 5, and 1 patient with an evaluable urine (i.e. M-spike > 200mg/24 hr). The FLC data was analyzed as the involved FLC concentration (iFLC), the difference between the involved and uninvolved FLC concentration (dFLC), and the FLC K/L ratio (rFLC). The coefficients of variability (CV) were determined for each methodology in each patient sample set, and the average CVs were determined. Igs were quantitated by immunonephelometry using a Siemens BNII and Siemens reagent sets; kappa and lambda FLC were quantitated using a Siemens BNII and Freelite reagent sets from The Binding Site; M-spikes were quantitated using Helena SPIFE SPE and reagent sets. Results The CVs for the Ig quantitation, SPEP M-spike, FLC quantitation, and urine M-spike in each of the patient groups are listed in the table: Our laboratory's interassay analytic CV for replicate samples are 4-5% for Ig quantitation, 6-8% for SPEP M-spikes, 6-7% for FLC quantitation, and 5-7% for urine M-spikes. The analytic CVs of the methods are similar, but the total (analytic + biologic) CVs are very different. The samples have been selected by restricting the variability of serum M-spike values; when we apply the same criteria to the IgG quantitation, the IgG total CV comes closer to the serum M-spike CVs. The remaining differences, however, may be due to biologic variability contributed by polyclonal Ig. The total CV for iFLC is similar to the urine M-spike CV and suggests a previously unrecognized large biologic CV for serum FLC. The iFLC and dFLC CVs were comparable but were smaller than the rFLC CV. Conclusion The variability of the serum and urine M-spike, Ig, and FLC measurements confirm the IMWG recommendations for patient monitoring. If a patient has a measurable M-spike >1 g/dL, then the serum M-spike should be followed. If there is no measurable disease, then the iFLC can be monitored, provided that the rFLC is abnormal and the iFLC concentration is >10 mg/dL. Although the number of patients with evaluable urine M-spikes in this study is small, larger studies may confirm the utility of serum FLC compared to urine M-spike for monitoring patients with monoclonal gammopathies. Disclosures No relevant conflicts of interest to declare.
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Ciba, Manuel, Robert Bestel, Christoph Nick, Guilherme Ferraz de Arruda, Thomas Peron, Comin César Henrique, Luciano da Fontoura Costa, Francisco Aparecido Rodrigues, and Christiane Thielemann. "Comparison of Different Spike Train Synchrony Measures Regarding Their Robustness to Erroneous Data From Bicuculline-Induced Epileptiform Activity." Neural Computation 32, no. 5 (May 2020): 887–911. http://dx.doi.org/10.1162/neco_a_01277.
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As synchronized activity is associated with basic brain functions and pathological states, spike train synchrony has become an important measure to analyze experimental neuronal data. Many measures of spike train synchrony have been proposed, but there is no gold standard allowing for comparison of results from different experiments. This work aims to provide guidance on which synchrony measure is best suited to quantify the effect of epileptiform-inducing substances (e.g., bicuculline, BIC) in in vitro neuronal spike train data. Spike train data from recordings are likely to suffer from erroneous spike detection, such as missed spikes (false negative) or noise (false positive). Therefore, different timescale-dependent (cross-correlation, mutual information, spike time tiling coefficient) and timescale-independent (Spike-contrast, phase synchronization (PS), A-SPIKE-synchronization, A-ISI-distance, ARI-SPIKE-distance) synchrony measures were compared in terms of their robustness to erroneous spike trains. For this purpose, erroneous spike trains were generated by randomly adding (false positive) or deleting (false negative) spikes (in silico manipulated data) from experimental data. In addition, experimental data were analyzed using different spike detection threshold factors in order to confirm the robustness of the synchrony measures. All experimental data were recorded from cortical neuronal networks on microelectrode array chips, which show epileptiform activity induced by the substance BIC. As a result of the in silico manipulated data, Spike-contrast was the only measure that was robust to false-negative as well as false-positive spikes. Analyzing the experimental data set revealed that all measures were able to capture the effect of BIC in a statistically significant way, with Spike-contrast showing the highest statistical significance even at low spike detection thresholds. In summary, we suggest using Spike-contrast to complement established synchrony measures because it is timescale independent and robust to erroneous spike trains.
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Salvagno, Gian, Brandon Henry, Piazza di, Laura Pighi, Nitto de, Damiano Bragantini, Gian Gianfilippi, and Giuseppe Lippi. "Anti-spike S1 IgA, anti-spike trimeric IgG, and anti-spike RBD IgG response after BNT162b2 COVID-19 mRNA vaccination in healthcare workers." Journal of Medical Biochemistry 40, no. 4 (2021): 327–34. http://dx.doi.org/10.5937/jomb0-32373.
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Background: Most studies on immune response after coronavirus disease 2019 (COVID-19) vaccination focused on serum IgG antibodies and cell-mediated immunity, discounting the role of anti-SARS-CoV-2 neutralizing IgA antibodies in preventing viral infection. This study was aimed to quantify serum IgG and IgA neutralizing antibodies after mRNA COVID-19 vaccination in baseline SARS-CoV-2 seronegative healthcare workers. Methods: The study population consisted of 181 SARSCoV-2 seronegative healthcare workers (median age 42 years, 59.7% women), receiving two doses of Pfizer COVID-19 vaccine BNT162b2 (Comirnaty). Serum samples were collected before receiving the first vaccine dose, 21 days (before the second vaccine dose) and 50 days afterwards. We then measured anti-spike trimeric IgG (Liaison XL, DiaSorin), anti-spike receptor binding domain (RBD) IgG (Access 2, Beckman Coulter) and anti-spike S1 subunit IgA (ELISA, Euroimmun). Results were presented as median and interquartile range (IQR). Results: Vaccine administration elicited all anti-SARS-CoV2 antibodies measured. Thirty days after the second vaccine dose, 100% positivization occurred for anti-spike trimeric IgG and anti-spike RBD IgG, whilst 1.7% subjects remained anti-spike S1 IgA negative. The overall increase of antibodies level ratio over baseline after the second vaccine dose was 576.1 (IQR, 360.7-867.8) for anti-spike trimeric IgG, 1426.0 (IQR, 742.0-2698.6) for anti-spike RBD IgG, and 20.2 (IQR, 12.5-32.1) for anti-spike S1 IgA. Significant inverse association was found between age and overall increase of anti-spike trimeric IgG (r=-0.24; p=0.001) and anti-spike S1 IgA (r=-0.16; p=0.028), but not with anti-spike RBD IgG (r=-0.05; p=0.497). Conclusions: mRNA COVID-19 vaccination elicits sustained serum levels of anti-spike trimeric IgG and anti-spike RBD IgG, while also modestly but significantly increasing those of anti-spike S1 IgA.
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Kang, Youngnam, Mitsuru Saito, Hajime Sato, Hiroki Toyoda, Yoshinobu Maeda, Toshihiro Hirai, and Yong-Chul Bae. "Involvement of Persistent Na+ Current in Spike Initiation in Primary Sensory Neurons of the Rat Mesencephalic Trigeminal Nucleus." Journal of Neurophysiology 97, no. 3 (March 2007): 2385–93. http://dx.doi.org/10.1152/jn.01191.2006.
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It was recently shown that the persistent Na+ current ( INaP) is generated in the proximal axon in response to somatic depolarization in neocortical pyramidal neurons, although the involvement of INaP in spike initiation is still unclear. Here we show a potential role of INaP in spike initiation of primary sensory neurons in the mesencephalic trigeminal nucleus (MTN) that display a backpropagation of the spike initiated in the stem axon toward the soma in response to soma depolarization. Riluzole (10 μM) and tetrodotoxin (TTX, 10 nM) caused an activation delay or a stepwise increase in the threshold for evoking soma spikes (S-spikes) without affecting the spike itself. Simultaneous patch-clamp recordings from the soma and axon hillock (AH) revealed that bath application of 50 nM TTX increased the delay in spike activation in response to soma depolarization, leaving the spike-backpropagation time from the AH to soma unchanged. This indicates that the increase in activation delay occurred in the stem axon. Furthermore, under a decreasing intracellular concentration gradient of QX-314 from the soma to AH created by QX-314–containing and QX-314–free patch pipettes, the amplitude and maximum rate of rise (MRR) of AH-spikes decreased with an increase in the activation delay following repetition of current-pulse injections, whereas S-spikes displayed decreases of considerably lesser degree in amplitude and MRR. This suggests that compared to S-spikes, AH-spikes more accurately reflect the attenuation of axonal spike by QX-314, consistent with the nature of spike backpropagation. These observations strongly suggest that low-voltage–activated INaP is involved in spike initiation in the stem axon of MTN neurons.
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Galimidi, Rachel, Joshua Klein, Maria Politzer, Shiyu Bai, Michael Seaman, Michel Nussenzweig, Anthony West, and Pamela Bjorkman. "Intra-spike crosslinking overcomes antibody evasion by HIV-1 (VIR1P.1131)." Journal of Immunology 194, no. 1_Supplement (May 1, 2015): 74.8. http://dx.doi.org/10.4049/jimmunol.194.supp.74.8.
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Abstract Antibodies developed during HIV-1 infection lose efficacy as the viral spike mutates. We postulated that anti-HIV-1 antibodies primarily bind monovalently because HIV’s low spike density impedes bivalent binding through inter-spike crosslinking, and the spike structure prohibits bivalent binding through intra-spike crosslinking. Monovalent binding reduces avidity and potency, thus expanding the range of mutations permitting antibody evasion. To test this idea, we engineered antibody-based molecules capable of bivalent binding through intra-spike crosslinking. We used DNA as a “molecular ruler” to measure intra-epitope distances on virion-bound spikes and construct intra-spike crosslinking molecules. Optimal bivalent reagents exhibited up to 2.5 orders-of-magnitude increased potency (>100-fold average increases across virus panels) and identified conformational states of virion-bound spikes. The demonstration that intra-spike crosslinking lowers the concentration of antibodies required for neutralization supports the hypothesis that low spike densities facilitate antibody evasion and the use of molecules capable of intra-spike crosslinking for therapy or passive protection.
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Kobiljski, Borislav, and Srbislav Dencic. "Heterosis in crosses between wheat genotypes with different spike architecture." Zbornik Matice srpske za prirodne nauke, no. 102 (2002): 71–75. http://dx.doi.org/10.2298/zmspn0201071k.
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In order to estimate hybrid vigor, wheat genotypes differing in spike architecture (normal, tetrastichon and branched) were crossed and the F1 and F2 generations analyzed for the number of fertile spikelets/spike, number of grains/spike and grain weight/spike. The parents used for crossing were Sava (normal spike), Forlani (normal spike), ZG T 171/1 (tetrastichon spike) and ZG 172 (branched spike). The F1 and F2 progenies, except those from the cross Sava x Forlani, had a lower number of fertile spikelets/spike compared with the better parent. In the crosses between genotypes with normal and branched spikes, the F1 and F2 progenies formed significantly fewer grains/spike. On the other hand, the F1 of the crosses between genotypes with normal and tetrastichon spike showed a significant level of heterosis with respect to the number of grains/spike, particularly the cross Forlani x ZG T 171/1. In regard to grain weight/spike, significant heterosis was detected in all crosses except Sava x ZG 172. The crosses between genotypes with normal and tetrastichon spikes that exhibited significant heterosis for two main yield components were most promising in the context of hybrid wheat development. Such crosses deserve further attention and investigation.
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Parra, Lucas C., Jeffrey M. Beck, and Anthony J. Bell. "On the Maximization of Information Flow Between Spiking Neurons." Neural Computation 21, no. 11 (November 2009): 2991–3009. http://dx.doi.org/10.1162/neco.2009.04-06-184.
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A feedforward spiking network represents a nonlinear transformation that maps a set of input spikes to a set of output spikes. This mapping transforms the joint probability distribution of incoming spikes into a joint distribution of output spikes. We present an algorithm for synaptic adaptation that aims to maximize the entropy of this output distribution, thereby creating a model for the joint distribution of the incoming point processes. The learning rule that is derived depends on the precise pre- and postsynaptic spike timings. When trained on correlated spike trains, the network learns to extract independent spike trains, thereby uncovering the underlying statistical structure and creating a more efficient representation of the incoming spike trains.
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Khurana, Shashank, Kojiro Suzuki, and Ethirajan Rathakrishnan. "Flow field behavior with Reynolds number variance around a spiked body." Modern Physics Letters B 30, no. 30 (November 7, 2016): 1650362. http://dx.doi.org/10.1142/s0217984916503620.
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An experimental visualization study was performed to investigate the dependence of the pressure hill height and the influence zone expanse, for flow past a spiked body with different nose configurations, over a Reynolds number range from 2278 to 4405 to establish the vortex shedding process, and applicability in low speed flow regime for effective pressure reduction. It is found that the spike reduces the radius of curvature of the approaching streamline, leading to the deflection of the streamlines towards the shoulder of the basic body, resulting in a narrow zone of the positive pressure hill at the body nose. It is also observed that the pressure hill length and the influence zone expanse decrease with the introduction of spike over the present range of Reynolds numbers. For Reynolds numbers less than 2700, spike with conical nose is found to be more efficient than the spikes with other nose shapes of the present study in reducing the positive pressure at the nose of the blunt body. For higher Reynolds numbers, greater than 2700, the size of the vortex at the junction of the spike and basic body is the largest for the spike with hemispherical nose, and emerges as a potential candidate for application in possible wind-design resistant structures.
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Katzmann, Jerry A., Melissa R. Snyder, S. Vincent Rajkumar, Robert A. Kyle, Terry M. Therneau, Joanne T. Benson, and Angela Dispenzieri. "Long-Term Biological Variation of Serum Protein Electrophoresis M-Spike, Urine M-Spike, and Monoclonal Serum Free Light Chain Quantification: Implications for Monitoring Monoclonal Gammopathies." Clinical Chemistry 57, no. 12 (December 1, 2011): 1687–92. http://dx.doi.org/10.1373/clinchem.2011.171314.
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BACKGROUND We analyzed serial data in patients with clinically stable monoclonal gammopathy to determine the total variation of serum M-spikes [measured with serum protein electrophoresis (SPEP)], urine M-spikes [measured with urine protein electrophoresis (UPEP)], and monoclonal serum free light chain (FLC) concentrations measured with immunoassay. METHODS Patients to be studied were identified by (a) no treatment during the study interval, (b) no change in diagnosis and <5 g/L change in serum M-spike over the course of observation; (c) performance of all 3 tests (SPEP, UPEP, FLC immunoassay) in at least 3 serial samples that were obtained 9 months to 5 years apart; (d) serum M-spike ≥10 g/L, urine M-spike ≥200 mg/24 h, or clonal FLC ≥100 mg/L. The total CV was calculated for each method. RESULTS Among the cohort of 158 patients, 90 had measurable serum M-spikes, 25 had urine M-spikes, and 52 had measurable serum FLC abnormalities. The CVs were calculated for serial SPEP M-spikes (8.1%), UPEP M-spikes (35.8%), and serum FLC concentrations (28.4%). Combining these CVs and the interassay analytical CVs, we calculated the biological CV for the serum M-spike (7.8%), urine M-spike (35.5%), and serum FLC concentration (27.8%). CONCLUSIONS The variations in urine M-spike and serum FLC measurements during patient monitoring are similar and are larger than those for serum M-spikes. In addition, in this group of stable patients, a measurable serum FLC concentration was available twice as often as a measurable urine M-spike.
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Uramoto, Takumi, and Hiroyuki Torikai. "A Calcium-Based Simple Model of Multiple Spike Interactions in Spike-Timing-Dependent Plasticity." Neural Computation 25, no. 7 (July 2013): 1853–69. http://dx.doi.org/10.1162/neco_a_00462.
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Spike-timing-dependent plasticity (STDP) is a form of synaptic modification that depends on the relative timings of presynaptic and postsynaptic spikes. In this letter, we proposed a calcium-based simple STDP model, described by an ordinary differential equation having only three state variables: one represents the density of intracellular calcium, one represents a fraction of open state NMDARs, and one represents the synaptic weight. We shown that in spite of its simplicity, the model can reproduce the properties of the plasticity that have been experimentally measured in various brain areas (e.g., layer 2/3 and 5 visual cortical slices, hippocampal cultures, and layer 2/3 somatosensory cortical slices) with respect to various patterns of presynaptic and postsynaptic spikes. In addition, comparisons with other STDP models are made, and the significance and advantages of the proposed model are discussed.
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Brady, K. D., K. A. Wagner, A. H. Tashjian, and D. E. Golan. "Alterations in the frequency and shape of Ca2+ fluctuations in GH4C1 cells induced by thyrotropin-releasing hormone and Bay K 8644." Biochemical Journal 306, no. 2 (March 1, 1995): 399–406. http://dx.doi.org/10.1042/bj3060399.
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We have examined statistically the actions of thyrotropin-releasing hormone (TRH) and Bay K 8644, an L-type Ca(2+)-channel agonist, on the frequency and shape of cytosolic Ca2+ spikes in individual GH4C1 rat pituitary cells. TRH induced a brief (0-40 s) suppression of Ca2+ spikes followed by a period (40-200 s) of increased spike frequency. TRH treatment reduced the rate of rise and amplitude of Ca2+ spikes, and increased the rate of fall, relative to spontaneous spikes before treatment. TRH had no significant effect on the correlation between spike amplitude and the spike decay time constant tau, suggesting that the increased rate of fall was due to enhanced Ca2+ extrusion and not to decreased Ca(2+)-induced Ca2+ release. Bay K rapidly (t1/2 = 9-13 s) induced a 2-fold increase in the rate of rise of spikes with no change in the total rise time, leading to an increase in spike amplitude. It increased by 2-fold the fall time of spikes, as predicted solely by the previously observed relationship between spike amplitude and fall time. Bay K therefore appeared to increase the number of Ca2+ channels participating in each spike event without altering the kinetics of channel activation or deactivation, and without influencing Ca2+ extrusion. After addition of Bay K, the interval between spikes gradually (t1/2 approximately 100 s) increased, whereas the rate of rise remained constant and maximal. To explain these actions of TRH and Bay K, we postulate that a fraction of L-type Ca2+ channels are inactivated during each spike and must be re-activated in order to participate in a subsequent spike. We conclude further that the changes in spike frequency and profiles induced by these secretagogues are most consistent with a model in which TRH induces increases in both Ca2+ influx and efflux while Bay K induces a large increase in Ca2+ influx but has little effect on efflux.
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Jacobs, F. J., and P. A. G. van der Geest. "Spiking band‐limited traces with a relative‐entropy algorithm." GEOPHYSICS 56, no. 7 (July 1991): 1003–14. http://dx.doi.org/10.1190/1.1443109.
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A novel method for the inversion of band‐limited seismic traces to full bandwidth reflectivity traces, is based on a probabilistic spiky model of the reflectivity trace, in which position indicators and amplitudes of the spikes occur as random variables, and relies on relative entropy inference from information theory. First, an a priori model for general reflectivity traces in the prospect is derived from nearby wells. Second, the a priori distribution is updated into an a posteriori distribution for the specific trace being studied by the addition of the Fourier data of the seismic trace within a passband. Uncertainty about the Fourier coefficients can be accounted for by specification of a noise variance, which implicitly is infinite outside the passband. The update with relative entropy inference is justified because of its relationship with Bayesian inference. Application of maximum a posteriori (MAP) estimation to the a posteriori distribution results in the most likely spiky reflectivity trace of full bandwidth. A numerical algorithm for obtaining the MAP estimates of spike positions and spike amplitudes is derived from the concept of continuation and is described in detail. The algorithm avoids searching among all possible patterns of spike positions.
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Oram, Mike W., Nicholas G. Hatsopoulos, Barry J. Richmond, and John P. Donoghue. "Excess Synchrony in Motor Cortical Neurons Provides Redundant Direction Information With That From Coarse Temporal Measures." Journal of Neurophysiology 86, no. 4 (October 1, 2001): 1700–1716. http://dx.doi.org/10.1152/jn.2001.86.4.1700.
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Previous studies have shown that measures of fine temporal correlation, such as synchronous spikes, across responses of motor cortical neurons carries more directional information than that predicted from statistically independent neurons. It is also known, however, that the coarse temporal measures of responses, such as spike count, are not independent. We therefore examined whether the information carried by coincident firing was related to that of coarsely defined spike counts and their correlation. Synchronous spikes were counted in the responses from 94 pairs of simultaneously recorded neurons in primary motor cortex (MI) while monkeys performed arm movement tasks. Direct measurement of the movement-related information indicated that the coincident spikes (1- to 5-ms precision) carry ∼10% of the information carried by a code of the two spike counts. Inclusion of the numbers of synchronous spikes did not add information to that available from the spike counts and their coarse temporal correlation. To assess the significance of the numbers of coincident spikes, we extended the stochastic spike count matched (SCM) model to include correlations between spike counts of the individual neural responses and slow temporal dependencies within neural responses (∼30 Hz bandwidth). The extended SCM model underestimated the numbers of synchronous spikes. Therefore as with previous studies, we found that there were more synchronous spikes in the neural data than could be accounted for by this stochastic model. However, the SCM model accounts for most ( R 2 = 0.93 ± 0.05, mean ± SE) of the differences in the observed number of synchronous spikes to different directions of arm movement, indicating that synchronous spiking is directly related to spike counts and their broad correlation. Further, this model supports the information theoretic analysis that the synchronous spikes do not provide directional information beyond that available from the firing rates of the same pool of directionally tuned MI neurons. These results show that detection of precisely timed spike patterns above chance levels does not imply that those spike patterns carry information unavailable from coarser population codes but leaves open the possibility that excess synchrony carries other forms of information or serves other roles in cortical information processing not studied here.
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Gong, Xiajing, Wu Li, and Hualou Liang. "Spike-field Granger causality for hybrid neural data analysis." Journal of Neurophysiology 122, no. 2 (August 1, 2019): 809–22. http://dx.doi.org/10.1152/jn.00246.2019.
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Neurotechnological innovations allow for simultaneous recording at various scales, ranging from spiking activity of individual neurons to large neural populations’ local field potentials (LFPs). This capability necessitates developing multiscale analysis of spike-field activity. A joint analysis of the hybrid neural data is crucial for bridging the scales between single neurons and local networks. Granger causality is a fundamental measure to evaluate directional influences among neural signals. However, it is mainly limited to inferring causal influence between the same type of signals—either LFPs or spike trains—and not well developed between two different signal types. Here we propose a model-free, nonparametric spike-field Granger causality measure for hybrid data analysis. Our measure is distinct from existing methods in that we use “binless” spikes (precise spike timing) rather than “binned” spikes (spike counts within small consecutive time windows). The latter clearly distort the information in the mixed analysis of spikes and LFP. Therefore, our spectral estimate of spike trains is directly applied to the neural point process itself, i.e., sequences of spike times rather than spike counts. Our measure is validated by an extensive set of simulated data. When the measure is applied to LFPs and spiking activity simultaneously recorded from visual areas V1 and V4 of monkeys performing a contour detection task, we are able to confirm computationally the long-standing experimental finding of the input-output relationship between LFPs and spikes. Importantly, we demonstrate that spike-field Granger causality can be used to reveal the modulatory effects that are inaccessible by traditional methods, such that spike→LFP Granger causality is modulated by the behavioral task, whereas LFP→spike Granger causality is mainly related to the average synaptic input. NEW & NOTEWORTHY It is a pressing question to study the directional interactions between local field potential (LFP) and spiking activity. In this report, we propose a model-free, nonparametric spike-field Granger causality measure that can be used to reveal directional influences between spikes and LFPs. This new measure is crucial for bridging the scales between single neurons and neural networks; hence it represents an important step to explicate how the brain orchestrates information processing.
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Conrad, Erin C., Samuel B. Tomlinson, Jeremy N. Wong, Kelly F. Oechsel, Russell T. Shinohara, Brian Litt, Kathryn A. Davis, and Eric D. Marsh. "Spatial distribution of interictal spikes fluctuates over time and localizes seizure onset." Brain 143, no. 2 (December 20, 2019): 554–69. http://dx.doi.org/10.1093/brain/awz386.
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Abstract The location of interictal spikes is used to aid surgical planning in patients with medically refractory epilepsy; however, their spatial and temporal dynamics are poorly understood. In this study, we analysed the spatial distribution of interictal spikes over time in 20 adult and paediatric patients (12 females, mean age = 34.5 years, range = 5–58) who underwent intracranial EEG evaluation for epilepsy surgery. Interictal spikes were detected in the 24 h surrounding each seizure and spikes were clustered based on spatial location. The temporal dynamics of spike spatial distribution were calculated for each patient and the effects of sleep and seizures on these dynamics were evaluated. Finally, spike location was assessed in relation to seizure onset location. We found that spike spatial distribution fluctuated significantly over time in 14/20 patients (with a significant aggregate effect across patients, Fisher’s method: P < 0.001). A median of 12 sequential hours were required to capture 80% of the variability in spike spatial distribution. Sleep and postictal state affected the spike spatial distribution in 8/20 and 4/20 patients, respectively, with a significant aggregate effect (Fisher’s method: P < 0.001 for each). There was no evidence of pre-ictal change in the spike spatial distribution for any patient or in aggregate (Fisher’s method: P = 0.99). The electrode with the highest spike frequency and the electrode with the largest area of downstream spike propagation both localized the seizure onset zone better than predicted by chance (Wilcoxon signed-rank test: P = 0.005 and P = 0.002, respectively). In conclusion, spikes localize seizure onset. However, temporal fluctuations in spike spatial distribution, particularly in relation to sleep and post-ictal state, can confound localization. An adequate duration of intracranial recording—ideally at least 12 sequential hours—capturing both sleep and wakefulness should be obtained to sufficiently sample the interictal network.
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Putney, Joy, Rachel Conn, and Simon Sponberg. "Precise timing is ubiquitous, consistent, and coordinated across a comprehensive, spike-resolved flight motor program." Proceedings of the National Academy of Sciences 116, no. 52 (December 16, 2019): 26951–60. http://dx.doi.org/10.1073/pnas.1907513116.
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Sequences of action potentials, or spikes, carry information in the number of spikes and their timing. Spike timing codes are critical in many sensory systems, but there is now growing evidence that millisecond-scale changes in timing also carry information in motor brain regions, descending decision-making circuits, and individual motor units. Across all of the many signals that control a behavior, how ubiquitous, consistent, and coordinated are spike timing codes? Assessing these open questions ideally involves recording across the whole motor program with spike-level resolution. To do this, we took advantage of the relatively few motor units controlling the wings of a hawk moth,Manduca sexta. We simultaneously recorded nearly every action potential from all major wing muscles and the resulting forces in tethered flight. We found that timing encodes more information about turning behavior than spike count in every motor unit, even though there is sufficient variation in count alone. Flight muscles vary broadly in function as well as in the number and timing of spikes. Nonetheless, each muscle with multiple spikes consistently blends spike timing and count information in a 3:1 ratio. Coding strategies are consistent. Finally, we assess the coordination of muscles using pairwise redundancy measured through interaction information. Surprisingly, not only are all muscle pairs coordinated, but all coordination is accomplished almost exclusively through spike timing, not spike count. Spike timing codes are ubiquitous, consistent, and essential for coordination.
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Franke, Felix, Robert Pröpper, Henrik Alle, Philipp Meier, Jörg R. P. Geiger, Klaus Obermayer, and Matthias H. J. Munk. "Spike sorting of synchronous spikes from local neuron ensembles." Journal of Neurophysiology 114, no. 4 (October 2015): 2535–49. http://dx.doi.org/10.1152/jn.00993.2014.
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Synchronous spike discharge of cortical neurons is thought to be a fingerprint of neuronal cooperativity. Because neighboring neurons are more densely connected to one another than neurons that are located further apart, near-synchronous spike discharge can be expected to be prevalent and it might provide an important basis for cortical computations. Using microelectrodes to record local groups of neurons does not allow for the reliable separation of synchronous spikes from different cells, because available spike sorting algorithms cannot correctly resolve the temporally overlapping waveforms. We show that high spike sorting performance of in vivo recordings, including overlapping spikes, can be achieved with a recently developed filter-based template matching procedure. Using tetrodes with a three-dimensional structure, we demonstrate with simulated data and ground truth in vitro data, obtained by dual intracellular recording of two neurons located next to a tetrode, that the spike sorting of synchronous spikes can be as successful as the spike sorting of nonoverlapping spikes and that the spatial information provided by multielectrodes greatly reduces the error rates. We apply the method to tetrode recordings from the prefrontal cortex of behaving primates, and we show that overlapping spikes can be identified and assigned to individual neurons to study synchronous activity in local groups of neurons.
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Torres, David J., Andres Romero, Wes Colgan, and Ulises M. Ricoy. "A low-cost computational approach to analyze spiking activity in cockroach sensory neurons." Advances in Physiology Education 45, no. 1 (March 1, 2021): 145–53. http://dx.doi.org/10.1152/advan.00034.2020.
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Undergraduates use a spike sorting routine developed in Octave to analyze the spiking activity generated from mechanical stimulation of spines of cockroach legs with the inexpensive SpikerBox amplifier and the free software Audacity. Students learn the procedures involved in handling the cockroaches and recording extracellular action potentials (spikes) with the SpikerBox apparatus as well as the importance of spike sorting for analysis in neuroscience. The spike sorting process requires students to choose the spike threshold and spike selection criteria and interact with the clustering process that forms the groups of similar spikes. Once the spike groups are identified, interspike intervals and neuron firing frequencies can be calculated and analyzed. A classic neurophysiology lab exercise is thus adapted to be interdisciplinary for underrepresented students in a small rural college.
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Ardelean, Eugen-Richard, Andreea Coporîie, Ana-Maria Ichim, Mihaela Dînșoreanu, and Raul Cristian Mureșan. "A study of autoencoders as a feature extraction technique for spike sorting." PLOS ONE 18, no. 3 (March 9, 2023): e0282810. http://dx.doi.org/10.1371/journal.pone.0282810.
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Spike sorting is the process of grouping spikes of distinct neurons into their respective clusters. Most frequently, this grouping is performed by relying on the similarity of features extracted from spike shapes. In spite of recent developments, current methods have yet to achieve satisfactory performance and many investigators favour sorting manually, even though it is an intensive undertaking that requires prolonged allotments of time. To automate the process, a diverse array of machine learning techniques has been applied. The performance of these techniques depends however critically on the feature extraction step. Here, we propose deep learning using autoencoders as a feature extraction method and evaluate extensively the performance of multiple designs. The models presented are evaluated on publicly available synthetic and real “in vivo” datasets, with various numbers of clusters. The proposed methods indicate a higher performance for the process of spike sorting when compared to other state-of-the-art techniques.
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Ghormade, Ashish S., and P. C. Haldavnekar. "Effect of Nitrogen and Spacing on Flowering Parameters of Spider Lily (Hymenocallis littoralis L.)." International Journal of Current Microbiology and Applied Sciences 11, no. 3 (March 10, 2022): 146–56. http://dx.doi.org/10.20546/ijcmas.2022.1103.017.
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The present investigation entitled “Effect of nitrogen and spacing on flowering of spider lily (Hymenocallis littoralis L.)” was undertaken at College of Horticulture, Dr. Balasaheb Sawant Konkan Krishi Vidyapeeth, Dapoli during the year 2019-20 and 2020-21 by considering the commercial importance of spider lily under Konkan agro-climatic conditions. The experiment was laid out in a split plot design using four levels of nitrogen and three levels of spacing with three replications along with the common dosage of phosphorous (150 kg ha-1) and potassium (100 kg ha-1). The observations were recorded on various flowering parameters viz., such as days taken for first spike emergence, days taken for first flower emergence, number of spikes per plant, spike length, spike breadth and number of buds per spike. Days taken for first spike emergence (182.04) and first flower emergence (191.02) were recorded as lowest in N4 (150 kg ha-1). The highest number of spikes per plant (2.73) and flower bud per spike (16.15) were recorded in N1 (300 kg ha-1). However, with regards to effect of spacing, S2 (60 × 60 cm) recorded the lowest days taken for first spike (183.86) and first flower emergence (193.25), while the highest number of spikes per plant (2.33) and number of buds per spike (14.25) was noticed in S3 (30 × 60 cm). Spike length and breadth were found to be non-significant with respect to effect of nitrogen, spacing and their interaction.
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Moldakarimov, Samat, Maxim Bazhenov, and Terrence J. Sejnowski. "Feedback stabilizes propagation of synchronous spiking in cortical neural networks." Proceedings of the National Academy of Sciences 112, no. 8 (February 9, 2015): 2545–50. http://dx.doi.org/10.1073/pnas.1500643112.
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Precisely timed action potentials related to stimuli and behavior have been observed in the cerebral cortex. However, information carried by the precise spike timing has to propagate through many cortical areas, and noise could disrupt millisecond precision during the transmission. Previous studies have demonstrated that only strong stimuli that evoke a large number of spikes with small dispersion of spike times can propagate through multilayer networks without degrading the temporal precision. Here we show that feedback projections can increase the number of spikes in spike volleys without degrading their temporal precision. Feedback also increased the range of spike volleys that can propagate through multilayer networks. Our work suggests that feedback projections could be responsible for the reliable propagation of information encoded in spike times through cortex, and thus could serve as an attentional mechanism to regulate the flow of information in the cortex. Feedback projections may also participate in generating spike synchronization that is engaged in cognitive behaviors by the same mechanisms described here for spike propagation.
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Klindworth, D. L., N. D. Williams, and L. R. Joppa. "Inheritance of supernumerary spikelets in a tetraploid wheat cross." Genome 33, no. 4 (August 1, 1990): 509–14. http://dx.doi.org/10.1139/g90-075.
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The supernumerary spikelet (SS) trait of durum wheat (Triticum turgidum L.), including the four-rowed and ramified spike types, is characterized by an increased number of spikelets per spike. To determine the inheritance of this trait, the tetraploid ramified spike cultivar PI349056 was crossed reciprocally to normal-spike 'Langdon' durum, and the F1 was backcrossed to each parent. The F1, F2, F3, BC1F1, and BC1F2 were classified for SS expression. Additionally, PI349056 was crossed to the 'Langdon' 2D(2A) disomic substitution line to study linkage of SS genes. The SS trait was recessive to normal spike, and both four-rowed spike and ramified spike progeny were observed in the segregating generations. Segregation in F3 and BC1F2 families indicated that SS in PI349056 was quantitatively inherited, controlled by a major recessive gene and numerous minor genes. Normal-spiked plants selected in families homozygous for the major gene indicated that the major gene did not produce SS when the minor genes were absent. Selection of normal-spiked plants in the F3 and F4 of 'Langdon' 2D(2A) disomic substitution/PI349056 indicated that the minor SS genes were not linked to the major gene on chromosome 2A.Key words: Triticum, branched spike, ramified spike, four-rowed spike.
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Więcław, Helena. "Morphological variability of the Carex oederi s. l. inflorescence." Biodiversity: Research and Conservation 21, no. 1 (January 1, 2011): 13–18. http://dx.doi.org/10.2478/v10119-011-0003-0.
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Morphological variability of theCarex oederis. l. inflorescenceThe most variable features describingCarex oederis. l. include: (i) the distance between two lower female spikes, (ii) the length of the peduncle of a lower female spike, (iii) the distance between two upper female spikes, (iv) the length of inflorescence and peduncle of a male spike. Most of observed stems had (3)4-5 female spikes, which were crowded around a sessile and short male spike. Specimens with fewer female spikes (2-3) were characterized generally by their loose positioning on a stem (occasionally a lower female spike was distant and had a peduncle) and the presence of usually longer male spikes on a peduncle. In conclusion,C. oederis. l. is highly variable morphologically. In the investigated materials, there are no apparent discontinuities. Further (planned) biometric research will be extended to the characteristics of the perygynium and vegetative features.
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Kramer, Mark A., Lauren M. Ostrowski, Daniel Y. Song, Emily L. Thorn, Sally M. Stoyell, McKenna Parnes, Dhinakaran Chinappen, et al. "Scalp recorded spike ripples predict seizure risk in childhood epilepsy better than spikes." Brain 142, no. 5 (March 25, 2019): 1296–309. http://dx.doi.org/10.1093/brain/awz059.
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Abstract In the past decade, brief bursts of fast oscillations in the ripple range have been identified in the scalp EEG as a promising non-invasive biomarker for epilepsy. However, investigation and clinical application of this biomarker have been limited because standard approaches to identify these brief, low amplitude events are difficult, time consuming, and subjective. Recent studies have demonstrated that ripples co-occurring with epileptiform discharges (‘spike ripple events’) are easier to detect than ripples alone and have greater pathological significance. Here, we used objective techniques to quantify spike ripples and test whether this biomarker predicts seizure risk in childhood epilepsy. We evaluated spike ripples in scalp EEG recordings from a prospective cohort of children with a self-limited epilepsy syndrome, benign epilepsy with centrotemporal spikes, and healthy control children. We compared the rate of spike ripples between children with epilepsy and healthy controls, and between children with epilepsy during periods of active disease (active, within 1 year of seizure) and after a period of sustained seizure-freedom (seizure-free, >1 year without seizure), using semi-automated and automated detection techniques. Spike ripple rate was higher in subjects with active epilepsy compared to healthy controls (P = 0.0018) or subjects with epilepsy who were seizure-free ON or OFF medication (P = 0.0018). Among epilepsy subjects with spike ripples, each month seizure-free decreased the odds of a spike ripple by a factor of 0.66 [95% confidence interval (0.47, 0.91), P = 0.021]. Comparing the diagnostic accuracy of the presence of at least one spike ripple versus a classic spike event to identify group, we found comparable sensitivity and negative predictive value, but greater specificity and positive predictive value of spike ripples compared to spikes (P = 0.016 and P = 0.006, respectively). We found qualitatively consistent results using a fully automated spike ripple detector, including comparison with an automated spike detector. We conclude that scalp spike ripple events identify disease and track with seizure risk in this epilepsy population, using both semi-automated and fully automated detection methods, and that this biomarker outperforms analysis of spikes alone in categorizing seizure risk. These data provide evidence that spike ripples are a specific non-invasive biomarker for seizure risk in benign epilepsy with centrotemporal spikes and support future work to evaluate the utility of this biomarker to guide medication trials and tapers in these children and predict seizure risk in other at-risk populations.
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Raju, Venkateshwarla Rama. "Investigation of multi-site micro recordings of subthalamic nucleus neurons using machine learning MER with DBS in Parkinson`s – A simulation study." IP Indian Journal of Neurosciences 7, no. 4 (January 15, 2022): 287–91. http://dx.doi.org/10.18231/j.ijn.2021.052.
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Multineural spikes were acquired with a multisite electrode placed in the hippocampus pyramidal cell layer of non-primate anesthetized snitch animals. If the impedance of each electrode-site is relatively low and the distance amongst electrode sites is appropriately miniatured, a spike generated by a neuron is parallelly recorded at multielectrode sites with different amplitudes. The covariance between the spike of the at each electrode-point and a template was computed as a damping-factor due to the volume conduction of the spike from the neuron to electrode-site. Computed damping factors were vectorized and analyzed by simple but elegant hierarchical-clustering using a multidimensional statistical-test. Since a cluster of damping vectors was shown to correspond to an antidromically identified neuron, spikes of distinct neurons are classified by suggesting to the scatterings of damping vectors. Errors in damping vector computing due to partially overlapping spikes were minimized by successively subtracting preceding spikes from raw data. Clustering errors due to complex-spike-bursts (i.e., spikes with variable-amplitudes) were prevented by detecting such bursts and using only the first spike of a burst for clustering.
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Panchev, Christo, and Stefan Wermter. "Spike-timing-dependent synaptic plasticity: from single spikes to spike trains." Neurocomputing 58-60 (June 2004): 365–71. http://dx.doi.org/10.1016/j.neucom.2004.01.068.
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Demb, Jonathan B., Peter Sterling, and Michael A. Freed. "How Retinal Ganglion Cells Prevent Synaptic Noise From Reaching the Spike Output." Journal of Neurophysiology 92, no. 4 (October 2004): 2510–19. http://dx.doi.org/10.1152/jn.00108.2004.
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Synaptic vesicles are released stochastically, and therefore stimuli that increase a neuron's synaptic input might increase noise at its spike output. Indeed this appears true for neurons in primary visual cortex, where spike output variability increases with stimulus contrast. But in retinal ganglion cells, although intracellular recordings (with spikes blocked) showed that stronger stimuli increase membrane fluctuations, extracellular recordings showed that noise at the spike output is constant. Here we show that these seemingly paradoxical findings occur in the same cell and explain why. We made intracellular recordings from ganglion cells, in vitro, and presented periodic stimuli of various contrasts. For each stimulus cycle, we measured the response at the stimulus frequency (F1) for both membrane potential and spikes as well as the spike rate. The membrane and spike F1 response increased with contrast, but noise (SD) in the F1 responses and the spike rate was constant. We also measured membrane fluctuations (with spikes blocked) during the response depolarization and found that they did increase with contrast. However, increases in fluctuation amplitude were small relative to the depolarization (<10% at high contrast). A model based on estimated synaptic convergence, release rates, and membrane properties accounted for the relative magnitudes of fluctuations and depolarization. Furthermore, a cell's peak spike response preceded the peak depolarization, and therefore fluctuation amplitude peaked as the spike response declined. We conclude that two extremely general properties of a neuron, synaptic convergence and spike generation, combine to minimize the effects of membrane fluctuations on spiking.
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Legendy, C. R., and M. Salcman. "Bursts and recurrences of bursts in the spike trains of spontaneously active striate cortex neurons." Journal of Neurophysiology 53, no. 4 (April 1, 1985): 926–39. http://dx.doi.org/10.1152/jn.1985.53.4.926.
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Simultaneous recordings were made from small collections (2-7) of spontaneously active single units in the striate cortex of unanesthetized cats, by means of chronically implanted electrodes. The recorded spike trains were computer scanned for bursts of spikes, and the bursts were catalogued and studied. The firing rates of the neurons ranged from 0.16 to 32 spikes/s; the mean was 8.9 spikes/s, the standard deviation 7.0 spikes/s. Bursts of spikes were assigned a quantitative measure, termed Poisson surprise (S), defined as the negative logarithm of their probability in a random (Poisson) spike train. Only bursts having S greater than 10, corresponding to an occurrence rate of about 0.01 bursts/1,000 spikes in a random spike train, were considered to be of interest. Bursts having S greater than 10 occurred at a rate of about 5-15 bursts/1,000 spikes, or about 1-5 bursts/min. The rate slightly increased with spike rate; averaging about 2 bursts/min for neurons having 3 spikes/s and about 4.5 bursts/min for neurons having 30 spikes/s. About 21% of the recorded units emitted significantly fewer bursts than the rest (below 1 burst/1,000 spikes). The percentage of these neurons was independent of spike rate. The spike rate during bursts was found to be about 3-6 times the average spike rate; about the same for longer as for shorter bursts. Bursts typically contained 10-50 spikes and lasted 0.5-2.0 s. When the number of spikes in the successively emitted bursts was listed, it was found that in some neurons these numbers were not distributed at random but were clustered around one or more preferred values. In this sense, bursts occasionally "recurred" a few times in a few minutes. The finding suggests that neurons are highly reliable. When bursts of two or more simultaneously recorded neurons were compared, the bursts often appeared to be temporally close, especially between pairs of neurons recorded by the same electrode; but bursts seldom started and ended simultaneously on two channels. Recurring bursts emitted by one neuron were occasionally accompanied by time-locked recurring bursts by other neurons.
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Kahlon, Maninder, and Stephen G. Lisberger. "Changes in the Responses of Purkinje Cells in the Floccular Complex of Monkeys After Motor Learning in Smooth Pursuit Eye Movements." Journal of Neurophysiology 84, no. 6 (December 1, 2000): 2945–60. http://dx.doi.org/10.1152/jn.2000.84.6.2945.
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We followed simple- and complex-spike firing of Purkinje cells (PCs) in the floccular complex of the cerebellum through learned modifications of the pursuit eye movements of two monkeys. Learning was induced by double steps of target speed in which initially stationary targets move at a “learning” speed for 100 ms and then change to either a higher or lower speed in the same direction. In randomly interleaved control trials, targets moved at the learning speed in the opposite direction. When the learning direction was theon direction for simple-spike responses, learning was associated with statistically significant changes in simple-spike firing for 10 of 32 PCs. Of the 10 PCs that showed significant expressions of learning, 8 showed changes in simple-spike output in the expected direction: increased or decreased firing when eye acceleration increased or decreased through learning. There were no statistically significant changes in simple-spike responses or eye acceleration during pursuit in the control direction. When the learning direction was in the off direction for simple-spike responses, none of 15 PCs showed significant correlates of learning. Although changes in simple-spike firing were recorded in only a subset of PCs, analysis of the population response showed that the same relationship between population firing and eye acceleration obtained before and after learning. Thus learning is associated with changes that render the modified population response appropriate to drive the changed behavior. To analyze complex-spike firing during learning we correlated complex-spike firing in the second, third, and fourth 100 ms after the onset of target motion with the retinal image motion in the previous 100 ms. Data were largely consistent with previous evidence that image motion drives complex spikes with a direction selectivity opposite that for simple spikes. Comparison of complex-spike responses at different times after the onset of control and learning target motions in the learning direction implied that complex spikes could guide learning during decreases but not increases in eye acceleration. Learning caused increases or decreases in the sensitivity of complex spikes to image motion in parallel with changes in eye acceleration. Complex-spike responses were similar in all PCs, including many in which learning did not modify simple-spike responses. Our data do not disprove current theories of cerebellar learning but suggest that these theories would have to be modified to account for simple- and complex-spike firing of floccular Purkinje cells reported here.
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Stone, L. S., and S. G. Lisberger. "Visual responses of Purkinje cells in the cerebellar flocculus during smooth-pursuit eye movements in monkeys. II. Complex spikes." Journal of Neurophysiology 63, no. 5 (May 1, 1990): 1262–75. http://dx.doi.org/10.1152/jn.1990.63.5.1262.
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1. We report the complex-spike responses of two groups of Purkinje cells (P-cells). The cell were classified according to their simple-spike firing during smooth eye movements evoked by visual and vestibular stimuli with the use of established criteria (Lisberger and Fuchs 1978; Stone and Lisberger 1990). During pursuit with the head fixed, ipsi gaze-velocity P-cells (GVP-cells) showed increased simple-spike firing when gaze moved toward the side of the recording, whereas down GVP-cells showed increased simple-spike firing when gaze moved downward. 2. During pursuit of sinusoidal target motion, the complex-spike firing rate was modulated out-of-phase with the simple-spike firing rate. Ipsi GVP-cells showed increased complex-spike firing during pursuit away from the side of the recording, and down GVP-cells showed increased complex-spike firing during upward pursuit. The strength of the complex-spike response increased as a function of the frequency of sinusoidal target motion. 3. GVP-cells showed directionally selective complex-spike responses during the initiation of pursuit to ramp target motion. Ipsi GVP-cells had increased complex-spike firing 100 ms after the onset of contralaterally directed target motion and decreased complex-spike activity after the onset of ipsilaterally directed target motion. Down GVP-cells had increased complex-spike firing 100 ms after the onset of upward target motion and decreased firing after the onset of downward target motion. As during sinusoidal target motion, each cell's simple- and complex-spike responses had the opposite directional preferences. 4. When the monkeys fixated a stationary target during a transient vestibular stimulus, the retinal slip caused by the 14-ms latency of the vestibuloocular reflex (VOR) affected the complex-spike firing rate. For ipsi GVP-cells, ipsilateral head motion caused transient contralateral image motion and an increase in complex-spike firing. The same vestibular stimulus in darkness caused an almost identical eye movement but had no effect on complex-spike firing. We conclude that complex spikes in ipsi GVP-cells are driven by contralaterally directed image motion. 5. To determine the events surrounding complex-spike firing during pursuit, we triggered averages of eye and target velocity on the occurrence of complex spikes during pursuit of sine-wave target motion. The averages revealed a transient pulse of retinal image motion that peaked approximately 100 ms before the complex spike. We conclude that complex spikes during steady-state pursuit are driven by the retinal slip associated with imperfect pursuit.(ABSTRACT TRUNCATED AT 400 WORDS)
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Zając, Tadeusz, Wiesław Szafrański, and Jacek Strojny. "Kernel mass of winter triticale depending on placing position in a spikelet and a spike, with regard to its productiveness." Acta Agrobotanica 57, no. 1-2 (2013): 175–86. http://dx.doi.org/10.5586/aa.2004.017.
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The investigations were carried outin 1996-1997 on degraded chernozem developed from loess. The winter triticale cv. 'Presto' cultivated after 4 forecrops (spring cereals with red clover undersown and triticale in pure stand). Studied were correlation between the number of spikeIets and kernels and their placing position in a spike and spikelet, and the grain weight from three spike size groups. The number of productive spikelets per spike and fertility of inflorescence per spikelet, measured as a number of kernels, were the biggest in big spikes group. Kernels placed in positions 1 and 2 in a kernel had the biggest mass, whereas the kernels developed from the inflorescence in positions 3 and 4 were conspicuous for their smaller mass, particularly in the small and medium-size spike groups. The analysis of correlation coefficient values revealed that grain weight per spike was strongly correlated with the number of kernels per spike in all determined size classes. Also a significant effect of single kemel weight on yield per spike was noticed, but the coefficient value was lower (r=0.30). Spikelets in positions from 3 to 7 level (on both sides of spike) had the greatest share in grain weight per spike for the smallest spike group, whereas for medium- size and big spikes respectively spikelets in positions 3 through 9 and 2 through 10.
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Zanos, Theodoros P., Patrick J. Mineault, and Christopher C. Pack. "Removal of Spurious Correlations Between Spikes and Local Field Potentials." Journal of Neurophysiology 105, no. 1 (January 2011): 474–86. http://dx.doi.org/10.1152/jn.00642.2010.
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Single neurons carry out important sensory and motor functions related to the larger networks in which they are embedded. Understanding the relationships between single-neuron spiking and network activity is therefore of great importance and the latter can be readily estimated from low-frequency brain signals known as local field potentials (LFPs). In this work we examine a number of issues related to the estimation of spike and LFP signals. We show that spike trains and individual spikes contain power at the frequencies that are typically thought to be exclusively related to LFPs, such that simple frequency-domain filtering cannot be effectively used to separate the two signals. Ground-truth simulations indicate that the commonly used method of estimating the LFP signal by low-pass filtering the raw voltage signal leads to artifactual correlations between spikes and LFPs and that these correlations exert a powerful influence on popular metrics of spike–LFP synchronization. Similar artifactual results were seen in data obtained from electrophysiological recordings in macaque visual cortex, when low-pass filtering was used to estimate LFP signals. In contrast LFP tuning curves in response to sensory stimuli do not appear to be affected by spike contamination, either in simulations or in real data. To address the issue of spike contamination, we devised a novel Bayesian spike removal algorithm and confirmed its effectiveness in simulations and by applying it to the electrophysiological data. The algorithm, based on a rigorous mathematical framework, outperforms other methods of spike removal on most metrics of spike–LFP correlations. Following application of this spike removal algorithm, many of our electrophysiological recordings continued to exhibit spike–LFP correlations, confirming previous reports that such relationships are a genuine aspect of neuronal activity. Overall, these results show that careful preprocessing is necessary to remove spikes from LFP signals, but that when effective spike removal is used, spike–LFP correlations can potentially yield novel insights about brain function.
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Doiron, Brent, André Longtin, Ray W. Turner, and Leonard Maler. "Model of Gamma Frequency Burst Discharge Generated by Conditional Backpropagation." Journal of Neurophysiology 86, no. 4 (October 1, 2001): 1523–45. http://dx.doi.org/10.1152/jn.2001.86.4.1523.
Full textAbstract:
Pyramidal cells of the electrosensory lateral line lobe (ELL) of the weakly electric fish Apteronotus leptorhynchus have been shown to produce oscillatory burst discharge in the γ-frequency range (20–80 Hz) in response to constant depolarizing stimuli. Previous in vitro studies have shown that these bursts arise through a recurring spike backpropagation from soma to apical dendrites that is conditional on the frequency of action potential discharge (“conditional backpropagation”). Spike bursts are characterized by a progressive decrease in inter-spike intervals (ISIs), and an increase of dendritic spike duration and the amplitude of a somatic depolarizing afterpotential (DAP). The bursts are terminated when a high-frequency somatic spike doublet exceeds the dendritic spike refractory period, preventing spike backpropagation. We present a detailed multi-compartmental model of an ELL basilar pyramidal cell to simulate somatic and dendritic spike discharge and test the conditions necessary to produce a burst output. The model ionic channels are described by modified Hodgkin-Huxley equations and distributed over both soma and dendrites under the constraint of available immunocytochemical and electrophysiological data. The currents modeled are somatic and dendritic sodium and potassium involved in action potential generation, somatic and proximal apical dendritic persistent sodium, and KV3.3 and fast transient A-like potassium channels distributed over the entire model cell. The core model produces realistic somatic and dendritic spikes, differential spike refractory periods, and a somatic DAP. However, the core model does not produce oscillatory spike bursts with constant depolarizing stimuli. We find that a cumulative inactivation of potassium channels underlying dendritic spike repolarization is a necessary condition for the model to produce a sustained γ-frequency burst pattern matching experimental results. This cumulative inactivation accounts for a frequency-dependent broadening of dendritic spikes and results in a conditional failure of backpropagation when the intraburst ISI exceeds dendritic spike refractory period, terminating the burst. These findings implicate ion channels involved in repolarizing dendritic spikes as being central to the process of conditional backpropagation and oscillatory burst discharge in this principal sensory output neuron of the ELL.
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CHAWLA, S. L., M. A. PATEL, SUDHA PATIL, DIPAL BHATT, and R. B. PATEL. "Effect of land configuration and integrated nutrient management on growth, quality and yield of tuberose (Polianthes tuberosa) var. Prajwal." Indian Journal of Agricultural Sciences 88, no. 12 (December 11, 2018): 1854–58. http://dx.doi.org/10.56093/ijas.v88i12.85435.
Full textAbstract:
Present investigation was carried out to standardize the land configuration and nutrients for better quality and yield of tuberose (Polianthes tuberose L) spikes on heavy black soil of Navsari (Gujarat) during 2011-12 to 2013-14. The experiment was laid out in split-plot design having four levels of land configuration (main plot) and three levels of nutrients (sub plot).The results indicated that planting of tuberose bulbs in 3 rows on raised bed (90 cm width) recorded significantly early sprouting (21.73 days) with maximum sprouting percentage (98.28), plant height (65.10 cm), leaves/plant (76.79), leaf area (105.24 cm2), florets/spike (43.52), rachis length (32.38 cm), spike length (102.46cm), spike duration (16.00 days), vase life (13.55 days), spikes/plant (2.45), spikes/ha (188850.31), bulbs/plant (13.09), bulbs/ha (1030790) and bulblets/plant (29.11). In nutrient management, application of fertilizer dose (300:200:100NPK kg/ha/year) along with FYM @ 15 t/ha/year recorded early sprouting (23.15 days) with maximum sprouting percentage (96.04), plant height (63.44 cm), leaves/plant (71.16), leaf area (99.56 cm2), florets/spike (39.93), rachis length (30.99 cm), spike length (97.94 cm), spike duration (14.18 days) and vase life (12.07 days), spikes/plant (2.23), spikes/ha (195577.74), bulbs/ plant (10.63), bulbs/ha (928560.00) and bulblets/plant (28.83). Raised bed planting had favourable effect on growth and yield of tuberose as compared to ridge and furrow and flat bed planting.
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El-Wakeel, Sally E., Mohamed Mansour, Ashgan M. Abd El-Azeem, Sahar A. Ebrahim, and Tahany Noreldin. "Field and Economic Evaluation of Barley Productivity as Affected by Seed Rates and Slow-release Nitrogen Fertilizer Levels under Rainfed Conditions." Asian Journal of Advances in Agricultural Research 24, no. 4 (March 29, 2024): 16–26. http://dx.doi.org/10.9734/ajaar/2024/v24i4499.
Full textAbstract:
A field experiment was conducted at the north western coast of Egypt under rainfed conditions to study the effects of seed rates (70, 95 and 120 kg ha-1) and nitrogen fertilizer treatments (0, 35, 70 and 105 kg N ha-1) of Ensiabeen-40% N as slow-release fertilizer compared with 105 kg N ha-1 as Ammonium nitrate (33.5%N) on productivity of barley cultivar Giza134. This investigation was conducted during 2019/2020 and 2020/2021 winter growing seasons. The treatments were laid out in a split plot design, with three replications. Plant height, spike length, number of grins spike-1, number of spikes per m2, 1000 grain weight, biological and grain yield were recorded. In addition, total income and net return (LE)/hactare were calculated. The results indicated that mean squares due to seasons, seed rates, nitrogen levels and their interactions were significant for most studied traits. Mean performance of the studied traits as affected by seasons, seed rates and nitrogen levels showed that, the most desirable values were obtained by SR1 for spike length (6.13cm), number of grains spike-1 (48.78 grain) and 1000 grain weight (42.15g), from SR2 for Biological yield (6.02 ton ha-1) and grain yield (1.85 ton ha-1) and from SR3 for plant height (78.28cm) and number of spikes m-2 (180.11 spike). For nitrogen level effects, N4 recorded the most favorable values for all studied traits; plant height (81.48cm), spike length (6.33cm), number of grains spike-1 (49.99 grain), number of spikes m-2 (187.60 spike), Biological yield (6.88 ton ha-1), grain yield (2.12 ton ha-1) and 1000 grain weight (42.89g). Grain yield exhibited highly significant and positive correlation with each of plant height (r= 0.833**), spike length(r=0.621**), number of grains spike-1 (r=0.768**), number of spikes m-2(r=0.880**) and weight of 1000 grains (r= 0.661**). The most contributing variable in the total variation of grain yield were number of spikes m-2, number of grains spike-1 and spike length. These variables contributed by 92.9% in the grain yield variation. The results also indicated that, the highest values in the total income were 19149 and 24990 pound.hec-1 respectively, and net return were 9492 and 15498 pound.hec-1 obtained from the interaction between seed rate of 5kg ha-1 (SR2) and 105 unit of slow release fertilizer (N4) during the two growing seasons. It could recommend this treatment to maximize the total income for the farmers in such location.
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Stiber, Michael. "Spike Timing Precision and Neural Error Correction: Local Behavior." Neural Computation 17, no. 7 (July 1, 2005): 1577–601. http://dx.doi.org/10.1162/0899766053723069.
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The effects of spike timing precision and dynamical behavior on error correction in spiking neurons were investigated. Stationary discharges—phase locked, quasiperiodic, or chaotic—were induced in a simulated neuron by presenting pacemaker presynaptic spike trains across a model of a prototypical inhibitory synapse. Reduced timing precision was modeled by jittering presynaptic spike times. Aftereffects of errors—in this communication, missed presynaptic spikes—were determined by comparing postsynaptic spike times between simulations identical except for the presence or absence of errors. Results show that the effects of an error vary greatly depending on the ongoing dynamical behavior. In the case of phase lockings, a high degree of presynaptic spike timing precision can provide significantly faster error recovery. For nonlocked behaviors, isolated missed spikes can have little or no discernible aftereffects (or even serve to paradoxically reduce uncertainty in postsynaptic spike timing), regardless of presynaptic imprecision. This suggests two possible categories of error correction: high-precision locking with rapid recovery and low-precision nonlocked with error immunity.
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Froemke, Robert C., Ishan A. Tsay, Mohamad Raad, John D. Long, and Yang Dan. "Contribution of Individual Spikes in Burst-Induced Long-Term Synaptic Modification." Journal of Neurophysiology 95, no. 3 (March 2006): 1620–29. http://dx.doi.org/10.1152/jn.00910.2005.
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Long-term synaptic modification depends on the relative timing of individual pre- and postsynaptic spikes, but the rules governing the effects of multispike bursts remain to be fully understood. In particular, some studies suggest that the spike timing dependence of synaptic modification breaks down with high-frequency bursts. In this study, we characterized the effects of pre- and postsynaptic bursts on long-term modification of layer 2/3 synapses in visual cortical slices from young rats. We found that, while pairing-induced synaptic modification depends on the burst frequency, this dependence can be explained in terms of the timing of individual pre- and postsynaptic spikes. Later spikes in each burst are less effective in synaptic modification, but spike efficacy is regulated differently in pre- and postsynaptic bursts. Presynaptically, spike efficacy is progressively weakened, in parallel with short-term synaptic depression. Postsynaptically, spike efficacy is suppressed to a lesser extent, and it depends on postsynaptic potassium channel activation. Such timing-dependent interaction among multiple spikes can account for synaptic modifications induced by a variety of spike trains, including the frequency-dependent transition from depression to potentiation induced by a postsynaptic burst preceding a presynaptic burst.
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Diggelmann, Roland, Michele Fiscella, Andreas Hierlemann, and Felix Franke. "Automatic spike sorting for high-density microelectrode arrays." Journal of Neurophysiology 120, no. 6 (December 1, 2018): 3155–71. http://dx.doi.org/10.1152/jn.00803.2017.
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High-density microelectrode arrays can be used to record extracellular action potentials from hundreds to thousands of neurons simultaneously. Efficient spike sorters must be developed to cope with such large data volumes. Most existing spike sorting methods for single electrodes or small multielectrodes, however, suffer from the “curse of dimensionality” and cannot be directly applied to recordings with hundreds of electrodes. This holds particularly true for the standard reference spike sorting algorithm, principal component analysis-based feature extraction, followed by k-means or expectation maximization clustering, against which most spike sorters are evaluated. We present a spike sorting algorithm that circumvents the dimensionality problem by sorting local groups of electrodes independently with classical spike sorting approaches. It is scalable to any number of recording electrodes and well suited for parallel computing. The combination of data prewhitening before the principal component analysis-based extraction and a parameter-free clustering algorithm obviated the need for parameter adjustments. We evaluated its performance using surrogate data in which we systematically varied spike amplitudes and spike rates and that were generated by inserting template spikes into the voltage traces of real recordings. In a direct comparison, our algorithm could compete with existing state-of-the-art spike sorters in terms of sensitivity and precision, while parameter adjustment or manual cluster curation was not required. NEW & NOTEWORTHY We present an automatic spike sorting algorithm that combines three strategies to scale classical spike sorting techniques for high-density microelectrode arrays: 1) splitting the recording electrodes into small groups and sorting them independently; 2) clustering a subset of spikes and classifying the rest to limit computation time; and 3) prewhitening the spike waveforms to enable the use of parameter-free clustering. Finally, we combined these strategies into an automatic spike sorter that is competitive with state-of-the-art spike sorters.
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McLachlan, Richard S., and Neda Lubus. "Cortical Location of Benign Paroxysmal Rhythms in the Electrocorticogram." Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 29, no. 2 (May 2002): 154–58. http://dx.doi.org/10.1017/s031716710012092x.
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Abstract:Background:Six/second spike waves, 14 and 6/second positive spikes and small sharp spikes are apiculate paroxysmal rhythms in the electroencephalogram, thought to be of no diagnostic importance. The cortical origin of these discharges is documented in this report.Methods:These waveforms were assessed in recordings from the surface of the cerebral cortex using implanted subdural electrodes in 61 patients monitored for possible epilepsy surgery.Results:Eight patients had 6/second spike wave, four had 14 and 6/second positive spikes and 3 had small sharp spikes. The 6/second spike waves were localised to the posterior cingulate gyrus, a more restricted region than would be predicted from scalp recordings and the 14 and 6/second spikes to the posterior mesial temporal cortex. Small sharp spikes were more widely distributed but also predominated in the posterior mesial temporal area. None of the discharges were congruent with the focus of seizure origin and no interaction with other interictal spikes was found.Conclusions:These benign paroxysmal rhythms can appear incidentally in the electrocorticograms of patients with focal epilepsy and should not be confused with focal pathological spike activity or considered to be of any value in localizing the seizure focus.
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Hooper, Scott L., Christoph Guschlbauer, Géraldine von Uckermann, and Ansgar Büschges. "Different Motor Neuron Spike Patterns Produce Contractions With Very Similar Rises in Graded Slow Muscles." Journal of Neurophysiology 97, no. 2 (February 2007): 1428–44. http://dx.doi.org/10.1152/jn.01014.2006.
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Graded muscles produce small twitches in response to individual motor neuron spikes. During the early part of their contractions, contraction amplitude in many such muscles depends primarily on the number of spikes the muscle has received, not the frequency or pattern with which they were delivered. Stick insect ( Carausius morosus) extensor muscles are graded and thus would likely show spike-number dependency early in their contractions. Tonic stimulations of the extensor motor nerve showed that the response of the muscles differed from the simplest form of spike-number dependency. However, these differences actually increased the spike-number range over which spike-number dependency was present. When the motor nerve was stimulated with patterns mimicking the motor neuron activity present during walking, amplitude during contraction rises also depended much more on spike number than on spike frequency. A consequence of spike-number dependency is that brief changes in spike frequency do not alter contraction slope and we show here that extensor motor neuron bursts with different spike patterns give rise to contractions with very similar contraction rises. We also examined in detail the early portions of a large number of extensor motor neuron bursts recorded during single-leg walking and show that these portions of the bursts do not appear to have any common spike pattern. Although alternative explanations are possible, the simplest interpretation of these data is that extensor motor neuron firing during leg swing is not tightly controlled.
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Zhang, Jiyuan, Shanshan Jia, Zhaofei Yu, and Tiejun Huang. "Learning Temporal-Ordered Representation for Spike Streams Based on Discrete Wavelet Transforms." Proceedings of the AAAI Conference on Artificial Intelligence 37, no. 1 (June 26, 2023): 137–47. http://dx.doi.org/10.1609/aaai.v37i1.25085.
Full textAbstract:
Spike camera, a new type of neuromorphic visual sensor that imitates the sampling mechanism of the primate fovea, can capture photons and output 40000 Hz binary spike streams. Benefiting from the asynchronous sampling mechanism, the spike camera can record fast-moving objects and clear images can be recovered from the spike stream at any specified timestamps without motion blurring. Despite these, due to the dense time sequence information of the discrete spike stream, it is not easy to directly apply the existing algorithms of traditional cameras to the spike camera. Therefore, it is necessary and interesting to explore a universally effective representation of dense spike streams to better fit various network architectures. In this paper, we propose to mine temporal-robust features of spikes in time-frequency space with wavelet transforms. We present a novel Wavelet-Guided Spike Enhancing (WGSE) paradigm consisting of three consecutive steps: multi-level wavelet transform, CNN-based learnable module, and inverse wavelet transform. With the assistance of WGSE, the new streaming representation of spikes can be learned. We demonstrate the effectiveness of WGSE on two downstream tasks, achieving state-of-the-art performance on the image reconstruction task and getting considerable performance on semantic segmentation. Furthermore, We build a new spike-based synthesized dataset for semantic segmentation. Code and Datasets are available at https://github.com/Leozhangjiyuan/WGSE-SpikeCamera.
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H. Berjis, Zaid, and Ahmed K. Al-sulaifanie. "Neural Spike Sorting And Classification." Journal Of Duhok University 23, no. 2 (December 9, 2020): 166–78. http://dx.doi.org/10.26682/sjuod.2020.23.2.18.
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Spike sorting is the process of separating the extracellular recording of the brain signal into one unit activity. There are a number of proposed algorithms for this purpose, but there is still no acceptable solution. In this paper a spike sorting method has been proposed based on the Euclidean distance of the most effective features of spikes represented by principle components (PCs) of the detected and aligned spikes. The assessments of the method, based on signal-to-noise ratio (SNR) representing background noise, showed that the method performed spike sorting to a high level of accuracy.
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Kreuz, Thomas, Mario Mulansky, and Nebojsa Bozanic. "SPIKY: a graphical user interface for monitoring spike train synchrony." Journal of Neurophysiology 113, no. 9 (May 2015): 3432–45. http://dx.doi.org/10.1152/jn.00848.2014.
Full textAbstract:
Techniques for recording large-scale neuronal spiking activity are developing very fast. This leads to an increasing demand for algorithms capable of analyzing large amounts of experimental spike train data. One of the most crucial and demanding tasks is the identification of similarity patterns with a very high temporal resolution and across different spatial scales. To address this task, in recent years three time-resolved measures of spike train synchrony have been proposed, the ISI-distance, the SPIKE-distance, and event synchronization. The Matlab source codes for calculating and visualizing these measures have been made publicly available. However, due to the many different possible representations of the results the use of these codes is rather complicated and their application requires some basic knowledge of Matlab. Thus it became desirable to provide a more user-friendly and interactive interface. Here we address this need and present SPIKY, a graphical user interface that facilitates the application of time-resolved measures of spike train synchrony to both simulated and real data. SPIKY includes implementations of the ISI-distance, the SPIKE-distance, and the SPIKE-synchronization (an improved and simplified extension of event synchronization) that have been optimized with respect to computation speed and memory demand. It also comprises a spike train generator and an event detector that makes it capable of analyzing continuous data. Finally, the SPIKY package includes additional complementary programs aimed at the analysis of large numbers of datasets and the estimation of significance levels.
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Arancillo, Marife, Joshua J. White, Tao Lin, Trace L. Stay, and Roy V. Sillitoe. "In vivo analysis of Purkinje cell firing properties during postnatal mouse development." Journal of Neurophysiology 113, no. 2 (January 15, 2015): 578–91. http://dx.doi.org/10.1152/jn.00586.2014.
Full textAbstract:
Purkinje cell activity is essential for controlling motor behavior. During motor behavior Purkinje cells fire two types of action potentials: simple spikes that are generated intrinsically and complex spikes that are induced by climbing fiber inputs. Although the functions of these spikes are becoming clear, how they are established is still poorly understood. Here, we used in vivo electrophysiology approaches conducted in anesthetized and awake mice to record Purkinje cell activity starting from the second postnatal week of development through to adulthood. We found that the rate of complex spike firing increases sharply at 3 wk of age whereas the rate of simple spike firing gradually increases until 4 wk of age. We also found that compared with adult, the pattern of simple spike firing during development is more irregular as the cells tend to fire in bursts that are interrupted by long pauses. The regularity in simple spike firing only reached maturity at 4 wk of age. In contrast, the adult complex spike pattern was already evident by the second week of life, remaining consistent across all ages. Analyses of Purkinje cells in alert behaving mice suggested that the adult patterns are attained more than a week after the completion of key morphogenetic processes such as migration, lamination, and foliation. Purkinje cell activity is therefore dynamically sculpted throughout postnatal development, traversing several critical events that are required for circuit formation. Overall, we show that simple spike and complex spike firing develop with unique developmental trajectories.