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Boileau, Etienne, i Christoph Dieterich. "RNA Modification Level Estimation with pulseR". Genes 9, nr 12 (10.12.2018): 619. http://dx.doi.org/10.3390/genes9120619.
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RNA modifications regulate the complex life of transcripts. An experimental approach called LAIC-seq was developed to characterize modification levels on a transcriptome-wide scale. In this method, the modified and unmodified molecules are separated using antibodies specific for a given RNA modification (e.g., m6A). In essence, the procedure of biochemical separation yields three fractions: Input, eluate, and supernatent, which are subjected to RNA-seq. In this work, we present a bioinformatics workflow, which starts from RNA-seq data to infer gene-specific modification levels by a statistical model on a transcriptome-wide scale. Our workflow centers around the pulseR package, which was originally developed for the analysis of metabolic labeling experiments. We demonstrate how to analyze data without external normalization (i.e., in the absence of spike-ins), given high efficiency of separation, and how, alternatively, scaling factors can be derived from unmodified spike-ins. Importantly, our workflow provides an estimate of uncertainty of modification levels in terms of confidence intervals for model parameters, such as gene expression and RNA modification levels. We also compare alternative model parametrizations, log-odds, or the proportion of the modified molecules and discuss the pros and cons of each representation. In summary, our workflow is a versatile approach to RNA modification level estimation, which is open to any read-count-based experimental approach.
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Kumar, N. Pavan, i V. H. Patankar. "Design and development of water-immersible two-channel high-voltage spike pulser for under-water inspection and gauging of pipes". Review of Scientific Instruments 93, nr 1 (1.01.2022): 014703. http://dx.doi.org/10.1063/5.0072733.
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Cai, Changsi, Qiushi Ren, Neal J. Desai, Joseph F. Rizzo i Shelley I. Fried. "Response variability to high rates of electric stimulation in retinal ganglion cells". Journal of Neurophysiology 106, nr 1 (lipiec 2011): 153–62. http://dx.doi.org/10.1152/jn.00956.2010.
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To improve the quality of prosthetic vision, it is important to understand how retinal neurons respond to electric stimulation. Previous studies present conflicting reports as to the maximum rate at which retinal ganglion cells can “follow” pulse trains, i.e., generate one spike for each pulse of the train. In the present study, we measured the response of 5 different types of rabbit retinal ganglion cells to pulse trains of 100–700 Hz. Surprisingly, we found significant heterogeneity in the ability of different types to follow pulse trains. For example, brisk transient (BT) ganglion cells could reliably follow pulse rates up to 600 pulses per second (PPS). In contrast, other types could not even follow rates of 200 PPS. There was additional heterogeneity in the response patterns across those types that could not follow high-rate trains. For example, some types generated action potentials in response to approximately every other pulse, whereas other types generated one spike per pulse for a few consecutive pulses and then did not generate any spikes in response to the next few pulses. Interestingly, in the types that could not follow high-rate trains, we found a second type of response: many pulses of the train elicited a biphasic waveform with an amplitude much smaller than that of standard action potentials. This small waveform was often observed following every pulse for which a standard spike was not elicited. A possible origin of the small waveform and its implication for effective retinal stimulation are discussed.
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Shim, Chi Hyun, Ki Moon Nam, Yong Woon Parc i Dong Eon Kim. "Isolated terawatt sub-attosecond high-energy x-ray pulse generated by an x-ray free-electron laser". APL Photonics 7, nr 5 (1.05.2022): 056105. http://dx.doi.org/10.1063/5.0067074.
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The endless quest for dynamics in natural phenomena has resulted in the generation and application of attosecond pulses to trace electron dynamics in atomic and molecular systems. The next challenge is to generate powerful pulses on the zeptosecond time scale, which is currently inaccessible. Through a simulation study, a new type of x-ray source that can generate an isolated terawatt sub-attosecond pulse at high-energy x rays by combining attosecond pulse technology with free-electron laser technology is proposed. The successful generation of a sub-attosecond pulse necessitates the consideration of nanometer-wide current-spikes, the sub-attosecond pulse amplification, and pulse duration and background noise control. The underlying interaction mechanism between a sub-attosecond pulse and a current-spike is closely investigated using the simulation results. The proposed method is expected to produce an isolated ∼700 zs pulse with a peak output of 2.9 TW at a photon energy of 247.5 keV.
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Tanner, Kylie M., Chinyere Obasi, Ian A. Herrick i L. Stan Leung. "Effects of Propofol on Hippocampal Synaptic Transmission in Behaving Rats". Anesthesiology 93, nr 2 (1.08.2000): 463–72. http://dx.doi.org/10.1097/00000542-200008000-00026.
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Background The action of propofol has been studied in vitro and in vivo, but the effects of intravenously administered propofol on synaptic transmission in freely behaving rats have not been studied before. Methods Rats were implanted with recording electrodes in the dentate gyrus and with stimulation electrodes in the medial perforant path (MPP). Paired pulses at different interpulse intervals (IPIs) were delivered to the MPP, and average evoked potentials were recorded in the dentate gyrus before and after a bolus of propofol (10 or 20 mg/kg administered intravenously) or control vehicle was injected via femoral vein cannula. Because of the layered structure of the hippocampus, population excitatory postsynaptic potentials and population spikes could be distinguished and analyzed. Results Propofol has no significant effect on the population excitatory postsynaptic potentials or population spike evoked by a single MPP stimulus pulse. However, paired-pulse inhibition of the dentate population spikes was increased at IPI of 20 and 30 ms. Paired-pulse inhibition of the population spike was most prominent when tail pinch response was lost (deep and moderate anesthesia), but it persisted during light anesthesia. At 200 ms IPI, paired-pulse facilitation of population spikes was observed during moderate anesthesia in most rats. Conclusions In freely behaving rats, intravenous propofol enhanced paired-pulse inhibition at < 50 ms IPI, likely by enhancing gamma-aminobutyric acid A receptor-mediated inhibition. Propofol also increased paired-pulse facilitation at 200 ms IPI through an unknown mechanism, which may contribute to the neuroexcitatory effect of propofol.
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Saito, Mitsuru, Yoshinaka Murai, Hajime Sato, Yong-Chul Bae, Tadashi Akaike, Masahiko Takada i 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, nr 4 (październik 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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Gomez, G., i J. Atema. "Temporal resolution in olfaction II: time course of recovery from adaptation in lobster chemoreceptor cells". Journal of Neurophysiology 76, nr 2 (1.08.1996): 1340–43. http://dx.doi.org/10.1152/jn.1996.76.2.1340.
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1. Adaptation and disadaptation rates determine the temporal response properties of sensory receptor cells. In chemoreception, temporal filter properties of receptor cells are poorly understood. We studied the time course of disadaptation in lobster antennular chemoreceptor cells by using in situ high-resolution stimulus measurement and extracellularly recorded spike responses. Fifteen receptor cells were each tested with two series (one at 10 microM, one at 100 microM) of three odor (hydroxyproline) pulses: a 200-ms test pulse, a 5-s adapting pulse, and a 200-ms probe pulse after time intervals ranging from 1 to 60 s. After complete adaptation by the adapting pulse, individual cells recovered at different rates. After 1 s, a third of the cells responded with a mean response of 3 spikes/cell, representing approximately 20% recovery. All cells fully recovered between 10 and 30 s. Mean full recovery was within 25 s, with a time constant of 14 s, independent of stimulus concentration.
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Butkus, Paulius, Sonata Tolvaišienė i Sebastjanas Kurčevskis. "Validation of a SPICE Model for High Frequency Electroporation Systems". Electronics 8, nr 6 (23.06.2019): 710. http://dx.doi.org/10.3390/electronics8060710.
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In this paper, we present an analysis and a validation of a simulation program with integrated circuit emphasis (SPICE) model for a pulse forming circuit of a high frequency electroporation system, which can deliver square-wave sub-microsecond (100–900 ns) electric field pulses. The developed SPICE model is suggested for use in evaluation of transient processes that occur due to high frequency operations in prototype systems. A controlled crowbar circuit was implemented to support a variety of biological loads and to ensure a constant electric pulse rise and fall time during electroporation to be independent of the applied buffer bioimpedance. The SPICE model was validated via a comparison of the simulation and experimental results obtained from the already existing prototype system. The SPICE model results were in good agreement with the experimental results, and the model complexity was found to be sufficient for analysis of transient processes. As result, the proposed SPICE model can be useful for evaluation and compensation of transient processes in sub-microsecond pulsed power set-ups during the development of new prototypes.
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Fried, S. I., H. A. Hsueh i F. S. Werblin. "A Method for Generating Precise Temporal Patterns of Retinal Spiking Using Prosthetic Stimulation". Journal of Neurophysiology 95, nr 2 (luty 2006): 970–78. http://dx.doi.org/10.1152/jn.00849.2005.
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The goal of retinal prosthetic devices is to generate meaningful visual information in patients that have lost outer retinal function. To accomplish this, these devices should generate patterns of ganglion cell activity that closely resemble the spatial and temporal components of those patterns that are normally elicited by light. Here, we developed a stimulus paradigm that generates precise temporal patterns of activity in retinal ganglion cells, including those patterns normally generated by light. Electrical stimulus pulses (≥1-ms duration) elicited activity in neurons distal to the ganglion cells; this resulted in ganglion cell spiking that could last as long as 100 ms. However, short pulses, <0.15 ms, elicited only a single spike within 0.7 ms of the leading edge of the pulse. Trains of these short pulses elicited one spike per pulse at frequencies ≤250 Hz. Patterns of short electrical pulses (derived from normal light elicited spike patterns) were delivered to ganglion cells and generated spike patterns that replicated the normal light patterns. Finally, we found that one spike per pulse was elicited over almost a 2.5:1 range of stimulus amplitudes. Thus a common stimulus amplitude could accommodate a 2.5:1 range of activation thresholds, e.g., caused by differences arising from cell biophysical properties or from variations in electrode-to-cell distance arising when a multielectrode array is placed on the retina. This stimulus paradigm can generate the temporal resolution required for a prosthetic device.
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Wüstenberg, Daniel G., Milena Boytcheva, Bernd Grünewald, John H. Byrne, Randolf Menzel i Douglas A. Baxter. "Current- and Voltage-Clamp Recordings and Computer Simulations of Kenyon Cells in the Honeybee". Journal of Neurophysiology 92, nr 4 (październik 2004): 2589–603. http://dx.doi.org/10.1152/jn.01259.2003.
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The mushroom body of the insect brain is an important locus for olfactory information processing and associative learning. The present study investigated the biophysical properties of Kenyon cells, which form the mushroom body. Current- and voltage-clamp analyses were performed on cultured Kenyon cells from honeybees. Current-clamp analyses indicated that Kenyon cells did not spike spontaneously in vitro. However, spikes could be elicited by current injection in approximately 85% of the cells. Of the cells that produced spikes during a 1-s depolarizing current pulse, approximately 60% exhibited repetitive spiking, whereas the remaining approximately 40% fired a single spike. Cells that spiked repetitively showed little frequency adaptation. However, spikes consistently became broader and smaller during repetitive activity. Voltage-clamp analyses characterized a fast transient Na+ current ( INa), a delayed rectifier K+ current ( IK,V), and a fast transient K+ current ( IK,A). Using the neurosimulator SNNAP, a Hodgkin–Huxley-type model was developed and used to investigate the roles of the different currents during spiking. The model led to the prediction of a slow transient outward current ( IK,ST) that was subsequently identified by reevaluating the voltage-clamp data. Simulations indicated that the primary currents that underlie spiking are INa and IK,V, whereas IK,A and IK,ST primarily determined the responsiveness of the model to stimuli such as constant or oscillatory injections of current.
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Achour, Yahia, Jacek Starzyński i Kazimierz Jakubiuk. "New Architecture of Solid-State High-Voltage Pulse Generators". Energies 15, nr 13 (1.07.2022): 4823. http://dx.doi.org/10.3390/en15134823.
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The application of the nanosecond pulsed electric field (nsPEF) for biomedical treatments has gained more interest in recent decades due to the development of pulsed power technologies which provides the ability to control the electric field dose applied during tests. In this context, the proposed paper describes a new architecture of solid-state high-voltage pulse generators (SS-HVPG) designed to generate fully customised sequences of quasi-rectangular pulses. The idea is based on the combination of semiconductor switches (IGBT/MOSFET) known for their flexibility and controllability with special magnetic switches to build compact and modular generators. The proposed structure is inspired by the most known pulse generator of Marx, but mixes its two variants for negative and positive polarities. Thus, the polarity of the generated pulses can be freely selected. In addition to that, the use of IGBTs/MOSFET ensures a tunable repetition rate and pulse width. The capacitors are charged via a series of magnetic switches and a flyback DC–DC converter which provides fast and efficient charging and also an adjustable amplitude of the output pulses. The design can be easily simplified giving two other modified structures, based on the same idea, for mono-polar operating (only positive or only negative pulses) with a reduced number of switches. A SPICE simulation of the generator and results of experimental tests carried out on a three stages generator are presented. The obtained results confirm the operating principle and the claimed performances of the new structure.
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Kang, Youngnam, Mitsuru Saito, Hajime Sato, Hiroki Toyoda, Yoshinobu Maeda, Toshihiro Hirai i 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, nr 3 (marzec 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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Goldberg, Jesse H., Michael A. Farries i Michale S. Fee. "Integration of cortical and pallidal inputs in the basal ganglia-recipient thalamus of singing birds". Journal of Neurophysiology 108, nr 5 (1.09.2012): 1403–29. http://dx.doi.org/10.1152/jn.00056.2012.
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The basal ganglia-recipient thalamus receives inhibitory inputs from the pallidum and excitatory inputs from cortex, but it is unclear how these inputs interact during behavior. We recorded simultaneously from thalamic neurons and their putative synaptically connected pallidal inputs in singing zebra finches. We find, first, that each pallidal spike produces an extremely brief (∼5 ms) pulse of inhibition that completely suppresses thalamic spiking. As a result, thalamic spikes are entrained to pallidal spikes with submillisecond precision. Second, we find that the number of thalamic spikes that discharge within a single pallidal interspike interval (ISI) depends linearly on the duration of that interval but does not depend on pallidal activity prior to the interval. In a detailed biophysical model, our results were not easily explained by the postinhibitory “rebound” mechanism previously observed in anesthetized birds and in brain slices, nor could most of our data be characterized as “gating” of excitatory transmission by inhibitory pallidal input. Instead, we propose a novel “entrainment” mechanism of pallidothalamic transmission that highlights the importance of an excitatory conductance that drives spiking, interacting with brief pulses of pallidal inhibition. Building on our recent finding that cortical inputs can drive syllable-locked rate modulations in thalamic neurons during singing, we report here that excitatory inputs affect thalamic spiking in two ways: by shortening the latency of a thalamic spike after a pallidal spike and by increasing thalamic firing rates within individual pallidal ISIs. We present a unifying biophysical model that can reproduce all known modes of pallidothalamic transmission—rebound, gating, and entrainment—depending on the amount of excitation the thalamic neuron receives.
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Parc, Yong, Chi Shim i Dong Kim. "Toward the Generation of an Isolated TW-Attosecond X-ray Pulse in XFEL". Applied Sciences 8, nr 9 (7.09.2018): 1588. http://dx.doi.org/10.3390/app8091588.
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The isolated terawatt (TW) attosecond (as) hard X-ray pulse will expand the scope of ultrafast science, including the examination of phenomena that have not been studied before, such as the dynamics of electron clouds in atoms, single-molecule imaging, and examining the dynamics of hollow atoms. Therefore, several schemes for the generation of an isolated TW-as X-ray pulse in X-ray free electron laser (XFEL) facilities have been proposed with the manipulation of electron properties such as emittance or current. In a multi-spike scheme, a series of current spikes were employed to amplify the X-ray pulse. A single-spike scheme in which a TW-as X-ray pulse can be generated by a single current spike was investigated for ideal parameters for the XFEL machine. This paper reviews the proposed schemes and assesses the feasibility of each scheme.
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Saito, Yasuhiko, i Tadashi Isa. "Electrophysiological and Morphological Properties of Neurons in the Rat Superior Colliculus. I. Neurons in the Intermediate Layer". Journal of Neurophysiology 82, nr 2 (1.08.1999): 754–67. http://dx.doi.org/10.1152/jn.1999.82.2.754.
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To begin characterizing the neural elements underlying the dynamic properties of local circuits in the mammalian superior colliculus (SC), electrophysiological and morphological properties of individual neurons in the intermediate layer [stratum griseum intermediale (SGI)] were investigated using whole cell patch-clamp recording and intracellular staining with biocytin in slice preparations from young (17–22 days old) and adult rats (7–8 wk old). Voltage responses to depolarizing current pulses of 223 neurons recorded in young rats were classified into six subclasses: regular-spiking neurons ( n = 113), interspike intervals during depolarizing current pulses were constant; late-spiking neurons ( n = 48), initiation of repetitive firing was delayed markedly from the onset of depolarizing pulses because of a transient hyperpolarization caused by A-like currents; burst-spiking neurons ( n = 29), transient burst firing due to low-threshold Ca2+ channels were observed at the firing threshold level; fast-spiking neurons ( n = 19), constant repetitive firings at frequencies >100 Hz were observed for the duration of the depolarizing pulse; neurons with marked spike frequency adaptation ( n = 11), interspike intervals more than doubled due to spike frequency adaptation during depolarizing pulses; and neurons with rapid spike inactivation ( n = 3), spike amplitude rapidly reduced, width increased during depolarizing pulses, and spiking was terminated after generating a few spikes. In response to hyperpolarizing current pulses, two different types of inward rectification were observed; time-dependent inward rectification by hyperpolarization-activated current ( I h; n = 29) and time-independent inward rectification ( n = 111). Morphological analysis showed that neurons expressing time-dependent inward rectification by I h had large somata, extended divergent dendrites dorsally into the superficial layers, and projected axons ventrally and sometimes dorsally, all characteristic features of wide-field vertical cells. Other neurons exhibited heterogeneous morphological properties, such as multipolar, fusiform, horizontal, or pyramidal-shaped cells. In adult rats, a total of 44 neurons showed similar electrophysiological properties except for the last type. These results indicate that the local circuits of the SC include neurons with at least five different firing properties and two different rectification properties; each with distinct electrophysiological and morphological characteristics that may be correlated with the functional output of the SC.
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Pare, D., H. C. Pape i J. Dong. "Bursting and oscillating neurons of the cat basolateral amygdaloid complex in vivo: electrophysiological properties and morphological features". Journal of Neurophysiology 74, nr 3 (1.09.1995): 1179–91. http://dx.doi.org/10.1152/jn.1995.74.3.1179.
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1. To characterize the physiological properties of lateral and basolateral (BL) amygdaloid neurons, intracellular recordings were performed in barbiturate-anesthetized cats. Morphological identification of recorded cells was achieved by intracellular injection of neurobiotin. Two types of physiologically identified projection neurons were distinguished in the BL and lateral nuclei. 2. The first type of neurons prevailed in the BL nucleus (80% of BL cells). Their resting membrane potential (Vm) averaged -66 +/- 4.9 (SE) mV. They generated stereotyped spike doublets or bursts in response to threshold depolarizing pulses. In most cells, depolarizing pulses of higher amplitude elicited spike bursts or doublets at a shorter latency followed by a nonadapting train of single spikes whose frequency rose with the amplitude of the current pulses. However, 15% of BL bursting neurons generated repetitive spike bursts or doublets in response to prolonged depolarizing current pulses. The response of BL bursting neurons to hyperpolarizing current pulses revealed the presence of slow inward rectification in the form of a depolarizing sag, thus suggesting the presence of a hyperpolarization-activated current. 3. The second type of neurons prevailed in the lateral nucleus. Their resting Vm was quite polarized (-74 +/- 2.85 mV) and they generated slow Vm oscillations (2-10 Hz) upon steady depolarization beyond congruent to -62 mV. The frequency of the oscillation increased with the amount of depolarizing current. In the majority of cells, analysis of voltage responses to subthreshold current pulses revealed the presence of voltage- and time-dependent rectification in the depolarizing direction. Current pulses that brought the Vm to -65 mV and beyond elicited a voltage response that reached an early peak and then decayed. Increasing the amplitude of the pulse decreased the latency of the early peak until it triggered an action potential. Current-voltage plots demonstrated inward rectification in the depolarizing direction. At the break of hyperpolarizing current pulses applied at depolarized levels, the Vm overshot prepulse values and generated one or more oscillatory cycles. 4. An important proportion of bursting and oscillating neurons (45.8% and 29%, respectively) were physiologically identified as projection neurons by antidromic invasion from the basal forebrain, entorhinal cortex, or perirhinal cortex. The conduction velocity of bursting and oscillating neurons estimated from the latency of antidromic spikes was low (< or = 2.5 m/s). 5. Most bursting and oscillating neurons of the BL nucleus were spiny cells with a pyramidal morphology. Four to eight dendritic trunks emerged from the apex, base, and sides of their triangular soma.(ABSTRACT TRUNCATED AT 400 WORDS)
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Rekling, J. C., J. Champagnat i M. Denavit-Saubie. "Electroresponsive properties and membrane potential trajectories of three types of inspiratory neurons in the newborn mouse brain stem in vitro". Journal of Neurophysiology 75, nr 2 (1.02.1996): 795–810. http://dx.doi.org/10.1152/jn.1996.75.2.795.
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1. The electrophysiological properties of inspiratory neurons were studied in a rhythmically active thick-slice preparation of the newborn mouse brain stem maintained in vitro. Whole cell patch recordings were performed from 60 inspiratory neurons within the rostral ventrolateral part of the slice with the aim of extending the classification of inspiratory neurons to include analysis of active membrane properties. 2. The slice generated a regular rhythmic motor output recorded as burst of action potentials on a XII nerve root with a peak to peak time of 11.5 +/- 3.4 s and a duration of 483 +/- 54 ms (means +/- SD, n = 50). Based on the electroresponsive properties and membrane potential trajectories throughout the respiratory cycle, three types of inspiratory neurons could be distinguished. 3. Type-1 neurons were spiking in the interval between the inspiratory potentials (n = 9) or silent with a resting membrane potential of -48.6 +/- 10.1 mV and an input resistance of 306 +/- 130 M omega (n = 15). The spike activity between the inspiratory potentials was burst-like with spikes riding on top of an underlying depolarization (n = 11) or regular with no evidence of bursting (n = 12). Hyperpolarization of the neurons below threshold for spike initiation did not reveal any underlying phasic synaptic activity, that could explain the bursting behavior. 4. Type-1 neurons showed delayed excitation after hyperpolarizing square current pulses or when the neurons were depolarized from a hyperpolarized level. This membrane behavior resembles the response seen in other CNS neurons expressing an IA. The response to 1-s long depolarizing pulses with a large current strength showed signs of activation of an active depolarizing membrane response leading to a transient reduction in the spike amplitude. The relationship between the membrane potential and the amplitude of square current pulses (Vm-I) showed a small upward rectification below -70 mV, and spike adaptation throughout a 1-s pulse had a largely linear time course. 5. Type-1 neurons depolarized and started to fire spikes 398 +/- 102 ms (n = 20) before the upstroke of the integrated XII nerve discharge. The inspiratory potential was followed by fast hyperpolarization, a short fast-repolarizing phase (1,040 +/- 102 ms, n = 5) and a longer slow-repolarizing phase (lasting until the next inspiratory discharge). 6. Type-2 neurons were spiking in the interval between the inspiratory potentials with no evidence of bursting behavior and had an input resistance of 296 +/- 212 M omega (n = 26). The response to hyperpolarizing pulses revealed an initial sag and postinhibitory rebound depolarization. This membrane behavior resembles the response seen in other CNS neurons expressing an Ih. The Vm-I relationship was linear at depolarized potentials and showed a marked upward rectification below -60 mV. Spike trains elicited by 1-s long pulses showed a pronounced early and late adaptation. 7. Type-2 neurons depolarized and started to fire spikes 171 +/- 87 ms (n = 23) before the upstroke of the integrated XII nerve discharge. The inspiratory potential had a variable amplitude from cell to cell and was followed by a short hyperpolarization in the cells displaying a large amplitude inspiratory potential.(ABSTRACT TRUNCATED AT 250 WORDS)
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Hamaguchi, Kosuke, Masato Okada i Kazuyuki Aihara. "Variable Timescales of Repeated Spike Patterns in Synfire Chain with Mexican-Hat Connectivity". Neural Computation 19, nr 9 (wrzesień 2007): 2468–91. http://dx.doi.org/10.1162/neco.2007.19.9.2468.
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Repetitions of precise spike patterns observed both in vivo and in vitro have been reported for more than a decade. Studies on the spike volley (a pulse packet) propagating through a homogeneous feedforward network have demonstrated its capability of generating spike patterns with millisecond fidelity. This model is called the synfire chain and suggests a possible mechanism for generating repeated spike patterns (RSPs). The propagation speed of the pulse packet determines the temporal property of RSPs. However, the relationship between propagation speed and network structure is not well understood. We studied a feedforward network with Mexican-hat connectivity by using the leaky integrate-and-fire neuron model and analyzed the network dynamics with the Fokker-Planck equation. We examined the effect of the spatial pattern of pulse packets on RSPs in the network with multistability. Pulse packets can take spatially uniform or localized shapes in a multistable regime, and they propagate with different speeds. These distinct pulse packets generate RSPs with different timescales, but the order of spikes and the ratios between interspike intervals are preserved. This result indicates that the RSPs can be transformed into the same template pattern through the expanding or contracting operation of the timescale.
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Hamilton, K. A., i J. S. Kauer. "Patterns of intracellular potentials in salamander mitral/tufted cells in response to odor stimulation". Journal of Neurophysiology 62, nr 3 (1.09.1989): 609–25. http://dx.doi.org/10.1152/jn.1989.62.3.609.
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1. Changes in membrane potential and temporal patterns of spikes were analyzed in 30 output cells in the salamander olfactory bulb in response to stimulation with 1-s pulses of the odorants isoamyl acetate, cineole, and camphor. The odor responses were more complex than responses to electrical stimulation of the olfactory nerve or olfactory tracts, with which they were compared. Most began with hyperpolarization and contained prolonged hyperpolarizing and depolarizing potentials that appeared to be compound postsynaptic potentials. These potentials were related to periods of spike inhibition and excitation. The temporal patterns of the responses resembled S-type (for suppression) and E-type (for excitation) patterns described previously in extracellular-unit studies. 2. In single cells, graded but nonmonotonic changes in the responses were observed with increases in the odor concentration from 10(-3) to 10(-1) vapor-phase saturation. Abrupt changes from one category of temporal response pattern to another were generally not observed in response to different concentrations of a single odorant but were frequently observed when the stimulus was changed from one odorant to another. 3. In S-type patterns, the first event was always membrane hyperpolarization and spike inhibition, regardless of the odor concentration. At all concentrations, simple S-type responses were observed in which a single period of hyperpolarization and inhibition lasted several seconds. At moderate to high concentrations, complex S-type responses were observed in which a period of excitation followed an initial period of hyperpolarization and inhibition. In these responses, spikes were often elicited near the termination of the odor pulse, occasionally as early as 300-400 ms after pulse onset. A prolonged period of inhibition followed the period of excitation. 4. In E-type patterns, the first event depended on the odor concentration. At all concentrations, complex responses were observed in which a period of excitation occurred with short latency, followed by a period of inhibition. At low to moderate concentrations, a brief initial period of hyperpolarization preceded the excitation. This initial period of hyperpolarization was always shorter than those in complex S-type responses to equivalent concentrations. However, the range of spike latencies overlapped that of S-type responses to high concentrations. With increasing odor concentration, spike latencies in the E-type responses decreased relative to the onset and peak of the initial hyperpolarization. At high concentrations. spikes were frequently elicited preceding a single period of hyperpolarization and inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)
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Liu, Y., F. Y. Li, M. Zeng, M. Chen i Z. M. Sheng. "Ultra-intense attosecond pulses emitted from laser wakefields in non-uniform plasmas". Laser and Particle Beams 31, nr 2 (2.05.2013): 233–38. http://dx.doi.org/10.1017/s0263034613000220.
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AbstractA scheme of generating ultra-intense attosecond pulses in ultra-relativistic laser interaction with under-dense plasmas is proposed. The attosecond pulse emission is caused by an oscillating transverse current sheet formed by an electron density spike composed of trapped electrons in the laser wakefield and the residual transverse momentum of electrons left behind the laser pulse when its front is strongly modulated. As soon as the attosecond pulse emerges, it tends to feed back to further enhance the transverse electron momentum and the transverse current. Consequently, the attosecond pulse is enhanced and developed into a few cycles later until the density spike is depleted out due to the pump laser depletion. To control the formation of the transverse current sheet, a non-uniform plasma slab with an up-ramp density profile in front of a uniform region is adopted, which enables one to obtain attosecond pulses with higher amplitudes than that in a uniform plasma slab.
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Levi, Rafael, Otar Akanyeti, Aleksander Ballo i James C. Liao. "Frequency response properties of primary afferent neurons in the posterior lateral line system of larval zebrafish". Journal of Neurophysiology 113, nr 2 (15.01.2015): 657–68. http://dx.doi.org/10.1152/jn.00414.2014.
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The ability of fishes to detect water flow with the neuromasts of their lateral line system depends on the physiology of afferent neurons as well as the hydrodynamic environment. Using larval zebrafish ( Danio rerio), we measured the basic response properties of primary afferent neurons to mechanical deflections of individual superficial neuromasts. We used two types of stimulation protocols. First, we used sine wave stimulation to characterize the response properties of the afferent neurons. The average frequency-response curve was flat across stimulation frequencies between 0 and 100 Hz, matching the filtering properties of a displacement detector. Spike rate increased asymptotically with frequency, and phase locking was maximal between 10 and 60 Hz. Second, we used pulse train stimulation to analyze the maximum spike rate capabilities. We found that afferent neurons could generate up to 80 spikes/s and could follow a pulse train stimulation rate of up to 40 pulses/s in a reliable and precise manner. Both sine wave and pulse stimulation protocols indicate that an afferent neuron can maintain their evoked activity for longer durations at low stimulation frequencies than at high frequencies. We found one type of afferent neuron based on spontaneous activity patterns and discovered a correlation between the level of spontaneous and evoked activity. Overall, our results establish the baseline response properties of lateral line primary afferent neurons in larval zebrafish, which is a crucial step in understanding how vertebrate mechanoreceptive systems sense and subsequently process information from the environment.
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Nowak, Lionel G., Rony Azouz, Maria V. Sanchez-Vives, Charles M. Gray i David A. McCormick. "Electrophysiological Classes of Cat Primary Visual Cortical Neurons In Vivo as Revealed by Quantitative Analyses". Journal of Neurophysiology 89, nr 3 (1.03.2003): 1541–66. http://dx.doi.org/10.1152/jn.00580.2002.
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To facilitate the characterization of cortical neuronal function, the responses of cells in cat area 17 to intracellular injection of current pulses were quantitatively analyzed. A variety of response variables were used to separate the cells into subtypes using cluster analysis. Four main classes of neurons could be clearly distinguished: regular spiking (RS), fast spiking (FS), intrinsic bursting (IB), and chattering (CH). Each of these contained significant subclasses. RS neurons were characterized by trains of action potentials that exhibited spike frequency adaptation. Morphologically, these cells were spiny stellate cells in layer 4 and pyramidal cells in layers 2, 3, 5, and 6. FS neurons had short-duration action potentials (<0.5 ms at half height), little or no spike frequency adaptation, and a steep relationship between injected current intensity and spike discharge frequency. Morphologically, these cells were sparsely spiny or aspiny nonpyramidal cells. IB neurons typically generated a low frequency (<425 Hz) burst of spikes at the beginning of a depolarizing current pulse followed by a tonic train of action potentials for the remainder of the pulse. These cells were observed in all cortical layers, but were most abundant in layer 5. Finally, CH neurons generated repetitive, high-frequency (350–700 Hz) bursts of short-duration (<0.55 ms) action potentials. Morphologically, these cells were layer 2–4 (mainly layer 3) pyramidal or spiny stellate neurons. These results indicate that firing properties do not form a continuum and that cortical neurons are members of distinct electrophysiological classes and subclasses.
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Reynolds, Stephanie, Therese Abrahamsson, Per Jesper Sjöström, Simon R. Schultz i Pier Luigi Dragotti. "CosMIC: A Consistent Metric for Spike Inference from Calcium Imaging". Neural Computation 30, nr 10 (październik 2018): 2726–56. http://dx.doi.org/10.1162/neco_a_01114.
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In recent years, the development of algorithms to detect neuronal spiking activity from two-photon calcium imaging data has received much attention, yet few researchers have examined the metrics used to assess the similarity of detected spike trains with the ground truth. We highlight the limitations of the two most commonly used metrics, the spike train correlation and success rate, and propose an alternative, which we refer to as CosMIC. Rather than operating on the true and estimated spike trains directly, the proposed metric assesses the similarity of the pulse trains obtained from convolution of the spike trains with a smoothing pulse. The pulse width, which is derived from the statistics of the imaging data, reflects the temporal tolerance of the metric. The final metric score is the size of the commonalities of the pulse trains as a fraction of their average size. Viewed through the lens of set theory, CosMIC resembles a continuous Sørensen-Dice coefficient—an index commonly used to assess the similarity of discrete, presence/absence data. We demonstrate the ability of the proposed metric to discriminate the precision and recall of spike train estimates. Unlike the spike train correlation, which appears to reward overestimation, the proposed metric score is maximized when the correct number of spikes have been detected. Furthermore, we show that CosMIC is more sensitive to the temporal precision of estimates than the success rate.
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Nisenbaum, E. S., Z. C. Xu i C. J. Wilson. "Contribution of a slowly inactivating potassium current to the transition to firing of neostriatal spiny projection neurons". Journal of Neurophysiology 71, nr 3 (1.03.1994): 1174–89. http://dx.doi.org/10.1152/jn.1994.71.3.1174.
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1. Neostriatal spiny projection neurons display a prominent slowly depolarizing (ramp) potential and long latency to spike discharge in response to intracellular current pulses. The contribution of a slowly inactivating A-current (IAs) to this delayed excitation was investigated in a neostriatal slice preparation using current pulse protocols incorporating information based on the known voltage dependence, kinetics, and pharmacological properties of IAs. 2. Depolarizing intracellular current pulses evoked a slowly developing ramp potential that could last for seconds without reaching steady state and continued until either the pulse was terminated or spike threshold was reached. The slope of the ramp potential was dependent on the level of depolarization achieved by the membrane, and the apparent activation threshold for this ramp depolarization was approximately -65 mV. 3. Application of low concentrations of 4-aminopyridine (4-AP, 30-100 microM) or dendrotoxin (DTX, 30 nM), which are known to selectively block IAs, reduced both the slope of the ramp potential and the latency to first spike discharge. As has been described previously, blockade of inward Na+ and Ca2+ currents with tetrodotoxin (TTX, 1 microM) and cadmium (400 microM) also reduced the slope of the ramp depolarization. 4. A conditioning-test pulse protocol was used to examine the voltage dependence of inactivation of the ramp potential and long first spike latency. In the absence of a conditioning pulse, the test pulse evoked a slowly rising ramp potential and a spike with a long latency to discharge. A conditioning depolarization to approximately -60 mV decreased the slope of the ramp potential and the latency to first spike discharge evoked by the test pulse. A conditioning hyperpolarization to potentials below -100 mV, increased first spike latency. Application of a low concentration of 4-AP (100 microM) abolished the influence of prior membrane potential on the slope of the ramp depolarization and the latency to first spike discharge. 5. The kinetics of recovery from inactivation of the 4-AP-sensitive current were studied in the presence of TTX and cadmium by depolarizing cells to approximately -50 mV and then stepping to approximately -90 mV for increasing periods of time (0.5-5.0 s) before delivering a test pulse. The amplitude of the test pulse response decreased as a function of the hyperpolarizing step duration. When the test pulse response amplitudes were plotted against the hyperpolarizing step duration, the points reflected an exponential decay with an average time constant of 2.05 +/- 1.38 (SD) s.(ABSTRACT TRUNCATED AT 400 WORDS)
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Bansal, Himanshu, Gur Pyari i Sukhdev Roy. "Optogenetic Generation of Neural Firing Patterns with Temporal Shaping of Light Pulses". Photonics 10, nr 5 (13.05.2023): 571. http://dx.doi.org/10.3390/photonics10050571.
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The fundamental process of information processing and memory formation in the brain is associated with complex neuron firing patterns, which can occur spontaneously or be triggered by sensory inputs. Optogenetics has revolutionized neuroscience by enabling precise manipulation of neuronal activity patterns in specified neural populations using light. However, the light pulses used in optogenetics have been primarily restricted to square waveforms. Here, we present a detailed theoretical analysis of the temporal shaping of light pulses in optogenetic excitation of hippocampal neurons and neocortical fast-spiking interneurons expressed with ultrafast (Chronos), fast (ChR2), and slow (ChRmine) channelrhodopsins. Optogenetic excitation has been studied with light pulses of different temporal shapes that include square, forward-/backward ramps, triangular, left-/right-triangular, Gaussian, left-/right-Gaussian, positive-sinusoidal, and left-/right-positive sinusoidal. Different light shapes result in significantly different photocurrent amplitudes and kinetics, spike-timing, and spontaneous firing rate. For short duration stimulations, left-Gaussian pulse results in larger photocurrent in ChR2 and Chronos than square pulse of the same energy density. Time to peak photocurrent in each opsin is minimum at right-Gaussian pulse. The optimal pulse width to achieve peak photocurrent for non-square pulses is 10 ms for Chronos, and 50 ms for ChR2 and ChRmine. The pulse energy to evoke spike in hippocampal neurons can be minimized on choosing square pulse with Chronos, Gaussian pulse with ChR2, and positive-sinusoidal pulse with ChRmine. The results demonstrate that non-square waveforms generate more naturalistic spiking patterns compared to traditional square pulses. These findings provide valuable insights for the development of new optogenetic strategies to better simulate and manipulate neural activity patterns in the brain, with the potential to improve our understanding of cognitive processes and the treatment of neurological disorders.
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Trebushinin, Andrei, Gianluca Geloni, Svitozar Serkez, Giuseppe Mercurio, Natalia Gerasimova, Theophilos Maltezopoulos, Marc Guetg i Evgeny Schneidmiller. "Experimental Demonstration of Attoseconds-at-Harmonics at the SASE3 Undulator of the European XFEL". Photonics 10, nr 2 (27.01.2023): 131. http://dx.doi.org/10.3390/photonics10020131.
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We report on observations of single spike spectra (3–13% of events) upon employing a previously proposed method for single spike generation via harmonic conversion. The method was tested at the soft X-ray SASE3 undulator of the European XFEL. The first part of the undulator allows one to amplify bunching at the fundamental as well as the higher harmonics. The downstream undulator is tuned to a harmonic, the fourth in our case, to amplify pulses with a shorter duration. We estimate the generated pulse duration within such a subset of short pulses at a level of 650 as. Considering the demonstrated probability of single spike events, this method is attractive for high repetition-rate free electron lasers.
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Lu, Hui, Hyungju Park i Mu-Ming Poo. "Spike-timing-dependent BDNF secretion and synaptic plasticity". Philosophical Transactions of the Royal Society B: Biological Sciences 369, nr 1633 (5.01.2014): 20130132. http://dx.doi.org/10.1098/rstb.2013.0132.
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In acute hippocampal slices, we found that the presence of extracellular brain-derived neurotrophic factor (BDNF) is essential for the induction of spike-timing-dependent long-term potentiation (tLTP). To determine whether BDNF could be secreted from postsynaptic dendrites in a spike-timing-dependent manner, we used a reduced system of dissociated hippocampal neurons in culture. Repetitive pairing of iontophoretically applied glutamate pulses at the dendrite with neuronal spikes could induce persistent alterations of glutamate-induced responses at the same dendritic site in a manner that mimics spike-timing-dependent plasticity (STDP)—the glutamate-induced responses were potentiated and depressed when the glutamate pulses were applied 20 ms before and after neuronal spiking, respectively. By monitoring changes in the green fluorescent protein (GFP) fluorescence at the dendrite of hippocampal neurons expressing GFP-tagged BDNF, we found that pairing of iontophoretic glutamate pulses with neuronal spiking resulted in BDNF secretion from the dendrite at the iontophoretic site only when the glutamate pulses were applied within a time window of approximately 40 ms prior to neuronal spiking, consistent with the timing requirement of synaptic potentiation via STDP. Thus, BDNF is required for tLTP and BDNF secretion could be triggered in a spike-timing-dependent manner from the postsynaptic dendrite.
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Cho, Hyojong, i Sungjun Kim. "Short-Term Memory Dynamics of TiN/Ti/TiO2/SiOx/Si Resistive Random Access Memory". Nanomaterials 10, nr 9 (12.09.2020): 1821. http://dx.doi.org/10.3390/nano10091821.
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In this study, we investigated the synaptic functions of TiN/Ti/TiO2/SiOx/Si resistive random access memory for a neuromorphic computing system that can act as a substitute for the von-Neumann computing architecture. To process the data efficiently, it is necessary to coordinate the information that needs to be processed with short-term memory. In neural networks, short-term memory can play the role of retaining the response on temporary spikes for information filtering. In this study, the proposed complementary metal-oxide-semiconductor (CMOS)-compatible synaptic device mimics the potentiation and depression with varying pulse conditions similar to biological synapses in the nervous system. Short-term memory dynamics are demonstrated through pulse modulation at a set pulse voltage of −3.5 V and pulse width of 10 ms and paired-pulsed facilitation. Moreover, spike-timing-dependent plasticity with the change in synaptic weight is performed by the time difference between the pre- and postsynaptic neurons. The SiOx layer as a tunnel barrier on a Si substrate provides highly nonlinear current-voltage (I–V) characteristics in a low-resistance state, which is suitable for high-density synapse arrays. The results herein presented confirm the viability of implementing a CMOS-compatible neuromorphic chip.
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Gardner, E. P., C. I. Palmer, H. A. Hamalainen i S. Warren. "Simulation of motion on the skin. V. Effect of stimulus temporal frequency on the representation of moving bar patterns in primary somatosensory cortex of monkeys". Journal of Neurophysiology 67, nr 1 (1.01.1992): 37–63. http://dx.doi.org/10.1152/jn.1992.67.1.37.
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1. To assess the mechanisms used by cortical neurons to sense motion across the skin, we applied pulsatile stimuli to a series of adjacent positions on the glabrous skin of the hand using a computer-controlled OPTACON stimulator. We describe responses of 129 single neurons in primary somatosensory cortex of alert monkeys to a horizontal bar pattern that was displaced proximally or distally in 1.2-mm steps at 10-, 20-, and 40-ms intervals (100, 50, and 25 Hz, respectively). These frequencies span the range in which apparent motion is transformed perceptually in humans from a smooth uninterrupted sweep into a series of distinct pulses that are resolved as separate events. The experiments are thus designed to decipher the neural correlates distinguishing continuous motion from discrete taps. 2. Cortical receptive fields mapped with moving bar patterns spanned 5-24 rows on the tactile array (16.2 +/- 5.4, mean +/- SD). Over 40% of the fields encompassed 18 or more rows (greater than or equal to 21.6 mm), allowing these neurons to integrate spatial information from an entire image displayed on the OPTACON. Cortical receptive fields are considerably larger than those of mechanoreceptors mapped with the same moving bar patterns (4.2 +/- 2.3 rows, mean +/- SD), reflecting convergent inputs in subcortical and cortical relays. Responses were either relatively uniform across the field or strongest at the initial point of entry, depending on the frequency of stimulation. A sharply defined field center was absent from most of the cells recorded in this study. 3. Temporal frequency of stimulation appears to be a major determinant of cortical firing patterns. Low-frequency stimuli are more effective in activating cortical neurons, producing more spikes per sweep and greater phase-locking to individual stimuli than do high frequencies. The total spike output of cortical neurons is proportional to the pulse interval over the range 10-40 ms, increasing linearly by an average of 5.9 spikes/10-ms increase in pulse period. Peak firing rates and modulation amplitude are also highest when pulses are presented at long intervals, falling significantly as the stimulation frequency rises. The reduction in firing at high pulse rates is apparently due to central mechanisms, as both rapidly adapting and Pacinian corpuscle afferents display nearly constant spike outputs and uniform sensitivity within the field when tested with identical bar patterns. Central networks thus behave as low-pass filters, reducing cortical responses to rapidly applied sequential stimuli.(ABSTRACT TRUNCATED AT 400 WORDS)
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Di, Shi Chun, Dong Bo Wei, Guan Xin Chi, Zhen Long Wang i J. T. Jiang. "Research on Energy Saving EDM Pulsed Power Supply with Cyclically Superimposed Chopper Circuit". Key Engineering Materials 315-316 (lipiec 2006): 516–20. http://dx.doi.org/10.4028/www.scientific.net/kem.315-316.516.
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This paper presents an energy saving electrical discharge machining (EDM) pulsed power supply, the principle of which is introduced. This pulsed power supply possesses no current-limiting resistors used in conventional EDM pulsed power supplies and no energy storage inductors applied in most other energy saving pulsed power supplies. Direct current from DC power supply is chopped to form many branches of paralleling spike pulse currents and the current branches are then combined into the desired pulse current for EDM machining through cyclic superimposition. The calculation method of energy loss is then analyzed. The short-circuit and contrastive machining experiments proved that the new pulsed power supply was capable of performing stable machining with higher machining efficiency and less main-machining-circuit energy loss than those of conventional EDM pulsed power supplies.
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Zorović, M., i B. Hedwig. "Processing of species-specific auditory patterns in the cricket brain by ascending, local, and descending neurons during standing and walking". Journal of Neurophysiology 105, nr 5 (maj 2011): 2181–94. http://dx.doi.org/10.1152/jn.00416.2010.
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The recognition of the male calling song is essential for phonotaxis in female crickets. We investigated the responses toward different models of song patterns by ascending, local, and descending neurons in the brain of standing and walking crickets. We describe results for two ascending, three local, and two descending interneurons. Characteristic dendritic and axonal arborizations of the local and descending neurons indicate a flow of auditory information from the ascending interneurons toward the lateral accessory lobes and point toward the relevance of this brain region for cricket phonotaxis. Two aspects of auditory processing were studied: the tuning of interneuron activity to pulse repetition rate and the precision of pattern copying. Whereas ascending neurons exhibited weak, low-pass properties, local neurons showed both low- and band-pass properties, and descending neurons represented clear band-pass filters. Accurate copying of single pulses was found at all three levels of the auditory pathway. Animals were walking on a trackball, which allowed an assessment of the effect that walking has on auditory processing. During walking, all neurons were additionally activated, and in most neurons, the spike rate was correlated to walking velocity. The number of spikes elicited by a chirp increased with walking only in ascending neurons, whereas the peak instantaneous spike rate of the auditory responses increased on all levels of the processing pathway. Extra spiking activity resulted in a somewhat degraded copying of the pulse pattern in most neurons.
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Nyushkov, Boris, Aleksey Ivanenko, Gleb Vishnyakov, Alexey Kharauzov i Sergey Smirnov. "Active Compensation of Differential Group Delay in a Dual-Wavelength Pulsed Fiber Laser Driven by Quasi-Synchronous Pumping". Photonics 10, nr 1 (31.12.2022): 42. http://dx.doi.org/10.3390/photonics10010042.
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We report on synchronized dual-wavelength (1.07 μm and 1.24 μm) pulsed lasing driven by a quasi-synchronous primary pumping (at 0.98 μm) of an Yb-doped fiber laser, which incorporates also a P2O5-doped fiber as an intracavity Raman converter. The original method developed for such lasing does not require saturable absorbers (or optical modulators) and dispersion management. We demonstrated that the mechanism of the quasi-synchronous pumping enables the aforesaid stationary lasing in spite of significant differential group delay (DGD) inevitably acquired by light pulses with such different wavelengths during an intracavity round trip due to large normal chromatic dispersion. This DGD can be actively compensated at every round trip by the forced “acceleration” of the pulses at 1.07 μm in the Yb-doped active fiber due to the overrated frequency of the quasi-synchronous pumping at 0.98 μm. This mechanism is related to the particular pulse amplification dynamics in a such gain-modulated active fiber. The demonstrated approach to synchronized dual-wavelength pulsed lasing in a single-cavity fiber laser features remarkable simplicity and reliability. Our proof-of-concept setup enabled the stable two-wavelength generation of regular trains of nanosecond pulses with energy up to 34 nJ at equal repetition rates.
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Mamedov, N. V., A. S. Rohmanenkov i A. A. Solodovnikov. "Magnetic field influence on the Penning discharge characteristics". Journal of Physics: Conference Series 2064, nr 1 (1.11.2021): 012039. http://dx.doi.org/10.1088/1742-6596/2064/1/012039.
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Abstract In this work characteristics of pulsed penning ion source for miniature linear accelerators was investigated by experimental measurements and PIC (Particle-In-Cell) simulations. The paper presents dependences of the discharge current and extracted current on intensities of the uniform magnetic field for different pressure. Also, typical examples of the current pulse waveforms obtained by PIC simulation and experiment for different magnetic field are presented. The simulated electron and ion distributions inside discharge gap give qualitative explanation of the experimentally observed fluctuations in current pulses. These current fluctuations arise as a result of the violation of the electric field axial symmetry due to the electron spoke movement of the towards the anode.
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Borrell, Jordan A., Dora Krizsan-Agbas, Randolph J. Nudo i Shawn B. Frost. "Activity dependent stimulation increases synaptic efficacy in spared pathways in an anesthetized rat model of spinal cord contusion injury". Restorative Neurology and Neuroscience 40, nr 1 (8.04.2022): 17–33. http://dx.doi.org/10.3233/rnn-211214.
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Background: Closed-loop neuromodulation systems have received increased attention in recent years as potential therapeutic approaches for treating neurological injury and disease. Objective: The purpose of this study was to assess the ability of intraspinal microstimulation (ISMS), triggered by action potentials (spikes) recorded in motor cortex, to alter synaptic efficacy in descending motor pathways in an anesthetized rat model of spinal cord injury (SCI). Methods: Experiments were carried out in adult, male, Sprague Dawley rats with a moderate contusion injury at T8. For activity-dependent stimulation (ADS) sessions, a recording microelectrode was used to detect neuronal spikes in motor cortex that triggered ISMS in the spinal cord grey matter. SCI rats were randomly assigned to one of four experimental groups differing by: a) cortical spike-ISMS stimulus delay (10 or 25 ms) and b) number of ISMS pulses (1 or 3). Four weeks after SCI, ADS sessions were conducted in three consecutive 1-hour conditioning bouts for a total of 3 hours. At the end of each conditioning bout, changes in synaptic efficacy were assessed using intracortical microstimulation (ICMS) to examine the number of spikes evoked in spinal cord neurons during 5-minute test bouts. A multichannel microelectrode recording array was used to record cortically-evoked spike activity from multiple layers of the spinal cord. Results: The results showed that ADS resulted in an increase in cortically-evoked spikes in spinal cord neurons at specific combinations of spike-ISMS delays and numbers of pulses. Efficacy in descending motor pathways was increased throughout all dorsoventral depths of the hindlimb spinal cord. Conclusions: These results show that after an SCI, ADS can increase synaptic efficacy in spared pathways between motor cortex and spinal cord. This study provides further support for the potential of ADS therapy as an effective method for enhancing descending motor control after SCI.
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Ramos, Antonio, Abelardo Ruiz i Enrique Riera. "Modeling Pulsed High-Power Spikes in Tunable HV Capacitive Drivers of Piezoelectric Wideband Transducers to Improve Dynamic Range and SNR for Ultrasonic Imaging and NDE". Sensors 21, nr 21 (28.10.2021): 7178. http://dx.doi.org/10.3390/s21217178.
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The signal-to-noise ratios (SNR) of ultrasonic imaging and non-destructive evaluation (NDE) applications can be greatly improved by driving each piezoelectric transducer (single or in array) with tuned HV capacitive-discharge drivers. These can deliver spikes with kW pulsed power at PRF ≈ 5000 spikes/s, achieving levels higher even than in CW high-power ultrasound: up to 5 kWpp. These conclusions are reached here by applying a new strategy proposed for the accurate modeling of own-design re-configurable HV capacitive drivers. To obtain such rigorous spike modeling, the real effects of very high levels of pulsed intensities (3–10 A) and voltages (300–700 V) were computed. Unexpected phenomena were found: intense brief pulses of driving power and probe emitted force, as well as nonlinearities in semiconductors, though their catalog data include only linear ranges. Fortunately, our piezoelectric and circuital devices working in such an intense regime have not shown serious heating problems, since the finally consumed “average” power is rather small. Intensity, power, and voltage, driving wideband transducers from our capacitive drivers, are researched here in order to drastically improve (∆ >> 40 dB) their ultrasonic “net dynamic range available” (NDRA), achieving emitted forces > 240 Newtonspp and receiving ultrasonic signals of up to 76–205 Vpp. These measurements of ultrasonic pulsed voltages, received in NDE and Imaging, are approximately 10,000 larger than those usual today. Thus, NDRA ranges were optimized for three laboratory capacitive drivers (with six commercial transducers), which were successfully applied in the aircraft industry for imaging landing flaps in Boeing wings, despite suffering acoustic losses > 120 dB.
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Hopp, F. A., J. L. Seagard i J. P. Kampine. "Comparison of four methods of averaging nerve activity". American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 251, nr 4 (1.10.1986): R700—R711. http://dx.doi.org/10.1152/ajpregu.1986.251.4.r700.
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Four methods of averaging nerve activity, moving time average (Analog), integration (Integrated), counting spikes (Spikes), and counting pulses from a voltage-to-frequency converter (VFC), were used to analyze artificial pulse trains and renal, carotid sinus, and vagal nerve activities. Results of the methods were compared using least-squares linear regression and correlation to determine the linearity of each method with respect to changes in frequency, amplitude, and width of pulse trains and the degree of agreement between methods. The methods that respond to total voltage (Analog, Integrated, and VFC) were linear with respect to input pulse train modulations and agreed closely with each other when averaging pulse trains, summating pulses, and nerve activity. Spikes were linear with respect to frequency modulation but not with respect to amplitude changes, pulse width changes, or pulse summations. In general, Spikes did not agree as well with Analog, Integrated, and VFC as these methods agreed with each other when averaging nerve activity. The degree of agreement was a function of the voltage threshold for Spikes and the level of nerve activity. Two methods of minimizing noise and obtaining a zero reference level for nerve activity were compared: setting a voltage threshold, such that noise was below and activity above threshold, was found to shift the base-line activity toward zero and compress phasic changes in activity; and recording the average noise level from a crushed nerve and subtracting it from averaged activity shifted the base-line activity toward zero with no change in the phasic component.
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Kang, Wonkyu, Kyoungmin Woo, Hyon Na, Chi Kang, Tae-Sik Yoon, Kyung Kim i Hyun Lee. "Analog Memristive Characteristics of Square Shaped Lanthanum Oxide Nanoplates Layered Device". Nanomaterials 11, nr 2 (9.02.2021): 441. http://dx.doi.org/10.3390/nano11020441.
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Square-shaped or rectangular nanoparticles (NPs) of lanthanum oxide (LaOx) were synthesized and layered by convective self-assembly to demonstrate an analog memristive device in this study. Along with non-volatile analog memory effect, selection diode property could be co-existent without any implementation of heterogeneous multiple stacks with ~1 μm thick LaOx NPs layer. Current–voltage (I–V) behavior of the LaOx NPs resistive switching (RS) device has shown an evolved current level with memristive behavior and additional rectification functionality with threshold voltage. The concurrent memristor and diode type selector characteristics were examined with electrical stimuli or spikes for the duration of 10–50 ms pulse biases. The pulsed spike increased current levels at a read voltage of +0.2 V sequentially along with ±7 V biases, which have emulated neuromorphic operation of long-term potentiation (LTP). This study can open a new application of rare-earth LaOx NPs as a component of neuromorphic synaptic device.
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Agnesi, Filippo, Abirami Muralidharan, Kenneth B. Baker, Jerrold L. Vitek i Matthew D. Johnson. "Fidelity of frequency and phase entrainment of circuit-level spike activity during DBS". Journal of Neurophysiology 114, nr 2 (sierpień 2015): 825–34. http://dx.doi.org/10.1152/jn.00259.2015.
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High-frequency stimulation is known to entrain spike activity downstream and upstream of several clinical deep brain stimulation (DBS) targets, including the cerebellar-receiving area of thalamus (VPLo), subthalamic nucleus (STN), and globus pallidus (GP). Less understood are the fidelity of entrainment to each stimulus pulse, whether entrainment patterns are stationary over time, and how responses differ among DBS targets. In this study, three rhesus macaques were implanted with a single DBS lead in VPLo, STN, or GP. Single-unit spike activity was recorded in the resting state in motor cortex during VPLo DBS, in GP during STN DBS, and in STN and pallidal-receiving area of motor thalamus (VLo) during GP DBS. VPLo DBS induced time-locked spike activity in 25% ( n = 15/61) of motor cortex cells, with entrained cells following 7.5 ± 7.4% of delivered pulses. STN DBS entrained spike activity in 26% ( n = 8/27) of GP cells, which yielded time-locked spike activity for 8.7 ± 8.4% of stimulus pulses. GP DBS entrained 67% ( n = 14/21) of STN cells and 32% ( n = 19/59) of VLo cells, which showed a higher fraction of pulses effectively inhibiting spike activity (82.0 ± 9.6% and 86.1 ± 16.6%, respectively). Latency of phase-locked spike activity increased over time in motor cortex (58%, VPLo DBS) and to a lesser extent in GP (25%, STN DBS). In contrast, the initial inhibitory phase observed in VLo and STN during GP DBS remained stable following stimulation onset. Together, these data suggest that circuit-level entrainment is low-pass filtered during high-frequency stimulation, most notably for glutamatergic pathways. Moreover, phase entrainment is not stationary or consistent at the circuit level for all DBS targets.
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Naud, Richard, Dave Houtman, Gary J. Rose i André Longtin. "Counting on dis-inhibition: a circuit motif for interval counting and selectivity in the anuran auditory system". Journal of Neurophysiology 114, nr 5 (1.11.2015): 2804–15. http://dx.doi.org/10.1152/jn.00138.2015.
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Information can be encoded in the temporal patterning of spikes. How the brain reads these patterns is of general importance and represents one of the greatest challenges in neuroscience. We addressed this issue in relation to temporal pattern recognition in the anuran auditory system. Many species of anurans perform mating decisions based on the temporal structure of advertisement calls. One important temporal feature is the number of sound pulses that occur with a species-specific interpulse interval. Neurons representing this pulse count have been recorded in the anuran inferior colliculus, but the mechanisms underlying their temporal selectivity are incompletely understood. Here, we construct a parsimonious model that can explain the key dynamical features of these cells with biologically plausible elements. We demonstrate that interval counting arises naturally when combining interval-selective inhibition with pulse-per-pulse excitation having both fast- and slow-conductance synapses. Interval-dependent inhibition is modeled here by a simple architecture based on known physiology of afferent nuclei. Finally, we consider simple implementations of previously proposed mechanistic explanations for these counting neurons and show that they do not account for all experimental observations. Our results demonstrate that tens of millisecond-range temporal selectivities can arise from simple connectivity motifs of inhibitory neurons, without recourse to internal clocks, spike-frequency adaptation, or appreciable short-term plasticity.
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Pinato, Giulietta, i Jens Midtgaard. "Regulation of Granule Cell Excitability by a Low-Threshold Calcium Spike in Turtle Olfactory Bulb". Journal of Neurophysiology 90, nr 5 (listopad 2003): 3341–51. http://dx.doi.org/10.1152/jn.00560.2003.
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Granule cells excitability in the turtle olfactory bulb was analyzed using whole cell recordings in current- and voltage-clamp mode. Low-threshold spikes (LTSs) were evoked at potentials that are subthreshold for Na spikes in normal medium. The LTSs were evoked from rest, but hyperpolarization of the cell usually increased their amplitude so that they more easily boosted Na spike initiation. The LTS persisted in the presence of TTX but was antagonized by blockers of T-type calcium channels. The voltage dependence, kinetics, and inactivation properties of the LTS were characteristic of a low-threshold calcium spike. The threshold of the LTS was slightly above the resting potential but well below the Na spike threshold, and the LTS was often evoked in isolation in normal medium. Tetraethylammonium (TEA) and 4-aminopyridine (4-AP) had only minimal effects on the LTS but revealed the presence of a high-threshold Ca2+ spike (HTS), which was antagonized by Cd2+. The LTS displayed paired-pulse attenuation, with a timescale for recovery from inactivation of about 2 s at resting membrane potential. The LTS strongly boosted Na spike initiation; with repetitive stimulation, the long recovery of the LTS governed Na spike initiation. Thus the olfactory granule cells possess an LTS, with intrinsic kinetics that contribute to sub- and suprathreshold responses on a timescale of seconds. This adds a new mechanism to the early processing of olfactory input.
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Stone, L. S., i 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, nr 5 (1.05.1990): 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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Cui, Jianxia, Carmen C. Canavier i Robert J. Butera. "Functional Phase Response Curves: A Method for Understanding Synchronization of Adapting Neurons". Journal of Neurophysiology 102, nr 1 (lipiec 2009): 387–98. http://dx.doi.org/10.1152/jn.00037.2009.
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Phase response curves (PRCs) for a single neuron are often used to predict the synchrony of mutually coupled neurons. Previous theoretical work on pulse-coupled oscillators used single-pulse perturbations. We propose an alternate method in which functional PRCs (fPRCs) are generated using a train of pulses applied at a fixed delay after each spike, with the PRC measured when the phasic relationship between the stimulus and the subsequent spike in the neuron has converged. The essential information is the dependence of the recovery time from pulse onset until the next spike as a function of the delay between the previous spike and the onset of the applied pulse. Experimental fPRCs in Aplysia pacemaker neurons were different from single-pulse PRCs, principally due to adaptation. In the biological neuron, convergence to the fully adapted recovery interval was slower at some phases than that at others because the change in the effective intrinsic period due to adaptation changes the effective phase resetting in a way that opposes and slows the effects of adaptation. The fPRCs for two isolated adapting model neurons were used to predict the existence and stability of 1:1 phase-locked network activity when the two neurons were coupled. A stability criterion was derived by linearizing a coupled map based on the fPRC and the existence and stability criteria were successfully tested in two-simulated-neuron networks with reciprocal inhibition or excitation. The fPRC is the first PRC-based tool that can account for adaptation in analyzing networks of neural oscillators.
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Gao, Zi-Qi, Yun-Feng Wu, Hai-Yan Liu, Ze-Xin Zhang, Jin-Rong Tian i Yan-Rong Song. "Bound noise-like pulse generation from Yb-doped passively mode-locked fiber lasers". Laser Physics Letters 19, nr 9 (10.08.2022): 095103. http://dx.doi.org/10.1088/1612-202x/ac787c.
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Abstract We demonstrated two different types of bound noise-like pulses (NLPs) in ytterbium-doped mode-locked fiber lasers using the nonlinear polarization rotation technique. In the anomalous dispersion area, there were multiple spikes in the intensity autocorrelation (IAC) trace. In the normal dispersion area, the spike presented only in the center the of IAC trace. The results of the experiment show that the bound state NLPs may have partial coherence.
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Weckstrom, M., M. Jarvilehto i K. Heimonen. "Spike-like potentials in the axons of nonspiking photoreceptors". Journal of Neurophysiology 69, nr 1 (1.01.1993): 293–96. http://dx.doi.org/10.1152/jn.1993.69.1.293.
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1. The voltage responses to light of dark-adapted cockroach photoreceptors were recorded from the somata in the retina and the axons below the two basement membranes. 2. One or more spike-like fast depolarizations superimposed on the graded receptor potential were recorded in photoreceptor axons identified by Lucifer yellow injections. These spikes are voltage dependent in as much as they could be elicited with depolarizing current pulses as well as with light stimuli. In photoreceptor somata only graded receptor potentials were recorded. 3. The physiological function of these axonal spikes may be to serve as an amplification mechanism that counteracts the unfavorable combination of photoreceptor geometry and electrical properties.
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Wang, Jiaoyan, Xiaoshan Zhao i Chao Lei. "Pulse Inputs Affect Timings of Spikes in Neurons with or Without Time Delays". International Journal of Nonlinear Sciences and Numerical Simulation 20, nr 3-4 (26.05.2019): 257–67. http://dx.doi.org/10.1515/ijnsns-2017-0070.
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AbstractInputs can change timings of spikes in neurons. But it is still not clear how input’s parameters for example injecting time of inputs affect timings of neurons. HR neurons receiving both weak and strong inputs are considered. How pulse inputs affecting neurons is studied by using the phase-resetting curve technique. For a single neuron, weak pulse inputs may advance or delay the next spike, while strong pulse inputs may induce subthreshold oscillations depending on parameters such as injecting timings of inputs. The behavior of synchronization in a network with or without coupling delays can be predicted by analysis in a single neuron. Our results can be used to predict the effects of inputs on other spiking neurons.
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Schmitz, Patrick. "Comparative Study on Pulsed Laser Welding Strategies for Contacting Lithium-Ion Batteries". Advanced Materials Research 1140 (sierpień 2016): 312–19. http://dx.doi.org/10.4028/www.scientific.net/amr.1140.312.
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The transition towards renewable energy implicates more decentralized and time-dependent ways of energy generation. In order to deal with the resulting fluctuation in energy supply, local storage systems are necessary. Larger systems may consist of thousands of battery cells. Therefore, the reliable interconnection between the individual battery cells is the basic prerequisite for the production of these systems. It has been demonstrated that laser beam welding is a suitable process for the contacting of batteries. However, due to the high requirements regarding the heat input and the reproducibility of the joining process, further investigations are necessary. Within this work, experiments on pulsed laser beam welding of nickel-plated DC04 steel were conducted. Four different pulsed welding strategies were analyzed in a preliminary study in order to develop a method for obtaining suitable process parameters while reducing the amount of free parameters. Subsequently, a comparative study between the rectangular pulse, the shaped pulse, the spike pulse and the sloping pulse was carried out. The weld seam properties as well as the electrical and the mechanical properties of the connection joints were evaluated. The results presented in this paper indicate a high eligibility of pulsed laser beam welding as a joining process for the connection of battery cells. For all analyzed pulsed welding strategies a homogeneous weld seam without full penetration was observed. Similar electrical resistances for all strategies were measured despite the comparatively small total joint area for the discretely pulsed weld seams.
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Evans, Colin G., Bjoern Ch Ludwar i Elizabeth C. Cropper. "Mechanoafferent Neuron With An Inexcitable Somatic Region: Consequences for the Regulation of Spike Propagation and Afferent Transmission". Journal of Neurophysiology 97, nr 4 (kwiecień 2007): 3126–30. http://dx.doi.org/10.1152/jn.01341.2006.
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In the Aplysia mechanoafferent B21, afferent transmission is in part regulated via the control of active spike propagation. When B21 is peripherally activated at its resting membrane potential, spikes fail to propagate to an output process, and afferent transmission does not occur. In this report, we show that the propagation failure is in part a result of the fact that the somatic region of B21 is relatively inexcitable. We isolate this region and demonstrate that net currents evoked by depolarizing pulses are outward. Furthermore, we show that all-or-none spikes are not triggered when current is injected. Previous reports have, however shown that spiking is triggered when current is somatically injected and cells are intact. We demonstrate that spikes evoked under these circumstances do not originate in the soma. Instead they originate in an adjacent part of the neuron that is excitable (the medial process). In summary, we show that the mechanoafferent B21 consists of excitable input and output processes separated by a relatively inexcitable somatic region. A potential advantage of this arrangement is that somatic depolarization can be used to modify spike propagation from the input to the output processes without altering the encoding of peripherally generated activity.
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Contreras, D., R. Curro Dossi i M. Steriade. "Bursting and tonic discharges in two classes of reticular thalamic neurons". Journal of Neurophysiology 68, nr 3 (1.09.1992): 973–77. http://dx.doi.org/10.1152/jn.1992.68.3.973.
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1. Two types of cat reticular (RE) thalamic cells were disclosed by means of intracellular recordings under urethan anesthesia. The RE neurons were identified by their typical depolarizing spindle oscillations in response to synchronous stimulation of the internal capsule. 2. In type I neurons (n = 41), depolarizing current pulses induced tonic firing at the resting or slightly depolarized membrane potential (Vm) and triggered high-frequency spike bursts at a Vm more negative than -75 mV. As well, these cells discharged rebound bursts at the break of a hyperpolarizing current pulse. Internal capsule stimulation elicited spindle sequences made off by depolarizing waves giving rise to spike bursts. 3. Type II cells (n = 9) did not discharge spike bursts to large depolarizing current pulses even when the Vm reached -100 mV, nor did they fire rebound bursts after long-lasting hyperpolarizing current pulses or spike bursts riding on the rhythmic depolarizing components of spindle sequences. 4. Compared with type I cells, type II cells showed less frequency accommodation during tonic firing. The latter neuronal class discharged at high frequencies (40 Hz) with slight DC depolarization, approximately 8-10 Hz at the resting Vm, and no underlying synaptic or subthreshold oscillatory events could be detected when the firing was blocked by DC hyperpolarization. 5. The presence of two cell classes in the RE nucleus challenges the common view that this nucleus consists of a single neuronal class. We suggest that a different set of conductances is present in type II RE neurons, thus preventing the low-threshold Ca2+ current from dominating the behavior of these cells.
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Opromolla, Michele, i Vittoria Petrillo. "Two-Color TeraHertz Radiation by a Multi-Pass FEL Oscillator". Applied Sciences 11, nr 14 (14.07.2021): 6495. http://dx.doi.org/10.3390/app11146495.
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In this paper, we show that an electron beam produced by a super-conducting linac, driven in a sequence of two undulator modules of different periods, can generate two-color Terahertz radiation with wavelengths ranging from 100 μm to 2 μm. The generated pulses are synchronized, both MW-class, and highly coherent. Their specific properties and generation will be discussed in detail. Besides the single-spike pulse structure, usually observed in oscillators, we show that both the THz pump and probe can be modulated in a coherent comb of pulses, enabling periodic excitation and stroboscopic measurements.
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ELSON, ROBERT, i HANS-JOACHIM PFLÜGER. "The Activity of a Steering Muscle in Flying Locusts". Journal of Experimental Biology 120, nr 1 (1.01.1986): 421–41. http://dx.doi.org/10.1242/jeb.120.1.421.
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1. The pleuroaxillary muscle of a forewing (M85) or hindwing (M114) in the locust is supplied by two motor neurones. Each of the two motor neurones innervates a different part of the muscle. Single impulses in these motor neurones produce small twitches in the muscle which tetanize at about 30 Hz. At the wingbeat frequency they show considerable tonic tension upon which ripples are superimposed, 1:1 for each stimulus pulse. 2. During sustained, straight, tethered flight, the motor neurones spike rhythmically, producing one (leas often two) spike(s) per wingbeat in the first half of each downstroke. At the end of flight, when the wing is folded, a high-frequency, unpatterned burst of spikes occurs. 3. During flight-like motor activity where rhythmic sensory feedback is reduced, the pleuroaxillary muscle of a hindwing spikes throughout the ‘wingbeat’ cycle, with little sign of rhythm. 4. The forewing muscle, M85, responds to imposed rolling during flight by advancing the timing of its spike, increasing the number of spikes at each wingbeat, and recruiting a second motor unit on the side which is rotated downwards; converse changes occur on the side that is rolled upwards. The magnitude of the time-shift response in M85 depends on the angular position of the locust about the roll axis. The hindwing muscle shows similar changes in the number of spikes and in recruitment. 5. Motor neurones of both the forewing and hindwing muscles can spike in response to imposed rolling in locusts that are not flying. Excitation increases on the side that is rolled down. The response to angular movement about the roll axis is primarily phasic and is dependent on visual cues. 6. It is concluded that these muscles take part in steering behaviour during corrective reactions. Activation is increased on the side where more lift must be produced. Similar changes of activity in these muscles may play a role in active steering manoeuvres.