Добірка наукової літератури з теми "Mirror activation pattern"

Based on inflow explanations, the predictions related to EMG activity during imagery of a dumbbell and manipulandum curl were that EMG activity: (a) increases, relative to baseline, in both the biceps and triceps of the active arm; (b) is localized to muscles used in executing the real movement; and (c) mirrors the pattern of activity observed during the real movement. Based on literature which suggests that EMG activity during imagery may be due to expectancy effects, it was also hypothesized that EMG activity would be greater during imagery for those who were aware of the predictions of inflow explanations than for those who were unaware of those predictions. Undergraduate students (N = 60) completed a series of real and imagined dumbbell and manipulandum curls. For both movements, biceps and triceps EMG activity was measured in both the passive and active arms during baseline, imagery, and real movement conditions. No EMG differences were found between those who were aware or unaware of the predictions derived from inflow explanations. For both curls, average EMG biceps and triceps activity was significantly greater in the active arm during imagery than during baseline. Pattern analysis showed that the EMG activation patterns for biceps and triceps did not mirror the triphasic EMG pattern observed during the real movement. Results did not support the mirroring hypothesis (e.g., the psychoneuro-muscular theory), as the pattern of increased activation during imagery did not reflect that observed during the real movement.

Abstract After a hint from Lang et al.'s (1997) defence cascade, researchers considered cognitive process experienced when encountering mental stress to be composed of four elements: (serially) first attention (Attent), second unpleasant affect (UnplAff) and sometimes pleasant affect (PlAff), and third cognitive coping (CogCop). The present study investigates the effect of each cognitive element on the provocation of the well-known vascular-dominant reaction pattern during mirror tracing: elevation of mean blood pressure mainly because of increases in total peripheral resistance. Twenty-four male students first underwent four computer-simulated mirror-tracing practices of 3 min each, then a 7 min adaptation followed by a 3 min baseline, and further four kinds of actual mirror tracing trials (Attent, UnplAff, PlAff, and CogCop) of 3 min each. Results on the cardiovascular measures indicated that every mirror-tracing trial indisputably provoked the vascular-dominant reaction pattern. An alpha-adrenergic vascular sympathetic activation was heightened. Self-report measures on the four cognitive elements suggested that heightened Attent seemed to contribute to provoking the reaction pattern. Although the UnplAff and PlAff trials had an active coping feature in a narrow sense, they could not provoke the cardiac-dominant reaction pattern. Differences in task difficulty among the mirror tracings could not explain the results. The implications of these results are discussed in order to better understand cardiovascular hemodynamics during mental stress.

dHAND is a basic helix-loop-helix (bHLH) transcription factor essential for cardiovascular development. Here we analyze its pattern of expression and functional role during chick limb development. dHAND expression was observed in the lateral plate mesoderm prior to emergence of the limb buds. Coincident with limb initiation, expression of dHAND became restricted to the posterior half of the limb bud. Experimental procedures that caused mirror-image duplications of the limb resulted in mirror-image duplications of the pattern of dHAND expression along the anterior-posterior axis. Retroviral overexpression of dHAND in the limb bud produced preaxial polydactyly, corresponding to mild polarizing activity at the anterior border. At the molecular level, misexpression of dHAND caused ectopic activation of members of the Sonic hedgehog (Shh) pathway, including Gli and Patched, in the anterior limb bud. A subset of infected embryos displayed ectopic anterior activation of Shh. Other factors implicated in anterior-posterior polarization of the bud such as the most 5′ Hoxd genes and Bmp2 were also ectopically activated at the anterior border. Our results indicate a role for dHAND in the establishment of anterior-posterior polarization of the limb bud.

The activation of listener's motor system during speech processing was first demonstrated by the enhancement of electromyographic tongue potentials as evoked by single-pulse transcranial magnetic stimulation (TMS) over tongue motor cortex. This technique is, however, technically challenging and enables only a rather coarse measurement of this motor mirroring. Here, we applied TMS to listeners’ tongue motor area in association with ultrasound tissue Doppler imaging to describe fine-grained tongue kinematic synergies evoked by passive listening to speech. Subjects listened to syllables requiring different patterns of dorso-ventral and antero-posterior movements (/ki/, /ko/, /ti/, /to/). Results show that passive listening to speech sounds evokes a pattern of motor synergies mirroring those occurring during speech production. Moreover, mirror motor synergies were more evident in those subjects showing good performances in discriminating speech in noise demonstrating a role of the speech-related mirror system in feed-forward processing the speaker's ongoing motor plan.

This paper presents the diamond nucleation using combustion activation chemical vapor deposition (CACVD) by 0.95 volumetric ratio of O2 /C2H2 under atmospheric pressure. The main point of our work is to develop the CACVD technique for synthesize the semiconductor materials, which is developed for electronic devices application. The surface nucleation of substrate was studied by using surface pretreatment. The results of surface nucleation on mirror-silicon, polished silicon by diamond powder, silicon-dioxide (SiO2), and polished SiO2 by diamond powder, are significantly different. It can be concluded that the silicon-dioxide mask technique is useful for nucleated diamond protection whereas the polished silicon by diamond powder is suitable for nucleated diamond generation. These techniques are applied for the pattern fabrication.

We investigated the neural substrates involved in visuo-haptic neuronal convergence using an additive-factors design in combination with fMRI. Stimuli were explored under three sensory modality conditions: viewing the object through a mirror without touching (V), touching the object with eyes closed (H), or simultaneously viewing and touching the object (VH). This modality factor was crossed with a task difficulty factor, which had two levels. On the basis of an idea similar to the principle of inverse effectiveness, we predicted that increasing difficulty would increase the relative level of multisensory gain in brain regions where visual and haptic sensory inputs converged. An ROI analysis focused on the lateral occipital tactile–visual area found evidence of inverse effectiveness in the left lateral occipital tactile–visual area, but not in the right. A whole-brain analysis also found evidence for the same pattern in the anterior aspect of the intraparietal sulcus, the premotor cortex, and the posterior insula, all in the left hemisphere. In conclusion, this study is the first to demonstrate visuo-haptic neuronal convergence based on an inversely effective pattern of brain activation.

Bone morphogenetic protein-2 (BMP-2) has been implicated in the polarizing region signalling pathway, which specifies pattern across the antero-posterior of the developing vertebrate limb. Retinoic acid and Sonic Hedgehog (SHH) can act as polarizing signals; when applied anteriorly in the limb bud, they induce mirror-image digit duplications and ectopic Bmp-2 expression in anterior mesenchyme. In addition, the two signals can activate Fgf-4 expression in anterior ridge and HoxD expression in anterior mesenchyme. We tested the role of BMP-2 in this signalling cascade by ectopically expressing human BMP-2 (hBMP-2) at the anterior margin of the early wing bud using a replication defective retroviral vector, and found that ectopic expression of Fgf-4 was induced in the anterior part of the apical ectodermal ridge, followed later by ectopic expression of Hoxd-11 and Hoxd-13 in anterior mesenchyme. This suggests that BMP-2 is involved in regulating Fgf-4 and HoxD gene expression in the normal limb bud. Ectopically expressed hBMP-2 also induced duplication of digit 2 and bifurcation of digit 3, but could not produce the mirror-image digit duplications obtained with SHH-expressing cells. These results suggest that BMP-2 may be involved primarily in maintenance of the ridge, and in the link between patterning and outgrowth of the limb bud.

During vertebrate embryogenesis, the neuroectoderm differentiates into neural tissues and also into non-neural tissues such as the choroid plexus in the brain and the retinal pigment epithelium in the eye. The molecular mechanisms that pattern neural and non-neural tissues within the neuroectoderm remain unknown. We report that FGF9 is normally expressed in the distal region of the optic vesicle that is destined to become the neural retina, suggesting a role in neural patterning in the optic neuroepithelium. Ectopic expression of FGF9 in the proximal region of the optic vesicle extends neural differentiation into the presumptive retinal pigment epithelium, resulting in a duplicate neural retina in transgenic mice. Ectopic expression of constitutively active Ras is also sufficient to convert the retinal pigment epithelium to neural retina, suggesting that Ras-mediated signaling may be involved in neural differentiation in the immature optic vesicle. The original and the duplicate neural retinae differentiate and laminate with mirror-image polarity in the absence of an RPE, suggesting that the program of neuronal differentiation in the retina is autonomously regulated. In mouse embryos lacking FGF9, the retinal pigment epithelium extends into the presumptive neural retina, indicating a role of FGF9 in defining the boundary of the neural retina.

Neuronal synchronization, reflected in the EEG pattern, is the mechanism by which the brain integrates different types of information contained in a speech message and presented in different areas of the brain (for example, phonological, spelling, semantic and syntactic information). The process of understanding a sentence consists of two groups of interrelated cognitive operations: it begins with searching in memory for phonological, syntactic and semantic properties of words, which is followed by integrating information into a general idea of the sentence meaning. The stage of searching for words in adults results in an increase in the theta rhythm power. The stage of integrating words into a sentence results in the growth of theta, beta, and gamma rhythms. At the same time, the growth of theta rhythm is more typical for children than for adults. Higher rhythms reactivity during speech perception indicates better developed speech skills in children. Under conditions of relative relaxation, the EEG of children with a high level of speech development is characterized by a moderate power level of theta and beta rhythms and a high level of alpha and mu rhythms. It is assumed that a key role in the process of understanding speech is played by the so-called «action perception circuits», surrounding the Sylvian sulcus of the left hemisphere. The «action perception circuits» are composed of nerve cells capable of providing the speech signals perception and generation. The most important subgroup of neurons included in the «action perception circuits» are mirror neurons that are activated when performing and observing actions. The desynchronization of the EEG mu rhythm is considered as mirror neurons activation marker. In several studies, it revealed that the level of mirror neurons activation and the level of speech understanding in children are connected. It is a topic of great interest to research the mu rhythm alpha and beta components reactivity both during the production of speech and during the perception of another person speech. At present, it is becoming obvious that analyzing the EEG rhythms power changes during the speech understanding in different scenarios could be used to identify the mechanisms of the brain language network and speech disorders. The revealed patterns make it possible to propose ways of correcting the children speech development using EEG biological feedback methods.

This article investigates the relationship between the interconnectivity and simulated dynamics of the thalamocortical system from the specific perspective of attempting to maximize the diversity of cortical states. This is achieved by designing the dynamics such that they favor opposing activity between adjacent regions, thus promoting dynamic diversity while avoiding widespread activation or de-activation. The anti-ferromagnetic Ising model with Metropolis dynamics is adopted and applied to four variations of the large-scale connectivity of the cat thalamocortical system: (a) considering only cortical regions and connections; (b) considering the entire thalamocortical system; (c) the same as in (b) but with the thalamic connections rewired so as to maintain the statistics of node degree and node degree correlations; and (d) as in (b) but with attenuated weights of the connections between cortical and thalamic nodes. A series of interesting findings are obtained, including the identification of specific substructures revealed by correlations between the activity of adjacent regions in case (a) and a pronounced effect of the thalamic connections in splitting the thalamocortical regions into two large groups of nearly homogenous opposite activation (i.e. cortical regions and thalamic nuclei, respectively) in cases (b) and (c). The latter effect is due to the existence of dense connections between cortical and thalamic regions and the lack of interconnectivity between the latter. Another interesting result regarding case (d) is the fact that the pattern of thalamic correlations tend to mirror that of the cortical regions. The possibility to control the level of correlation between the cortical regions by varying the strength of thalamocortical connections is also identified and discussed.

Traditionally, symbols chosen from complex modulation alphabets such as QAM and PSK are used to convey information bits, and complex fades introduced by the channel are viewed as detrimental effects that cause amplitude and phase distortion to the transmitted symbols. An alternative and interesting approach is to consider the complex channel fade coefficients themselves to constitute a modulation alphabet (referred to as `channel alphabet'). An example of this approach is a recently proposed `media-based modulation (MBM)' scheme, which uses digitally controllable parasitic elements (called as radio frequency mirrors) near the transmit antenna(s) to create the channel alphabet. Each radio frequency (RF) mirror can be either ON or OFF. A mirror allows the incident RF signal to pass through it transparently when it is ON, and reflects back the incident RF signal when it is OFF. The ON/OFF status of the mirrors is called as `mirror activation pattern (MAP)'. The channel alphabet needs to be known only at the receiver and not at the transmitter. MBM has been shown to achieve significant performance gains compared to conventional modulation schemes. In this thesis, we investigate the performance of MBM in various scenarios like transmission with feedback, differential transmission, imperfect channel state information, full-duplex communications, and cooperative relaying. The contributions in this thesis are three-fold. In the first part, we investigate the performance of some interesting physical layer techniques when applied to MBM. First, we combine MBM with generalized spatial modulation (GSM), and investigate its performance. Next, we study the performance of feedback based mirror activation pattern (MAP) selection (analogous to transmit antenna selection in multi-antenna systems), and phase compensation and constellation rotation (PC-CR) techniques in MBM. We also analyze the diversity orders achieved by the ED-based MAP selection scheme and the PC-CR scheme. In the second part, we deal with channel estimation aspects in MBM. First, we present a differential MBM (DMBM) scheme which does not require estimation of channel modulation alphabet at the receiver for detection. We also propose a low-complexity maximum-likelihood (ML) detection algorithm for DMBM. Next, we analyze the effect of imperfect channel estimation on the bit error performance of MBM. We analyze the performance for two types of detectors, namely, i) the commonly studied mismatched detector, and ii) the true ML detector that maximizes the likelihood by taking the statistics of the channel estimate into account. In the final part, we investigate the performance of full-duplex (FD) communication using MBM, and compare it with that of FD with conventional modulation schemes. First, we investigate the FD communication using MBM and DMBM in a point-to-point setting, and present detectors for signal detection. Next, we analyze the performance of a two-hop three-node FD relay network, where the source and relay nodes transmit using MBM. The relay uses decode-and-forward (DF) relaying protocol. Next, we investigate the performance of MBM in a two-way relaying network, where two FD nodes exchange information with the help of a FD relay node using DF protocol.