Somatosensory system

About: Somatosensory system is a research topic. Over the lifetime, 6371 publications have been published within this topic receiving 316900 citations.

Deep Layer Somatosensory Cortical Neurons Initiate Spike-and-Wave Discharges in a Genetic Model of Absence Seizures

Abstract: Typical absence has long been considered as the prototypic form of generalized nonconvulsive epileptic seizures. Recent investigations in patients and animal models suggest that absence seizures could originate from restricted regions of the cerebral cortex. However, the cellular and local network processes of seizure initiation remain unknown. Here, we show that absence seizures in Genetic Absence Epilepsy Rats from Strasbourg, a well established genetic model of this disease, arise from the facial somatosensory cortex. Using in vivo intracellular recordings, we found that epileptic discharges are initiated in layer 5/6 neurons of this cortical region. These neurons, which show a distinctive hyperactivity associated with a membrane depolarization, lead the firing of distant cortical cells during the epileptic discharge. Consistent with their ictogenic properties, neurons from this "focus" exhibit interictal and preictal oscillations that are converted into epileptic pattern. These results confirm and extend the "focal hypothesis" of absence epilepsy and provide a cellular scenario for the initiation and generalization of absence seizures.

Microstimulation of the primate neostriatum. II. Somatotopic organization of striatal microexcitable zones and their relation to neuronal response properties.

Abstract: Sensorimotor response properties of neostriatal neurons were characterized in conjunction with assessments of the motor effects of intrastriatal microstimulation in unanesthetized rhesus monkeys. Neuronal activity and microexcitability were assessed at 250- to 500-micron intervals and, in some cases, at 25- to 100-micron intervals. The results are based on the functional characterization of 878 putamen and 224 caudate neurons and analysis of the effects of microstimulation at each of these recording sites. Recording/stimulation sites were located between stereotaxic planes A6 and A22 in 81 microelectrode tracks from three monkeys. A total of 443 (50.4%) putamen neurons showed discrete responses to the sensorimotor examination. Of neurons with sensorimotor responses, 232 (52.4%) showed increased rates of discharge in relation to both active and passive movements of specific body parts. An additional 193 (43.6%) cells increased their rates of discharge only during the monkey's active movements of specific body parts. The remaining 18 (4.0%) cells appeared to respond exclusively to passive somatosensory stimulation. The sensorimotor response areas of putamen neurons ranged in size from an entire limb to a single joint. Putamen neurons were somatotopically organized throughout the rostrocaudal extent of the nucleus. Neurons with sensorimotor response areas involving the leg were located in the dorsolateral putamen, those with orofacial representations were located ventromedially, and those with arm representations were located in an intermediate position. Microstimulation evoked discrete movements of individual body parts at 21.6% of the 878 putamen sites. Over 95% (181/190) of the effective sites were located within the central half of the rostrocaudal extent of the putamen, between stereotaxic planes A10 and A17. The pattern of somatotopic organization revealed by microstimulation was the same as that derived from sensorimotor response properties of putamen neurons. Moreover, a close correspondence was observed between the movements evoked from a given SMZ and the functional properties of local neurons. In contrast to the results obtained in the putamen, none of the 224 stimulation sites in the caudate nucleus was microexcitable, and only 17 (7.6%) of the caudate neurons had definable sensorimotor response properties. This is consistent with the view that the primate putamen, by virtue of its anatomic connections with the sensorimotor and premotor cortical fields, is more directly involved in motor functions, whereas the caudate nucleus, by virtue of its connections with cortical "association" areas, is involved in more complex behavioral functions.

Somatosensory input to auditory association cortex in the macaque monkey.

Abstract: We investigated the convergence of somatosensory and auditory inputs in within subregions of macaque auditory cortex. Laminar current source density and multiunit activity profiles were sampled wit...