Somatosensory system

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

Steady State Responses: Electrophysiological Assessment of Sensory Function in Schizophrenia

Abstract: Persons with schizophrenia experience subjective sensory anomalies and objective deficits on assessment of sensory function. Such deficits could be produced by abnormal signaling in the sensory pathways and sensory cortex or later stage disturbances in cognitive processing of such inputs. Steady state responses (SSRs) provide a noninvasive method to test the integrity of sensory pathways and oscillatory responses in schizophrenia with minimal task demands. SSRs are electrophysiological responses entrained to the frequency and phase of a periodic stimulus. Patients with schizophrenia exhibit pronounced auditory SSR deficits within the gamma frequency range (35-50 Hz) in response to click trains and amplitude-modulated tones. Visual SSR deficits are also observed, most prominently in the alpha and beta frequency ranges (7-30 Hz) in response to high-contrast, high-luminance stimuli. Visual SSR studies that have used the psychophysical properties of a stimulus to target specific visual pathways predominantly report magnocellular-based deficits in those with schizophrenia. Disruption of both auditory and visual SSRs in schizophrenia are consistent with neuropathological and magnetic resonance imaging evidence of anatomic abnormalities affecting the auditory and visual cortices. Computational models suggest that auditory SSR abnormalities at gamma frequencies could be secondary to gamma-aminobutyric acid-mediated or N-methyl-D-aspartic acid dysregulation. The pathophysiological process in schizophrenia encompasses sensory processing that probably contributes to alterations in subsequent encoding and cognitive processing. The developmental evolution of these abnormalities remains to be characterized.

Somatosensory, multisensory, and task-related neurons in cortical area 7b (PF) of unanesthetized monkeys.

Abstract: 1. The goal of this study was to quantitatively characterize the response properties of somatosensory and multisensory neurons in cortical area 7b (or PF) of monkeys that were behaviorally trained ...

The origin of corticospinal projection neurons in rat

Abstract: The distribution of corticospinal projection neurons in adult rats was determined using a retrograde tracing technique. Horseradish peroxidase (HRP) and an emulsifier (Nonidet) were injected into the 5th and 6th segments of the cervical spinal cord. The greatest concentrations of HRP-positive neurons were distributed in area 4 and rostral area 6/8 (motor cortices) and medial area 3 and caudal area 2 (somatosensory cortices). The largest labeled neurons were in areas 4 and 3. HRP-positive neurons were absent or few in regions of motor and somatosensory fields which contained the face representation. Less dense concentrations of retrogradely labeled neurons were also in posterior parietal and association areas 14, 39 and 40, rostral occipital visual areas 18a and 18b, and anterior cingulate and prefrontal areas 24a, 24b, and 32. The topography of the corticospinal pathway was determined by injecting HRP without Nonidet into the cervical, upper thoracic, lower thoracic, or lumbar spinal cord. Although the distribution of labeled neurons decreased with distance down the spinal cord, the size of the corticospinal neurons in each cytoarchitectonic area was not significantly different regardless of where the injection was placed. For example, upper thoracic cord injections retrogradely labeled neurons in each of the regions containing neurons filled by cervical cord injections, however, lumbar injections retrogradely labeled neurons only in caudal areas 4 and 3 and in area 18b. The distribution of corticospinal neurons in rats is similar to the organization of the corticospinal system in higher animals. The origin of corticospinal neurons in occipital and cingulate cortices may be related to visuomotor and visceromotor control.

Single-unit analysis of the human ventral thalamic nuclear group: somatosensory responses.

Abstract: 1. We have studied the functional and somatotopic properties of 531 single mechanoreceptive thalamic neurons in humans undergoing stereotactic surgery for the control of movement disorders and pain. The majority of these somatosensory cells had small receptive fields (RFs) and were activated in a reproducible manner by mechanical stimuli applied to the skin or deep tissues. These neurons, which we termed "lemniscal," could be further classified into those responding to stimulation of cutaneous (76% of lemniscal sensory cells) or deep (24%) structures. 2. The incidence of neurons having cutaneous or mucosal RFs in the perioral region, thumb, and fingers (66%) was much higher than that of neurons having RFs elsewhere on the body. Most of the deep cells were activated by movements of and/or mechanical stimuli delivered to muscles or tendons controlling the elbow, wrist, and fingers. 3. Sequences of cells spanning several millimeters in the parasagittal plane often exhibited overlapping RFs. However, RFs changed markedly for cells separated by the same distances in the mediolateral direction. This suggests that the cutaneous somatotopic representation of each region of the body is organized into relatively thin sheets of cells oriented in the parasagittal plane. 4. By comparing neuronal RFs in different parasagittal planes in thalamus of individual patients we have identified a mediolateral representation of body surface following the sequence from: intraoral structures, face, thumb through fifth finger to palm, with forearm and leg laterally. 5. Along many trajectories in the parasagittal plane the sequence of cells with overlapping RFs was interrupted by another sequence of cells with RFs corresponding to a different body region. The RFs of the intervening sequence characteristically represented body regions known to be located more medially in thalamus (see 3 above). These findings could be explained if the lamellae postulated above were laterally convex. 6. Cells responding to deep stimulation (deep cells) could be further classified into those responding to joint movement (63%), deep pressure (15%), or both (22%). Deep cells were found usually at the anterior-dorsal border and sometimes at the posterior border of the region containing cells responding to cutaneous stimuli. Although there was some overlap in the RFs, deep cells representing wrist were found medial to those representing elbow, and both of these were found medial to cells representing leg.(ABSTRACT TRUNCATED AT 400 WORDS)