Somatosensory system

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

Large-scale functional reorganization in adult monkey cortex after peripheral nerve injury.

Abstract: In adult monkeys, peripheral nerve injuries induce dramatic examples of neural plasticity in somatosensory cortex. It has been suggested that a cortical distance limit exists and that the amount of plasticity that is possible after injury is constrained by this limit. We have investigated this possibility by depriving a relatively large expanse of cortex by transecting and ligating both the median and the ulnar nerves to the hand. Electrophysiological recording in cortical areas 3b and 1 in three adult squirrel monkeys no less than 2 months after nerve transection has revealed that cutaneous responsiveness is regained throughout the deprived cortex and that a roughly normal topographic order is reestablished for the reorganized cortex.

Ventrolateral and dorsomedial somatosensory association cortex damage produces distinct somesthetic syndromes in humans

Abstract: Five somatosensory cortices have distinctive somatotopic representations, cytoarchitecture, and connectivity: primary somatosensory cortex (SI), ventrolateral association cortices (SII, SIII, and SIV), and dorsomedial association cortex (supplementary sensory area). Patients with focal lesions of ventrolateral (n = 5) and dorsomedial (n = 6) somatosensory association cortices (SACs) and hemiparetic (n = 8) and neurologically normal control patients (n = 14) underwent detailed somesthetic testing that encompassed basic, intermediate, and complex (tactile object recognition) somesthetic functions. Dorsomedial lesions acutely caused severe disruption of somesthetic processing and severe apraxia when the area of damage was extensive and involved anterior and posterior cortices. In contrast, ventrolateral lesions caused tactile agnosia. Chronically, sensorimotor function following dorsomedial damage improved considerably. Tactile agnosia following ventrolateral damage, however, was readily detectable for years following onset. Functional differences between ventrolateral and dorsomedial SACs may reflect parallel processing in dual somatosensory systems.

Bilateral receptive field neurons and callosal connections in the somatosensory cortex.

Abstract: Earlier studies recording single neuronal activity with bilateral receptive fields in the primary somatosensory cortex of monkeys and cats agreed that the bilateral receptive fields were related exclusively to the body midline and that the ipsilateral information reaches the cortex via callosal connections since they are dense in the cortical region representing the midline structures of the body while practically absent in the regions representing the distal extremities. We recently found a substantial number of neurons with bilateral receptive fields on hand digits, shoulders–arms or legs–feet in the caudalmost part (areas 2 and 5) of the postcentral gyrus in awake Japanese monkeys ( Macaca fuscata ). I review these results, discuss the functional implications of this bilateral representation in the postcentral somatosensory cortex from a behavioural standpoint and give a new interpretation to the midline fusion theory.

Development of order in the rat trigeminal system.

Abstract: The trigeminal system of the rat is characterized by a high degree of order. The pattern of the distribution of vibrissae follicles on the face is replicated at each synaptic station between face and somatosensory cortex (Belford and Killackey, '80). The present study details the development of the trigeminal nerve, its intrinsic organization, and its relationship with its peripheral and central targets. We have observed that at early embryonic ages (E12 and E13) the trigeminal ganglion neurons grow out in straight lines without crossing, and the distance between these neurons and their peripheral and central targets is very short. We have found that fibers reach the periphery before follicle formation is first detectable (E14). At all ages, the trigeminal fibers show a marked tendency to fasciculate. After the development of the pattern of vibrissae follicles on the face, the pattern of fasciculation within the nerve can be clearly related to the rows of vibrissae and the buccal pad. This peripherally related order in the nerve was experimentally verified by injecting horseradish peroxidase into the follicles of individual rows and selectively sectioning portions of the nerve. Further, we provide evidence that the discrete brainstem pattern reflecting vibrissae distribution develops after organization is detectable in the nerve and in a temporal sequence from lateral to medial, which replicates the developmental sequence of vibrissae follicles from ocular to nasal on the face. This sequence is detectable in both the distribution of afferent terminals as measured with succinic dehydrogenase histochemistry and of horseradish peroxidase back-labeled trigeminothalamic relay cells. We interpret our results as suggesting that a number of factors may play a role in the establishment of specific neuronal topographies in the rodent trigeminal system.