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Psychophysical elements of place and modality specificity in the thalamic somatic sensory nucleus (ventral caudal, vc) of awake humans.

Abstract：

:Discrete anatomic structures in the monkey somatic sensory thalamus may segregate input arising from different peripheral receptors and from different parts of the body. It has been proposed that these structures serve as components of modality- and place-specific pathways from the periphery to the cortex. We now test this hypothesis by examining the modality- and place-specific segregation of sensations at sites where microstimulation (microA currents) within the region of ventral caudal (Vc; human principal somatic sensory nucleus) evokes somatic sensations. Microstimulation was delivered in an ascending staircase protocol consisting of different numbers of pulses (4-100) presented at different frequencies (10-200 Hz) during awake thalamic surgery for movement disorders. The results demonstrate that the part of the body where microstimulation evoked sensation (projected field) and the descriptors of nonpainful sensations were usually uniform across the staircase. These results strongly support the existence of psychophysical elements of place and modality specificity in the Vc thalamus. The proportion of sites at which the sensation included more than one part of the body almost always stayed constant over current intervals (plateaus) of 10 microA. Similar plateaus were not found for sites with more than one descriptor, suggesting that elements of modality-specificity are smaller than and located within those for place-specificity. The intensity of sensations varied with the number of stimulation pulses for mechanical/tingle and cool sensations. The results provide strong evidence for psychophysically defined elements that are responsible for modality specificity of nonpainful sensations, place specificity, and intensity coding of somatic sensation in the human thalamus.

journal_name

J Neurophysiol

journal_title

Journal of neurophysiology

authors

Patel S,Ohara S,Dougherty PM,Gracely RH,Lenz FA

doi

10.1152/jn.00756.2005

subject

Has Abstract

pub_date

2006-02-01 00:00:00

pages

646-59

issue

eissn

0022-3077

issn

1522-1598

pii

00756.2005

journal_volume

pub_type

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Psychophysical elements of place and modality specificity in the thalamic somatic sensory nucleus (ventral caudal, vc) of awake humans.