Tactile discrimination task not disturbed by thalamic stimulation.
The major pathway of human somatosensation passes through the ventrocaudal nucleus (Vc) of the thalamus. We tested the effect of direct electrical stimulation of the Vc on tactile discrimination in 5 Parkinson patients undergoing stereotactic thalamotomy. Raised gratings with lines 3, 4, or 6 mm apart were used. Patients had to actively touch test patterns placed in the hand contralateral to the thalamus under operation and compare it with a reference 3-mm grating held continuously in their other hand. Their performance was best for 6-mm, followed by 3-mm and then by 4-mm patterns regardless of electrical stimulation. Under Vc stimulation, patients recognized the 4-mm gratings slightly better. This can be explained either by the nature of thalamocortical interaction, which makes it resistant to external noise, or by the involvement of other pathways that circumvent the effect of thalamic stimulation.
Abbassian
A H
AH
Department of Epistemology and Cognitive Sciences, School of Intelligent Systems, Institute for Studies in Theoretical Physics and Mathematics, Tehran, Iran. abbnet@mail.ipm.ir
Shahzadi
S
S
Afraz
S R
SR
Fazl
A
A
Moradi
F
F
D000328:Adult; D016009:Chi-Square Distribution; D004192:Discrimination, Psychological / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000601:surgery; D013238:Stereotaxic Techniques; D013788:Thalamus / Q000502:physiology*; D014110:Touch / Q000502:physiology*