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Biphasic reorganization of somatotopy in the primary motor cortex follows facial nerve lesions in adult rats.

Authors
Type
Published Article
Journal
Neuroscience Letters
0304-3940
Publisher
Elsevier
Publication Date
Volume
203
Issue
3
Pages
179–182
Identifiers
PMID: 8742022
Source
Medline

Abstract

Effects of facial nerve transection were studied on muscle responses evoked by electrical stimulation in the primary motor cortex (MI) of adult rats. In intact animals, activated muscles varied according to the somatotopic representation map, and responses were restricted to the contralateral side. Unilateral transection of the facial nerve extinguished contralateral vibrissal responses, while ipsilateral vibrissae began to respond within 4 min. This abnormal response (primary change) was transient and gradually disappeared within hours to days. Instead, contralateral movements of forepaw and eye/eyelid muscles could be evoked from increasing portions of the former vibrissal field (secondary change), in which many points became unresponsive. After 4 days, the former vibrissal field had shrunk to a small central part, where ipsilateral vibrissae responsiveness remained. The secondary modification was stable for at least 2 weeks. Since the primary change is rapid, transient and may be mimicked by picrotoxin, it may be based on disinhibition of commissural connections, while the secondary change is longlasting and therefore may include some form of reorganization of associational synapses.

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