Activation of the primary motor cortex by somatosensory stimulation in adult rats is mediated mainly by associational connections from the somatosensory cortex

Farkas, Tamás and Kis, Zsolt and Toldi, József and Wolff, Joachim R. (1999) Activation of the primary motor cortex by somatosensory stimulation in adult rats is mediated mainly by associational connections from the somatosensory cortex. Neuroscience, 90 (2). pp. 353-361. ISSN 0306-4522

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Abstract

In anaesthetized adult rats, facial nerve injury causes a disinhibition of the interhemispheric connections between homotopic representation fields in the primary motor cortex with a latency of 4 min (Toldi et al., 1996, Neurosci. Lett. 203, 179-182). One possible explanation for the induction of such rapid changes is an alteration of the somatosensory input to the motor cortex. To test this hypothesis, unit activity in primary motor cortex was recorded during electrical stimulation of trigeminal afferents in the contralateral whisker-pad. About one-third of all recorded primary motor cortex neurons responded with latencies shorter than in the ventrolateral and posterior nuclei of the thalamus. Responses failed at stimulation frequencies greater than or equal to 10 Hz and after elimination or inactivation of the somatosensory cortex. Within primary motor cortex, the activatable neurons displayed a bilaminar distribution and were identified as pyramidal neurons by neurobiotin labelling.

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