[Changes in the synaptic apparatus of the associative area (field 5b) of the cat cerebral cortex following destruction of the lateral posterior thalamic nucleus].

Quantity of normal and degenerating axonal terminals (AT) in area 5b of the associative cortex of cat was studied 2, 4 and 30 days after the electrolytic lesion of the thalamic nucleus lateralis posterior (LP). It was established that the quantity of degenerating AT in area 5b two and four days after the LP lesion was 7.4 and 7.2%, respectively. Four days after LP lesions the quantity of normal AT diminished by 16.4%, which was a direct result of excitatory AT degeneration. 40% of vanished AT formed synapses on dendrites and 60%--on spines. The quantity of axosomatic synapses in area 5b did not change after the LP lesion. Consequently, neurons in area 5b receive direct excitatory, predominantly axospinal input from LP. 30 days after LP lesions the total number of AT in area 5b was lower by 100% as compared with the control. Results and peculiarities of reinnervation in area 5b after degeneration of thalamocortical synapses are discussed.