[Neocortex neuronal reactions induced by substantia innominata stimulation in cats]

Neuronal impulse activity in the sensorimotor cortex after Substantia Innominata (SI) stimulation has been studied in cats during conditioned placing with food reinforcement. SI stimulation was delivered 1 or 3 seconds before the conditioned sound stimuli. The results of the investigation show that SI stimulation does not change sensorimotor cortex impulse activity but at the same time it inhibits the background activity. Reactions of 32% (after 1 s) and 33% (after 3 s) of the somatosensory cortex neurones were increased to conditioned stimuli and conditioned movement after preliminary SI stimulation. The appearance of impulse responses in some neurones which showed no initial reactions to conditioned stimuli was caused by SI stimulation. Preliminary SI stimulation may cause not only excitatory but also inhibitory effect on somatosensory cortical neurones. In case of 1 s interval between SI stimulation and conditioned stimuli presentation there were only 6% of cells with such inhibition, but in case of 3 s interval there were 33% of such reactions. SI stimulation shortened the latencies of the conditioned movement 2-3 times. Modulatory influence of acetylcholine from SI neurones to neocortical activity is discussed.