Electrical activity of cerebral cortex in the cat during closure of simple form of a temporary connection

The closure of a simple form of temporary connection of the summation reflex type was studied by combining light flashes with subthreshold electrical stimulation of the cortical site of representation of the right forelimb in the cat. Summation, i.e., forepaw flexion, occurred both when two subthreshold stimuli were applied simultaneously and when there was a short (tens of milliseconds) interval between the stimuli. The sequence of stimulus presentation (current + light or light + current) was immaterial. During summation there occurred changes in the configuration of the direct cortical response recorded at a distance of 2-3 mm from the stimulation site. Neurophysiological analysis of the electrical correlates of establishment of the simple form of temporary connection (study of neuronal activity, the effect of some pharmacological agents, testing by paired stimuli) suggests that the mechanism of closure under study is dependent on induction relations manifested by the enhancement of phasic changes in excitatory 2nd inhibitory processes. When the current + light combination was used, two phases of neural activity were characteristic: inhibition and a subsequent rebound. With the light + current combination, these phases were preceded by a phase of primary excitation.