| Abstract: | In experiments on immobilized unanesthetized rabbits selective automatic reinforcement of certain ranges of short and long interspike intervals in spontaneous unit activity recorded from single cortical units was given by means of a nociceptive stimulus. Analysis of postinterval histograms showed that the total number of intervals reinforceable by nociceptive stimuli is reduced as a result of the consequent reorganization of the firing pattern. If short intervals are reinforced the mean firing rate is reduced and the probability of appearance of long intervals immediately after the short reinforcements is increased. After reinforcement of long intervals the mean firing rate was increased in one group of cortical neurons, with a corresponding decrease in the total number of long intervals. In the other group of cells a decrease in the number of long intervals was accompanied by a decrease in the mean firing rate of the cells. It is postulated that reorganization of the firing pattern is determined by the level of synchronization of ascending activating influences and by their summation with phases of excitation and inhibition in reciprocally interacting neuron populations.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 4, pp. 339–348, July–August, 1972. |
