[Effect of stimulus intensity on neuronal reactions of the frontal region of the cat cortex].

The pulse activity of neurons of the cortex frontal region was studied in cat under conditions of acute experiment under chloralose (70 mg/kg) by means of extracellular recording. The stimulus intensity varied in the near threshold range (15-16 db over the threshold of a summarized evoked potentional). A comparative analysis of the neuronal responses of specific (field S1) and nonspecific projections demonstrated similar in principle reconstructions with an increase in the stimulus intensity: a decrease in the latent period, rise in total frequency and phase of the discharge, an increase in the response probability. However, a relatively stable level of the latent period and the response probability were achieved for neurons of specific projection at the stimulus intensity equal 3-5 of threshold units, and for neurons of nonspecific projections at the stimulus intensity equal to 10-15 of threshold units. All sensory projections in the frontal cortex are formed by two inputs: short-latent low-threshold and long-latent high-threshold. Analysis of modal conditioned differences in threshold sensitivity and duration of the latent period of the polysensory neurons responses gives reason to assume the convergence of different modal signals right on cortical neurons.