[Effect of local cortical exclusion on evoked potentials in the reticular formation occurring in response to...

The evoked potentials in different nuclei of the reticular formation were studied in unanesthetized immobilized rats. Evoked potentials in response to electrical stimulation of the forepaw were registered under normal conditions and during cooling of the somatosensory cortex (S1) in the representation area of one the forepaws. It was found that evoked potentials in the reticular formation change according to the degree of depression of the cortex primary response to the same stimulus during cooling. The peak time of the main negative wave increased from 409-50 ms to 60-80 ms with simultaneous decrease of its amplitude up to complete depression during deep cooling of the cortex. The wave with peak latency 14 ms in the ventral reticular nucleus changed in some manner, but less. Parallel registered evoked potentials in response to the stimulation of another paw were preserved in the same points of the reticular formation without changes or they decreased in their value with preservation of their parameters. Thus, during cooling of the cortex there is a selective change in the reticular formation of that signal, the representation area of which in the cortex is depressed. Obviously, the normal development of both late and early components of reticular evoked potentials to the somatic stimuli requires the inflow of an additional corticofugal signal, formed by transformation of the same signal in the corresponding area of the somatosensory cortex.