[Effect of local superficial cooling of the rat cerebral cortex on unit activity of neurons--hypothetical sources of corticofugal signals].

Unit activity and primary responses (PR) in the cortex area SI and evoked potentials (EP) in the striatum of the rat's brain were recorded during electrocutaneous stimulation of the contralateral forepaw. The cortex in the area of sensory representation of the stimulated extremity was cooled superficially, which promoted an increase of the PR amplitude in the cooling zone. Such cooling facilitated EP to the same stimulus in the striatum. The facilitation was accompanied by changes in time parameters of the neuronal responses in the 5th and 6th layers of the cortex: the latency and spike responses increased, a rhythmic organization of the responses either appeared or (if it was presented before cooling) became more intensive and period of the rhythm got longer. An increase in the spike number and amplitude of PR evoked by cooling in response to applied stimulus was not so high as an increase in the EP amplitude in the striatum and did not completely coincide with it in time. The data obtained permitted suggesting that the effect of corticofugal signals on the sensory reaction in the striatum was rather due to their time organization then to intensity.