Analysis of interaction between evoked potentials to stimuli of different modalities in the auditory, sensomotor, and visual cortex in cats.

Abstract

1. By the use of a method of paired stimulation of different modalities (clicks and electrodermal stimulation of the orbicularis muscle), acting in two different orders — “clicks + EDS” and “EDS + clicks” — differences were found in the recovery cycles of global EPs recorded simultaneously in the auditory, sensomotor, and visual areas of the neocortex. In the auditory cortex, in response to stimulation applied in the order “clicks + EDS” and with short intervals between stimuli (20–70 msec) in the pair, a stage of complete blockade of EPs to testing EDS is observed; if stimulation is in the opposite order (“EDS + clicks”) the amplitude of EPs to testing clicks is independent of the previous action of EDS and commensurate with the amplitude of EPs to isolated clicks. In the sensomotor and visual areas of the cortex two EPs are recorded, one to clicks and one to EDS, during application of paired stimuli both in the “clicks + EDS” and “EDS + clicks” order. 2. Changes in EPs to paired stimulation described above characterized the functional organization of inputs to the cortical areas tested for clicks and EDS: In the auditory area functioning of the input for the inadequate nociceptive stimulus is wholly dependent on the presence or absence of previous afferentation from the adequate acoustic stimulus, whereas activation of the input for the adequate stimulus is relatively independent; in the sensomotor and visual areas functioning of the inputs for both stimuli is relatively independent.