Rapid resistance shifts in cat cortex during click-evoked responses.

Abstract

Electrical resistance and click evoked potentials were recorded simultaneously through the same electrodes acutely placed in the auditory cortex of cats. During the course of the evoked potential (EP), the resistance between electrodes changed by about one part in 105, first decreasing, then increasing and finally returning to the baseline in about 100ms. The evoked resistance shifts (ERS) and the EP had similar distributions on the cortical surface, but the EP attained its maximum amplitude at a depth of about 1.0 mm with a waveshape independent of depth. The amplitude of the ERS was more strongly affected than that of the EP by trauma, anesthetic level and temperature changes. Click initiated neural impulses reaching the cortex activate some process yielding the ERS in addition to initiating those events yielding the EP. Data are not yet available to identify the mechanisms involved in generating the ERS, but events associated with permeability changes in neuronal membranes may be responsible.