Effects of spreading cortical depression on cardiac and somatomotor conditioned responses.

Abstract

Spreading cortical depression (s.c.d.), elicited by the direct application of potassium chloride to the dura of the rat brain, has been reported to disturb motor functions and learning. In most previous studies these two effects have been confounded. A conditioned response (c.r.) in heart rate was employed in the present investigation in an attempt to separate the effects of s.c.d. on neural integrative and associative processes from the effects on motor performance.The typical cardiac c.r. was acceleration of heart rate (h.r.) during the conditioning stimulus (c.s.) followed by a secondary acceleration after the c.s. terminated. Spreading cortical depression did not alter the initial cardiac acceleration observed during the c.s. although somatomotor (shuttle box avoidance) c.r.'s were almost completely eliminated by it. The second component of the cardiac c.r., h.r. acceleration after the c.s. had terminated, was not observed during s.c.d. Apparently this second component is more easily affected by s.c.d. because it is not under direct sensory control and is therefore dependent upon memory processes. It is concluded that s.c.d. produces a decrement in spontaneous or operant behavior but has little or no influence on environmentally triggered or involuntary behavior.