An analysis of some correlates of steady potentials in mammalian cerebral cortex

Abstract

An analysis of some aspects of steady potential (SP) phenomena, especially in relation to some earlier experiments on SP correlates of hyperventilation and of epileptiform potentials during spreading depression is presented. The findings by others of SP shift with asphyxia, anoxia, cerebral ischemia and excess CO 2 do not appear to explain the positive cortical SP shift during brief hyperventilation. While the polarity (and amplitude) and the incidence of epileptiform (and other) potentials show some correlations with intrinsic SP level and polarity across cell layers, such as the cerebral cortex, these correlations are far from consistent in degree or direction in all different conditions or neural tissues. On the other hand, the correlations of these functions with changes in SP that are induced by polarizing currents applied across such cell layers are highly consistent. Reasons are offered for considering this latter relationship to be a more significant index of the role of SP in these functions. In discussing the possible mechanisms that may produce the observed synchronization or coupling of epileptiform potentials at different points on the cortex, it is suggested that the local process which permits or facilitates the development of such potentials should be considered as one that is potentially distinct from more purely synchronizing mechanisms.