Hypothermia and Electrical Activity of Cerebral Cortex

Abstract

Changes in cortical excitability incident to brain cooling have been examined on several occasions, utilizing spontaneous ECG,^1-3 evoked response^4-6 or cortical threshold for seizure discharge.^7-9 However, the effects of cold upon slower components of cortical potentials have not been studied, owing largely, we believe, to the general use of capacity coupled amplifiers which attenuate slow frequencies. In earlier studies from this laboratory direct current (d.c.) recording has been utilized, permitting accurate recording of slow changes in cortical potential. Evoked potentials studied in this fashion have been (1) the direct cortical response recorded from a cortical site immediately adjoining a surface-stimulating electrode; (2) recruiting response to repetitive stimulation of the midline thalamus; (3) evoked response of visual cortex activated by brief shocks to optic nerve or light flashes to retina.^10-13 Graphically, the usual short-latency, fast component of evoked response is followed by a slower component of longer