Abstract
Three types of direct cortical response, that is, a simple surface-negative potential (N) and two types of positive-negative potential (PNI and PNII), elicited with maximal stimuli in rabbits were analyzed by application of asphyxia, mechanical pressure, hypothermia and paired stimuli. Observation was focused upon slow potentials of the response.
1. The N and the negative waves of both PNI and PNII were almost equally vulnerable to asphyxia. The positive waves of the latter responses were more resistant to asphyxia than the negative potentials.
2. The negative waves of both types of diphasic response were readily affected by mechanical pressure, while the N and the positive wave of the diphasic response resisted mechanical pressure.
3. The negative wave of the diphasic response showed an increase in amplitude over the temperature range from 27° to 21°C. The N and the positive wave of the diphasic response showed only a decrease in amplitude at low temperatures. An increase in duration occurred in all the responses as the temperature was lowered.
4. The N conditioned with a maximal stimulus showed a prolonged phase of depression lasting for about 500 msec. The positive wave of the diphasic response recovered almost completely in about 100 msec. and at intervals longer than 100 msec. it showed often a phase of slight depression. The negative wave began to recover later than the positive one, and showed a phase of supernormality at intervals from 140 to 500 msec.
