Electrophysiological correlates of slow periodicity of cardiac rhythm

Regular changes in frequency of cardiac contractions with a period of more than 10 sec were investigated in acute experimentation on immobilized cats. Possible conditions for the origination of decasecond periodicity of cardiac rhythm are examined. Quantitative characteristics are presented. It is shown that spontaneous galvanic skin surges can be grouped in relation to phases of slow oscillations in cardiac rhythm. In some experiments synchronous decasecond oscillations were registered in the frequency of cardiac contractions with change in amplitudes of electrical responses of the hippocampus to stimulation of the amygdaloid complex. The possible functional significance of slow modulation in the frequency of cardiac contractions and the mechanisms responsible for determining the association of observed phenomena are discussed.