Phase relations between carotid pressure and ongoing electrocortical activity.

The behavioral significance of changes in the cardiovascular system has been a major source of controversy in psychophysiology. In view of this, it is surprising that so few studies have examined the relationship between cardiac events and electrocortical (EEG) activity in human subjects. In the present study, this relationship was examined by comparing phase, amplitude and frequency of EEG activity sampled during systolic and diastolic pressure recorded from the carotid artery of resting subjects. The results indicated that rhythmic oscillations of the EEG (particularly those in the alpha range) were time-locked to the carotid pressure wave, and EEG samples taken during systolic and diastolic pressure were distinctly out of phase. In addition, EEG activity sampled during systolic pressure was comprised of slower frequencies than EEG activity sampled during diastolic pressure. It was suggested that the relationship between cardiac events and behavior may be mediated in part by influences of the cardiovascular system on electrocortical rhythms.