Lacey and Lacey hypothesize the presence of cortical inhibitory influences which result from the cardiac events which initiate baroreceptor discharge. The current study provides evidence of cardiac-related cortical inhibitory influences when normal humans are required to attend to environmental input and respond to the information they perceive (fixed foreperiod reaction time task). Averaged EEG waveforms time locked to pulse transit time (PTT) were comprised of slower frequencies than averaged EEG waveforms randomly selected from the same cardiac cycles, and pre-PTT EEG was comprised of slower frequencies than post-PTT EEG in the averaged waveforms. Results of this experiment raise the speculation that cardiovascular events may modulate brain activity with variations in baroreceptor discharge setting constraints on cortical excitability on a beat-to-beat basis.