Heartbeat evoked potentials (HEP): topography and influence of cardiac awareness and focus of attention.

Heartbeat evoked potentials (HEP) were recorded from good and poor heartbeat perceivers under two conditions differing in focus of attention. Under the first condition (ATT), subjects were instructed to count their heartbeats. Under the second condition (DIS), subjects were distracted from their heartbeats by having them count external tones. Electrical brain activity was recorded from 19 electrodes. EEG epochs were triggered by the R wave of the EKG. Analyses of variance yielded a significant difference for focus of attention in HEP amplitudes at central electrodes (Cz, C3, and C4) in the latency range 350-550 msec post R wave. No significant differences occurred between good and poor perceivers. The interaction between the Group and Condition factors was significant at F4, C4 and T6. The potential map of good perceivers showed a fronto-temporal positivity, which was reduced in poor perceivers. Our data suggest that paying attention to an internal event such as the heartbeat can modify the cortical evoked response associated with that event.