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Previous studies investigating correlations in brain activity between isolated pairs have found significantly correlated brain activity in approximately 20% of participant pairs when one member is engaged in a specified task and the other is not. Participants who demonstrate correlated electroencephalogram (EEG) activity might hypothetically be expected to demonstrate correlated heart rate (HR) activity. Research questions explored whether there were correlations between HR, dominant heart rate variability (HRV) frequencies, and prestimulus HR responses among individuals in participant pairs.
Participants included 14 pairs of people who were known to each other, and expressed a sense of familiarity and connectedness. They were physically isolated while HR and EEG measures were simultaneously recorded. One participant, the "sender," was shown a randomly timed video image of the other, interspersed with a blank screen. The other participant, the "receiver," was in an electromagnetically sealed chamber with a video camera focused on his/her face. Senders were asked to use the video image as a reminder of their intentional task of focusing on the sense of connection they felt with their partner. Moment-to-moment HR fluctuations averaged across a group of 3 participant pairs with the highest EEG correlations between senders and receivers (high EEG group) were compared with the same measures in a group of 3 participant pairs who had the smallest absolute EEG correlations (low EEG group).
The high EEG group demonstrated a statistically significant normalized HR correlation, while the low EEG group did not reach statistical significance. Results from power spectral density analysis of the range of frequencies suggested that the high EEG group had a dominant 0.1 Hz range, associated with autonomic nervous system balance, while the low EEG group showed a dominant 0.04 Hz range, associated with higher sympathetic nervous system activation. Participants in the high EEG group also appeared to demonstrate a prestimulus heart rate response that was not evident in the low EEG group. Although participant numbers are small, the possibility that heart rate and heart rate variability patterns are correlated at a distance is a new finding. Prestimulus HR response occurring nonlocally in relation to both time and space is also a new finding.