Correlations between brain electrical activities of two spatially separated human subjects

Six channels electroencephalogram (EEG) were recorded simultaneously from pairs of separated human subjects in two acoustically and electromagnetically shielded rooms. While brain electric responses to visual pattern-reversal stimuli were elicited in one subject, the other subject relaxed without stimulation. EEGs of both subjects were averaged at times of stimulus onset, effective voltage of the averaged signals was computed within a running window, and expressed as ratio (Q) to the effective voltage of averaged EEG signal from non-stimulation periods. These ratios in non-stimulated subjects at the latency of the maximum response in stimulated subjects were analysed. Significant departures of Q ratios from reference distributions, based on baseline EEG in non-stimulation periods, were found in most non-stimulated subjects. The results indicate that correlations between brain activities of two separated subjects may occur, although no biophysical mechanism is known. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.