Parietal electroencephalogram beta asymmetry and selective attention to angry facial expressions in healthy human subjects.

Research on cerebral affective processing in humans has concentrated on the lateralization of the prefrontal cortex. However, the parietal cortex also seems to play a role in motivation and emotion. In the present study the lateralized role of the parietal cortex in motivated attention was investigated, using an electrophysiological correlate of brain activity (electroencephalogram (EEG)) and a modified Dot probe task, which indexes selective, i.e. avoidant or vigilant attention for angry faces in a spatial display. Twenty-two participants underwent an EEG baseline recording from the F3, F4, P3 and P4 electrode positions, which was followed by the modified Dot probe task. Spectral power in 1 Hz frequency bins were derived for each electrode site and transformed to power density values in the 8-12 Hz (alpha) and 13-30 Hz (beta) frequency range. Log-transformed prefrontal and parietal asymmetries and bias scores for selective attention to angry and happy faces were calculated. Results showed a highly significant relationship between the asymmetry in parietal EEG beta activity and the attentional response to the angry face. Relative more right-sided parietal EEG activity in the beta frequency domain was predictive of a more avoidant response to angry facial expression. This finding suggests that asymmetrical parietal beta activity might be linked to the behavioural dimensions of approach and withdrawal.