Patterns of brain electrical activity during facial signs of emotion in 10-month-old infants.

This study examined electroencephalogram (EEG) asymmetries during the presence of discrete facial signs of emotion. Thirty-five 10-month-old infants were tested in a standard stranger- and mother-approach paradigm that included abrief separation from their mother. Infant facial expres-sion was videotaped, and brain electrical ctivity from left and right frontal and parietal regions was recorded. The videotapes were coded with two different discrete facial coding systems. Artifact-free periods of EEG were extracted that were coincident with the expression ofthe emotions of joy, anger, and sadness. The data revealed different patterns of EEG asymmetry depending on the type of facial expression and vocal expression of affect hat was observed. Expressions of joy that involved facial actions of both zygomatic and orbicularis oculi were seen more often in response to mother ap-proach, whereas smiles that did not involve the action of orbiculaxis oculi were seen more often in response to approach of the stranger. The former type of smile was associated with relative l ft frontal activation, whereas the latter type was associated with right frontal activation. Facial expressions of anger and sadness exhibited in the absence of crying were associated with left frontal activation, whereas these same facial expressions during crying were associated with right frontal activation. These data underscore the usefulness of EEG measures of hemispheric activation i differentiating