Brain oscillations differentiate the picture of one's own grandmother.

The present report introduces, as a first study, the concept and methods of oscillatory brain dynamics to analyze well-known (familiar) and unfamiliar face processing in the 800 ms following a face presentation. We analyzed event-related oscillations in young, healthy subjects (N=26) by using three types of stimulation: (1) a simple light signal, (2) the picture of the face of an anonymous elderly lady and (3) the picture of the subjects' own grandmother. We found a number of significant peak to peak amplitude measures in all frequency bands in the time period of 0-500 ms, allowing a differentiation between perception of the subjects' own grandmother, the unknown elderly face and the light stimulation. The results showed increased event-related oscillatory responses elicited by the unknown face compared to the known grandmother a) in the theta responses (4-8 Hz) at T(6) (46%), b) in the gamma (28-48 Hz) responses at C(z) (22%) and C(3) (38%) and c) in the beta responses at F(4) (46%), C(z) (47%) and P(3) (105%). In contrast, the subjects' own grandmother elicited 20% increased fast theta (6-8 Hz) oscillations at F(4) compared to the unknown face. Delta responses dissociated face from simple light processing, as reflected in the observation of approx. 50% higher amplitudes at the occipital compared to the frontal locations during face perception. We conclude that the described multiple brain oscillations clearly differentiate the known and unknown faces with varied degrees of selective-responsiveness in a short time window between 0 and 800 ms. Furthermore, the results are in conceptual accordance with the "selectively distributed processing" hypothesis.