Social perception in the infant brain: gamma oscillatory activity in response to eye gaze

Abstract

Gamma band oscillatory brain activity was measured to examine the neural basis of 4-month-old infants' perception of eye gaze direction. Infants were presented with photographic images of upright and inverted female faces directing their gaze towards them or to the side. Direct gaze compared to averted gaze in upright faces elicited increased early evoked gamma activity at occipital channels indicating enhanced neural processing during the earliest steps of face encoding. Direct gaze also elicited a later induced gamma burst over right prefrontal channels, suggesting that eye contact detection might recruit very similar cortical regions as in adults. An induced gamma burst in response to averted gaze was observed over right posterior regions, which might reflect neural processes associated with shifting spatial attention. Inverted faces did not produce such effects, confirming that the gamma band oscillations observed in response to gaze direction are specific to upright faces. These data demonstrate the use of gamma band oscillations in examining the development of social perception and suggest an early specialization of brain regions known to process eye gaze.

Fig. 1

Evoked (phase-locked) gamma-band (20–60 Hz) EEG responses to averted and direct gaze. The time-frequency plot represents the average amplitude of oscillatory activation measured at the five occipital electrodes marked on the scalp surface maps (right). The rectangles in the time-frequency plots indicate the gamma bursts that were significantly different from baseline. A: Upright face condition, B: Inverted face condition.

Fig. 2

Induced gamma-band (20–90 Hz) EEG responses to averted and direct gaze in the context of an upright face. The time-frequency plots represent the average oscillatory activity measured at electrodes over the right hemisphere marked on the scalp surface maps (right). A: Prefrontal activation, B: Posterior activation.