Eye gaze is a fundamental component of human communication. During the first post-natal year, infants rapidly learn that the gaze of others provides socially significant information. In addition, infants are sensitive to several emotional expressions. However, little is known regarding how eye contact influences the way the infant brain processes emotional expressions. We measured 4-month-old infants' brain electric activity to assess neural processing of faces displaying neutral, happy and angry emotional expressions when accompanied by direct and averted eye gaze. The results show that processing of angry facial expressions was influenced by eye gaze. In particular, infants showed enhanced neural processing of angry expressions when these expressions were accompanied by direct eye gaze. These results show that by 4 months of age, the infant detects angry emotional expressions, and the infant brain processes their relevance to the self.

Joint attention develops during the first year of life but little is known about its effects on long-term memory. We investigated whether joint attention modulates long-term memory in 9-month-old infants. Infants were familiarized with visually presented objects in either of two conditions that differed in the degree of joint attention (high versus low). EEG indicators in response to old and novel objects were probed directly after the familiarization phase (immediate recognition), and following a 1-week delay (delayed recognition). In immediate recognition, the amplitude of positive slow-wave activity was modulated by joint attention. In the delayed recognition, the amplitude of the Pb component differentiated between high and low joint attention. In addition, the positive slow-wave amplitude during immediate and delayed recognition correlated with the frequency of infants' looks to the experimenter during familiarization. Under both high-and low-joint-attention conditions, the processing of unfamiliar objects was associated with an enhanced Nc component. Our results show that the degree of joint attention modulates EEG during immediate and delayed recognition. We conclude that joint attention affects long-term memory processing in 9-month-old infants by enhancing the relevance of attended items.

The aim of this study was to investigate neural dynamics of audiovisual temporal fusion processes in 6-month-old infants using event-related brain potentials (ERPs). In a habituation-test paradigm, infants did not show any behavioral signs of discrimination of an audiovisual asynchrony of 200 ms, indicating perceptual fusion. In a subsequent EEG experiment, audiovisual synchronous stimuli and stimuli with a visual delay of 200 ms were presented in random order. In contrast to the behavioral data, brain activity differed significantly between the two conditions. Critically, N1 and P2 latency delays were not observed between synchronous and fused items, contrary to previously observed N1 and P2 latency delays between synchrony and perceived asynchrony. Hence, temporal interaction processes in the infant brain between the two sensory modalities varied as a function of perceptual fusion versus asynchrony perception. The visual recognition components Pb and Nc were modulated prior to sound onset, emphasizing the importance of anticipatory visual events for the prediction of auditory signals. Results suggest mechanisms by which young infants predictively adjust their ongoing neural activity to the temporal synchrony relations to be expected between vision and audition.