Early cortical specialization for face-to-face communication in human infants
This study examined the brain bases of early human social cognitive abilities. Specifically, we investigated whether cortical regions implicated in adults' perception of facial communication signals are functionally active in early human development. Four-month-old infants watched two kinds of dynamic scenarios in which a face either established mutual gaze or averted its gaze, both of which were followed by an eyebrow raise with accompanying smile. Haemodynamic responses were measured by near-infrared spectroscopy, permitting spatial localization of brain activation (experiment 1), and gamma-band oscillatory brain activity was analysed from electroencephalography to provide temporal information about the underlying cortical processes (experiment 2). The results revealed that perceiving facial communication signals activates areas in the infant temporal and prefrontal cortex that correspond to the brain regions implicated in these processes in adults. In addition, mutual gaze itself, and the eyebrow raise with accompanying smile in the context of mutual gaze, produce similar cortical activations. This pattern of results suggests an early specialization of the cortical network involved in the perception of facial communication cues, which is essential for infants' interactions with, and learning from, others.
Near infrared spectroscopy reveals neural activation during face perception in infants and adults
We used near infrared spectroscopy to measure changes in cerebral oxygenation in both human infants and adults as they viewed images of faces or control “visual noise” stimuli. At an occipital site, adults showed a significant increase in oxyhaemoglobin and a contrasting pattern of results was observed in infants. While the same general difference between the processing of the two stimuli was observed, a larger decrease in oxyhemoglobin concentration in response to faces than to visual noise was found in infants. These results demonstrate that near infrared spectroscopy can detect differences in stimulus processing induced by a complex visual stimulus in both infants and adults.