[Brain activity during face processing in infants]

It has been shown that infants prefer looking at faces to looking at equally complex, non-facial visual stimuli. Many behavioral studies have illustrated that infants process faces differently from other objects. In agreement with these findings, recent neuropsychological studies provide evidence indicating face-specific brain activity in infants. The present paper reviews the psychological studies investigating the infant's brain activity for faces, using brain-imaging techniques, such as near-infrared spectroscopy (NIRS). Near-infrared spectroscopy (NIRS) is a new and increasingly used brain imaging technique, which is particularly suitable for use with young infants. Studies using NIRS have reported face-specific brain activation in the temporal area. When 5- to 8-month-old infants view upright faces, a significant increase in oxy-hemoglobin (oxy-Hb) was observed in the right temporal area. Such face-specific brain activity in infants becomes view-invariant at the age of 8 months, but not at 5 months. More recently, an NIRS study employing the adaptation paradigm revealed that the identity of faces was processed in the bilateral temporal area. Additionally, face-specific brain activity was observed for not only static face images, but also for dynamic facial point-light displays. We found that concentrations of oxy-Hb increased in the right temporal area during the presentation of an upright facial point-light display compared to that during the baseline period. Finally, we discuss the possibility of developmental changes in brain activity from infancy to childhood and adolescence as well as in atypical development.