Abstract
Since the first study of Otsuka et al. (2007), we have clarified the neural responses to face perception using near-infrared spectroscopy (NIRS) with awake infants (Nakato et al., 2009; Honda et al., 2010; Ichikawa et al., 2010; Nakato et al., 2011; Nakato et al., in press). These studies demonstrated that the right temporal cortex of infant's brain was activated during the presentation of faces and that the neural responses to face processing can be matured by the age of 7 to 8 months. However, it remains unknown how the neural mechanism related to face perception is matured during infancy.
The present study was a longitudinal investigation of the neural responses in infants aged from 3 to 8 months. All participants were measured the hemodynamic responses with NIRS at each age. The experimental stimuli were images of 5 unfamiliar female frontal and profile views as the test stimulus, and those of 5 different vegetables as the base stimulus. Measurement area for brain activity was in the bilateral temporal cortex. The experimental stimuli, the experimental procedure, and the measurement area were identical with those of Nakato et al. (2009).
The result in the presentation of the frontal view showed that the number of the activated channels increased in the right temporal cortex than in the left temporal in all age groups. In addition, the activated channels were mainly located at the posterior and the inferior regions in the right temporal cortex for all age groups. These findings suggest the dominance of the right temporal cortex for face perception would emerge in infants as young as 3 months old. Our longitudinal data implies that the superiority to the neural responses in the right temporal cortex for face perception would develop at an early age during infancy.
This research was supported by a Grant-in-Aid for Scientific Research (20119007 to RK.