Abstract
Near-infrared spectroscopy (NIRS) can detect the change in hemodynamic responses on infants' brain. Our previous studies used NIRS to measure the concentration of oxy-Hb and total-Hb on infants' face processing (Otsuka et al., 2007; Nakato et al., in press). These studies indicated that (1) the right hemisphere in the brain was activated when infants looked at the upright faces as compared the inverted faces, and (2) the developmental differences between 5- and 8-month-olds appeared in the presentation on the frontal views and the profile views. The results suggest that the right temporal area is dominant for the perception of faces in infants as well as adults. Recognition of mother's face is important for infants to develop their social communication. Previous studies demonstrated that 3-month-olds could discriminate between their mother' face and stranger' face (Barrera and Maurer, 1981), and the ability of recognition of mother's face is developed by 6 months of the age (de Haan and Nelson, 1997). We investigated the infants' brain activity on their mother's face presentation by NIRS. The participants were seven healthy 6- to 8-month-olds. The stimuli consisted of full color photo images of 5 vegetables, 5 unfamiliar female faces, and mother face. Infants looked each photo image passively as long as they could. Our finding was that the data of total-Hb concentrations in the right temporal regions increased in the presentation of both mother's and unfamiliar faces. This result is consistent with the previous NIRS data (Otsuka et al., 2007; Nakato et al., in press) which showed the right temporal regions are involved in perception of faces in infants. And more interestingly, the concentration of total-Hb was greater activated for mother's face, as compared strangers' faces. This increased hemodynamic response implies the specific mechanism for mother's face recognition in infants' brain.
This research was supported by Kakigi's group of RISTEX (Japan Science and Technology Agency) and a Grant-in-Aid for Scientific Research (18000090) from Japan Society for the Promotion of Science. We thank Aki Tsuruhara, Midori Takashima, Yuka Yamazaki, and Megumi Kobayashi for their help in collecting the data.