title: Prefrontal Function Engaging in External-Focused Attention in 5- to 6-Month-Old Infants: A Suggestion for Default Mode Network.
abstract: The present study used functional near-infrared spectroscopy (fNIRS) to measure 5- to 6-month-old infants' hemodynamic response in the prefrontal cortex (PFC) to visual stimuli differing in saliency and social value. Nineteen Japanese 5- to 6-month-old infants watched video clips of Peek-a-Boo (social signal) performed by an anime character (AC) or a human, and hand movements without social signal performed by an AC. The PFC activity of infants was measured by 22-channel fNIRS, while behaviors including looking time were recorded simultaneously. NIRS data showed that infants' hemodynamic responses in the PFC generally decreased due to these stimuli, and the decrease was most prominent in the frontopolar (FP), covering medial PFC (MPFC), when infants were viewing Peek-a-Boo performed by an AC. Moreover, the decrease was more pronounced in the dorsolateral PFC (DLPFC) when infants were viewing Peek-a-Boo performed by an AC than by a human. Accordingly, behavioral data revealed significantly longer looking times when Peek-a-Boo was performed by an AC than by a human. No significant difference between Peek-a-Boo and non-Peek-a-Boo conditions was observed in either measure. These findings indicate that infants at this age may prefer stimuli with more salient features, which may be more effective in attracting their attentions. In conjunction with our previous findings on responses to self-name calling in infants of similar age, we hypothesize that the dynamic function of the MPFC and its vicinity (as part of default mode network (DMN): enhanced by self-focused stimuli, attenuated by externally focused stimuli), which is consistently observed in adults, may have already emerged in 5- to 6-month-old infants.
authors.affiliation: Department of Psychology, Faculty of Letters, Keio UniversityYokohama, Japan; Center for Life-Span Development of Communication Skills, Keio UniversityYokohama, Japan.
authors.forename: Mingdi
authors.initials: M
authors.lastname: Xu
authors.affiliation: Department of Psychology, Faculty of Letters, Keio UniversityYokohama, Japan; Center for Life-Span Development of Communication Skills, Keio UniversityYokohama, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Hoshino
authors.affiliation: Department of Psychology, Faculty of Letters, Keio UniversityYokohama, Japan; Global Centre for Advanced Research on Logic and Sensibility, Keio UniversityTokyo, Japan.
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Yatabe
authors.affiliation: Graduate School of Human Relations, Keio University Tokyo, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Matsuda
authors.affiliation: Center for Exploratory Research, Research and Development Group, Hitachi, Ltd. Hatoyama, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sato
authors.affiliation: Center for Exploratory Research, Research and Development Group, Hitachi, Ltd. Hatoyama, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Maki
authors.affiliation: Brain Science Business Unit, Innovation Promotion Division, Hitachi High-Technologies Corporation Tokyo, Japan.
authors.forename: Mina
authors.initials: M
authors.lastname: Yoshimura
authors.affiliation: Department of Psychology, Faculty of Letters, Keio UniversityYokohama, Japan; Center for Life-Span Development of Communication Skills, Keio UniversityYokohama, Japan; Global Centre for Advanced Research on Logic and Sensibility, Keio UniversityTokyo, Japan.
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Minagawa
keywords: attention; default mode network (DMN); fNIRS; infant; prefrontal cortex (PFC)