title: Contrast reversal of the eyes impairs infants' face processing: a near-infrared spectroscopic study.
abstract: Human can easily detect other's eyes and gaze from early in life. Such sensitivity is supported by the contrast polarity of human eyes, which have a white sclera contrasting with the darker colored iris (Kobayashi & Kohshima, (1997). Nature, 387, 767-768; Kobayashi & Kohshima, (2001). Journal of Human Evolution, 40, 419-435). Recent studies suggest that the contrast polarity around the eyes plays an important role in infants' face processing. Newborns preferred upright face images to inverted ones in contrast-preserved faces, but not in contrast-reversed faces (Farroni et al., (2005). Proceedings of National Academy of Sciences of the United States of America, 102, p. 17245-17250). Seven- to 8-month-old infants failed to discriminate between faces when the contrast polarity of eyes was reversed (Otsuka et al., (2013). Journal of Experimental Child Psychology, 115, 598-606). Neuroimaging study with adults revealed that full-negative faces induced less activation in the right fusiform gyrus than either full-positive faces or negative faces with contrast-preserved eyes (Gilad et al., (2009). Proceedings of National Academy of Sciences of the United States of America, 106, p. 5353-5358). In the present study, we investigated whether contrast-reversed eyes diminish infants' brain activity related to face processing. We measured hemodynamic responses in the bilateral temporal area of 5- to 6-month-old infants. Their hemodynamic responses to faces with positive eyes and those with negative eyes were compared against the baseline activation during the presentation of object images. We found that the presentation of faces with positive eyes increased the concentration of oxy-Hb in the right temporal area and those of total-Hb in the bilateral temporal areas. No such change occurred for faces with negative eyes. Our results suggest the importance of contrast polarity of the eyes in the face-selective neural responses from early development.
authors.affiliation: Department of Psychology, Chuo University, Hachioji, Tokyo 192-0393, Japan; Research and Development Initiative, Chuo University, Chiyoda, Tokyo 112-8551, Japan; Japan Society for the Promotion of Sciences, Chiyoda, Tokyo 102-8471, Japan. Electronic address: ichihiro@tamacc.chuo-u.ac.jp.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ichikawa
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Otsuka
authors.forename: So
authors.initials: S
authors.lastname: Kanazawa
authors.forename: Masami K
authors.initials: MK
authors.lastname: Yamaguchi
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kakigi
mesh_terms: D015350:Contrast Sensitivity / Q000502:physiology*; D005128:Eye Diseases / Q000175:diagnosis* / Q000503:physiopathology*; D005145:Face; D005260:Female; D006454:Hemoglobins; D006801:Humans; D007223:Infant; D008297:Male; D010108:Oxyhemoglobins / Q000378:metabolism; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D019265:Spectroscopy, Near-Infrared; D013702:Temporal Lobe / Q000378:metabolism; D013997:Time Factors
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin
keywords: Contrast polarity; Eyes; Infants; NIRS; Near-infrared spectroscopy; Negation