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Open Access Highly Accessed Research article

The processing of faces across non-rigid facial transformation develops at 7 month of age: a fNIRS-adaptation study

Megumi Kobayashi12*, Yumiko Otsuka3, So Kanazawa4, Masami K Yamaguchi5 and Ryusuke Kakigi1

Author Affiliations

1 Department of Integrative Physiology, National Institute for Physiological Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki, Aichi 444-8585, Japan

2 Japan Society for the Promotion of Science, 5-3-1, Koujimachi, Chiyoda, Tokyo 102-0083, Japan

3 School of Psychology, The University of Sydney, Sydney, NSW 2006, Australia

4 Department of Psychology, Japan Women’s University, 1-1-1, Nishi-ikuta, Tama, Kawasaki, Kanagawa 214-8565, Japan

5 Department of Psychology, Chuo University, 742-1, Higashi-nakano, Hachioji, Tokyo 192-0393, Japan

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BMC Neuroscience 2014, 15:81  doi:10.1186/1471-2202-15-81

Published: 26 June 2014

Abstract

Background

Using near-infrared spectroscopy (NIRS), our previous neural adaptation studies found that infants’ bilateral temporal regions process facial identity (FiHN 5:153, 2011). In addition, we revealed that size-invariant processing of facial identity develops by 5 months of age (NR 23:984-988, 2012), while view-invariant processing develops around 7 months of age (FiHN 5:153, 2011). The aim in the current study was to examine whether infants’ brains process facial identity across the non-rigid transformation of facial features by using the neural adaptation paradigm. We used NIRS to compare hemodynamic changes in the bilateral temporal areas of 5- to 6-month-olds and 7- to 8-month-olds during presentations of an identical face and of different faces.

Results

We found that (1) the oxyhemoglobin concentration around the T5 and T6 positions increased significantly during the presentation of different faces only in 7- to 8-month-olds and (2) 7- to 8-month-olds, but not 5- to 6-month-olds, showed attenuation in these channels to the presentation of the same face rather than to the presentation of different faces, regardless of non-rigid changes in facial features.

Conclusions

Our results suggest that the processing of facial identity with non-rigid facial transformation develops around 7 months after birth.