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Megumi Kobayashi, Yumiko Otsuka, So Kanazawa, Masami K. Yamaguchi, Ryusuke Kakigi; Do infant represent the facial identity in a viewpoint-invariant manner? The neural adaptation study as measured by near-infrared spectroscopy. Journal of Vision 2011;11(11):445. doi: https://doi.org/10.1167/11.11.445.
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© ARVO (1962-2015); The Authors (2016-present)
Neural adaptation paradigm using fMRI (fMRI-adaptation) is well established to examine the neural basis of the representation of object including face. We have applied the neural adaptation paradigm to NIRS measurement in infants and found that infants' temporal region showed an attenuated response (adaptation) during the repeated presentation of identical face (Kobayashi et al., VSS 2010). In the present study, we extended our findings of neural adaptation as measured by NIRS and showed that the temporal region of infant brain represented the facial identity in a view-invariant manner.
We measured the hemodynamic responses in the bilateral temporal region from twelve 5- to 6-month-old infants and from twelve 7- to 8-month-old infants by using NIRS (Hitachi ETG-4000 system). In each trial, infants were shown sequence of five facial images that gradually change in the viewpoint from left- to right-three-quarter view or vice versa. In the different-identity condition faces changed in the identity as well as in the viewpoint. In the same-identity condition, identity was held constant across the different views. The hemodynamic responses to the faces in both conditions were contrasted against the activation during the baseline period where various images of vegetables were shown. An attenuated response in the same-identity condition compared to the different-identity condition would suggest a viewpoint-invariant representation of facial identity in infants.
We found that the channels around T5 and T6 position in the 7- to 8-month-olds, but not 5- to 6-month-olds, showed a significant increase in the hemodynamic responses during the different-identity condition compared to the object baseline. Further, the hemodynamic responses were significantly attenuated in the same-identity condition compared to that in the different-identity condition. Our results suggest that facial identity is represented in a viewpoint-invariant manner in 7- to 8-month-old infants.
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