Abstract
Recent adult functional magnetic resonance imaging (fMRI) studies reported that face-sensitive cortical areas showed attenuated responses to the repeated presentation of an identical facial image compared to the presentation of different facial images (fMRI-adaptation effects: e.g., Andrews and Ewbank, 2004). Building upon this finding, the current study, employing the adaptation paradigm, used near-infrared spectroscopy (NIRS) to explore the neural basis of face processing in infants. In Experiment 1, we compared hemodynamic responses in the bilateral temporal regions during the repeated presentation of the same face (the same-face condition) and the sequential presentation of different faces (the different-face condition). We found that (1) hemodynamic responses in the channels around the T5 and T6 regions increased during the presentation of different faces compared to those during the presentation of different objects; and that (2) these channels showed significantly lower response in the same-face condition than in the different-face condition, demonstrating the neural adaptation effect in 5- to 8-month-olds as measured by NIRS. In Experiment 2, when faces in both the same-face and different-face conditions were changed in viewpoint, lower hemodynamic responses in the same-face condition were found in 7- to 8-month-olds but not in 5- to 6-month-olds. Our results suggest that faces are represented in a viewpoint-invariant manner in 7- and 8-month-old infants.
Highlights
Near-infrared spectroscopy (NIRS) is a non-invasive neuroimaging method that measures changes in concentrations of oxyhemoglobin, deoxyhemoglobin, and totalhemoglobin
We obtained hemodynamic responses from 12 infants who looked at the stimuli for more than three trials in both the same-face and different-face conditions
We obtained hemodynamic responses from 12 5- to 6-monthold and 12 7- to 8-month-old infants who looked at the stimuli for more than three trials in both the same-face and different-face conditions
Summary
Near-infrared spectroscopy (NIRS) is a non-invasive neuroimaging method that measures changes in concentrations of oxyhemoglobin (oxy-Hb), deoxyhemoglobin (deoxy-Hb), and totalhemoglobin (total-Hb; Villringer and Chance, 1997; Hoshi et al, 2001). Previous studies conducting simultaneously measurement of NIRS and functional magnetic resonance imaging (fMRI) during the simple motor task revealed that there is a strong correlation between signals measured with NIRS and fMRI (Toronov et al, 2001, 2007; Strangman et al, 2002). In the recent study, Cui et al (2011) showed such correlation between NIRS and fMRI signals even for cognitive task. NIRS is reliable method to measure the brain activation. Unlike fMRI and positron emission tomography (PET), NIRS can record even if the subjects’ body and brain do not remain in fixed position. NIRS makes it possible to measure the brain activities of infants while they are awake
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