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Adriano Boremanse, Ernesto Palmero-Soler, Benvenuto Jacob, Bruno Rossion; Robust visual adaptation to face identity over the right occipito-temporal cortex: a steady-state visual potential approach. Journal of Vision 2010;10(7):564. doi: 10.1167/10.7.564.
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© ARVO (1962-2015); The Authors (2016-present)
Over recent years, visual adaptation has been used as a tool to probe the response properties of face-sensitive areas of the visual cortex in neuroimaging studies (e.g., Grill-Spector et al., 2006), as well as in scalp event-related potentials studies which aim to clarify the time-course of sensitivity to facial features and their integration in the human brain (e.g., Jacques et al., 2007). However, this approach is often limited by low signal-to-noise ratio (SNR), as well as the ambiguity of measurement and quantification of adaptation effects. Here we tested the sensitivity of the visual system to face identity adaptation using steady-state visual evoked potentials (SSVEP, Regan, 1966). Twelve subjects were submitted to a 90s sequence of faces presented at a constant rate (3.5Hz or faces/second) while high-density electroencephalogram (EEG) was recorded (128 channels). Fast-Fourier Transform (FFT) of EEG data showed a clear and specific response at the fundamental frequency (3.5Hz) and its harmonics (7Hz, 10.…) over posterior electrode sites. EEG power at 3.5Hz over a few contiguous occipito-temporal channels of the right hemisphere was much larger when face identity changed at that rate than when the same face was repeated throughout the sequence. Significant effects of face identity adaptation were found in every single participant following a few minutes of EEG recording only. This effect was not due to low-level feature adaptation, since it was observed despite large changes of face size, but disappeared for faces presented upside-down. This first demonstration of SSVEP adaptation to face identity in the human brain confirms previous observations using a much simpler, faster and higher SNR approach. It offers a promising tool to study unambiguously and more comfortably the sensitivity to processing of visual features in individual faces in various populations presenting a much lower SNR of their electrical brain responses (e.g., infants, brain-damaged patients).
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