Robust sensitivity to facial identity in the right human occipito-temporal cortex as revealed by steady-state visual-evoked potentials.

Understanding how the human brain discriminates complex visual patterns, such as individual faces, is an important issue in Vision Science. Here we tested sensitivity to individual faces using steady-state visual-evoked potentials (SSVEPs). Twelve participants were presented with 90-s sequences of faces appearing at a constant rate (3.5 faces/s) while high-density electroencephalogram (EEG) was recorded. Fast Fourier Transform (FFT) of EEG showed a large response at the fundamental stimulation frequency (3.5 Hz) over posterior electrode sites. This response was much larger when the face identity changed at that rate (different faces) than when an identical face was repeated. The reduction of signal in the identical face condition was not due to low-level feature adaptation, since it was observed despite changes of stimulus size, and was localized specifically over the right lateral occipital cortex. Moreover, the difference between conditions disappeared when faces were inverted. This first observation of habituation of the SSVEP to repeated face identity in the human brain provides further evidence for face individualization in the right occipito-temporal cortex by means of a simple, fast, and high signal-to-noise approach. Most importantly, it offers a promising tool to study the sensitivity to visual features of individual faces and objects in the human brain.