Abstract
The ability to extract the identity of faces across substantial variations in angular head orientation is critical for face recognition, yet the underlying neural mechanism is not well understood. Using a validated paradigm with fast periodic visual stimulation in electroencephalography (EEG; Liu-Shuang, Norcia, & Rossion, 2014, Neuropsychologia), we investigated the tuning function of face identity perception in 20 observers across 7 ranges of viewpoint variations: 0° (no change), ±15°, ±30°, ±45°, ±60°, ±75°, ±90°. In each 60-s stimulation sequence, images of one single face identity, randomly chosen from our stimulus set, were displayed successively at a rapid rate of F = 6 Hz (6 images/s), interleaved with different face identities at fixed intervals of every 7th face (F/7 Hz = 0.86 Hz). Critically, at every stimulation cycle, faces varied randomly both in viewpoint within a predefined range (e.g. in the ±45° condition, faces were shown between -45° and +45° in steps of 5°) and in size between 80% and 120%. Periodic EEG responses at 6 Hz captured general visual processing of the face stimuli, while those at 0.86 Hz and harmonics captured face individualisation. All observers showed significant face individualisation responses, peaking over bilateral occipito-temporal regions. These responses decreased linearly with increasing viewpoint variations (responses decreased by > 50% between 0° and ±90° conditions), suggesting reduced face identity discrimination. Analysing the face individualisation response in the time-domain revealed a dissociation between an early (~200–300 ms) view-sensitive response and a later (~300–600 ms) view-invariant response, both peaking over the same bilateral occipito-temporal regions. These findings suggest two separate view-based face recognition processes, where an initial reduced ability to discriminate face identities due to viewpoint variations is complemented partly by a later, high-level view-invariant process.
Meeting abstract presented at VSS 2017