The time course of the inversion effect during individual face discrimination

Area of Science:

• Cognitive Neuroscience
• Human Face Perception

Background:

• The face inversion effect (FIE) is a well-established phenomenon where upside-down faces are harder to discriminate.
• Previous research implicated the fusiform face area in the FIE, but the precise timing of its neural basis remained unclear.

Purpose of the Study:

• To determine the time course of the face inversion effect on neural coding of facial identity.
• To investigate when face inversion impacts the brain's ability to distinguish between individual faces.

Main Methods:

• Event-related potentials (ERPs) were recorded during an adaptation paradigm using upright and inverted faces.
• Participants viewed an adapting face followed by a test face of the same or different identity.

Main Results:

• A reduced ERP signal over occipitotemporal sites, indicative of identity adaptation, occurred around 160 ms for upright faces.
• This adaptation effect was delayed by approximately 30 ms and reduced in magnitude for inverted faces.
• The N170 time window showed the earliest neural signature of the FIE.

Conclusions:

• Face inversion impacts the early encoding of facial identity in the occipitotemporal cortex as early as 160 ms after stimulus onset.
• These findings provide indirect evidence for holistic face processing occurring by 160 ms, as inversion disrupts feature integration.