Sub-exemplar shape tuning in human face-related areas

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Visual Perception

Background:

• Human face recognition exhibits remarkable selectivity, even for unfamiliar faces.
• The underlying neuronal mechanisms for this high selectivity remain poorly understood.
• Two models, labeled-line and coarse coding, propose different principles for face selectivity.

Purpose of the Study:

• To parametrically examine the shape and selectivity profile of face-related visual areas.
• To investigate whether face selectivity follows a labeled-line or coarse coding principle.
• To explore the relationship between fMRI-adaptation and behavioral face perception.

Main Methods:

• Functional magnetic resonance (fMRI)-adaptation paradigm.
• Presentation of unfamiliar face stimuli morphed across a continuum.
• Parametric examination of neuronal population tuning and selectivity.

Main Results:

• The fusiform face area (FFA) demonstrated high face sensitivity.
• Full recovery from fMRI-adaptation occurred even with subtle facial differences (<35% morph).
• Psychophysical detectability of facial differences correlated with fMRI-adaptation release.

Conclusions:

• Results support the labeled-line model for face recognition.
• High sensitivity to face changes is linked to narrow tuning of neuronal populations.
• fMRI-adaptation closely reflects behavioral face perception and neuronal responses.