Lower-level stimulus features strongly influence responses in the fusiform face area

Area of Science:

• Neuroscience
• Visual Perception
• Cognitive Neuroscience

Background:

• The fusiform face area (FFA) is known for selective responses to faces.
• The influence of lower-order visual properties on FFA function is not fully understood.

Purpose of the Study:

• To investigate how lower-level visual stimulus dimensions affect FFA responses.
• To determine if FFA responses are invariant to changes in size, position, contrast, and viewpoint.

Main Methods:

• Used functional Magnetic Resonance Imaging (fMRI) to measure FFA activity.
• Presented standardized face stimuli with independent variations in size, position, contrast, and viewpoint.
• Correlated FFA responses with responses in V1 (primary visual cortex).

Main Results:

• FFA responses were significantly influenced by variations in size, position, contrast, and viewpoint.
• FFA response functions strongly correlated with V1 responses (r = 0.95-0.99).
• FFA responses could be modeled by combining local contrast and cortical magnification factor, similar to V1.
• Lower-level variations sometimes dominated FFA responses and could even shift selectivity from faces to objects.

Conclusions:

• FFA responses are not invariant to lower-level visual properties.
• A substantial portion of FFA activity reflects lower-level visual processing.
• Understanding these lower-level influences is crucial for comprehending face perception.