Horizontal tuning for faces originates in high-level Fusiform Face Area

Area of Science:

• Neuroscience
• Visual Perception
• Cognitive Science

Background:

• Face perception relies on specialized visual processing.
• Horizontal orientation of facial information is suggested to be privileged.
• The role of early visual cortex (V1) versus high-level face areas (OFA, FFA) in orientation processing is unclear.

Purpose of the Study:

• To investigate the orientation sensitivity of V1, OFA, and FFA to different angles of face information.
• To determine if orientation processing in high-level face areas depends on stimulus properties like orientation.
• To explore the interaction between primary and high-level visual processing.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was used to measure brain activity.
• Participants viewed face images filtered for horizontal, vertical, or oblique orientations.
• Stimuli were presented upright, inverted, and phase-scrambled.

Main Results:

• The FFA showed strongest activation for horizontal information in upright faces, distinguishing it from oblique angles.
• Activation patterns in the right FFA and OFA could differentiate upright from inverted faces based on horizontal information only.
• V1 showed reduced sensitivity to horizontal orientations, possibly due to adaptive whitening, and impaired orientation decoding for meaningless stimuli.

Conclusions:

• Specialized face processing in the OFA and FFA critically depends on encoding horizontal facial cues.
• Primary visual cortex (V1) processing is influenced by higher-order stimulus structure.
• Visual system levels interact to modulate the processing of specific orientation ranges based on stimulus relevance and task demands.