Individual variation in the functional lateralization of human ventral temporal cortex: Local competition and...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Human Brain Imaging

Background:

• The ventral temporal cortex (VTC) is crucial for high-level vision, exhibiting functional lateralization for word and face processing.
• Word processing is typically left-lateralized, while face processing is right-lateralized, with laterality indices (LI) quantifying this.
• The precise mechanisms driving face lateralization in the VTC, particularly the role of local competition and long-range connectivity, remain debated.

Purpose of the Study:

• To investigate the underlying mechanisms of VTC functional lateralization, specifically testing theories of local competition and long-range coupling for word and face processing.
• To differentiate between specific face-word competition and more general local representational interactions influencing VTC organization.
• To examine the influence of long-range connections with language and social processing regions on VTC lateralization patterns.

Main Methods:

• Utilized functional MRI (fMRI) in an in-house experiment to measure neural responses and calculate laterality indices (LI) for word and face selectivity.
• Analyzed the large-scale Human Connectome Project (HCP) dataset to examine broader local LI interactions and long-range coupling effects across diverse participants.
• Correlated LIs of VTC responses to different categories (words, faces, tools, bodies) and with LIs of other brain regions involved in language and social processing.

Main Results:

• No evidence for local competition between word and face representations driving VTC lateralization; correlations between word and face LIs were not consistently negative.
• Found evidence for generic local interactions: face and tool LIs were anti-correlated, while face and body LIs were positively correlated.
• Demonstrated significant long-range coupling: VTC text LI correlated positively with other text-processing regions, and VTC face LI showed distinct negative and positive correlations with language and social processing regions, respectively.

Conclusions:

• VTC lateralization, including for face perception, is shaped by general local representational competition and cooperation rather than specific word-face competition.
• Long-range coupling plays a significant role, with face lateralization influenced by interactions with social processing areas in the posterior temporal lobe.
• These findings suggest a complex interplay of local and long-range network dynamics in organizing specialized visual processing within the human ventral temporal cortex.