Multiple Adjoining Word- and Face-Selective Regions in Ventral Temporal Cortex Exhibit Distinct Dynamics.

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Object recognition models are constrained by category-selectivity maps in the human ventral temporal cortex (VTC).
• Lateral-medial response biases relate to visual field viewing habits (central vs. peripheral).
• Limited understanding exists regarding the temporal dynamics and precise locations of centrally viewed object-processing networks, such as those for faces and words.

Purpose of the Study:

• To map word- and face-selective regions within the VTC.
• To investigate the relative temporal dynamics and anatomical organization of these centrally viewed object-processing networks.
• To compare response latencies and pathways between word and face perception.

Main Methods:

• Intracranial recordings from 36 patients to map VTC regions.
• 7 Tesla functional Magnetic Resonance Imaging (fMRI) in healthy subjects for replication.
• Analysis of response latencies and spatial spread of selectivity.

Main Results:

• Partially overlapping yet anatomically distinct patches of face- and word-selectivity were identified in VTC.
• Word-selectivity found along the left posterior occipitotemporal sulcus, and also medial/anterior to face-selectivity on the fusiform gyrus.
• Left hemisphere word responses preceded right hemisphere responses by 125 ms; face response latency showed no hemispheric difference.
• Response patterns indicated a sequential activation: posterior fusiform for both, then spreading medially/laterally/anteriorly for words, and anteriorly for faces.
• Response delays between regions exceeded predictions from feedforward models.

Conclusions:

• A mosaic of face- and word-selective regions exists in VTC, with distinct anatomical locations and response timings.
• Differences in response timing and hemispheric involvement suggest specialized roles within a dynamic functional circuit for face and word perception.
• These findings illuminate extended, bilateral, and dynamic brain pathways crucial for face perception and reading.