Left perirhinal cortex codes for similarity in meaning between written words: Comparison with auditory word input

Area of Science:

• Neuroscience
• Cognitive Science
• Psycholinguistics

Background:

• The left perirhinal cortex is linked to associative coding.
• Prior research indicates fMRI response patterns in this area correlate with semantic similarity for written words.

Purpose of the Study:

• To investigate if the semantic similarity effect in the left perirhinal cortex extends to spoken words.
• To determine if this brain region acts as an amodal semantic hub.

Main Methods:

• An event-related fMRI experiment was conducted with 20 healthy subjects performing a property verification task.
• Participants processed concrete animate entities in either written or spoken modality.
• Semantic similarity was calculated from feature generation data, and fMRI activity patterns were analyzed to create similarity matrices.

Main Results:

• A significant correlation between semantic similarity and fMRI similarity was found only for written words.
• No such effect was observed for spoken words.
• No cross-modal effects were detected in the perirhinal cortex between written and auditory word processing.

Conclusions:

• The left perirhinal cortex's role in word processing appears to be at the level of visual processing.
• Findings do not support the hypothesis of the left perirhinal cortex functioning as an amodal semantic hub.
• This region's contribution is situated within the visual pathway, not at a convergence point for auditory and visual word processing.