How the brain processes different dimensions of argument structure complexity: evidence from fMRI

Area of Science:

• Neuroscience
• Psycholinguistics
• Cognitive Science

Background:

• Verbs are crucial for sentence processing, encoding argument structure (AS).
• Previous research focused on sentence-level tasks involving verb and argument integration.
• Investigating AS processing in isolation is essential for understanding verb-specific mechanisms.

Purpose of the Study:

• To investigate the neural correlates of argument structure (AS) processing using a verb-focused lexical decision task.
• To examine the effects of thematic role number, thematic option number, and argument mapping canonicity on brain activation.
• To differentiate verb processing from verb-argument integration in sentence comprehension.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed.
• A lexical decision task focused solely on verb processing was utilized.
• Three aspects of AS complexity were manipulated: thematic role number, thematic option number, and mapping canonicity (unaccusative, unergative, transitive verbs).

Main Results:

• Increased number of thematic roles correlated with greater activation in left posterior perisylvian regions, associated with accessing stored AS representations.
• The number of thematic options did not yield significant neural effects.
• Unaccusative verbs resulted in longer response times and increased activation in the left inferior frontal gyrus (IFG), indicating processing costs and supporting the IFG's role in noncanonical argument mapping.

Conclusions:

• The findings suggest distinct neural mechanisms for processing different facets of argument structure.
• Left posterior perisylvian regions are involved in accessing stored verb argument representations.
• The left inferior frontal gyrus plays a role in processing noncanonical argument structures, particularly evident with unaccusative verbs.