Differentiating hemispheric contributions to syntax and semantics in patients with left-hemisphere lesions

Area of Science:

• Neuroscience
• Cognitive Science
• Psycholinguistics

Background:

• Brain-behavior relationships are understood through brain-damaged patients.
• The roles of cerebral hemispheres in language functions remain debated.

Purpose of the Study:

• Investigate hemispheric roles in language functions using neuroimaging and behavioral data.
• Test a dual neurocognitive model of spoken language comprehension.

Main Methods:

• Studied 21 patients with chronic left hemisphere lesions and language impairments.
• Utilized structural and functional fMRI with a word-monitoring task.
• Employed joint independent components analysis to link structure, activity, and performance.

Main Results:

• Syntactic performance correlated with left frontotemporal network integrity and activity.
• Semantic performance correlated with right superior/middle temporal gyrus activity, irrespective of tissue integrity.
• Right temporal activity in semantic processing did not differ between patients and controls, suggesting degenerate organization.

Conclusions:

• Findings support a dual neurocognitive model where syntax is left-hemisphere dependent, and semantics involve bilateral networks.
• Right hemisphere activity can compensate for left hemisphere damage in semantic processing.
• Linguistic specificity is crucial for understanding language recovery post-lesion.