Structural connectivity subserving verbal fluency revealed by lesion-behavior mapping in stroke patients.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Verbal fluency tests (semantic and phonological) are standard cognitive assessments.
• Brain regions involved in verbal fluency are known, but anatomical connectivity is unclear.
• Understanding white-matter networks is essential for cognitive function research.

Purpose of the Study:

• To map the white-matter network associated with semantic and phonological fluency.
• To investigate the relationship between major white-matter tract integrity and fluency performance.
• To identify specific tracts critical for different types of verbal fluency in stroke patients.

Main Methods:

• Studied 51 stroke patients to assess verbal fluency and white-matter tract integrity.
• Measured semantic fluency using 3 cues and phonological fluency using 2 cues.
• Analyzed the integrity of 22 major white-matter tracts across the whole brain.

Main Results:

• Five left-lateralized tracts (anterior thalamic radiation, inferior fronto-occipital fasciculus, uncinate fasciculus, superior longitudinal fasciculus, and frontal aslant tract) correlated significantly with both fluency types.
• These correlations remained significant after controlling for confounding factors like lesion volume.
• Damage to the anterior thalamic radiation, inferior fronto-occipital fasciculus, and uncinate fasciculus disproportionately impaired semantic fluency compared to phonological fluency.

Conclusions:

• Identified specific white-matter tracts underpinning semantic and phonological verbal fluency.
• Demonstrated the critical role of left-lateralized tracts in verbal fluency.
• Provided insights into the neuroanatomical basis of verbal fluency and its distinct components.