Tests of generative semantic verbal fluency are widely used to study organization and representation of concepts in the human brain. Previous studies demonstrated that clustering and switching behavior during verbal fluency tasks is supported by multiple brain mechanisms associated with semantic memory and executive control. Previous work relied on manual assessments of semantic relatedness between words and grouping of words into semantic clusters. We investigated a computational linguistic approach to measuring the strength of semantic relatedness between words based on latent semantic analysis of word co-occurrences in a subset of a large online encyclopedia. We computed semantic clustering indices and compared them to brain network connectivity measures obtained with task-free fMRI in a sample consisting of healthy participants and those differentially affected by cognitive impairment. We found that semantic clustering indices were associated with brain network connectivity in distinct areas including fronto-temporal, fronto-parietal and fusiform gyrus regions. This study shows that computerized semantic indices complement traditional assessments of verbal fluency to provide a more complete account of the relationship between brain and verbal behavior involved organization and retrieval of lexical information from memory.
Bibliographical noteFunding Information:
This work was supported by NIH grants R01 LM009623 (PI – Pakhomov), P50 AG016574 (PI – Ron Petersen), U01 AG006786 (PI – Ron Petersen), R01 AG041851 (PIs – David Knopman and Cliff Jack), R01 AG011378 (PI – Cliff Jack), and the Robert H. and Clarice Smith and Abigail Van Buren Alzheimer’s Disease Research Program of the Mayo Foundation . We are also deeply grateful to the participants in this study, their families, and caregivers.
- Generative verbal fluency
- Latent semantic analysis
- Semantic clustering
- Semantic memory
- Task-free fMRI