Neuro-anatomic Substrates Supporting Category and Letter Fluency: Evidence from Voxel- and Connectome-based Lesion-Symptom Mapping

Poster Session E - Monday, March 31, 2025, 2:30 – 4:30 pm EDT, Back Bay Ballroom/Republic Ballroom

William Burns¹ (william_burns@urmc.rochester.edu), Emma Strawderman^1,3, Benedikt Winzer¹, Steven Meyers^1,2, Tyler Schmidt¹, Kevin Walter¹, Webster Pilcher^1,4, Bradford Mahon^1,5, Frank Garcea^1,3,5; ¹Department of Neurosurgery, University of Rochester Medical Center, ²Department of Imaging Sciences, University of Rochester Medical Center, ³Department of Neuroscience, University of Rochester Medical Center, ⁴Del Monte Institute for Neuroscience, University of Rochester Medical Center, ⁵Department of Psychology, Carnegie Mellon University

Verbal fluency is a neuropsychological assessment requiring participants to produce words from a semantic category (hereafter, category fluency), or words beginning with a specific letter (hereafter, letter fluency). Prior research suggests that engaging in category fluency emphasizes semantically-guided lexical retrieval, whereas engaging in letter fluency emphasizes phonological encoding of lexical-semantic representations. Here, 55 participants with lesions in the pre-operative phase of their neurosurgical care took part in the category fluency and letter fluency task, as well as a high-resolution T1 scan and diffusion MRI. Voxel-based and connectome-based lesion-symptom mapping related lesion sites and structural disconnectivity, respectively, to performance in the two fluency tasks. Two hypotheses were tested: (1) That lesions involving the left inferior frontal gyrus, the left anterior temporal lobe, and the underlying white matter would be associated with fewer items produced in the category fluency task (controlling for performance in the letter fluency task); and (2) That lesions involving the left posterior superior temporal gyrus, the left anterior supramarginal gyrus, and the underlying white matter would be associated with fewer items produced in the letter fluency task (controlling for performance in the category fluency task). Results confirmed both hypotheses: We provide causal lesion evidence that distinct lesion sites and structural disconnectivity patterns uniquely account for performance across the category and letter fluency tasks. Our results suggest that interactive yet dissociable networks underlie lexical-semantic and phonological processing to constrain the selection of words when engaging in the verbal fluency task.

Topic Area: LANGUAGE: Semantic