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A rose by any other name: Neural correlates of taxonomic and thematic naming errors post-stroke
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Poster E24 in Poster Session E, Thursday, October 26, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Nicholas Riccardi1, Deena Schwen Blackett2, Abigail Broadhead1, Chris Rorden1, Julius Fridriksson1, Leonardo Bonilha3, Rutvik H. Desai1; 1University of South Carolina, 2Medical University of South Carolina, 3Emory University School of Medicine
Introduction: People with aphasia make various types of naming errors (e.g., phonological, semantic). Neural correlates of different error types reveal the organization of the lexical-semantic system. The current study focused on two subtypes of semantic errors: taxonomic and thematic. If shown a dog, taxonomic errors are producing a category coordinate (wolf), superordinate (animal), or subordinate (schnauzer). A thematic error is producing a word that is associated via events or actions (leash). Neural correlates of taxonomic and thematic errors are partially dissociable, but the specific mechanisms remain controversial. Prior work from our group has shown that compromised white matter connectivity of left temporal pole is associated with higher proportion of thematic errors. Here, we add insight by using three complementary lesion-symptom mapping (LSM) techniques in both left and right hemisphere: voxel-, connectome-, and activity-based LSM (VLSM, CLSM, ALSM). Methods: Seventy-nine adults with aphasia completed the Philadelphia Naming Test (PNT) outside the scanner. In a separate session, they underwent anatomical scanning and a functional scan during which they named pictures (an in-house task with different stimuli than the PNT). PNT errors were coded in accordance with PNT scoring guidelines. Taxonomic and thematic error counts were converted to proportions out of the total error count (including phonological and other error types). We then conducted V-, C-, and ALSM to examine the neural correlates of taxonomic and thematic error proportions. Shared variance between the error type proportions were regressed out from each other (henceforth called TaxProp and ThemeProp). VLSM finds associations between damage to voxels and errors. CLSM uses a matrix of region-to-region white matter connectivity derived from probabilistic tractography and finds where weaker connectivity between a given pair of regions is related to errors. ALSM uses the BOLD signal during the independent picture naming task and finds where less brain activity during picture naming is associated with errors. Analyses were restricted to a bilateral mask of 26 Johns Hopkins University atlas regions (13 in each hemisphere) that covered much of the temporal, parietal, and frontal lobes. All analyses controlled for lesion volume and were permutation corrected for multiple comparisons (1000 perms, p < .05). Results: VLSM showed that damage to left middle temporal gyrus (MTG) was associated with higher ThemeProp. CLSM showed that weaker connectivity between regions in left anterior temporal lobe (ATL) and bilateral posterior cingulate (PCC) and right temporal gyri were associated with higher ThemeProp. V- and CLSM did not reveal results for TaxProp. However, ALSM showed that lower activity in bilateral PCC, right angular gyrus (AG), and right inferior frontal cortex (IFC) was associated with higher TaxProp. Trending ALSM results (p < .1) showed that greater activity in left IFC and left ATL was related to higher ThemeProp and TaxProp, respectively. Discussion: We used complementary techniques to demonstrate that the neural correlates of taxonomic and thematic errors are partially dissociable. Thematic errors were associated with disconnection between left ATL and bilateral lexical-semantic regions, and taxonomic errors were associated with lower brain activity in right inferior frontal and parietal cortices.
Topic Areas: Meaning: Lexical Semantics, Language Production