Poster E75, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
A cognitive impairment for sentence planning after focal damage to the Frontal Aslant Tract
Benjamin Chernoff1, Alex Teghipco1, Frank Garcea1,2, Susan Smith3, Webster Pilcher3, Bradford Mahon1,2,3; 1University of Rochester, 2Center For Visual Science, 3University of Rochester Medical Center
Frontal and temporal white-matter pathways have long been implicated in language processing, but the precise functional role of specific tracts is still under investigation. A functional role in speech planning has been proposed for a recently described pathway, the Frontal Aslant Tract (FAT), which connects Broca’s area to the pre-supplementary motor area (SMA). Here, we use longitudinal functional and structural MRI and behavioral testing to compare a 63-year old woman, AF, who had neurosurgery to remove a glioma in her left frontal lobe, with a 35 year old woman, AG, whose left anterior temporal lobe was resected to remove a hippocampal tumor. AF and AG, cognitively intact pre-operatively, exhibited specific and doubly dissociable behavioral deficits post-operatively: patient AF had dysfluent speech but no word finding difficulty, while patient AG had word finding difficulty but otherwise fluent speech. Probabilistic tractography showed that the FAT was damaged by the surgery in patient AF (but not AG) while the inferior longitudinal fasciculus was damaged by the surgery in patient AG (but not AF). We also found that changes in functional connectivity to Broca’s area directly related to areas of degraded structural connectivity. Specifically, there was decreased functional connectivity post-operatively between Broca’s area and pre-SMA in patient AF (but not patient AG), and decreased functional connectivity between Broca’s area and the middle/inferior temporal gyrus in patient AG (but not patient AF). These results motivate the novel hypothesis that the FAT serves as a key communicative link between sentence planning and lexical access processes.
Topic Area: LANGUAGE: Syntax