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Poster B71, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Speech processing with one hemisphere: word repetition in a patient with right hemisphereotomy

Chad S. Rogers1, Michael Jones1, Jacqueline M. Hampton1, Catherine Hoyt Drazen1, Matthew D. Smyth1, Jarod Roland1, Nico Dosenbach1, Jonathan E. Peelle1;1Washington University School of Medicine

Introduction A recurring discussion in the neurobiology of language pertains to the degree to which speech processing shows hemispheric lateralization. In the current study, we examined speech-related activation in a participant recovering from right hemisphereotomy, a surgical procedure used to treat epilepsy in which the vascularized right hemisphere is disconnected from the rest of the brain by severing white matter tracts. Given that the right hemisphere contributes to many aspects of language processing, our goal was to assess the degree to which cortical language networks may have reorganized to support these functions with a single hemisphere. Methods The hemispherotomy patient was a 24 year old female native speaker of English who was scanned 32 days following surgery. Immediately post-surgery, she was unable to walk, speak, or use her left arm. She was eventually able to walk with a cane, use her left arm with assistance, and her language abilities returned. At the time of her scanning session, she was able to comprehend and communicate with members of the research team, as well as able to comprehend and verbally repeat auditory stimuli. The hemisphereotomy patient and healthy right-handed controls (n=17, 14 female, age range 19-30, mean age = 24) each took part in a 2 hour scanning session in which structural and functional MRI scans were performed. fMRI scanning was performed using a sparse imaging protocol in which stimuli were presented during a silent gap between volume acquisitions. Four runs of fMRI scanning were performed (TR 3070 ms, TA 800 ms, voxel resolution 2.04 x 2.04 x 2 mm). The stimuli were audio recordings of 300 monosyllabic consonant vowel consonant (CVC) English words. As a control condition, sixty words were made unintelligible via single channel white noise-based vocoding. On half of trials participants were asked to say out loud the word they had just heard, for the other half of trials, participants were asked to listen carefully to the words. Results Figure 1 displays speech-related fMRI activation in the patient, healthy controls, and regions where the patient showed greater activation than controls (voxelwise FWE p < .05) for repetition trials. The cluster of greater activation for the patient rather than controls in the superior temporal gyrus (STG) is consistent with hemispheric reorganization of the speech perception network. Conclusions The results of the current study validate decades of prior behavioral post-operative studies that have shown remarkable recovery of verbal abilities in patients following hemisphereotomy. However, the region of greater activity in the superior temporal gyrus of the patient suggests a degree of cortical reorganization, with neuroplasticity compensating for the loss of the right hemisphere during speech processing.

Topic Area: Perception: Speech Perception and Audiovisual Integration

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