Poster F61, Tuesday, March 28, 8:00 – 10:00 am, Pacific Concourse
Induced oscillations during speaking distinguish variants of primary progressive aphasia
Leighton Hinkley1, Megan Cahill-Thompson1, Zachary Miller2, Kamalini Ranasinghe2, Bruce Miller2, Keith Vossel2, John Houde1, Marilu Gorno-Tempini2, Srikantan Nagarajan1; 1University of California, San Francisco, Department of Radiology and Biomedical Imaging, 2University of California, San Francisco, Memory and Aging Center
Primary progressive aphasia (PPA) is symptomatically characterized into three main subtypes: a non-fluent variant (nfvPPA) associated with apraxia of speech, a logopenic variant (lvPPA) with a loss of phonological abilities, and a semantic variant (svPPA) with loss of word conceptual knowledge. Each variant is also associated with atrophy in specific regions of the left hemisphere language network. Despite this, the neurophysiological mechanisms that serve these deficits are not clear. Here, we use MEG during linguistic tasks to investigate phases of speech encoding and preparation in these PPA variants and matched controls. MEG data was collected using a 275-channel whole head biomagnetometer (CTF) during a nonsense word repetition task. Data were reconstructed in source space using adaptive spatial filtering techniques following the auditory presentation of a nonsense word (speech encoding) and prior to the subject repeating the word (speech production). In the high-gamma band, MEG source space reconstructions localized to the left posterior superior temporal gyrus (STG) 75ms following stimulus presentation in the nfvPPA, svPPA and control groups but not the lvPPA group. In addition, an increase in high-gamma suppression bilaterally over the inferior frontal gyrus (IFG) 475ms following stimulus presentation and 475ms prior to the response was present in the lvPPA, svPPA and control groups but absent in the nfvPPA group. The temporal resolution of MEG allows us to separately examine activation in these brain regions during different phases of the task in detail. The findings demonstrate that MEG imaging can provide distinct neurophysiological signatures across these aphasia variants.
Topic Area: LANGUAGE: Development & aging