Left-sided Ventral Occipito-temporal Hypoactivity in PPA with History of Language-based Learning Disabilities
Zachary Miller1, Leighton Hinkley2, Rian Bogley1, Isabel Allen3, Bruce Miller1, Srikantan Nagarajan2, Maria Luisa Gorno Tempini1
1Neurology, 2Radiology, 3Department of Biostatistics, University of California, San Francisco, San Francisco, CA, USA
Objective:
To characterize functional language activity patterns in primary progressive aphasia (PPA), comparing individuals with and without histories of language-based learning disabilities (LDs).
Background:
Previously we identified elevated rates of language-based LDs among PPA variants compared to the general population, via retrospective chart-based review. Separately, in a group of healthy adults with a history of reading disability, we identified a distinct pattern of reduced activity in the left-sided ventral occipito-temporal (vOT) region, consistent with known theories of functional deficits present in individuals with developmental dyslexia. Here, using magnetoencephalography (MEG) imaging in a subset of PPA patients, we examined whether this vOT hypoactivity signal is present in PPA patients with LD histories.
Design/Methods:
MEG data were collected from 72 PPA patients during syllable reproduction and auditory noun-verb generation tasks using a 275-channel biomagnetometer. We compared 19 PPA patients with documented language-based LDs (including 11 logopenic variant PPA, 3 semantic dementia PPA, and 5 nonfluent variant PPA) against 53 PPA patients without LDs (including 11 logopenic variant PPA, 27 semantic dementia PPA, and 15 nonfluent variant PPA).
Results:
After correcting for atrophy, PPA patients with LDs exhibited decreased (p<0.05 cluster corrected) activity in left-sided vOT regions compared to those without LDs. This reduction mirrored the pattern observed in healthy controls with LDs, particularly affecting the posterior middle temporal gyrus and visual word form area.
Conclusions:
PPA patients with a history of language-based LDs demonstrate a consistent pattern of reduced left-sided vOT activity, identical to findings in older healthy individuals with a history of reading disability. These results underscore the validity of our retrospective chart-based review in capturing LDs in dementia populations and validate MEG as a tool for detecting neuronal activity patterns associated with LD histories in aging cohorts.
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