Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States
CL Dale
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, United States
S Lukic
Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States
LBN Hinkley
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, United States
M Lauricella
Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States
W Shwe
Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States
D Mizuiri
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, United States
S Honma
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, United States
Z Miller
Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States
B Miller
Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States
JF Houde
Department of Otolaryngology, University of California, San Francisco, San Francisco, United States
ML Gorno-Tempini
Memory and Aging Center, Department of Neurology, University of California, San Francisco, San Francisco, United States; Department of Neurology, Dyslexia Center University of California, San Francisco, San Francisco, United States
SS Nagarajan
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, United States; Department of Otolaryngology, University of California, San Francisco, San Francisco, United States
Semantic representations are processed along a posterior-to-anterior gradient reflecting a shift from perceptual (e.g., it has eight legs) to conceptual (e.g., venomous spiders are rare) information. One critical region is the anterior temporal lobe (ATL): patients with semantic variant primary progressive aphasia (svPPA), a clinical syndrome associated with ATL neurodegeneration, manifest a deep loss of semantic knowledge. We test the hypothesis that svPPA patients perform semantic tasks by over-recruiting areas implicated in perceptual processing. We compared MEG recordings of svPPA patients and healthy controls during a categorization task. While behavioral performance did not differ, svPPA patients showed indications of greater activation over bilateral occipital cortices and superior temporal gyrus, and inconsistent engagement of frontal regions. These findings suggest a pervasive reorganization of brain networks in response to ATL neurodegeneration: the loss of this critical hub leads to a dysregulated (semantic) control system, and defective semantic representations are seemingly compensated via enhanced perceptual processing.
