title: Category-specific semantic memory: converging evidence from bold fMRI and Alzheimer's disease.
abstract: Patients with Alzheimer's disease have category-specific semantic memory difficulty for natural relative to manufactured objects. We assessed the basis for this deficit by asking healthy adults and patients to judge whether pairs of words share a feature (e.g. "banana:lemon-COLOR"). In an fMRI study, healthy adults showed gray matter (GM) activation of temporal-occipital cortex (TOC) where visual-perceptual features may be represented, and prefrontal cortex (PFC) which may contribute to feature selection. Tractography revealed dorsal and ventral stream white matter (WM) projections between PFC and TOC. Patients had greater difficulty with natural than manufactured objects. This was associated with greater overlap between diseased GM areas correlated with natural kinds in patients and fMRI activation in healthy adults for natural kinds. The dorsal WM projection between PFC and TOC in patients correlated only with judgments of natural kinds. Patients thus remained dependent on the same neural network as controls during judgments of natural kinds, despite disease in these areas. For manufactured objects, patients' judgments showed limited correlations with PFC and TOC GM areas activated by controls, and did not correlate with the PFC-TOC dorsal WM tract. Regions outside of the PFC-TOC network thus may help support patients' judgments of manufactured objects. We conclude that a large-scale neural network for semantic memory implicates both feature knowledge representations in modality-specific association cortex and heteromodal regions important for accessing this knowledge, and that patients' relative deficit for natural kinds is due in part to their dependence on this network despite disease in these areas.
authors.affiliation: Frontotemporal Degeneration Center, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-4283, USA. mgrossma@mail.med.upenn.edu
authors.forename: Murray
authors.initials: M
authors.lastname: Grossman
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Peelle
authors.forename: Edward E
authors.initials: EE
authors.lastname: Smith
authors.forename: Corey T
authors.initials: CT
authors.lastname: McMillan
authors.forename: Philip
authors.initials: P
authors.lastname: Cook
authors.forename: John
authors.initials: J
authors.lastname: Powers
authors.forename: Michael
authors.initials: M
authors.lastname: Dreyfuss
authors.forename: Michael F
authors.initials: MF
authors.lastname: Bonner
authors.forename: Lauren
authors.initials: L
authors.lastname: Richmond
authors.forename: Ashley
authors.initials: A
authors.lastname: Boller
authors.forename: Emily
authors.initials: E
authors.lastname: Camp
authors.forename: Lisa
authors.initials: L
authors.lastname: Burkholder
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008568:Memory / Q000502:physiology*; D012660:Semantics; D055815:Young Adult