title: Gray and White Matter Contributions to Cognitive Frontostriatal Deficits in Non-Demented Parkinson's Disease.
abstract: OBJECTIVE
  This prospective investigation examined: 1) processing speed and working memory relative to other cognitive domains in non-demented medically managed idiopathic Parkinson's disease, and 2) the predictive role of cortical/subcortical gray thickness/volume and white matter fractional anisotropy on processing speed and working memory.
  
  
  METHODS
  Participants completed a neuropsychological protocol, Unified Parkinson's Disease Rating Scale, brain MRI, and fasting blood draw to rule out vascular contributors. Within group a priori anatomical contributors included bilateral frontal thickness, caudate nuclei volume, and prefrontal white matter fractional anisotropy.
  
  
  RESULTS
  Idiopathic Parkinson's disease (n = 40; Hoehn & Yahr stages 1-3) and non-Parkinson's disease 'control' peers (n = 40) matched on demographics, general cognition, comorbidity, and imaging/blood vascular metrics. Cognitively, individuals with Parkinson's disease were significantly more impaired than controls on tests of processing speed, secondary deficits on working memory, with subtle impairments in memory, abstract reasoning, and visuoperceptual/spatial abilities. Anatomically, Parkinson's disease individuals were not statistically different in cortical gray thickness or subcortical gray volumes with the exception of the putamen. Tract Based Spatial Statistics showed reduced prefrontal fractional anisotropy for Parkinson's disease relative to controls. Within Parkinson's disease, prefrontal fractional anisotropy and caudate nucleus volume partially explained processing speed. For controls, only prefrontal white matter was a significant contributor to processing speed. There were no significant anatomical predictors of working memory for either group.
  
  
  CONCLUSIONS
  Caudate nuclei volume and prefrontal fractional anisotropy, not frontal gray matter thickness, showed unique and combined significance for processing speed in Parkinson's disease. Findings underscore the relevance for examining gray-white matter interactions and also highlight clinical processing speed metrics as potential indicators of early cognitive impairment in PD.
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.|University of Florida Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Price
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Jared
authors.initials: J
authors.lastname: Tanner
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Nguyen
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Nadine A
authors.initials: NA
authors.lastname: Schwab
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Sandra
authors.initials: S
authors.lastname: Mitchell
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Slonena
authors.affiliation: Department of Biostatistics, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Babette
authors.initials: B
authors.lastname: Brumback
authors.affiliation: Department of Neurology, University of Florida, Gainesville, Florida, United States of America.|University of Florida Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Okun
authors.affiliation: Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Mareci
authors.affiliation: Department of Clinical and Health Psychology, University of Florida, Gainesville, Florida, United States of America.|University of Florida Center for Movement Disorders and Neurorestoration, Gainesville, Florida, United States of America.
authors.forename: Dawn
authors.initials: D
authors.lastname: Bowers
mesh_terms: D000368:Aged; D001931:Brain Mapping / Q000379:methods*; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000473:pathology*; D003342:Corpus Striatum / Q000473:pathology*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology*; D066128:Gray Matter / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000473:pathology*; D066127:White Matter / Q000473:pathology*