title: A novel bedside task to tap inhibitory dysfunction and fronto-striatal atrophy in Parkinson's disease.
abstract: BACKGROUND
  Given the heterogeneity of mild cognitive deficits in non-demented Parkinson's disease (PD), sensitive and anatomically specific behavioural measures are crucial when evaluating cognition in this patient group. Inhibitory dysfunction is one such deficit increasingly being recognised in non-demented PD; however, few clinical measures exist to detect it and its associated fronto-striatal pathology.
  
  
  METHODS
  In 50 non-demented PD patients and 27 controls we employ a novel measure, the Excluded Letter Fluency (ELF) test, to objectively assess inhibitory dysfunction. ELF results were also contrasted with an established inhibitory measure (Hayling Test) and covaried against grey matter atrophy via voxel-based morphometry analysis in a subset of patients.
  
  
  RESULTS
  The findings show that patients made significantly more rule-break errors than controls on the ELF and this measure was more sensitive than the Hayling in detecting inhibitory dysfunction, classifying over 76% of patients in logistic regression analysis. Importantly, ELF rule-break errors correlated with grey matter atrophy in known inhibitory-control regions (orbitofrontal cortex, inferior frontal gyrus and ventral striatum).
  
  
  CONCLUSIONS
  The ELF is a brief bedside task that efficiently detects inhibitory dysfunction in non-demented PD. The utility of this novel behavioural measure is further substantiated by its anatomical specificity for fronto-striatal inhibitory control regions.
authors.affiliation: Neuroscience Research Australia, Sydney, Australia.
authors.forename: C
authors.initials: C
authors.lastname: O'Callaghan
authors.forename: S L
authors.initials: SL
authors.lastname: Naismith
authors.forename: J M
authors.initials: JM
authors.lastname: Shine
authors.forename: M
authors.initials: M
authors.lastname: Bertoux
authors.forename: S J G
authors.initials: SJ
authors.lastname: Lewis
authors.forename: M
authors.initials: M
authors.lastname: Hornberger
mesh_terms: D000368:Aged; D001284:Atrophy; D001519:Behavior / Q000502:physiology; D003072:Cognition Disorders / Q000503:physiopathology; D003704:Dementia / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000473:pathology / Q000503:physiopathology*
keywords: Cognition; Inhibitory dysfunction; Parkinson's disease; Voxel-based morphometry