title: The relationship between executive functions and fluid intelligence in Parkinson's disease.
abstract: BACKGROUND
  We recently demonstrated that decline in fluid intelligence is a substantial contributor to frontal deficits. For some classical 'executive' tasks, such as the Wisconsin Card Sorting Test (WCST) and Verbal Fluency, frontal deficits were entirely explained by fluid intelligence. However, on a second set of frontal tasks, deficits remained even after statistically controlling for this factor. These tasks included tests of theory of mind and multitasking. As frontal dysfunction is the most frequent cognitive deficit observed in early Parkinson's disease (PD), the present study aimed to determine the role of fluid intelligence in such deficits.
  
  
  METHODS
  We assessed patients with PD (n=32) and control subjects (n=22) with the aforementioned frontal tests and with a test of fluid intelligence. Group performance was compared and fluid intelligence was introduced as a covariate to determine its role in frontal deficits shown by PD patients.
  
  
  RESULTS
  In line with our previous results, scores on the WCST and Verbal Fluency were closely linked to fluid intelligence. Significant patient-control differences were eliminated or at least substantially reduced once fluid intelligence was introduced as a covariate. However, for tasks of theory of mind and multitasking, deficits remained even after fluid intelligence was statistically controlled.
  
  
  CONCLUSIONS
  The present results suggest that clinical assessment of neuropsychological deficits in PD should include tests of fluid intelligence, together with one or more specific tasks that allow for the assessment of residual frontal deficits associated with theory of mind and multitasking.
authors.affiliation: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Roca
authors.affiliation: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors.forename: F
authors.initials: F
authors.lastname: Manes
authors.affiliation: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors.forename: A
authors.initials: A
authors.lastname: Chade
authors.affiliation: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors.forename: E
authors.initials: E
authors.lastname: Gleichgerrcht
authors.affiliation: Laboratory of Neuroscience, Universidad Diego Portales, Chile.
authors.forename: O
authors.initials: O
authors.lastname: Gershanik
authors.affiliation: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors.forename: G G
authors.initials: GG
authors.lastname: Arévalo
authors.affiliation: Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina.
authors.forename: T
authors.initials: T
authors.lastname: Torralva
authors.affiliation: MRC Cognition and Brain Sciences Unit, Cambridge, UK.
authors.forename: J
authors.initials: J
authors.lastname: Duncan
mesh_terms: D000368:Aged; D056344:Executive Function / Q000502:physiology*; D006801:Humans; D007360:Intelligence / Q000502:physiology*; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D056345:Theory of Mind / Q000502:physiology