title: A conditioned response as a measure of impulsive-compulsive behaviours in Parkinson's disease.
abstract: OBJECTIVE
  Parkinson's Disease patients wore a device on the wrist that gave reminders to take levodopa and also measured bradykinesia and dyskinesia. Consumption of medications was acknowledged by placing the thumb on the device. Some patients performed this acknowledgement repeatedly and unconsciously. This study examines whether this behaviour reflected increased impulsivity.
  
  
  RESULTS
  Twenty five participants were selected because they had i) excess acknowledgements described above or ii) Impulsive-Compulsive Behaviours or iii) neither of these. A blinded assessor applied clinical scales to measure Impulsive-Compulsive Behaviours, cognition, depression, anxiety and apathy. A Response Ratio, representing the number of acknowledgements/number of doses (expressed as a percentage) was tightly correlated with ratings of Impulsive-Compulsive Behaviours (r² = 0.79) in 19/25 subjects. Some of these patients had dyskinesia, which was higher with extraneous responses than with response indicating medication consumption. Six of the 25 subjects had high Impulsive-Compulsive Behaviour Scores, higher apathy scores, low levels of dyskinesia and normal Response Ratios. Patients without ICB (low RR) also had low dyskinesia levels regardless of the relevance of the response.
  
  
  CONCLUSIONS
  An elevated Response Ratio is a specific measure of a type of ICB where increased incentive salience is attributed to cues by the presence of high striatal dopamine levels, manifested by high levels of dyskinesia. This study also points to a second form of ICBs which occur in the absence of dyskinesia, has normal Response Ratios and higher apathy scores, and may represent prefrontal pathology.
authors.affiliation: The Royal Melbourne Hospital, Parkville Victoria, Australia.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Evans
authors.affiliation: Florey Neuroscience Institute, University of Melbourne, Parkville Victoria, Australia.
authors.forename: Jade
authors.initials: J
authors.lastname: Kettlewell
authors.affiliation: St Vincent's Hospital, Fitzroy, Victoria, Australia.
authors.forename: Sarah
authors.initials: S
authors.lastname: McGregor
authors.affiliation: Florey Neuroscience Institute, University of Melbourne, Parkville Victoria, Australia ; St Vincent's Hospital, Fitzroy, Victoria, Australia.
authors.forename: Katya
authors.initials: K
authors.lastname: Kotschet
authors.affiliation: Florey Neuroscience Institute, University of Melbourne, Parkville Victoria, Australia.
authors.forename: Robert I
authors.initials: RI
authors.lastname: Griffiths
authors.affiliation: Florey Neuroscience Institute, University of Melbourne, Parkville Victoria, Australia ; St Vincent's Hospital, Fitzroy, Victoria, Australia ; Department of Medicine, St Vincent's Hospital, Fitzroy, Victoria, Australia.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Horne
mesh_terms: D000368:Aged; D001007:Anxiety / Q000188:drug therapy / Q000503:physiopathology; D057565:Apathy / Q000187:drug effects / Q000502:physiology; D003192:Compulsive Behavior / Q000188:drug therapy / Q000503:physiopathology*; D003213:Conditioning, Psychological / Q000187:drug effects / Q000502:physiology*; D003863:Depression / Q000188:drug therapy / Q000503:physiopathology; D007174:Disruptive, Impulse Control, and Conduct Disorders / Q000188:drug therapy / Q000503:physiopathology*; D020820:Dyskinesias / Q000188:drug therapy / Q000503:physiopathology; D006801:Humans; D018476:Hypokinesia / Q000188:drug therapy / Q000503:physiopathology; D007175:Impulsive Behavior / Q000187:drug effects / Q000502:physiology*; D007980:Levodopa / Q000627:therapeutic use; D008875:Middle Aged; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology*; D014894:Weights and Measures
chemical_list: D007980:Levodopa