Background A significant subset of patients with Parkinson’s disease (PD) suffer from impulse control disorders (ICDs). A hallmark feature of many ICDs is the pursuit of rewarding behaviours despite negative consequences. Recent evidence implicates the subthalamic nucleus (STN) and globus pallidus internus (GPi) in reward and punishment processing, and deep brain stimulation (DBS) of these structures has been associated with changes in ICD symptoms.
Methods We tested the hypothesis that in patients with PD diagnosed with ICD, neurons in the STN and GPi would be more responsive to reward-related stimuli and less responsive to loss-related stimuli. We studied a cohort of 43 patients with PD (12 with an ICD and 31 without) undergoing DBS electrode placement surgery. Patients performed a behavioural task in which their action choices were motivated by the potential for either a monetary reward or a monetary loss. During task performance, the activity of individual neurons was recorded in either the STN (n=100) or the GPi (n=100).
Results The presence of an ICD was associated with significantly greater proportions of reward responsive neurons (p<0.01) and significantly lower proportions of loss responsive neurons (p<0.05) in the STN, but not in the GPi.
Conclusions These findings provide further evidence of STN involvement in impulsive behaviour in the PD population.
- Parkinson’s Disease
- Impulse Control
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Contributors PJR contributed conception and design of the study, data collection, analysis, and interpretation, and drafting and revising the article. JBS, EO, RM, CP, and OC contributed in data collection and analysis. AG and MSO are co-senior authors on this manuscript and contributed in study design, data interpretation, and revision of final manuscript.
Funding The authors declare no grants or funding sources associated with this work.
Disclaimer MSO serves as a consultant for the National Parkinson Foundation, and has received research grants from NIH, NPF, the Michael J. Fox Foundation, the Parkinson Alliance, Smallwood Foundation, the Bachmann-Strauss Foundation, the Tourette Syndrome Association and the UF Foundation; he has previously received honoraria, but in the past >60 months has received no support from industry. MSO has received royalties for publications with Demos, Manson, Amazon, Smashwords, Books4Patients and Cambridge (movement disorders books); he is an associate editor for the New England Journal of Medicine Journal Watch Neurology. MSO has participated in CME and educational activities on movement disorders (in the last 36 months) sponsored by PeerView, Prime, QuantiaMD, WebMD, MedNet, Henry Stewart and by Vanderbilt University. The institution and not MSO receives grants from Medtronic, Abbvie, Allergan, and ANS/St Jude, and the PI has no financial interest in these grants. MSO participated as a site PI and/or co-I for several NIH, foundation and industry-sponsored trials over the years but has not received honoraria. PJR, OC, CP and AG have no conflicts of interest to report.
Competing interests None declared.
Ethics approval University of Florida Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.
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