Dopaminergic therapy affects learning and impulsivity in Parkinson's disease.

Authors

Nole M Hiebert, Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1
Ken N Seergobin, Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7
Andrew Vo, Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1
Hooman Ganjavi, Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1
Penny A MacDonald, Brain and Mind Institute, University of Western Ontario, London, Ontario, Canada, N6A 5B7 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1 & Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada, N6A 5C1

Document Type

Article

Publication Date

10-1-2014

Journal

Annals of Clinical and Translational Neurology

Volume

1

Issue

10

First Page

833

Last Page

843

URL with Digital Object Identifier

10.1002/acn3.128

Abstract

OBJECTIVE: The aim was to examine the effect of dopaminergic medication on stimulus-response learning versus performing decisions based on learning.

METHOD: To see the effect of dopaminergic therapy on stimulus-response learning and response selection, participants with Parkinson's disease (PD) were either tested on and/or off their prescribed dose of dopaminergic therapy during different testing days. Forty participants with PD and 34 healthy controls completed the experiment on consecutive days. On Day 1, participants learned to associate abstract images with spoken, "right" or "left" responses via feedback (Session 1). On Day 2, participants recalled these responses (Session 2) and indicated the location (i.e., right or left of center) of previously studied images intermixed with new images (Session 3).

RESULTS: Participants with PD off medication learned stimulus-response associations equally well compared to healthy controls. Learning was impaired by dopaminergic medication. Regardless of medication status, patients recalled the stimulus-response associations from Day 1 as well as controls. In Session 3 off medication, patients demonstrated enhanced facilitation relative to controls and patients on medication, when the stimulus location was congruent with the spoken response that was learned for the stimulus in Session 1.

INTERPRETATION: Learning in PD was comparable to that of healthy controls off medication. Learning was worsened by dopaminergic therapy in PD. We interpret greater facilitation in participants with PD off medication for congruent responses as evidence of greater impulsivity. This motor or reflexive impulsivity was normalized by medication in PD. These findings shed light on the cognitive profile of PD and have implications for dopaminergic treatment.