Role of dopamine in prioritizing memory content: Implications for Parkinson’s disease – Sharp – McGill

Principal Investigator : Dr Madeleine Sharp MD MSc - Montreal Neurological Institute - McGill University

Co-Investigator: Zhen-Yi Andy Ou - Montreal Neurological Institute - McGill University

Site: Montreal Neurological Institute

Background: Our capacity to remember is limited. Factors like reward and surprise play a role in selecting what should be stored in memory. The healthy brain relies on dopamine to signal the presence of reward or surprising features. In Parkinson’s disease, due to loss of dopamine, the brain loses its ability to accurately detect reward. An inability to prioritize the content of memory could lead to impairments in day-to-day cognitive function.

Objectives : The purpose of this study is to determine whether people with Parkinson’s disease lose the ability to prioritize information for storage into memory and to determine whether this explains other cognitive changes frequently reported such a slower cognitive processing or difficulty focusing. For this research study, we will recruit 200 participants, men and women, aged between 45 and 75.


1. Duration and number of visits

Your participation in this research project will include 4 visits, spread over a period of 2-5 months, each lasting about 2 hours.

2. Medication manipulation (applies to Parkinson’s patients only)

We are interested in the effects of levodopa, one of the medications that you take for your symptoms, on memory processes. In order to evaluate this, this study requires that you complete the study procedures once while taking your usual dose of levodopa (i.e. 2 visits, see below for details), and once after an overnight withdrawal of your Parkinson’s medications (levodopa or dopamine agonist-containing medication formulations). This means that you would be without medications for 14-18 hours. During this period, you will experience your usual OFF symptoms (e.g. tremor, stiffness, slowness), possibly in more severe form. By testing you in both the medicated and unmedicated state, we will be able to compare your performance on the tests and identify the effects of dopamine on the brain.

3. Tests and procedures

During your participation in this research study, the study doctor or a member of the research team will conduct the following tests and procedures:

Procedure Description
Cognitive testing and questionnaires We will ask you basic questions about demographics, your health history and your medications. You will also be asked to perform some short tests of memory and concentration. (Total 0.5 hours)
Computer tasks You will be asked to play a series of simple computer games where you will be asked to press a button on the keyboard in response to what appears on the screen.  (Total 1.5 hours)