Helping Parkinson’s patients confront the problems their treatment causes

Using pharmacogenetics to identify biomarkers for cognitive impairment in early PD

Poets long ago claimed our eyes to be a window into the mysteries of the soul. It turns out these vital organs are also portals allowing modern scientists to probe the daunting frontier of the human brain. In fact, some of the most recent and promising research on neurological disorders relies on observing something as simple as how our eyes move when we are carrying out mental tasks.

“This system has become a key tool to study cognition,” explains Doug Munoz, who maps eye movements as a way of determining how the brain is sending signals to the rest of the body. “If I understand the circuit through someone’s brain, I’m going to be able to map their abnormality onto that circuit and pinpoint where in their brain something’s wrong.”

Munoz, a professor in Queen’s University’s Centre for Neuroscience Studies, is specifically interested in tracking how individuals with Parkinson’s disease respond to medications that increase dopamine levels in the nervous system. While this approach can relieve many obvious symptoms, such as restoring motor control, some people suffer from major swings in dopamine levels that generate entirely new problems, such as impulsive behaviour.

“Patients can end up gambling wildly in casinos or making other poor decisions,” he says. At the same time, when dopamine levels crash these individuals become lethargic and prompted to take more drugs. As this cycle continues they may seldom have appropriate muscle or cognitive control, and have few alternatives for treatment.

By examining the eye movements of people with Parkinson’s coping with this challenge, Munoz is hoping to find a pattern that could reveal who is most susceptible to these negative consequences. If these observations can then be paired with saliva samples taken from participants, he suggests, it might be possible to pin down genetic factors at work to identify susceptible patients before they start on medication.

Initial findings at Queen’s have pointed in that direction, he adds, and support from Parkinson Canada is now enabling him to extend this work to two other Ontario research centres. With a larger pool of test subjects and much more data, Munoz is looking forward to solving one of the most frustrating and most challenging aspects of treating Parkinson’s disease.