Tāmaki Innovation Campus

Parkinson’s sufferers to benefit from PhD research

Hayley MacDonald in the movement neuroscience lab.
‘Fascinating lectures’ sparked Hayley MacDonald’s interest in Parkinson’s disease.

A self-described ‘passion for neuroscience’ drove Hayley MacDonald to her PhD study investigating response control in Parkinson’s disease patients.

She said it was a logical step from her 2009 BSc with its double major in Sport and Exercise Science and Physiology, with ‘fascinating lectures’ sparking her interest in Parkinson’s disease.

Volunteering as a subject in the Movement Neuroscience Laboratory not only helped in her honours dissertation, but also led to her present involvement, with her doctoral study supported by a W & B Miller Postgraduate Scholarship from the Neurological Foundation of New Zealand.

Hayley is hoping to shed new light on the role of movement networks within the brain during selective response control and help identify people at risk of developing impulsive behaviours when on specific Parkinson’s medications.

Parkinson’s disease is a relatively common progressive neurodegenerative condition affecting nearly five million people worldwide and about 1-2% of New Zealanders over 60. She explains how her PhD research is looking specifically at how the movement areas of the brain are involved during response control and the implications for individualised treatment of Parkinson’s disease.

“Response control, in the context of my research, means starting and cancelling anticipated movements; for example when waiting to go when the lights go green at an intersection and having to stop yourself when someone runs the red.”

Her research forms two major themes. The first is the movement areas of a healthy brain where she is using non-invasive brain stimulation techniques to examine the activity levels of connections between the brain and muscles. Certain forms of non-invasive brain stimulation can also be used as therapies but she is using it to investigate the pathway between the brain and muscles during response control.

The second theme investigates interactions between genes controlling levels of the chemical dopamine within the brain, specific Parkinson’s disease medications, response control, and impulsive behaviour. This part could help predict how a person will respond to certain Parkinson’s medications.

Hayley says that some patients (about 20%) become very impulsive on Parkinson’s medications and develop gambling problems, impulsive buying habits and binge eating tendencies, among other impulsive behaviours.

“These behaviours can have serious consequences. Currently there is no way to reliably predict who will show highly impulsive behaviours when beginning medication.”

So far her first PhD experiment and previous work has found some interesting behavioural results when looking at the selective component of response control in healthy people.

“My research will extend these findings and hopefully reveal the neural mechanisms responsible for these behavioural results. The computer based behavioural task I am using requires the participants to make an anticipated response when a moving indicator intercepts a target on the screen. Sometimes the participants need to cancel their response if they see the indicator automatically stop early before reaching the target.

"This particular task design hasn’t been used in the context of Parkinson’s disease before. The main difference with this task is that the responses are self-initiated rather than in response to external cues. This is important because self-initiated movements require greater use of the brain areas affected in Parkinson’s disease.”

Despite significant research internationally on identifying risk factors for developing impulsive behaviour on Parkinson’s disease medications, none have combined the analysis of dopamine genes and measures of response control to predict these impulsive behaviours.

Hayley hopes this combination of simple measures will ultimately be used by neurologists to identify patients who may respond badly to certain medications, allowing better individualised treatment of the disease.

Results from her first PhD experiment were published in the Journal of Neurophysiology and she presented her findings at the Australasian Winter Conference on Brain Research.

“I gained invaluable experience going through the peer review process and discussing my findings with other researchers, who sometimes presented interesting and opposing points of view. And, I’ve been pleasantly surprised that, through the process of doing my PhD, I’ve developed new skills that I wouldn’t have thought to be within my field of research, such as computer programming.”

One of the challenges she faces is recruiting a reasonable number of participants for clinical studies within the time constraints of her PhD. “Patient recruitment involving a condition like Parkinson’s disease, which can affect people quite differently, can be difficult. However I am lucky enough to have fantastic support from my supervisors and clinical advisors so I think this is a challenge we can meet.”

This article was first published in the March 2013 Tāmaki Update