Gambling on Parkinson Disease

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Brain region linked to Parkinson disease also involved in brain’s reward & motivation signals.
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Obsessive and compulsive behaviours can manifest in various ways: from spending excessive time on hobbies to extreme gambling.
The brain sends a reward sensation in response to certain behaviours. These behaviours include those that are inherently pleasurable (eg, helping others), culturally desirable (eg, gaining prestige, winning money) or necessary for survival of the species (eg, eating).
 
These sensations are created by the brain’s ‘reward system’—a network of brain cells (neurons) found in specific brain regions. Combined, these neurons act to either reinforce behaviours or deter behaviours.
 
Given the complexity of the brain and the difficulty of studying it in humans, many of the brain regions thought to be involved in the reward system are poorly defined.
 
To address this issue, Krembil Senior Scientist Dr. William Hutchison, in collaboration with Dr. Valerie Voon at Cambridge University UK, used an advanced approach to measure the activity of single neurons in a brain region known as the globus pallidus pars interna (GPi). This region was chosen because, to date, the GPi’s role in the brain’s reward system has only been suggested through preliminary data.
 
The approach involved inserting extremely small electrodes (microelectrodes) through the skull and into the GPi. The inconvenience of this procedure was minimized by carrying it out on patients who were already undergoing neurosurgery to treat motor diseases, including Parkinson disease and dystonia.
 
Once the microelectrodes were in place, patients were asked to complete a computer-based task in which they could gain or lose virtual money by responding to visual cues. The results showed that certain neurons in the GPi became active when patients lost virtual money.
 
Dr. Hutchison comments, “While the GPi is a known target for Parkinson disease, we are the first to show that individual neurons in this brain region respond to reward stimuli. This is particularly exciting because certain antiparkinson drugs have been shown to cause impulsive behaviours such as excessive gambling. Future studies will reveal whether GPi neurons are involved in these side effects.”
 
This work was supported by the Canadian Institutes of Health Research, the Wellcome Trust and the Toronto General & Western Hospital Foundation. AM Lozano is a Tier 1 Canada Research Chair in Neuroscience. University of Toronto MD PhD candidate Nicholas Howell carried out the work and is first author of the study.
 
Preliminary evidence for human globus pallidus pars interna neurons signaling reward and sensory stimuli. Howell NA, Prescott IA, Lozano AM, Hodaie M, Voon V, Hutchison WD. Neuroscience. doi: 10.1016/j.neuroscience.2016.04.020. 2016 Apr 22. [Pubmed abstract]