Objective:

 We here used a standard gambling task that involved risky decision-making. This permitted us to measure the effects of ventral tegmental area (VTA) deep brain stimulation (DBS) on impulsivity measured by both risk-seeking behaviour and time taken to make these choices.

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Background: Dopamine plays a key role in decision-making. Overstimulation within dopaminergic pathways can lead to impulsive behaviour, including a desire to take risks and faster deliberation times. These behavioural patterns can be observed under treatment with dopaminergic drugs in Parkinson’s disease. It has been proposed that endogenous dopamine controls reward-related decisions via the mesolimbic pathway, which originates in the VTA. Patients with DBS within the VTA hence offer a unique opportunity to study whether or not mesolimbic dopamine influences risky decision-making.

Method:

Eleven patients (49.45 ± 14.22 years, 6 female), who underwent VTA DBS surgery for headache, completed this task four times during 2 sessions in a powerful randomised double-cross-over design (ON-OFF/OFF-ON). The task (Rogers et al. 2003) comprised of 80 trials in which participants had to choose between two gambles of which one served as a “conservative gamble” and had a 50% chance of winning while the second option was an “experimental gamble”, with a variable probability of winning (high 0.6 or low 0.4) and magnitude of wins or losses (large, 70 points vs. small, 30 points). Because of this, the experimental gamble always had a higher risk than the control gamble but had an expected value that was sometimes higher or lower. The participants were instructed to maximise their wins by the end of the task. A mixed linear model was used to analyse the effect of VTA DBS on (1) the proportion of trials when the experimental gamble was chosen as well as (2) the time taken to decide.

Results:

 There was no main effect of DBS on the proportion of experimental gamble (p = .62) or the deliberation time (p= .13) found in our analysis.

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Conclusion:

DBS within the VTA did not significantly affect risky decision-making using a standard gambling task. This was despite DBS being generally effective for treating headache in these patients. The findings provide some evidence against VTA dopamine being critical for driving impulsivity, at least in this sample. Confirmation in a larger sample using a Bayesian design would be important.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/ventral-tegmental-deep-brain-stimulation-does-not-influence-risk-taking-behaviour-in-a-standard-gambling-task/