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. 2014 Oct;128(5):556-66.
doi: 10.1037/a0037128. Epub 2014 Jun 9.

Dopamine Modulates Novelty Seeking Behavior During Decision Making

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Free PMC article

Dopamine Modulates Novelty Seeking Behavior During Decision Making

Vincent D Costa et al. Behav Neurosci. .
Free PMC article

Abstract

Novelty seeking refers to the tendency of humans and animals to explore novel and unfamiliar stimuli and environments. The idea that dopamine modulates novelty seeking is supported by evidence that novel stimuli excite dopamine neurons and activate brain regions receiving dopaminergic input. In addition, dopamine is shown to drive exploratory behavior in novel environments. It is not clear whether dopamine promotes novelty seeking when it is framed as the decision to explore novel options versus the exploitation of familiar options. To test this hypothesis, we administered systemic injections of saline or GBR-12909, a selective dopamine transporter (DAT) inhibitor, to monkeys and assessed their novelty seeking behavior during a probabilistic decision making task. The task involved pseudorandom introductions of novel choice options. This allowed monkeys the opportunity to explore novel options or to exploit familiar options that they had already sampled. We found that DAT blockade increased the monkeys' preference for novel options. A reinforcement learning (RL) model fit to the monkeys' choice data showed that increased novelty seeking after DAT blockade was driven by an increase in the initial value the monkeys assigned to novel options. However, blocking DAT did not modulate the rate at which the monkeys learned which cues were most predictive of reward or their tendency to exploit that knowledge. These data demonstrate that dopamine enhances novelty-driven value and imply that excessive novelty seeking-characteristic of impulsivity and behavioral addictions-might be caused by increases in dopamine, stemming from less reuptake.

Figures

Figure 1
Figure 1. Task design
A) Sequence of events on a single trial. Following an initial fixation period, the choice options were presented and the animals made a saccade to one of the options to indicate their choice. A juice reward was then delivered probabilistically based on the assigned reward probability of the chosen cue. B) Novelty manipulation. A set of options was repeatedly presented for 10–30 trials, after which one of the existing options was replaced with a novel option. The novel option was randomly assigned its own reward probability. Novel options were introduced 32 times in a block of 650 trials. Trial Ni,j refers to the number of times, j, a particular set of choice options, i, was seen.
Figure 2
Figure 2. DAT blockade increases novelty seeking behavior and the initial value of novel options
A) Mean fraction of times each option was chosen. B) Mean initial value (vi0) of novel options and the mean value of the best alternative when the novel option was introduced, as estimated by the RL model for drug and saline sessions. C and D) The inverse temperature parameter β and choice entropy H—which summarize the overall balance in explore/exploit behavior—did not differ between the drug and saline conditions.
Figure 3
Figure 3. Reward related effects on novelty seeking
A) Fraction of times the novel option or best alternative option was selected broken out by A) the combined reward probabilities of the two alternative options, B) the reward probability of the cue replaced by the novel option, and C) reward receipt on the immediately preceding trial.
Figure 4
Figure 4. Dopamine does not affect learning rates
A) Learning rate parameter fit to blocks completed on GBR-12909 or saline. B) Fraction of times a novel option, with an assigned reward probability, was selected on GBR-12909 or saline up to 20 trials after its initial presentation. Choice data were smoothed with a 6 trial moving average kernel.

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