Working memory limitations and dopamine modulation in probabilistic reasoning

In the study of complex decision-making, researchers observed two macaque monkeys perform a task demanding extended evidence sampling. This task relied heavily on working memory, which is the cognitive system responsible for temporarily holding information available for processing. The monkeys were presented with a series of cues, each offering probabilistic evidence about which choice would yield a reward.

The researchers found that working memory limitations significantly impacted the monkeys' choices. Factors such as working memory decay, primacy (the tendency to remember items presented at the beginning of a sequence), recency (the tendency to remember items from the end of a sequence), and priming (the enhancement of performance on a task due to prior exposure to similar information) all played a role in the monkeys' decisions.

Despite individual differences in working memory capacity, both monkeys developed strategies that improved their decision-making, making their behavior nearly optimal.

To investigate the role of dopamine in working memory constraints on evidence accumulation, the researchers administered dopamine D1 receptor agonist and antagonist drugs to the monkeys during specific sessions. The D1 receptor agonist activated dopamine receptors, which led to a reduction in priming. Conversely, blocking the D1 receptors diminished working memory decay and altered the subjective evidence weights assigned to individual cues.

The findings of this study indicate that working memory constraints are a crucial factor in complex decision-making processes. Moreover, the researchers identified dopamine as a significant modulator of this process. By influencing working memory limitations and evidence accumulation, dopamine could potentially play a pivotal role in cognitive disorders and might offer new avenues for treatment.