Dopamine and norepinephrine differentially mediate the exploration-exploitation tradeoff.

Area of Science:

• Neuroscience
• Computational Neuroscience
• Behavioral Pharmacology

Background:

• Dopamine (DA) and norepinephrine (NE) are catecholamines implicated in neuropsychiatric disorders, influencing decision-making.
• While sharing a synthesis pathway, DA and NE operate in distinct circuits, yet are often assigned similar roles in computational models of exploration-exploitation.
• Understanding their differential roles is crucial for developing mechanistic hypotheses in computational psychiatry.

Approach:

• Mice performed a dynamic decision-making task (restless two-armed bandit) to assess exploration and exploitation.
• Systemic administration of DA receptor antagonist (flupenthixol) and agonist (apomorphine).
• Systemic administration of NE beta-receptor antagonist (propranolol) and agonist (isoproterenol).

Key Points:

• Dopamine receptor activity showed a bidirectional effect on exploration: increased DA decreased exploration, while decreased DA increased exploration.
• Beta-noradrenergic receptor activity modulated exploration, with effects dependent on sex.
• Reinforcement learning models indicated DA modulates exploration via decision noise, and NE via outcome sensitivity.

Conclusions:

• Catecholamine systems, dopamine and norepinephrine, play distinct roles in regulating the exploration-exploitation tradeoff.
• Mechanisms governing transitions between exploration and exploitation are sensitive to catecholamine function.
• Findings highlight differential contributions of NE and DA to mediating exploration in decision-making.