Tonic dopamine, uncertainty and basal ganglia action selection

Area of Science:

• Neuroscience
• Computational Neuroscience
• Decision Science

Background:

• Optimal decision-making under uncertainty necessitates flexible adaptation of behavior, involving exploration of alternatives and exploitation of known options.
• The basal ganglia (BG) are implicated in action selection and behavioral flexibility, but the precise mechanisms governing explore-exploit strategies remain incompletely understood.

Purpose of the Study:

• To propose and validate a computational model of the basal ganglia that explains how interactions between dopamine and cortical input mediate switches between exploratory and exploitative decisions.
• To investigate the role of tonic dopamine fluctuations in optimizing the explore-exploit balance in response to varying environmental uncertainty.

Main Methods:

• Development of a biologically detailed action selection circuit model incorporating dopamine-dependent striatal plasticity.
• Simulation of the model on a noisy Gaussian diffusion process to estimate underlying states and solve the explore-exploit problem.
• Analysis of the effects of fluctuating tonic dopamine levels on the model's decision-making precision and selectivity.

Main Results:

• The model successfully solved the explore-exploit problem, achieving performance comparable to an optimal Kalman filter.
• Fluctuating tonic dopamine levels, increasing under uncertainty, were critical for optimal model performance.
• Dopamine modulated the precision of action selection: reduced selectivity under high uncertainty promoted exploration, while enhanced selectivity under low uncertainty facilitated exploitation.

Conclusions:

• The basal ganglia circuit, modulated by dopamine, provides an effective mechanism for adaptive decision-making in non-stationary reward environments.
• The model offers insights into the neural basis of behavioral flexibility and generates testable predictions for neuropsychiatric and neurological disorders characterized by decision-making deficits.