ABSTRACT

This chapter describes the contribution of the basal ganglia (BG) to motivated behaviors. Damage to the limbic and associative BG networks produces symptoms like abulia and apathy. In the limbic BG, different circuits specialize in consummatory and preparatory components of motivated behavior. The nucleus accumbens shell is a critical node in a circuit for consummatory behavior, whereas the nucleus accumbens core is a critical node in a circuit for approach behavior and effort exertion. According to the present model, effort is determined largely by the gain of the reward rate controller, as it recruits any number of effective actions. A labile motivational hierarchy can explain the contributions of parallel cortico-BG circuits to motivated behavior. This hierarchy coordinates means and ends, selecting specific instrumental actions to satisfy specific needs and desires. It is implemented by parallel and interacting BG networks, which allows limbic BG outputs to exert a unidirectional influence on the sensorimotor network. Through learning, homeostatic error signals for essential physiological variables and predictors of error reduction in these variables can recruit the action hierarchy for the production of specific actions.