Chapter 3 - The ventral striatum: a heterogeneous structure involved in reward processing, motivation, and decision-making

Abstract

The ventral striatum is at the crossroads of neural networks that treat various aspects of reward processes and motivation. This chapter reviews the evidence for the involvement of the ventral striatum in the processes of reward, motivation, and decision-making based on three principal approaches used in nonhuman primates. The chapter concentrates on results from studies carried out in monkeys that enable to understand how the ventral striatum could be involved in these various functions. The discussion draws primarily on results obtained from three technical approaches: the study of the anatomical pathways traced by injection of classical and viral tracers, the recording of neuronal activity in monkeys engaged in different behavioral tasks, and the studies of behavioral effects produced by local perturbation of neuronal function within the ventral striatum. The anatomical approach has shown that the ventral striatum receives information from cortical areas implicated in the processes of reward and motivation and could take part in a heterogeneous aspect in these functions by their different ways of projections. Neuronal recordings in monkeys performing delay tasks confirmed the role of ventral striatum in the processes of reward and motivation while revealing a remarkable heterogeneity in the manner in which neuronal activity reflected these variables. Finally, the local activation of the neuronal activity clearly identified subterritories inside ventral striatum that appear to be devoted specifically to different aspects of motivation. The convergence of these results derived from different approaches provides strong evidence of the importance of ventral striatum in the treatment of reward, motivation, and decision-making.