Neuroanatomy of Reward: A View from the Ventral Striatum

Excerpt

The ability to predict and evaluate reward value, and use that information to develop and execute an action plan efficiently, requires: first, integration of incoming sensory information with reward value, expectation, and memory; second, the incorporation of that information with cognition to develop the plan; and finally, the motor control to execute it. However, the BG are traditionally considered to process information in parallel and segregated functional streams consisting of reward (limbic), associative (cognitive), and motor control circuits (Alexander and Crutcher 1990). Moreover, microcircuits within each region are thought to mediate different aspects of each function (Middleton and Strick 2002). Nonetheless, expressed behaviors are the result of a combination of complex information processing that involves all of frontal cortex. Indeed, appropriate responses to environmental stimuli require continual updating and learning to adjust behaviors according to new data. This requires coordination between sensory, limbic, cognitive, and motor systems. While the anatomical pathways are generally topographic from cortex through BG circuits, a large body of growing evidence supports a dual processing system. Thus, information is not only processed in parallel streams, but also through integrative mechanisms through which information can be transferred between functional circuits (Bar-Gad et al. 2000; Belin and Everitt 2008; Bevan, Clarke, and Bolam 1997; Draganski et al. 2008; Haber et al. 2006; Haber, Fudge, and McFarland 2000; Kolomiets et al. 2001; McFarland and Haber 2002b; Mena-Segovia et al. 2005; Percheron and Filion 1991). This chapter will first discuss the place of the reward circuit in the BG; second, how the sensory systems interface within this circuit; and third, the anatomical basis for integrating the reward circuit with cognition and motor control systems.