Linking reward expectation to behavior in the basal ganglia

Abstract

Psychological factors such as expected reward value can have strong effects on behavior. Although signals related to reward have been found in numerous brain regions, how these signals are used by the circuits that control action is unknown. A recent study suggests that neurons in the caudate nucleus of the basal ganglia could play a role in transforming expected reward into a spatially selective behavioral bias.Poor Paris was asked to make a decision that even Zeus had avoided. Who was the most beautiful goddess: Hera, Athena or Aphrodite? Fearful and uncertain about how his decision would be received by the losers, he triedtactfully but unsuccessfully -to declare a three-way tie. Told to make a decision, Paris received assurances that there would be no reprisals and, even better, was offered rewards by the goddesses to try to influence him. Hera promised that if he picked her, he would become the King of Asia, as well as the richest man alive. Athena promised that Paris would be victorious in all battles, and that he would become the most handsome and wise man in the world. Aphrodite offered, simply, the beautiful Helen of Troy. It was no contest: Aphrodite's reward easily biased Paris' decision in her favor.The fact that 'psychological' factors, including uncertainty and anticipated costs and benefits, biased the judgment of Paris and can affect similarly subjective decisions is to be expected. Perhaps more surprising is that these factors can also shape our ability to perform even mundane sensory-motor tasks, influencing how well and how quickly we perceive sensory stimuli and execute appropriate motor commands [1,2]. However, as central as these influences are to both complex and simple behaviors, little is known about the underlying neural mechanisms. For example, despite a growing body of work identifying neural circuits that represent information related to reward in the context of sensory -motor tasks [3], how these kinds of signals might influence behavior is a mystery. A recent study by Lauwereyns and colleagues has begun to shed light on this difficult issue [4]. The results describe neural signals in a region of the basal ganglia called the caudate nucleus that appear to relate anticipation of an uncertain reward with the preparation for a goal-directed eye movement.Caudate responses correspond to an advance bias In their study, Lauwereyns and colleagues trained monkeys to perform a 'biased saccade task' (BST). On a given trial, the monkey fixated a central spot of light until a target (another spot of light) appeared to the left or to the right. Once the target appeared, the monkey made a saccadic eye movement to it as quickly as possible. Then came the crucial feature of the task: after correctly making the saccade, the monkey was rewarded (with a sound plus a drop of liquid) only if the target was in one of the two possible locations. The rewarded location was fixed in blocks of 20 consecutive trials, such that only correct leftward saccades were rewarded in one block, only correct rightward sacc...

Structural MRI correlates for vulnerability and resilience to major depressive disorder

“…[42][43][44][45][46][47] The CSPT is a circuit that includes the PFC and regulates reward-seeking behaviours as well as anticipation and evaluation of rewarding stimuli. 48,49 Given that anhedonia is a key symptom in depression, the reduced grey matter volumes we found in both the HC-FHP group and patients with MDD might further strengthen the relation between CSPT dysfunctions and vulnerability to depression. In particular, the grey matter volume reductions found in our HC-FHP participants might also suggest that in high-risk individuals structural remodelling might take place in the hippocampus independently from the onset of MDD symptoms.…”

Subcortical volumes differentiate Major Depressive Disorder, Bipolar Disorder, and remitted Major Depressive Disorder

“…These circuits have been posited to form the core of the neural systems associated with abnormality in mood disorders Drevets, 2009, 2012). Specifically, these neural systems are involved in rewardseeking behaviors including reward anticipation and evaluation (Kawagoe et al, 1998;Gold, 2003). Importantly, a core symptom of depression is anhedonia, or the inability to experience pleasure; consequently, the CSPT and ASPT have been of considerable interest to researchers studying this disorder.…”

Modulation of Behavior by Expected Reward Magnitude Depends on Dopamine in the Dorsomedial Striatum

“…Environmental cues predictive of reward powerfully influence the vigor of reward-seeking responses (Gold 2003). For example, in addicts cues predictive of drug reward can elicit craving, support compulsive drug use or precipitate relapse to drug-seeking behavior (O'Brien et al 1998;Volkow et al 2006).…”