Anticipating instrumentally obtained and passively-received rewards: a factorial fMRI investigation

Abstract

During functional magnetic resonance imaging (fMRI), subjects saw cues signaling probabilities of 1.0, 0.5, and 0 of winning $1 for hitting a subsequent target, and cues signaling similar probabilities of reward delivery requiring no instrumental response. Non-instrumental reward anticipation did not elicit activation. Instrumental reward anticipation activated multiple nodes of the basal ganglia-thalamocortical motor circuit. Ventromesial striatum was activated by joint requirement for an instrumental response together with uncertain (but not certain) reward.

Figure 1

The Factorial Reward Anticipation (FRA) task. Trials lasted 6 s, and were separated by jittered intertrial intervals of 2–8 s. Subjects first saw one of six cues that signaled whether the subject needed to respond (squares) or to not respond (circles) to the target that followed, and what the consequences of the trial would be. In response trials, subjects were required to respond to the target during the 500 ms period when the target was displayed. The cue signaled a certain gain of $1 (square-$), a 50% chance of a $1 gain (square-?), or no gain (square-0) for hitting the target. In non-response trials, subjects did not respond to the targets, but viewed the identical range of signaled gain probabilities. Each trial concluded with 1.5 s of feedback of gain or non-gain..

Figure 2

Activation by anticipation of instrumental responding for uncertain reward. (A) linear contrast between responding for uncertain (p = 0.5) reward linearly contrasted with anticipation of responding for non-reward (p = 0) (B) linear contrast between responding for certain (p = 1.0) reward contrasted with anticipation of responding for non-reward (p = 0). All statistical maps are overlaid on a sample subject’s T1-weighted image, where Taliarach coordinate of each coronal view is shown.

Figure 3

Activation by a higher-order combination of reward with an instrumental response requirement. A) Instrumental-specific activation during anticipation of responding for uncertain (p = 0.5) reward versus no reward (p = 0), and (B) Instrumental-specific activation during anticipation of responding for certain (p = 1.0) reward versus no reward (p = 0).