No abstract

Decision makers often face choices whose consequences unfold over time. To explore the neural basis of such intertemporal choice behavior, we devised a novel two-alternative choice task with probabilistic reward delivery and contrasted two conditions that differed only in whether the outcome was revealed immediately or after some delay. In the immediate condition, we simply varied the reward probability of each option and the outcome was revealed immediately. In the delay condition, the outcome was revealed after a delay during which the reward probability was governed by a constant hazard rate. Functional imaging revealed a set of brain regions, such as the posterior cingulate cortex, parahippocampal gyri, and frontal pole, that exhibited activity uniquely associated with the temporal aspects of the task. This engagement of the so-called "default network" suggests that during intertemporal choice, decision makers simulate the impending delay via a process of prospection.

The feedback negativity (FN) has been shown to reflect the binary evaluation of possible outcomes in a context-dependent manner, but it is unclear whether context-dependence is based on global or local alternatives. A cued gambling task was used to examine whether the FN is sensitive to possible outcomes on a given trial, or the range of outcomes across trials. On 50% of trials, participants could break even or lose money; on remaining trials, participants could win or break even. Breaking even was an unfavorable outcome relative to all possibilities in the current task, but the best possible outcome on 50% of trials. Results indicated that breaking even elicited an FN in both contexts, and reward feedback was uniquely associated with an enhanced positivity. Results suggest that the magnitude of the FN depends on all possible outcomes within the current task and are consistent with the view that the FN reflects reward-related neural activity.

No abstract

The feedback negativity (FN), an early neural response that differentiates rewards from losses, appears to be generated in part by reward circuits in the brain. A prominent model of the FN suggests that it reflects learning processes by which environmental feedback shapes behavior. Although there is evidence that human behavior is more strongly influenced by rewards that quickly follow actions, in nonlaboratory settings, optimal behaviors are not always followed by immediate rewards. However, it is not clear how the introduction of a delay between response selection and feedback impacts the FN. Thus, the present study used a simple forced choice gambling task to elicit the FN, in which feedback about rewards and losses was presented after either 1 or 6 s. Results suggest that, at short delays (1 s), participants clearly differentiated losses from rewards, as evidenced in the magnitude of the FN. At long delays (6 s), on the other hand, the difference between losses and rewards was negligible. Results are discussed in terms of eligibility traces and the reinforcement learning model of the FN.