Hypnotic suggestions of safety reduce neuronal signals of delay discounting.

Waiting for delayed rewards is important to reach long-term goals, yet most people prefer immediate rewards. This tendency is called delay discounting. Evidence shows that people are more willing to wait for delayed rewards when they believe that the delayed reward is certain. We hypothesized that feeling safe makes delayed outcomes subjectively more certain, which should in turn reduce neuronal signals of delay discounting. We hypnotized 24 highly suggestible participants and gave them a suggestion to feel safe. We then used EEG to measure their brain responses to immediate and delayed rewards while they played a delayed gratification game. As compared to a control condition without hypnosis, participants that were suggested to feel safe under hypnosis reported feeling significantly safer. Further, their reward-related brain activity differentiated less between immediate and delayed rewards. We conclude that feeling safe makes delayed outcomes subjectively more certain and therefore reduces neuronal signals of delay discounting.

Reward positivity: Reward prediction error or salience prediction error?

The reward positivity is a component of the human ERP elicited by feedback stimuli in trial-and-error learning and guessing tasks. A prominent theory holds that the reward positivity reflects a reward prediction error signal that is sensitive to outcome valence, being larger for unexpected positive events relative to unexpected negative events (Holroyd & Coles, 2002). Although the theory has found substantial empirical support, most of these studies have utilized either monetary or performance feedback to test the hypothesis. However, in apparent contradiction to the theory, a recent study found that unexpected physical punishments also elicit the reward positivity (Talmi, Atkinson, & El-Deredy, 2013). The authors of this report argued that the reward positivity reflects a salience prediction error rather than a reward prediction error. To investigate this finding further, in the present study participants navigated a virtual T maze and received feedback on each trial under two conditions. In a reward condition, the feedback indicated that they would either receive a monetary reward or not and in a punishment condition the feedback indicated that they would receive a small shock or not. We found that the feedback stimuli elicited a typical reward positivity in the reward condition and an apparently delayed reward positivity in the punishment condition. Importantly, this signal was more positive to the stimuli that predicted the omission of a possible punishment relative to stimuli that predicted a forthcoming punishment, which is inconsistent with the salience hypothesis.

Sensitivity of frontal beta oscillations to reward valence but not probability.

Reward feedback elicits a brief increase in power in the high-beta frequency range of the human electroencephalogram (EEG) over frontal areas of the scalp, but the functional role of this oscillatory activity remains unclear. An observed sensitivity to reward expectation (HajiHosseini, Rodríguez-Fornells, and Marco-Pallarés, 2012; [2]) suggests that reward-related beta may index a reward prediction error (RPE) signal for reinforcement learning. To investigate this possibility we reanalyzed EEG data from two prior experiments that revealed RPEs in the human event-related brain potential (Holroyd and Krigolson, 2007 [12]; Holroydet al., 2008 [13]). We found that feedback stimuli that indicated reward, when compared to feedback stimuli that indicated no-reward, elicited relatively more beta power (20-30 Hz) over a frontal area of the scalp. However, beta power was not sensitive to feedback probability. These results indicate that reward-related beta does not index an RPE but rather relates to a different reward processing function.

The topographical N170: electrophysiological evidence of a neural mechanism for human spatial navigation.

We recently demonstrated that the latency of a component of the event-related brain potential, the topographical N170 (NT170), is sensitive to the spatial location of reward-related stimuli in a virtual maze environment, occurring earlier for rewards found following rightward turns compared to leftward turns. We suggested that this NT170 latency effect may result from phase reset of an ongoing theta rhythm by a parahippocampal system for spatial navigation. Here we tested several predictions that follow from this proposal, namely, that the effect is observed only when the rewards are presented in a spatial environment, that it is sensitive to individual differences in spatial ability, that it is localizable to the right parahippocampal region, and that it is consistent with partial phase resetting of an ongoing theta rhythm. These results hold promise for integrating ERP measures of spatial navigation with extensive animal, human, and computational literatures on parahippocampal function.

The feedback-related negativity reflects the binary evaluation of good versus bad outcomes.

Electrophysiological studies have utilized event-related brain potentials to study neural processes related to the evaluation of environmental feedback. In particular, the feedback-related negativity (FRN) has been shown to reflect the evaluation of monetary losses and negative performance feedback. Two experiments were conducted to examine whether or not the FRN is sensitive to the magnitude of negative feedback. In both experiments, participants performed simple gambling tasks in which they could receive a range of potential outcomes on each trial. Relative to feedback indicating monetary gain, feedback indicating non-rewards was associated with a FRN in both experiments; however, the magnitude of the FRN did not demonstrate sensitivity to the magnitude of non-reward in either experiment. These data suggest that the FRN reflects the early appraisal of feedback based on a binary classification of good versus bad outcomes. These data are discussed in terms of contemporary theories of the FRN, as well as appraisal processes implicated in emotional processing.

Knowing good from bad: differential activation of human cortical areas by positive and negative outcomes.

Previous research has identified a component of the event-related brain potential (ERP), the feedback-related negativity, that is elicited by feedback stimuli associated with unfavourable outcomes. In the present research we used event-related functional magnetic resonance imaging (fMRI) and electroencephalographic (EEG) recordings to test the common hypothesis that this component is generated in the caudal anterior cingulate cortex. The EEG results indicated that our paradigm, a time estimation task with trial-to-trial performance feedback, elicited a large feedback-related negativity (FRN). Nevertheless, the fMRI results did not reveal any area in the caudal anterior cingulate cortex that was differentially activated by positive and negative performance feedback, casting doubt on the notion that the FRN is generated in this brain region. In contrast, we found a number of brain areas outside the posterior medial frontal cortex that were activated more strongly by positive feedback than by negative feedback. These included areas in the rostral anterior cingulate cortex, posterior cingulate cortex, right superior frontal gyrus, and striatum. An anatomically constrained source model assuming equivalent dipole generators in the rostral anterior cingulate, posterior cingulate, and right superior frontal gyrus produced a simulated scalp distribution that corresponded closely to the observed scalp distribution of the FRN. These results support a new hypothesis regarding the neural generators of the FRN, and have important implications for the use of this component as an electrophysiological index of performance monitoring and reward processing.

Brain potentials associated with expected and unexpected good and bad outcomes.

The error-related negativity (ERN) is an event-related brain potential observed when subjects receive feedback indicating errors or monetary losses. Evidence suggests that the ERN is larger for unexpected negative feedback. The P300 has also been shown to be enhanced for unexpected feedback, but does not appear to be sensitive to feedback valence. The present study evaluated the role of expectations on the ERN and P300 in two experiments that manipulated the probability of negative feedback (25%, 50%, or 75%) on a trial-by-trial basis in experiment 1, and by varying the frequency of positive and negative feedback across blocks of trials in experiment 2. In both experiments, P300 amplitude was larger for unexpected feedback; however, the ERN was equally large for expected and unexpected negative feedback. These results are discussed in terms of the potential role of expectations in processing errors and negative feedback.

Reinforcement-related brain potentials from medial frontal cortex: origins and functional significance.

The development of the field of cognitive neuroscience has inspired a revival of interest in the brain mechanisms involved in the processing of rewards, punishments, and abstract performance feedback. One fruitful line of research in this area was initiated by the report of an electrophysiological brain potential in humans that was differentially sensitive to negative and positive performance feedback [J. Cogn. Neurosci. 9 (1997) 788]. Here we review current knowledge regarding the neural basis and functional significance of this feedback-evoked 'error-related negativity' (ERN). Our review is organized around a set of predictions derived from a recent theory, which holds that the ERN is associated with the arrival of a negative reward prediction error signal in anterior cingulate cortex.