The modulation of pain in reward processing is reflected by increased P300 and delta oscillation.

Pain elicits the desire for a reward to alleviate the unpleasant sensation. This may be a consequence of facilitated neural activities in the reward circuit. However, the temporal modulation of pain on reward processing remains unclear. We addressed this issue by recording electroencephalogram when participants received win or loss feedback in a simple gambling task. Pain treatment was conducted on 33 participants with topical capsaicin cream and on 33 participants with hand cream as a control. Results showed that pain generally increased the P300 amplitude for both types of feedback but did not affect feedback-related negativity (FRN). A significant interaction effect of treatment (painful, non-painful) and outcome (win, loss) was observed on delta oscillation as pain only enhanced the power of win feedback. In addition, the FRN and theta oscillation responded more to loss feedback, but this effect was unaffected by pain. These findings indicate that pain may enhance secondary value representation and evaluation processes of rewards, but does not influence primary distinction of reward or reward expectation. The temporal unfolding of how pain affects reward-related neural activities highlights the prominent impact of pain on high-level cognitive processes associated with reward.

Li X ，Zhou X ，Zheng H ，Wang C ... -  《-》

The Brain's Reward Response Occurs Even Without Actual Reward!

Fielding A ，Fu Y ，Franz EA 《-》

Enhanced neural responses to monetary rewards in methamphetamine use disordered individuals compared to healthy controls.

Converging evidence supports that addiction involves the pathological usurpation of normal reward processes. However, the nature and direction of reward processing dysfunction in substance abusers remain unclear. The current study explored the electrophysiological responses associated with different stages of reward processing in methamphetamine (MA) use disordered individuals. Electroencephalography recording was used to compare responses of 21 MA use disordered individuals and 22 healthy controls (HC) while participants engaged in a simple gambling task. Compared to HC, MA use disordered individuals made more risky choices following a loss outcome on a previous trial. During the reward anticipatory stage, MA use disordered individuals showed an enhanced stimulus-preceding negativity (SPN), as compared to HC. During the reward outcome stage, MA use disordered individuals showed an enhanced feedback-related negativity (FRN) for the losses versus gains as compared to HC. Furthermore, an enhanced P300 was observed under the gain condition, but not under the loss condition, in MA use disordered individuals as compared to HC. These findings provide further evidence that MA use disordered individuals have a sensitized neural response to non-drug rewards and support the impulsivity and incentive sensitization theories in MA use disordered individuals. The current study helps to elucidate the neural mechanisms of reward processing in MA use disordered individuals.

Wei S ，Zheng Y ，Li Q ，Dai W ，Sun J ，Wu H ，Liu X ... -  《-》

Problem gamblers exhibit reward hypersensitivity in medial frontal cortex during gambling.

Problem gambling (PG) is increasingly conceptualized as an addiction akin to substance abuse, rather than an impulse control disorder, however the mechanism of addiction remains unclear. Neuroimaging investigations have supported a "reward deficiency" hypothesis for PG by suggesting a blunted response to gambling, particularly in the striatum. Here we describe electrophysiological evidence of a hypersensitive response to gambling feedback in problem gamblers. Previous research in healthy participants has shown that feedback during gambling tasks triggers stereotypical neural responses including the Feedback-Related Mediofrontal Negativity (FRN), the feedback-related P300, and an increase in induced theta-band (4-8 Hz) power. We tested the theory that abnormal feedback processing characterizes brain activity in problem gamblers while gambling. EEG was recorded from non-gamblers and self-identified gamblers as they engaged in a computerized version of the Iowa Gambling Task. Feedback about valence (win vs. loss) triggered a FRN in both groups, but in gamblers this was preceded by an early-latency hypersensitive fronto-central difference to feedback. This early FRN was correlated with gambling severity and was localized to medial frontal cortex using distributed source imaging (CLARA). Gamblers also differed in responses to risk, showing a blunted P300 component and less EEG power in the theta band. Here we suggest that a more nuanced interpretation of reward deficiency is called for with respect to PG. For certain aspects of brain function, gamblers may exhibit hypersensitivity to reward feedback more akin to drug sensitization than reward deficiency. Our results also suggest that the neurologically normal brain employs dissociable systems in the processing of feedback from tasks involving risky decision making.

Oberg SA ，Christie GJ ，Tata MS 《-》

Mood congruent tuning of reward expectation in positive mood: evidence from FRN and theta modulations.

Positive mood broadens attention and builds additional mental resources. However, its effect on performance monitoring and reward prediction errors remain unclear. To examine this issue, we used a standard mood induction procedure (based on guided imagery) and asked 45 participants to complete a gambling task suited to study reward prediction errors by means of the feedback-related negativity (FRN) and mid-frontal theta band power. Results showed a larger FRN for negative feedback as well as a lack of reward expectation modulation for positive feedback at the theta level with positive mood, relative to a neutral mood condition. A control analysis showed that this latter result could not be explained by the mere superposition of the event-related brain potential component on the theta oscillations. Moreover, these neurophysiological effects were evidenced in the absence of impairments at the behavioral level or increase in autonomic arousal with positive mood, suggesting that this mood state reliably altered brain mechanisms of reward prediction errors during performance monitoring. We interpret these new results as reflecting a genuine mood congruency effect, whereby reward is anticipated as the default outcome with positive mood and therefore processed as unsurprising (even when it is unlikely), while negative feedback is perceived as unexpected.

Paul K ，Pourtois G 《-》