Search

Background Blunted reward processing has emerged as an endophenotype of major depressive disorder (MDD), but mechanistic understanding for this deficit remains elusive. The current event-related potential study examined whether this aberration is driven by the blunted effect of perceived control on reward processing. Methods We adapted a well-validated gambling task in which perceived control was exercised by choice in 29 individuals with current MDD and 31 healthy controls. We examined the reward positivity in response to personally chosen versus passively received rewards. Results We found that MDD patients relative to healthy controls exhibited a blunted reward positivity when rewards were delivered following voluntary choices but not when they were delivered following passive choices. This pattern was not observed during the relatively late stage, as indexed by the P300, of feedback processing. Limitation The current findings may be confounded with medication and anxiety. Conclusions These findings suggest that deficient reward processing in MDD is attributable to the deficiency in boosting reward responsivity by perceived control exercised by choice.

Sensation seeking is characterized by a strong need for novelty and has been associated with various risk-taking behaviors. Using the extreme between-group design, the current study investigated the electrophysiological mechanisms underlying habituation to novelty processing in sensation seeking. Twenty high sensation seekers (HSS) and 20 low sensation seekers (LSS) performed an auditory oddball task while their EEG was recorded. The results revealed that both the novelty P3 and midfrontal theta power decreased from the first to the second half for LSS but not for HSS. Additionally, this reduced vigilance was predicted by the experience-seeking subcomponent of sensation seeking. Together, our findings are supportive of an abnormal habituation to novel events in the sensation-seeking trait.

Previous research has demonstrated that reward-related neural activity is enhanced for choice relative to no-choice opportunities in the gain context. The current event-related potential study examined whether this modulatory effect of choice can be observed in both the gain and the loss contexts across anticipatory and consummatory phases of incentive processing. Thirty-two participants performed a simple choice task during which choices were made either by themselves (a choice condition) or by a computer (a no-choice condition) during a gain context (gain vs nongain) and a loss context (nonloss vs loss). Behaviorally, participants reported a higher level of perceived control in the choice than the no-choice condition as well as in the gain than loss context. During the anticipatory phase, the choice relative to the no-choice condition elicited an increased cue-P3 in the loss context and an enhanced stimulus-preceding negativity in the gain context. During the consummatory phase, the choice condition elicited a larger reward positivity (ΔRewP) than the no-choice condition in the gain relative to the loss context but a comparable feedback P3 across contexts. These findings demonstrate that the crucial role of voluntary choice in reward processing is contingent upon contextual valence.

The current study examined how the experience of choice by which individuals exercise control modulates risk processing during the anticipatory phase as indexed by the stimulus-preceding negativity (SPN), and the consummatory phase as indexed by the feedback-related negativity (FRN) and feedback P3 (fb-P3). Twenty-four participants performed a simple gambling task during which they could win or lose either a small (a low-risk condition) or a large (a high-risk condition) amount of points by either choosing freely between two doors (a choice condition) or accepting a computer-selected door (a no-choice condition) while their EEG was recorded. As expected, participants rated the high-risk condition as more risky than the low-risk condition and reported higher feelings of control for the choice versus no-choice condition. Regardless of the involvement of choice, risk processing in this task was associated with greater fb-P3 amplitudes. However, during the choice condition, risk processing was associated with a more negative SPN during the anticipatory phase and a more positive FRN during the consummatory phase, which was absent (the SPN) or reduced (the FRN) in the no-choice condition. These findings suggest that the modulation of risk processing by choice occurs during both the anticipatory phase and the consummatory phase, which may be driven by motivation salience imposed by control.

Previous research has shown that feedback evaluation is sensitive to monetary incentive. We investigated whether this sensitivity is driven by motivational salience (the difference between both rewarding and punishing events versus neutral events) or by motivational valence (the difference between rewarding and punishing events). Fifty-seven participants performed a monetary incentive delay task under a gain context, a loss context, and a neutral context with their electroencephalogram recorded. During the time domain, the feedback-related negativity (FRN) showed a motivational salience effect whereas the P3 displayed a reward valence effect. During the time-frequency domain, we observed a motivational salience effect for phase-locked theta power regardless of performance feedback, but a reward valence effect for non-phase-locked theta power in response to unsuccessful feedback. Moreover, we found a reward valence effect for phase-locked delta. These findings thus suggest that the affective modulation on feedback evaluation can be driven either by motivational valence or by motivational salience, which depends on the temporal dynamics (the FRN vs. the P3), the frequency dynamics (theta vs. delta power), as well as the phase dynamics (evoked vs. induced power).

Cancer stem cells are reportedly associated with drug resistance in glioma, but there are conflicting findings on the effects of cancer stem cells on drug resistance. The aim of the present study was to identify the underlying mechanisms of drug resistance in rat C6 glioma cells, through the use of Transwell invasion assays, flow cytometric and western blot analyses as well as immunohistochemical staining. The results revealed that acquisition of drug resistance by C6 cells enhanced migration ability in vivo and in vitro. Notably, drug resistance did not depend on the cancer stem cells of C6 cells, but on the increase of a side population phenotype. Blockade of the ABC transporter could increase sensitivity to temozolomide and temozolomide-induced apoptosis in C6 cells. Collectively, these data indicated that drug resistance of C6 cells was mediated by the side population phenotype rather than by cancer stem cells.

Effort expenditure not only discounts reward value prospectively but also accrues reward value retrospectively. To decompose the effort paradox in reward processing, the current event-related potential study investigated the neural dynamics underlying effects of effort expenditure on subsequent reward processing. Participants exerted one of two levels of effort to obtain an opportunity of winning a high or low amount of monetary reward, and we focused on electrophysiological activity during the anticipatory and consummatory phases of reward processing. During the anticipatory phase, the stimulus-preceding negativity was enhanced when potential high rewards were anticipated, but this reward effect disappeared following high-effort expenditure. During the consummatory phase, feedback-related ERPs were increased for high relative to low rewards, and this reward effect was enlarged following effort expenditure during the early stage (200–300 ms) as indexed by the reward positivity but not the late stage (400–600 ms) as indexed by the P3. Our findings provide a strong support for the psychological contrast theory and indicate that time matters in decomposing the effort paradox for reward processing such that effort expenditure reduces reward sensitivity during the anticipatory phase but enhances reward sensitivity during the consummatory phase.

The sensation-seeking trait is a potential endophenotype for various addictive behaviors. Using a nonclinical sample, the current ERP study examined the effects of sensation seeking on performance monitoring and response inhibition. Twenty high sensation seekers and 21 low sensation seekers were selected from a large sample based on their sensation-seeking score and performed a stop-signal task while their EEG was recorded. High relative to low sensation seekers displayed similar response inhibition in terms of performance measure and stop-P3 amplitudes. Compared to low sensation seekers, however, high sensation seekers exhibited a reduced stop-N2 for unsuccessful, but not successful, inhibition. Moreover, an enhanced go-N2 in response to go signals was observed for high versus low sensation seekers, irrespective of whether the go signals were followed by a stop signal or not. Together, our findings suggest that sensation seeking in nonclinical populations is related to individual variability in performance monitoring rather than response inhibition, which provides important implications for the prevention and intervention of addictive behaviors that are driven by trait sensation seeking.

Previous research found that the neural substrates underlying perceived control highly overlap those of reward system, especially during reward anticipation stage. The current event-related potential study examined whether the experience of choice by which individuals exercise control is modulated by reward probability during reward anticipation stage as indexed by the stimulus-preceding negativity (SPN). Thirty participants performed a cued gambling task during which choices could be made either by themselves (a choice condition) or by a computer (a no-choice condition) with three levels of reward probability (low, medium, and high) while their EEG was recording. As expected, the participants perceived higher control during the choice compared to no-choice condition. Correspondingly, the SPN was enhanced in the choice condition than the no-choice condition. Critically, the SPN choice effect was present when reward probability was high and medium, but was diminished when reward probability was low. These findings suggest that the perceived control as exercised by choice is associated with reward anticipation, which may be sensitive to the fundamental properties of reward.