Diversifying participation: The rarity of reporting racial demographics in neuroimaging research.

Functional neuroimaging has been instrumental to the field of cognitive neuroscience; however, its increasing prevalence has evoked conversations concerning limitations associated with reproducibility and bias. Prevailing racial, cultural, and socioeconomic biases in scientific research perpetuate demographic homogeneity in participation, contributing to failed replicability and generalizability and driving inaccurate representations of neurological normalcy. The current report employs systematic and exploratory search methods to investigate ongoing practices surrounding participant recruitment and documentation. The systematic search found that only 20 out of the 536 articles collected reported the race and ethnicity demographics of their participants, exposing a dearth of race and ethnicity demographics reporting in neuroimaging research. These results drive our recommendations for increased transparency and diversity surrounding research participation.

The reward positivity is sensitive to affective liking.

The EEG feature known as the Reward Positivity (RewP) is elicited by reward receipt and appears to reflect sensitively and specifically positive prediction errors during reinforcement learning. Yet, the RewP also is modulated by state and trait affect, suggesting that it has a more complex computational role than simple reinforcement surprise. We conducted a series of experiments aimed to investigate underlying affect processing reflected in the RewP during a reinforcement learning task. In the first experiment (N = 25), we manipulated the type of rewards a person could win (simple points or hedonically-appraised pictures). Although there were no differences in the amplitudes of the RewP for different types of rewards, there was a significant correlation between the individual rating of liking for the images and RewP amplitude. In a second experiment (N = 25), we manipulated reinforcement rates (easy vs. hard) and affective picture content (liked vs. ambivalent) to examine the potential interaction of prediction error and liking on RewP amplitude. We again found a significant relationship between liking and RewP amplitude, however, only in the hard condition. These findings suggest that the RewP reflects cortical computations of reward surprise as well as hedonic liking, identifying it as a possible nexus where multidimensional value is computed.

Decreases in the Late Positive Potential to Alcohol Images Among Alcohol Treatment Seekers Following Mindfulness-Based Relapse Prevention.

AIM: Heightened craving among individuals with alcohol use disorder (AUD) has been attributed to a hypersensitivity to alcohol cues in attentional brain networks. Active mindfulness training has been shown to help improve attentional control. Here, we examined alcohol cue-related hypersensitivity among individuals with AUD who received rolling group mindfulness-based relapse prevention (MBRP) in combination with transcranial direct current stimulation (tDCS), over right inferior frontal gyrus. METHODS: Participants (n = 68) viewed a series of emotionally negative, emotionally neutral and alcohol-related images. Following image presentation, participants were asked to rate their level of craving for the alcohol cues, and their level of negative affect evoked by neutral and negative cues. During the task, electroencephalogram (EEG) was recorded to capture an event-related component shown to relate to emotionally salient stimuli: the late positive potential (LPP). Participants who completed a follow-up EEG (n = 37) performed the task a second time after up to eight sessions of MBRP coupled with active or sham tDCS. RESULTS: We found that both craving ratings and the LPP significantly decreased in response to alcohol cues from pre- to post-treatment, but not for other image cues. The magnitude of alcohol image craving reductions was associated with the number of MBRP group sessions attended. Active tDCS was not associated with craving ratings, but it was associated with greater LPP amplitudes across image types. CONCLUSIONS: Taken together, these results suggest that disruption of alcohol-cue hypersensitivity in people with AUD may be a target mechanism of MBRP.

Novel rewards occlude the reward positivity, and what to do about it.

Both the Reward Positivity (RewP) and the novelty N2 component appear within the same spatio-temporal window. This signal overlap impedes the assessment of the RewP evoked by complex novel rewards like affective or motivational imagery. Here we conducted a series of experiments which successfully isolated signals of reward and novelty through spectral decomposition as well as with experimental manipulations that systematically removed the influence of novelty on the reward-evoking image. Together, these findings help explain the nature of this component overlap and provide methodological and analytic techniques for isolating reward- and novelty-specific computations to complex stimuli.

An EEG marker of reward processing is diminished in Parkinson's disease.

The electroencephalographic signal known as the Reward Positivity (RewP) scales with the reward prediction error following reward receipt. This signal is computationally identical to the dopamine-driven learning process relating to the discrepancy between reward expectation and reward acquisition. The current study aimed to investigate if the RewP is diminished in Parkinson's disease (PD). In this study, 28 people with PD and 28 age- and sex-matched healthy controls completed a reinforcement-learning task. In line with expectations, the RewP was smaller in persons with PD than in controls. Yet contrary to expectations, RewP amplitude did not differ in on vs. off medication conditions, and it was positively correlated with the number of years diagnosed with PD. We propose that this symptom-specific alteration in RewP may be a consequence of a common methodological procedure in PD research (e.g. restricted recruitment) or it might truly be a marker of early-stage disease (e.g. prior to network re-adaptation). These surprising findings motivate separate testable hypotheses for assessing aspects of PD with this novel neural marker of reward.

Rewarding images do not invoke the reward positivity: They inflate it.

Increasing evidence suggests that the reward positivity conforms to an axiomatic reward prediction error - that is, it closely follows the rule-like encoding of surprising reinforcers. However, a major limitation in these EEG studies is the over-reliance on a single class of secondary rewards like points or money, constraining dimensionality and limiting generalizability. In the current suite of studies we address this limitation by leveraging different classes of rewards outcomes, specifically emotionally pleasant pictures. Over a series of three experiments, participants were able to choose idiosyncratically preferred pictures as rewards. During the first two experiments, participants were rewarded with either high or low points or high or low preferred pictures. The reward positivity was modulated by points, but not by pictures (regardless of preference), which instead evoked enhanced N2 amplitudes. In a third study that paired high/low points and preferred/non-preferred pictures, the point-induced reward positivity was inflated by the presence of a preferred picture. In line with past research stating the reward positivity is primarily sensitive to positive reward prediction error, this report finds that it is also influenced by a liking dimension, which possibly acts as an affective state to frame the motivational aspect of extrinsic rewards.

The sound and the fury: Late positive potential is sensitive to sound affect.

Emotion is an emergent construct of multiple distinct neural processes. EEG is uniquely sensitive to real-time neural computations, and thus is a promising tool to study the construction of emotion. This series of studies aimed to probe the mechanistic contribution of the late positive potential (LPP) to multimodal emotion perception. Experiment 1 revealed that LPP amplitudes for visual images, sounds, and visual images paired with sounds were larger for negatively rated stimuli than for neutrally rated stimuli. Experiment 2 manipulated this audiovisual enhancement by altering the valence pairings with congruent (e.g., positive audio + positive visual) or conflicting emotional pairs (e.g., positive audio + negative visual). Negative visual stimuli evoked larger early LPP amplitudes than positive visual stimuli, regardless of sound pairing. However, time frequency analyses revealed significant midfrontal theta-band power differences for conflicting over congruent stimuli pairs, suggesting very early (∼500 ms) realization of thematic fidelity violations. Interestingly, late LPP modulations were reflective of the opposite pattern of congruency, whereby congruent over conflicting pairs had larger LPP amplitudes. Together, these findings suggest that enhanced parietal activity for affective valence is modality independent and sensitive to complex affective processes. Furthermore, these findings suggest that altered neural activities for affective visual stimuli are enhanced by concurrent affective sounds, paving the way toward an understanding of the construction of multimodal affective experience.

Cognitive states influence dopamine-driven aberrant learning in Parkinson's disease.

Individual differences in dopaminergic tone underlie tendencies to learn from reward versus punishment. These effects are well documented in Parkinson's patients, who vacillate between low and high tonic dopaminergic states as a function of medication. Yet very few studies have investigated the influence of higher-level cognitive states known to affect downstream dopaminergic learning in Parkinson's patients. A dopamine-dependent cognitive influence over learning would provide a candidate mechanism for declining cognitive integrity and motivation in Parkinson's patients. In this report we tested the influence of two high-level cognitive states (cost of conflict and value of volition) that have recently been shown to cause predictable learning biases in healthy young adults as a function of dopamine receptor subtype and dopaminergic challenge. It was hypothesized that Parkinson's patients OFF medication would have an enhanced cost of conflict and a decreased value of volition, and that these effects would be remediated or reversed ON medication. Participants included N = 28 Parkinson's disease patients who were each tested ON and OFF dopaminergic medication and 28 age- and sex-matched controls. The expected cost of conflict effect was observed in Parkinson's patients OFF versus ON medication, but only in those that were more recently diagnosed (<5 years). We found an unexpected effect in the value of volition task: medication compromised the ability to learn from difficult a-volitional (instructed) choices. This novel finding was also enhanced in recently diagnosed patients. The difference in learning biases ON versus OFF medication between these two tasks was strongly correlated, bolstering the idea that they tapped into a common underlying imbalance in dopaminergic tone that is particularly variable in earlier stage Parkinsonism. The finding that these decision biases are specific to earlier but not later stage disease may offer a chance for future studies to quantify phenotypic expressions of idiosyncratic disease progression.