Neural correlates of reward-related response tendencies in an equiprobable Go/NoGo task

Previous research has shown that motivational signals bias action over inaction, which may be due to putative inherent valence-action mappings, similar to those observed in the emotional domain. In the present functional magnetic resonance imaging (fMRI) study we sought to investigate the neural underpinnings of such reward-related response tendencies, and in particular, how valence-action compatibility effects arising from predominant response tendencies are reflected at the neural level, and whether overlapping emotional valence amplifies these effects. To this end, we employed an equiprobable (50:50) Go/NoGo task in which reward (reward/no-reward) and response mode (Go/NoGo) were signaled by orthogonal features of number targets that were overlaid on emotional images (positive, neutral, negative). Reward-related targets led to response facilitation (faster Go responses) and impairment in withholding responses (more NoGo commission errors), consistent with a reward-induced action bias. This pattern was paralleled by modulations in the left dorsolateral prefrontal cortex (dlPFC), with increased activity in no-reward as compared to reward-related Go trials, and the reversed pattern in NoGo trials. Albeit being processed in ventral visual areas, emotional background did not modulate performance in the present task, suggesting that irrelevant emotional information is globally outweighed by reward. In the current paradigm, which neither favors Go responses generally nor allows for differential preparation in Go versus NoGo trials, reward-related targets promote action over inaction. In turn, additional effort is needed to inhibit responses to these targets as well as to initiate responses to (less salient) no-reward targets, which may be considered as a downside of direct stimulus-reward associations

Are all behavioral reward benefits created equally? An EEG-fMRI study

Reward consistently boosts performance in cognitive tasks. Although many different reward manipulations exist, systematic comparisons are lacking. Reward effects on cognitive control are usually studied using monetary incentive delay (MID; cue-related reward information) or stimulus-reward association (SRA; target-related reward information) tasks. While for MID tasks, evidence clearly implicates reward-triggered global increases in proactive control, it is unclear how reward effects arise in SRA tasks, and in how far such mechanisms overlap during task preparation and target processing. Here, we address these questions with simultaneous EEG-fMRI using a Stroop task with four different block types. In addition to MID and SRA blocks, we used an SRA-task modification with reward-irrelevant cues (C-SRA) and regular reward-neutral Stroop-task blocks. Behaviorally, we observed superior performance for all reward conditions compared to Neutral, and more pronounced reward effects in the SRA and C-SRA blocks, compared to MID blocks. The fMRI data showed similar reward effects in value-related areas for events that signaled reward availability (MID cues and (C-)SRA targets), and comparable reward modulations in cognitive-control regions for all targets regardless of block type. This result pattern was echoed by the EEG data, showing clear markers of valuation and cognitive control, which only differed during task preparation, whereas reward-related modulations during target processing were again comparable across block types. Yet, considering only cue-related fMRI data, C-SRA cues triggered preparatory control processes beyond reward-unrelated MID cues, without simultaneous modulations in typical reward areas, implicating enhanced task preparation that is not directly driven by a concurrent neural reward-anticipation response

Heritability of cognitive and emotion processing during functional MRI in a twin sample

Despite compelling evidence that brain structure is heritable, the evidence for the heritability of task-evoked brain function is less robust. Findings from previous studies are inconsistent possibly reflecting small samples and methodological variations. In a large national twin sample, we systematically evaluated heritability of task-evoked brain activity derived from functional magnetic resonance imaging. We used established standardised tasks to engage brain regions involved in cognitive and emotional functions. Heritability was evaluated across a conscious and nonconscious Facial Expressions of Emotion Task (FEET), selective attention Oddball Task, N-back task of working memory maintenance, and a Go-NoGo cognitive control task in a sample of Australian adult twins (N ranged from 136 to 226 participants depending on the task and pairs). Two methods for quantifying associations of heritability and brain activity were utilised; a multivariate independent component analysis (ICA) approach and a univariate brain region-of-interest (ROI) approach. Using ICA, we observed that a significant proportion of task-evoked brain activity was heritable, with estimates ranging from 23% to 26% for activity elicited by nonconscious facial emotion stimuli, 27% to 34% for N-back working memory maintenance and sustained attention, and 32% to 33% for selective attention in the Oddball task. Using the ROI approach, we found that activity of regions specifically implicated in emotion processing and selective attention showed significant heritability for three ROIs, including estimates of 33%–34% for the left and right amygdala in the nonconscious processing of sad faces and 29% in the medial superior prefrontal cortex for the Oddball task. Although both approaches show similar levels of heritability for the Nonconscious Faces and Oddball tasks, ICA results displayed a more extensive network of heritable brain function, including additional regions beyond the ROI analysis. Furthermore, multivariate twin modelling of both ICA networks and ROI activation suggested a mix of common genetic and unique environmental factors that contribute to the associations between networks/regions. Together, the results indicate a complex relationship between genetic factors and environmental interactions that ultimately give rise to neural activation underlying cognition and emotion