Overlapping neural systems represent cognitive effort and reward anticipation

The effect of Huntington's disease on cognitive and physical motivation

Apathy is one of the most common neuropsychiatric features of Huntington's disease. A hallmark of apathy is diminished goal-directed behaviour, which is characterized by a lower motivation to engage in cognitively or physically effortful actions. However, it remains unclear whether this reduction in goal-directed behaviour is driven primarily by a motivational deficit and/or is secondary to the progressive cognitive and physical deficits that accompany more advanced disease. We addressed this question by testing 17 individuals with manifest Huntington's disease and 22 age-matched controls on an effort-based decision-making paradigm. Participants were first trained on separate cognitively and physically effortful tasks and provided explicit feedback about their performance. Next, they chose on separate trials how much effort they were willing to exert in each domain in return for varying reward. At the conclusion of the experiment, participants were asked to rate their subjective perception of task load. In the cognitive task, the Huntington's disease group were more averse to cognitive effort than controls. Although the Huntington's disease group were more impaired than controls on the task itself, their greater aversion to cognitive effort persisted even after controlling for task performance. This suggests that the lower levels of cognitive motivation in the Huntington's disease group relative to controls was most likely driven by a primary motivational deficit. In contrast, both groups expressed a similar preference for physical effort. Importantly, the similar levels of physical motivation across both groups occurred even though participants with Huntington's disease performed objectively worse than controls on the physical effort task, and were aware of their performance through explicit feedback on each trial. This indicates that the seemingly preserved level of physical motivation in Huntington's disease was driven by a willingness to engage in physically effortful actions despite a reduced capacity to do so. Finally, the Huntington's disease group provided higher ratings of subjective task demand than controls for the cognitive (but not physical) effort task and when assessing the mental (but not the physical) load of each task. Together, these results revealed a dissociation in cognitive and physical motivation deficits between Huntington's disease and controls, which were accompanied by differences in how effort was subjectively perceived by the two groups. This highlights that motivation is the final manifestation of a complex set of mechanisms involved in effort processing, which are separable across different domains of behaviour. These findings have important clinical implications for the day-to-day management of apathy in Huntington's disease.

Disentangling effort from probability of success: Temporal dynamics of frontal midline theta in effort-based reward processing

The ability to weigh a reward against the effort required to acquire it is critical for decision-making. However, extant experimental paradigms oftentimes confound increased effort demand with decreased reward probability, thereby obscuring neural correlates underlying these cognitive processes. To resolve this issue, we designed novel tasks that disentangled probability of success - and therefore reward probability - from effort demand. In Experiment 1, reward magnitude and effort demand were varied while reward probability was kept constant. In Experiment 2, effort demand and reward probability were varied while reward magnitude remained fixed. Electroencephalogram (EEG) data was recorded to explore how frontal midline theta (FMT; an electrophysiological index of mPFC function) and component P3 (an index of incentive salience) respond to effort demand, and reward magnitude and probability. We found no evidence that FMT tracked effort demands or net value during cue evaluation. At feedback, however, FMT power was enhanced for high compared to low effort trials, but not modulated by reward magnitude or probability. Conversely, P3 was sensitive to reward magnitude and probability at both cue and feedback phases and only integrated expended effort costs at feedback, such that P3 amplitudes continued to scale with reward magnitude and probability but were also increased for high compared to low effort reward feedback. These findings suggest that, when likelihood of success is equal, FMT power does not track net value of prospective effort-based rewards. Instead, expended cognitive effort potentiates FMT power and enhances the saliency of rewards at feedback. SIGNIFICANCE STATEMENT: The way the brain weighs rewards against the effort required to achieve them is critical for understanding motivational disorders. Current paradigms confound increased effort demand with decreased reward probability, making it difficult to disentangle neural activity associated with effort costs from those associated with reward likelihood. Here, we explored the temporal dynamics of effort-based reward (via frontal midline theta (FMT) and component P3) while participants underwent a novel paradigm that kept probability of reward constant between mental effort demand conditions. Our findings suggest that the FMT does not track net value and that expended effort enhances, instead of attenuates, the saliency of rewards.

Developmental differences in striatal recruitment by reward prospects as a function of attentional demand

Adolescent risk-taking has been attributed to earlier-developing motivational neurocircuitry that is poorly controlled by immature executive-control neurocircuitry. Functional magnetic resonance imaging findings of increased ventral striatum (VS) recruitment by reward prospects in adolescents compared to adults support this theory. Other studies found blunted VS recruitment by reward-predictive cues in adolescents compared to adults. Task features may explain this discrepancy but have never been systematically explored. Adolescents and adults performed a novel reward task that holds constant the expected value of all rewards but varies whether rewards are dependent on vigilance-intensive responding versus making a lucky choice during a relaxed response window. We examined group by sub-task contrast differences in activation of VS and more motoric regions of striatum in response to anticipatory cues. Reward anticipation in both task conditions activated portions of striatum in both groups. In voxel-wise comparison, adults showed greater anticipatory recruitment of VS in trials involving choice during a relaxed time window, not in the more vigilance-demanding trials as hypothesized. In accord with our hypotheses, however, adults showed greater activation in dorsal striatum and putamen volumes of interest during reward anticipation under vigilance-demanding conditions. Following trial outcome notifications, adolescents showed greater activation of the VS during reward notification but lower activation during loss notification. These data extend findings of cross-sectional age-group differences in incentive-anticipatory recruitment of striatum, by demonstrating in adults relatively greater recruitment of motor effector regions of striatum by attentional and motor demands.

Neural basis of cognitive control signals in anterior cingulate cortex during delay discounting

Cognitive control involves allocating cognitive effort according to internal needs and task demands and the Anterior Cingulate Cortex (ACC) is hypothesized to play a central role in this process. We investigated the neural basis of cognitive control in the ACC of rats performing an adjusting-amount delay discounting task. Decision-making in this this task can be guided by using either a lever-value tracking strategy, requiring a 'resource-based' form of cognitive effort or a lever-biased strategy requiring a 'resistance-based' form of cognitive effort. We found that ACC ensembles always tightly tracked lever value on each trial, indicative of a resource-based control signal. These signals were prevalent in the neural recordings and were influenced by the delay. A shorter delay was associated with devaluing of the immediate option and a longer delay was associated with overvaluing of the immediate option. In addition, ACC theta (6-12Hz) oscillations were observed at the choice point of rats exhibiting a resistance-based strategy. These data provide candidates of neural activity patterns in the ACC that underlie the use of 'resource-based' and 'resistance-based' cognitive effort. Furthermore, these data illustrate how strategies can be engaged under different conditions in individual subjects.

Effects of hearing acuity on psychophysiological responses to effortful speech perception

In recent studies, psychophysiological measures have been used as markers of listening effort, but there is limited research on the effect of hearing loss on such measures. The aim of the current study was to investigate the effect of hearing acuity on physiological responses and subjective measures acquired during different levels of listening demand, and to investigate the relationship between these measures. A total of 125 participants (37 males and 88 females, age range 37-72 years, pure-tone average hearing thresholds at the best ear between -5.0 to 68.8 dB HL and asymmetry between ears between 0.0 and 87.5 dB) completed a listening task. A speech reception threshold (SRT) test was used with target sentences spoken by a female voice masked by male speech. Listening demand was manipulated using three levels of intelligibility: 20 % correct speech recognition, 50 %, and 80 % (IL20 %/IL50 %/IL80 %, respectively). During the task, peak pupil dilation (PPD), heart rate (HR), pre-ejection period (PEP), respiratory sinus arrhythmia (RSA), and skin conductance level (SCL) were measured. For each condition, subjective ratings of effort, performance, difficulty, and tendency to give up were also collected. Linear mixed effects models tested the effect of intelligibility level, hearing acuity, hearing asymmetry, and tinnitus complaints on the physiological reactivity (compared to baseline) and subjective measures. PPD and PEP reactivity showed a non-monotonic relationship with intelligibility level, but no such effects were found for HR, RSA, or SCL reactivity. Participants with worse hearing acuity had lower PPD at all intelligibility levels and showed lower PEP baseline levels. Additionally, PPD and SCL reactivity were lower for participants who reported suffering from tinnitus complaints. For IL80 %, but not IL50 % or IL20 %, participants with worse hearing acuity rated their listening effort to be relatively high compared to participants with better hearing. The reactivity of the different physiological measures were not or only weakly correlated with each other. Together, the results suggest that hearing acuity may be associated with altered sympathetic nervous system (re)activity. Research using psychophysiological measures as markers of listening effort to study the effect of hearing acuity on such measures are best served by the use of the PPD and PEP.

Beta and theta oscillations track effort and previous reward in human basal ganglia and prefrontal cortex during decision making

Choosing whether to exert effort to obtain rewards is fundamental to human motivated behavior. However, the neural dynamics underlying the evaluation of reward and effort in humans is poorly understood. Here, we investigate this with chronic intracranial recordings from prefrontal cortex (PFC) and basal ganglia (BG; subthalamic nuclei and globus pallidus) in people with Parkinson's disease performing a decision-making task with offers that varied in levels of reward and physical effort required. This revealed dissociable neural signatures of reward and effort, with BG beta (12-20 Hz) oscillations tracking subjective effort on a single trial basis and PFC theta (4-7 Hz) signaling previous trial reward. Stimulation of PFC increased overall acceptance of offers in addition to increasing the impact of reward on choices. This work uncovers oscillatory mechanisms that guide fundamental decisions to exert effort for reward across BG and PFC, as well as supporting a causal role of PFC for such choices.

The scaling of mental computation in a sorting task

Many cognitive models provide valuable insights into human behavior. Yet the algorithmic complexity of candidate models can fail to capture how human reaction times scale with increasing input complexity. In the current work, we investigate the algorithms underlying human cognitive processes. Computer science characterizes algorithms by their time and space complexity scaling with problem size. We propose to use participants' reaction times to study how human computations scale with increasing input complexity. We tested this approach in a task where participants had to sort sequences of rectangles by their size. Our results showed that reaction times scaled close to linearly with sequence length and that participants learned and actively used latent structure whenever it was provided. This behavior was in line with a computational model that used the observed sequences to form hypotheses about the latent structures, searching through candidate hypotheses in a directed fashion. These results enrich our understanding of plausible cognitive models for efficient mental sorting and pave the way for future studies using reaction times to investigate the scaling of mental computations across psychological domains.

Need for cognition moderates the relief of avoiding cognitive effort

When making decisions, humans aim to maximize rewards while minimizing costs. The exertion of mental or physical effort has been proposed to be one those costs, translating into avoidance of behaviors carrying effort demands. This motivational framework also predicts that people should experience positive affect when anticipating demand that is subsequently avoided (i.e., a "relief effect"), but evidence for this prediction is scarce. Here, we follow up on a previous study [1] that provided some initial evidence that people more positively evaluated outcomes if it meant they could avoid performing an additional demanding task. However, the results from this study did not provide conclusive evidence that this effect was driven by effort avoidance. Here, we report two experiments that are able to do this. Participants performed a gambling task, and if they did not receive reward they would have to perform an orthogonal effort task. Prior to the gamble, a cue indicated whether this effort task would be easy or hard. We probed hedonic responses to the reward-related feedback, as well as after the subsequent effort task feedback. Participants reported lower hedonic responses for no-reward outcomes when high vs. low effort was anticipated (and later exerted). They also reported higher hedonic responses for reward outcomes when high vs. low effort was anticipated (and avoided). Importantly, this relief effect was smaller in participants with high need for cognition. These results suggest that avoidance of high effort tasks is rewarding, but that the size off this effect depends on the individual disposition to engage with and expend cognitive effort. They also raise the important question of whether this disposition alters the cost of effort per se, or rather offset this cost during cost-benefit analyses.

Computational mechanisms underlying the dynamics of physical and cognitive fatigue

The willingness to exert effort for reward is essential but comes at the cost of fatigue. Theories suggest fatigue increases after both physical and cognitive exertion, subsequently reducing the motivation to exert effort. Yet a mechanistic understanding of how this happens on a moment-to-moment basis, and whether mechanisms are common to both mental and physical effort, is lacking. In two studies, participants reported momentary (trial-by-trial) ratings of fatigue during an effort-based decision-making task requiring either physical (grip-force) or cognitive (mental arithmetic) effort. Using a novel computational model, we show that fatigue fluctuates from trial-to-trial as a function of exerted effort and predicts subsequent choices. This mechanism was shared across the domains. Selective to the cognitive domain, committing errors also induced momentary increases in feelings of fatigue. These findings provide insight into the computations underlying the influence of effortful exertion on fatigue and motivation, in both physical and cognitive domains.

Not all discounts are created equal: Regional activity and brain networks in temporal and effort discounting

Reward outcomes associated with costs like time delay and effort investment are generally discounted in decision-making. Standard economic models predict rewards associated with different types of costs are devalued in a similar manner. However, our review of rodent lesion studies indicated partial dissociations between brain regions supporting temporal- and effort-based decision-making. Another debate is whether options involving low and high costs are processed in different brain substrates (dual-system) or in the same regions (single-system). This research addressed these issues using coordinate-based, connectivity-based, and activation network-based meta-analyses to identify overlapping and separable neural systems supporting temporal (39 studies) and effort (20 studies) discounting. Coordinate-based activation likelihood estimation and resting-state connectivity analyses showed immediate-small reward and delayed-large reward choices engaged distinct regions with unique connectivity profiles, but their activation network mapping was found to engage the default mode network. For effort discounting, salience and sensorimotor networks supported low-effort choices, while the frontoparietal network supported high-effort choices. There was little overlap between the temporal and effort networks. Our findings underscore the importance of differentiating different types of costs in decision-making and understanding discounting at both regional and network levels.

The functional role of the precuneus

Recent advancements in computational approaches and neuroimaging techniques have refined our understanding of the precuneus. While previously believed to be largely a visual processing region, the importance of the precuneus in complex cognitive functions has been previously less familiar due to a lack of focal lesions in this deeply seated region, but also a poor understanding of its true underlying anatomy. Fortunately, recent studies have revealed significant information on the structural and functional connectivity of this region, and this data has provided a more detailed mechanistic understanding of the importance of the precuneus in healthy and pathologic states. Through improved resting-state functional MRI analyses, it has become clear that the function of the precuneus can be better understood based on its functional association with large scale brain networks. Dual default mode network systems have been well explained in recent years in supporting episodic memory and theory of mind; however, a novel 'para-cingulate' network, which is a subnetwork of the larger central executive network, with likely significant roles in self-referential processes and related psychiatric symptoms is introduced here and requires further clarification. Importantly, detailed anatomic studies on the precuneus structural connectivity inside and beyond the cingulate cortex has demonstrated the presence of large structural white matter connections, which provide an additional layer of meaning to the structural-functional significance of this region and its association with large scale brain networks. Together, the structural-functional connectivity of the precuneus has provided central elements which can model various neurodegenerative diseases and psychiatric disorders, such as Alzheimer's disease and depression.

Fatigue during acute systemic inflammation is associated with reduced mental effort expenditure while task accuracy is preserved

BACKGROUND

Earlier work within the physical domain showed that acute inflammation changes motivational prioritization and effort allocation rather than physical abilities. It is currently unclear whether a similar motivational framework accounts for the mental fatigue and cognitive symptoms of acute sickness. Accordingly, this study aimed to assess the relationship between fatigue, cytokines and mental effort-based decision making during acute systemic inflammation.

METHODS

Eighty-five participants (41 males; 18-30 years (M=23.0, SD=2.4)) performed a mental effort-based decision-making task before, 2 hours after, and 5 hours after intravenous administration of 1 ng/kg bacterial lipopolysaccharide (LPS) to induce systemic inflammation. Plasma concentrations of cytokines (interleukin (IL)-6, IL-8 and tumor necrosis factor (TNF)) and fatigue levels were assessed at similar timepoints. In the task, participants decided whether they wanted to perform (i.e., 'accepted') arithmetic calculations of varying difficulty (3 levels: easy, medium, hard) in order to obtain rewards (3 levels: 5, 6 or 7 points). Acceptance rates were analyzed using a binomial generalized estimated equation (GEE) approach with effort, reward and time as independent variables. Arithmetic performance was measured per effort level prior to the decisions and included as a covariate. Associations between acceptance rates, fatigue (self-reported) and cytokine concentrations levels were analyzed using partial correlation analyses.

RESULTS

Plasma cytokine concentrations and fatigue were increased at 2 hours post-LPS compared to baseline and 5 hours post-LPS administration. Acceptance rates decreased for medium, but not for easy or hard effort levels at 2 hours post-LPS versus baseline and 5 hours post-LPS administration, irrespective of reward level. This reduction in acceptance rates occurred despite improved accuracy on the arithmetic calculations itself. Reduced acceptance rates for medium effort were associated with increased fatigue, but not with increased cytokines.

CONCLUSION

Fatigue during acute systemic inflammation is associated with alterations in mental effort allocation, similarly as observed previously for physical effort-based choice. Specifically, willingness to exert mental effort depended on effort and not reward information, while task accuracy was preserved. These results extend the motivational account of inflammation to the mental domain and suggest that inflammation may not necessarily affect domain-specific mental abilities, but rather affects domain-general effort-allocation processes.

Pupillary response is associated with the reset and switching of functional brain networks during salience processing

The interface between processing internal goals and salient events in the environment involves various top-down processes. Previous studies have identified multiple brain areas for salience processing, including the salience network (SN), dorsal attention network, and the locus coeruleus-norepinephrine (LC-NE) system. However, interactions among these systems in salience processing remain unclear. Here, we simultaneously recorded pupillometry, EEG, and fMRI during an auditory oddball paradigm. The analyses of EEG and fMRI data uncovered spatiotemporally organized target-associated neural correlates. By modeling the target-modulated effective connectivity, we found that the target-evoked pupillary response is associated with the network directional couplings from late to early subsystems in the trial, as well as the network switching initiated by the SN. These findings indicate that the SN might cooperate with the pupil-indexed LC-NE system in the reset and switching of cortical networks, and shed light on their implications in various cognitive processes and neurological diseases.

More than a feeling: physiological measures of affect index the integration of effort costs and rewards during anticipatory effort evaluation

The notion that humans avoid effortful action is one of the oldest and most persistent in psychology. Influential theories of effort propose that effort valuations are made according to a cost-benefit trade-off: we tend to invest mental effort only when the benefits outweigh the costs. While these models provide a useful conceptual framework, the affective components of effort valuation remain poorly understood. Here, we examined whether primitive components of affective response-positive and negative valence, captured via facial electromyography (fEMG)-can be used to better understand valuations of cognitive effort. Using an effortful arithmetic task, we find that fEMG activity in the corrugator supercilii-thought to index negative valence-1) tracks the anticipation and exertion of cognitive effort and 2) is attenuated in the presence of high rewards. Together, these results suggest that activity in the corrugator reflects the integration of effort costs and rewards during effortful decision-making.

Mind the gender gap: The social neuroscience of belonging

Gender gaps persist in the 21st century, in many aspects of society and in many types of organisation. There are earnings gaps in almost all domains, reports of glass ceilings and the “missing middle” in business, finance, law and politics, and dramatic under-representation of women in many branches of science, even in the most “gender equal” countries. This is despite decades of effort to address them, including targeted legislation and many Diversity and Inclusion initiatives. Early essentialist, competence-based explanations for the existence of gender gaps have been largely discredited at the research level, although their persistence in the public consciousness and at the level of education and training can still negatively bias both individual self-belief and organisational processes. Contemporary essentialist explanations are now emerging, with claims that such gaps are the manifestations of the presence or absence of endogenous, brain-based characteristics underpinning career progression or career preferences. The focus remains on the individual as the source of gender imbalances. Less attention has been paid to the contextual aspects of organisations where gender gaps are evident, to inclusion (or the lack of it), or the availability of unbiased reward and progression pathways. Advances in 21st century social cognitive neuroscience are revealing the importance of external organisational processes as powerful brain-changing forces, with their potentially negative impact on self-belief and a sense of belonging. Key research is demonstrating the cortical and behavioural consequences of negative social experiences, with the activation of core inhibitory pathways associated with low self-esteem, lack of engagement, and eventual withdrawal. This paper will argue that reference to such research will provide better explanations for the persistence of gender gaps, and offer evidence-based insights into addressing gender gap issues. Importantly, this is not a rejection of an endogenous, brain-based explanation for gender gaps but the elaboration of a better-informed 21st century model, flagging up the need to take factors such as cultural stereotyping and organisational bias into account in any drive toward true gender equity, or genuinely levelled playing fields.

Connectivity Profile of Middle Inferior Parietal Cortex Confirms the Hypothesis About Modulating Cortical Areas

According to the correlated transmitter-receptor based structure of the inferior parietal cortex (IPC), this brain area is divided into three clusters, namely, the caudal, the middle and the rostral. Nevertheless, in associating different cognitive functions to the IPC, previous studies considered this part of the cortex as a whole and thus inconsistent results have been reported. Using multiband EPI, we investigated the connectivity profile of the middle IPC while forty-five participants performed a task requiring cognitive control. The middle IPC demonstrated functional associations which do not have similarities to a contributing part in the frontoparietal network, in processing cognitive control. At the same time, this cortical area showed negative functional connectivity with both the precuneus cortex, which is resting- state related, and brain areas related to general cognitive functions. That is, the functions of the middle IPC are not accommodated by the traditional categorization of different brain areas i.e. resting state-related or task-related networks and this advanced our hypothesis about modulating cortical areas. Such brain areas are characterized by their negative functional connectivity with parts of the cortex involved in task performance, proportional to the difficulty of the task; yet, their functional associations are inconsistent with the resting state-related cortical areas.

Learning when effort matters: neural dynamics underlying updating and adaptation to changes in performance efficacy

To determine how much cognitive control to invest in a task, people need to consider whether exerting control matters for obtaining rewards. In particular, they need to account for the efficacy of their performance-the degree to which rewards are determined by performance or by independent factors. Yet it remains unclear how people learn about their performance efficacy in an environment. Here we combined computational modeling with measures of task performance and EEG, to provide a mechanistic account of how people (i) learn and update efficacy expectations in a changing environment and (ii) proactively adjust control allocation based on current efficacy expectations. Across 2 studies, subjects performed an incentivized cognitive control task while their performance efficacy (the likelihood that rewards are performance-contingent or random) varied over time. We show that people update their efficacy beliefs based on prediction errors-leveraging similar neural and computational substrates as those that underpin reward learning-and adjust how much control they allocate according to these beliefs. Using computational modeling, we show that these control adjustments reflect changes in information processing, rather than the speed-accuracy tradeoff. These findings demonstrate the neurocomputational mechanism through which people learn how worthwhile their cognitive control is.

Learned industriousness as a translational mechanism in anorexia nervosa

It remains unexplained why some behaviours persist despite being non-hedonic and ostensibly aversive. This phenomenon is especially baffling when such behaviours are taken to excess in the form of psychopathology. Anorexia nervosa is one psychiatric disorder in which effortful behaviours that most people find unpleasant (suchas restrictive eating) are persistently performed. We propose thatthe social psychology theory of learned industriousness providesa novel mechanistic account for such phenomena. This theoryposits that high-effort behaviour can be conditioned to acquire secondary reinforcing properties through repeated pairing with reward. Accordingly, effort sensations become less aversive andmore appetitive, increasing willingness to engage in effortful behaviour. In this Perspective, we review pre-clinical behaviouraland biological data that support learned industriousness, contrast learned industriousness with other models of non-hedonic persistence (such as habit learning), highlight evidence that supports learned industriousness in individuals with anorexia nervosa and consider implications of the model, including translation to other psychiatric presentations.

Electrophysiological measures of conflict and reward processing are associated with decisions to engage in physical effort

Anterior cingulate cortex (ACC), a key brain region involved in cognitive control and decision making, is suggested to mediate effort- and value-based decision making, but the specific role of ACC in this process remains debated. Here we used frontal midline theta (FMT) and the reward positivity (RewP) to examine ACC function in a value-based decision making task requiring physical effort. We investigated whether (1) FMT power is sensitive to the difficulty of the decision or to selecting effortful actions, and (2) RewP is sensitive to the subjective value of reward outcomes as a function of effort investment. On each trial, participants chose to execute a low-effort or a high-effort behavior (that required squeezing a hand-dynamometer) to obtain smaller or larger rewards, respectively, while their brainwaves were recorded. We replicated prior findings that tonic FMT increased over the course of the hour-long task, which suggests increased application of control in the face of growing fatigue. RewP amplitude also increased following execution of high-effort compared to low-effort behavior, consistent with increased valuation of reward outcomes by ACC. Although neither phasic nor tonic FMT were associated with decision difficulty or effort selection per se, an exploratory analysis revealed that the interaction of phasic FMT and expected value of choice predicted effort choice. This interaction suggests that phasic FMT increases specifically under situations of decision difficulty when participants ultimately select a high-effort choice. These results point to a unique role for ACC in motivating and persisting at effortful behavior when decision conflict is high.

Reward, motivation and brain imaging in human healthy participants - A narrative review

Over the past 20 years there has been an increasing number of brain imaging studies on the mechanisms underlying reward motivation in humans. This narrative review describes studies on the neural mechanisms associated with reward motivation and their relationships with cognitive function in healthy human participants. The brain's meso-limbic dopamine reward circuitry in humans is known to control reward-motivated behavior in humans. The medial and lateral Pre-Frontal Cortex (PFC) integrate motivation and cognitive control during decision-making and the dorsolateral PFC (dlPFC) integrates and transmits signals of reward to the mesolimbic and meso-cortical dopamine circuits and initiates motivated behavior. The thalamus and insula influence incentive processing in humans and the motor system plays a role in response to action control. There are reciprocal relationships between reward motivation, learning, memory, imagery, working memory, and attention. The most common method of assessing reward motivation is the monetary incentive delay task (DMRT) and there are several meta-analyses of this paradigm. Genetics modulates motivation reward, and dopamine provides the basis for the interaction between motivational and cognitive control. There is some evidence that male adolescents take more risky decisions than female adolescents and that the lateralization of reward-related DA release in the ventral striatum is confined to men. These studies have implications for our understanding of natural reward and psychiatric conditions like addiction, depression and ADHD. Furthermore, the association between reward and memory can help develop treatment techniques for drug addiction that interfere with consolidation of memory. Finally, there is a lack of research on reward motivation, genetics and sex differences and this can improve our understanding of the relationships between reward, motivation and the brain.

Context-independent scaling of neural responses to task difficulty in the multiple-demand network

The multiple-demand (MD) network is sensitive to many aspects of cognitive demand, showing increased activation with more difficult tasks. However, it is currently unknown whether the MD network is modulated by the context in which task difficulty is experienced. Using functional magnetic resonance imaging, we examined MD network responses to low, medium, and high difficulty arithmetic problems within 2 cued contexts, an easy versus a hard set. The results showed that MD activity varied reliably with the absolute difficulty of a problem, independent of the context in which the problem was presented. Similarly, MD activity during task execution was independent of the difficulty of the previous trial. Representational similarity analysis further supported that representational distances in the MD network were consistent with a context-independent code. Finally, we identified several regions outside the MD network that showed context-dependent coding, including the inferior parietal lobule, paracentral lobule, posterior insula, and large areas of the visual cortex. In sum, a cognitive effort is processed by the MD network in a context-independent manner. We suggest that this absolute coding of cognitive demand in the MD network reflects the limited range of task difficulty that can be supported by the cognitive apparatus.

Distinct neural representations for prosocial and self-benefiting effort

Prosocial behaviors-actions that benefit others-are central to individual and societal well-being. Although the mechanisms underlying the financial and moral costs of prosocial behaviors are increasingly understood, this work has often ignored a key influence on behavior: effort. Many prosocial acts are effortful, and people are averse to the costs of exerting them. However, how the brain encodes effort costs when actions benefit others is unknown. During fMRI, participants completed a decision-making task where they chose in each trial whether to "work" and exert force (30%-70% of maximum grip strength) or "rest" (no effort) for rewards (2-10 credits). Crucially, on separate trials, they made these decisions either to benefit another person or themselves. We used a combination of multivariate representational similarity analysis and model-based univariate analysis to reveal how the costs of prosocial and self-benefiting efforts are processed. Strikingly, we identified a unique neural signature of effort in the anterior cingulate gyrus (ACCg) for prosocial acts, both when choosing to help others and when exerting force to benefit them. This pattern was absent for self-benefiting behaviors. Moreover, stronger, specific representations of prosocial effort in the ACCg were linked to higher levels of empathy and higher subsequent exerted force to benefit others. In contrast, the ventral tegmental area and ventral insula represented value preferentially when choosing for oneself and not for prosocial acts. These findings advance our understanding of the neural mechanisms of prosocial behavior, highlighting the critical role that effort has in the brain circuits that guide helping others.

Distinctive types of aversiveness are represented as the same in a portion of the dorsal anterior cingulate cortex: An fMRI study with the cue paradigm

Some studies have argued that the dorsal anterior cingulate cortex (dACC) is generally activated in response to aversive information, including pain, negative affect, and cognitive conflict. Other studies have claimed that the dACC has subdivisions, and each division has a specific function. By manipulating emotionally and cognitively aversive cues, the present study determined whether the dACC is generally responsive to aversiveness or it has subdivisions for specific forms of aversiveness. Conjunction functional magnetic resonance imaging (fMRI) analysis showed that emotionally and cognitively aversive cues activated the same portion of the dACC. When these cues were contiguously presented, the region demonstrated additive activity, further supporting the overlapping representation of the two different forms of aversiveness in the dACC. Additional effective connectivity analysis showed that the dACC was co-activated with different brain regions depending on the cue type, characterizing its behavioral control mechanism. Complementary multivariate analyses showed that the reaction time was negatively correlated with the activity of the dACC and that the activity of the dACC under the emotional cue was predicted by the individual state anxiety score but not under the cognitive cue. We also found that the superior part of the dACC was uniquely activated in response to cognitively aversive cues, partially supporting the functional segregation account. Collectively, our results provide evidence that the specific locus of the dACC is generally responsive to distinctive motivational information, whereas the other loci may have segregated functions. Discussion includes recent neurocomputational theories that seem to satisfactorily account for the present results.

Applying functional near-infrared spectroscopy and eye-tracking in a naturalistic educational environment to investigate physiological aspects that underlie the cognitive effort of children during mental rotation tests

Spatial cognition is related to academic achievement in science, technology, engineering, and mathematics (STEM) domains. Neuroimaging studies suggest that brain regions' activation might be related to the general cognitive effort while solving mental rotation tasks (MRT). In this study, we evaluate the mental effort of children performing MRT tasks by measuring brain activation and pupil dilation. We use functional near-infrared spectroscopy (fNIRS) concurrently to collect brain hemodynamic responses from children's prefrontal cortex (PFC) and an Eye-tracking system to measure pupil dilation during MRT. Thirty-two healthy students aged 9-11 participated in this experiment. Behavioral measurements such as task performance on geometry problem-solving tests and MRT scores were also collected. The results were significant positive correlations between the children's MRT and geometry problem-solving test scores. There are also significant positive correlations between dorsolateral PFC (dlPFC) hemodynamic signals and visuospatial task performances (MRT and geometry problem-solving scores). Moreover, we found significant activation in the amplitude of deoxy-Hb variation on the dlPFC and that pupil diameter increased during the MRT, suggesting that both physiological responses are related to mental effort processes during the visuospatial task. Our findings indicate that children with more mental effort under the task performed better. The multimodal approach to monitoring students' mental effort can be of great interest in providing objective feedback on cognitive resource conditions and advancing our comprehension of the neural mechanisms that underlie cognitive effort. Hence, the ability to detect two distinct mental states of rest or activation of children during the MRT could eventually lead to an application for investigating the visuospatial skills of young students using naturalistic educational paradigms.

A computational account of why more valuable goals seem to require more effortful actions

To decide whether a course of action is worth pursuing, individuals typically weigh its expected costs and benefits. Optimal decision-making relies upon accurate effort cost anticipation, which is generally assumed to be performed independently from goal valuation. In two experiments (n = 46), we challenged this independence principle of standard decision theory. We presented participants with a series of treadmill routes randomly associated to monetary rewards and collected both ‘accept’ versus ‘decline’ decisions and subjective estimates of energetic cost. Behavioural results show that higher monetary prospects led participants to provide higher cost estimates, although reward was independent from effort in our design. Among candidate cognitive explanations, they support a model in which prospective cost assessment is biased by the output of an automatic computation adjusting effort expenditure to goal value. This decision bias might lead people to abandon the pursuit of valuable goals that are in fact not so costly to achieve.

Neuronal correlates of selective attention and effort in visual area V4 are invariant of motivational context

Task demands can differentially engage two fundamental attention components: selectivity (spatial bias) and effort (total nonselective attentional intensity). The relative contributions and interactions of these components in modulating neuronal signals remain unknown. We recorded V4 neurons while monkeys' spatially selective attention and effort were independently controlled by adjusting either task difficulty or reward size at two locations. Neurons were robustly modulated by either selective attention or effort. Notably, increasing overall effort to improve performance at a distant site reduced neuronal responses even when performance was unchanged for receptive field stimuli. This interaction between attentional selectivity and effort was evident in single-trial spiking and can be explained by divisive normalization of spatially distributed behavioral performance at the single-neuron level. Changing motivation using task difficulty or reward produced indistinguishable effects. These results provide a cellular-level mechanism of how attention components integrate to modulate sensory processing in different motivational contexts.

Neural connectome features of procrastination: Current progress and future direction

Procrastination refers to an irrationally delay for intended courses of action despite of anticipating a negative consequence due to this delay. Previous studies tried to reveal the neural substrates of procrastination in terms of connectome-based biomarkers. Based on this, we proposed a unified triple brain network model for procrastination and pinpointed out what challenges we are facing in understanding neural mechanism of procrastination. Specifically, based on neuroanatomical features, the unified triple brain network model proposed that connectome-based underpinning of procrastination could be ascribed to the abnormalities of self-control network (i.e., dorsolateral prefrontal cortex, DLPFC), emotion-regulation network (i.e., orbital frontal cortex, OFC), and episodic prospection network (i.e., para-hippocampus cortex, PHC). Moreover, based on the brain functional features, procrastination had been attributed to disruptive neural circuits on FPN (frontoparietal network)-SCN (subcortical network) and FPN-SAN (salience network), which led us to hypothesize the crucial roles of interplay between these networks on procrastination in unified triple brain network model. Despite of these findings, poor interpretability and computational model limited further understanding for procrastination from theoretical and neural perspectives. On balance, the current study provided an overview to show current progress on the connectome-based biomarkers for procrastination, and proposed the integrative neurocognitive model of procrastination.

The influence of reward anticipation on conflict control in children and adolescents: Evidences from hierarchical drift-diffusion model and event-related potentials

Reward is deemed a performance reinforcer. The current study investigated how social and monetary reward anticipation affected cognitive control in 39 children, 40 adolescents, and 40 adults. We found that cognitive control performance improved with age in a Simon task, and the reaction time (RT) was modulated by the reward magnitude. The conflict monitoring process (target N2 amplitudes) of adolescents and the attentional control processes (target P3 amplitudes) of adolescents and adults could be adjusted by reward magnitude, suggesting that adolescents were more sensitive to rewards compared to children. Reward magnitudes influenced the neural process of attentional control with larger P3 in congruent trails than that in incongruent trials only in low reward condition. The result of hierarchical drift-diffusion model indicated that children had slower drift rates, higher decision threshold, and longer non-decision time than adolescents and adults. Adolescents had faster drift rates in monetary task than in social task under the high reward condition, and they had faster drift rates under high reward condition than no reward condition only in the monetary task. The correlation analysis further showed that adults' non-decision time and decision threshold correlated with conflict monitoring process (N2 responses) and attentional control process on conflicts (P3 responses). Adolescents' drift rates associated with neural process of attentional control. The current study reveals that reward magnitude and reward type can modulate cognitive control process, especially in adolescents.

Decision neuroscience and neuroeconomics: Recent progress and ongoing challenges

In the past decade, decision neuroscience and neuroeconomics have developed many new insights in the study of decision making. This review provides an overarching update on how the field has advanced in this time period. Although our initial review a decade ago outlined several theoretical, conceptual, methodological, empirical, and practical challenges, there has only been limited progress in resolving these challenges. We summarize significant trends in decision neuroscience through the lens of the challenges outlined for the field and review examples where the field has had significant, direct, and applicable impacts across economics and psychology. First, we review progress on topics including reward learning, explore-exploit decisions, risk and ambiguity, intertemporal choice, and valuation. Next, we assess the impacts of emotion, social rewards, and social context on decision making. Then, we follow up with how individual differences impact choices and new exciting developments in the prediction and neuroforecasting of future decisions. Finally, we consider how trends in decision-neuroscience research reflect progress toward resolving past challenges, discuss new and exciting applications of recent research, and identify new challenges for the field. This article is categorized under: Psychology > Reasoning and Decision Making Psychology > Emotion and Motivation.

Proposing a “Brain Health Checkup (BHC)” as a Global Potential “Standard of Care” to Overcome Reward Dysregulation in Primary Care Medicine: Coupling Genetic Risk Testing and Induction of “Dopamine Homeostasis”

In 2021, over 100,000 people died prematurely from opioid overdoses. Neuropsychiatric and cognitive impairments are underreported comorbidities of reward dysregulation due to genetic antecedents and epigenetic insults. Recent genome-wide association studies involving millions of subjects revealed frequent comorbidity with substance use disorder (SUD) in a sizeable meta-analysis of depression. It found significant associations with the expression of NEGR1 in the hypothalamus and DRD2 in the nucleus accumbens, among others. However, despite the rise in SUD and neuropsychiatric illness, there are currently no standard objective brain assessments being performed on a routine basis. The rationale for encouraging a standard objective Brain Health Check (BHC) is to have extensive data available to treat clinical syndromes in psychiatric patients. The BHC would consist of a group of reliable, accurate, cost-effective, objective assessments involving the following domains: Memory, Attention, Neuropsychiatry, and Neurological Imaging. Utilizing primarily PUBMED, over 36 years of virtually all the computerized and written-based assessments of Memory, Attention, Psychiatric, and Neurological imaging were reviewed, and the following assessments are recommended for use in the BHC: Central Nervous System Vital Signs (Memory), Test of Variables of Attention (Attention), Millon Clinical Multiaxial Inventory III (Neuropsychiatric), and Quantitative Electroencephalogram/P300/Evoked Potential (Neurological Imaging). Finally, we suggest continuing research into incorporating a new standard BHC coupled with qEEG/P300/Evoked Potentials and genetically guided precision induction of “dopamine homeostasis” to diagnose and treat reward dysregulation to prevent the consequences of dopamine dysregulation from being epigenetically passed on to generations of our children.

Frequency-domain analysis of fNIRS fluctuations induced by rhythmic mental arithmetic

Functional near‐infrared spectroscopy (fNIRS) is an increasingly used technology for imaging neural correlates of cognitive processes. However, fNIRS signals are commonly impaired by task‐evoked and spontaneous hemodynamic oscillations of non‐cerebral origin, a major challenge in fNIRS research. In an attempt to isolate the task‐evoked cortical response, we investigated the coupling between hemodynamic changes arising from superficial and deep layers during mental effort. For this aim, we applied a rhythmic mental arithmetic task to induce cyclic hemodynamic fluctuations suitable for effective frequency‐resolved measurements. Twenty university students aged 18–25 years (eight males) underwent the task while hemodynamic changes were monitored in the forehead using a newly developed NIRS device, capable of multi‐channel and multi‐distance recordings. We found significant task‐related fluctuations for oxy‐ and deoxy‐hemoglobin, highly coherent across shallow and deep tissue layers, corroborating the strong influence of surface hemodynamics on deep fNIRS signals. Importantly, after removing such surface contamination by linear regression, we show that the frontopolar cortex response to a mental math task follows an unusual inverse oxygenation pattern. We confirm this finding by applying for the first time an alternative method to estimate the neural signal, based on transfer function analysis and phasor algebra. Altogether, our results demonstrate the feasibility of using a rhythmic mental task to impose an oscillatory state useful to separate true brain functional responses from those of non‐cerebral origin. This separation appears to be essential for a better understanding of fNIRS data and to assess more precisely the dynamics of the neuro‐visceral link.

We proposed the use of rhythmic mental arithmetic tasks to induce cyclic oscillations in multi‐distance fNIRS signals measured on the forehead, suitable for effective frequency‐domain analysis to better identify the actual neural functional response. We confirm the impairment of deep signals by task‐evoked non‐cerebral confounds, while providing evidence for an inverse oxygenation response in the frontopolar cortex.

Contributions of dopamine-related basal ganglia neurophysiology to the developmental effects of incentives on inhibitory control

Inhibitory control can be less reliable in adolescence, however, in the presence of rewards, adolescents' performance often improves to adult levels. Dopamine is known to play a role in signaling rewards and supporting cognition, but its role in the enhancing effects of reward on adolescent cognition and inhibitory control remains unknown. Here, we assessed the contribution of basal ganglia dopamine-related neurophysiology using longitudinal MR-based assessments of tissue iron in rewarded inhibitory control, using an antisaccade task. In line with prior work, we show that neutral performance improves with age, and incentives enhance performance in adolescents to that of adults. We find that basal ganglia tissue iron is associated with individual differences in the magnitude of this reward boost, which is strongest in those with high levels of tissue iron, predominantly in adolescence. Our results provide novel evidence that basal ganglia neurophysiology supports developmental effects of rewards on cognition, which can inform neurodevelopmental models of the role of dopamine in reward processing during adolescence.

Neurofeedback-Augmented Mindfulness Training Elicits Distinct Responses in the Subregions of the Insular Cortex in Healthy Adolescents

Mindfulness training (MT) reduces self-referential processing and promotes interoception, the perception of sensations from inside the body, by increasing one’s awareness of and regulating responses to them. The posterior cingulate cortex (PCC) and the insular cortex (INS) are considered hubs for self-referential processing and interoception, respectively. Although MT has been consistently found to decrease PCC, little is known about how MT relates to INS activity. Understanding links between mindfulness and interoception may be particularly important for informing mental health in adolescence, when neuroplasticity and emergence of psychopathology are heightened. We examined INS activity during real-time functional magnetic resonance imaging neurofeedback-augmented mindfulness training (NAMT) targeting the PCC. Healthy adolescents (N = 37; 16 female) completed the NAMT task, including Focus-on-Breath (MT), Describe (self-referential processing), and Rest conditions, across three neurofeedback runs and two non-neurofeedback runs (Observe, Transfer). Regression coefficients estimated from the generalized linear model were extracted from three INS subregions: anterior (aINS), mid (mINS), and posterior (pINS). Mixed model analyses revealed the main effect of run for Focus-on-Breath vs. Describe contrast in aINS [R2 = 0.39] and pINS [R2 = 0.33], but not mINS [R2 = 0.34]. Post hoc analyses revealed greater aINS activity and reduced pINS activity during neurofeedback runs, and such activities were related to lower self-reported life satisfaction and less pain behavior, respectively. These findings revealed the specific involvement of insula subregions in rtfMRI-nf MT.

Cognitive Effort Exertion Enhances Electrophysiological Responses to Rewarding Outcomes

Recent work has highlighted neural mechanisms underlying cognitive effort-related discounting of anticipated rewards. However, findings on whether effort exertion alters the subjective value of obtained rewards are inconsistent. Here, we provide a more nuanced account of how cognitive effort affects subsequent reward processing in a novel task designed to assess effort-induced modulations of the Reward Positivity, an event-related potential indexing reward-related neural activity. We found that neural responses to both gains and losses were significantly elevated in trials requiring more versus less cognitive effort. Moreover, time-frequency analysis revealed that these effects were mirrored in gain-related delta, but not in loss-related theta band activity, suggesting that people ascribed more value to high-effort outcomes. In addition, we also explored whether individual differences in behavioral effort discounting rates and reward sensitivity in the absence of effort may affect the relationship between effort exertion and subsequent reward processing. Together, our findings provide evidence that cognitive effort exertion can increase the subjective value of subsequent outcomes and that this effect may primarily rely on modulations of delta band activity.

Task-induced subjective fatigue and resting-state striatal connectivity following traumatic brain injury

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Fatigue is a very frequent and disabling symptom in traumatic brain injury (TBI).

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Effects of task-induced fatigue on resting-state functional connectivity (rsFC).

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Striatal rsFC relates differently to subjective fatigue in TBI compared to controls.

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Default mode network rsFC relates similar to subjective fatigue in TBI and controls.

Background

People with traumatic brain injury (TBI) often experience fatigue, but an understanding of the neural underpinnings of fatigue following TBI is still lacking. This study used resting-state functional magnetic resonance imaging (rs-fMRI) to examine associations between functional connectivity (FC) changes and task-induced changes in subjective fatigue in people with moderate-severe TBI.

Methods

Sixteen people with moderate-severe TBI and 17 matched healthy controls (HC) performed an adaptive N-back task (working memory task) to induce cognitive fatigue. Before and after the task they rated their state fatigue level and underwent rs-fMRI. Seed-to-voxel analyses with seeds in areas involved in cognitive fatigue, namely the striatum and default mode network (DMN) including, medial prefrontal cortex and posterior cingulate cortex, were performed.

Results

The adaptive N-back task was effective in inducing fatigue in both groups. Subjective task-induced fatigue was positively associated with FC between striatum and precuneus in people with TBI, while there was a negative association in HC. In contrast, subjective task-induced fatigue was negatively associated with FC between striatum and cerebellum in the TBI group, while there was no association in HC. Similar associations between task-induced subjective fatigue and DMN FC were found across the groups.

Conclusions

Our results suggest that the subjective experience of fatigue was linked to DMN connectivity in both groups and was differently associated with striatal connectivity in people with moderate-severe TBI compared to HC. Defining fatigue-induced neuronal network changes is pertinent to the development of treatments that target abnormal neuronal activity after TBI.

Characterizing reward system neural trajectories from adolescence to young adulthood

Mixed findings exist in studies comparing brain responses to reward in adolescents and adults. Here we examined the trajectories of brain response, functional connectivity and task-modulated network properties during reward processing with a large-sample longitudinal design. Participants from the IMAGEN study performed a Monetary Incentive Delay task during fMRI at timepoint 1 (T1; n = 1304, mean age=14.44 years old) and timepoint 2 (T2; n = 1241, mean age=19.09 years). The Alcohol Use Disorders Identification Test (AUDIT) was administrated at both T1 and T2 to assess a participant’s alcohol use during the past year. Voxel-wise linear mixed effect models were used to compare whole brain response as well as functional connectivity of the ventral striatum (VS) during reward anticipation (large reward vs no-reward cue) between T1 and T2. In addition, task-modulated networks were constructed using generalized psychophysiological interaction analysis and summarized with graph theory metrics. To explore alcohol use in relation to development, participants with no/low alcohol use at T1 but increased alcohol use to hazardous use level at T2 (i.e., participants with AUDIT≤2 at T1 and ≥8 at T2) were compared against those with consistently low scores (i.e., participants with AUDIT≤2 at T1 and ≤7 at T2). Across the whole sample, lower brain response during reward anticipation was observed at T2 compared with T1 in bilateral caudate nucleus, VS, thalamus, midbrain, dorsal anterior cingulate as well as left precentral and postcentral gyrus. Conversely, greater response was observed bilaterally in the inferior and middle frontal gyrus and right precentral and postcentral gyrus at T2 (vs. T1). Increased functional connectivity with VS was found in frontal, temporal, parietal and occipital regions at T2. Graph theory metrics of the task-modulated network showed higher inter-regional connectivity and topological efficiency at T2. Interactive effects between time (T1 vs. T2) and alcohol use group (low vs. high) on the functional connectivity were observed between left middle temporal gyrus and right VS and the characteristic shortest path length of the task-modulated networks. Collectively, these results demonstrate the utility of the MID task as a probe of typical brain response and network properties during development and of differences in these features related to adolescent drinking, a reward-related behaviour associated with heightened risk for future negative health outcomes.

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Imaging data during reward anticipation at T1 (age 14) and T2 (age 19) was compared.

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Brain response decreased in subcortical areas and increased in cortical areas at T2.

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Functional connectivity (FC) with the ventral striatum increased at T2.

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Topological efficiency of task-modulated network increased at T2.

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The developmental pattern was altered in those who increased drinking most at T2.

Dissociable influences of reward and punishment on adaptive cognitive control

To invest effort into any cognitive task, people must be sufficiently motivated. Whereas prior research has focused primarily on how the cognitive control required to complete these tasks is motivated by the potential rewards for success, it is also known that control investment can be equally motivated by the potential negative consequence for failure. Previous theoretical and experimental work has yet to examine how positive and negative incentives differentially influence the manner and intensity with which people allocate control. Here, we develop and test a normative model of control allocation under conditions of varying positive and negative performance incentives. Our model predicts, and our empirical findings confirm, that rewards for success and punishment for failure should differentially influence adjustments to the evidence accumulation rate versus response threshold, respectively. This dissociation further enabled us to infer how motivated a given person was by the consequences of success versus failure.

The neural basis of effort valuation: A meta-analysis of functional magnetic resonance imaging studies

Choosing how much effort to expend is critical for everyday decisions. While several neuroimaging studies have examined effort-based decision-making, results have been highly heterogeneous, leaving unclear which brain regions process effort-related costs and integrate them with rewards. We conducted two meta-analyses of functional magnetic resonance imaging data to examine consistent neural correlates of effort demands (23 studies, 15 maps, 549 participants) and net value (15 studies, 11 maps, 428 participants). The pre-supplementary motor area (pre-SMA) scaled positively with pure effort demand, whereas the ventromedial prefrontal cortex (vmPFC) showed the opposite effect. Moreover, regions that have been previously implicated in value integration in other cost domains, such as the vmPFC and ventral striatum, were consistently involved in signaling net value. The opposite response patterns of the pre-SMA and vmPFC imply that they are differentially involved in the representation of effort costs and value integration. These findings provide conclusive evidence that the vmPFC is a central node for net value computation and reveal potential brain targets to treat motivation-related disorders.

Effective connectivity underlying reward-based executive control

Motivational influences on cognitive control play an important role in shaping human behavior. Cognitive facilitation through motivators such as prospective reward or punishment is thought to depend on regions from the dopaminergic mesocortical network, primarily the ventral tegmental area (VTA), inferior frontal junction (IFJ), and anterior cingulate cortex (ACC). However, how interactions between these regions relate to motivated control remains elusive. In the present functional magnetic resonance imaging study, we used dynamic causal modeling (DCM) to investigate effective connectivity between left IFJ, ACC, and VTA in a task-switching paradigm comprising three distinct motivational conditions (prospective monetary reward or punishment and a control condition). We found that while prospective punishment significantly facilitated switching between tasks on a behavioral level, interactions between IFJ, ACC, and VTA were characterized by modulations through prospective reward but not punishment. Our DCM results show that IFJ and VTA modulate ACC activity in parallel rather than by interaction to serve task demands in reward-based cognitive control. Our findings further demonstrate that prospective reward and punishment differentially affect neural control mechanisms to initiate decision-making.

Computational Modeling of Catecholamines Dysfunction in Alzheimer's Disease at Pre-Plaque Stage

Background:

Alzheimer’s disease (AD) etiopathogenesis remains partially unexplained. The main conceptual framework used to study AD is the Amyloid Cascade Hypothesis, although the failure of recent clinical experimentation seems to reduce its potential in AD research.

Objective:

A possible explanation for the failure of clinical trials is that they are set too late in AD progression. Recent studies suggest that the ventral tegmental area (VTA) degeneration could be one of the first events occurring in AD progression (pre-plaque stage).

Methods:

Here we investigate this hypothesis through a computational model and computer simulations validated with behavioral and neural data from patients.

Results:

We show that VTA degeneration might lead to system-level adjustments of catecholamine release, triggering a sequence of events leading to relevant clinical and pathological signs of AD. These changes consist first in a midfrontal-driven compensatory hyperactivation of both VTA and locus coeruleus (norepinephrine) followed, with the progression of the VTA impairment, by a downregulation of catecholamine release. These processes could then trigger the neural degeneration at the cortical and hippocampal levels, due to the chronic loss of the neuroprotective role of norepinephrine.

Conclusion:

Our novel hypothesis might contribute to the formulation of a wider system-level view of AD which might help to devise early diagnostic and therapeutic interventions.

Self-regulation of stress-related large-scale brain network balance using real-time fMRI neurofeedback

It has recently been shown that acute stress affects the allocation of neural resources between large-scale brain networks, and the balance between the executive control network and the salience network in particular. Maladaptation of this dynamic resource reallocation process is thought to play a major role in stress-related psychopathology, suggesting that stress resilience may be determined by the retained ability to adaptively reallocate neural resources between these two networks. Actively training this ability could hence be a potentially promising way to increase resilience in individuals at risk for developing stress-related symptomatology. Using real-time functional Magnetic Resonance Imaging, the current study investigated whether individuals can learn to self-regulate stress-related large-scale network balance. Participants were engaged in a bidirectional and implicit real-time fMRI neurofeedback paradigm in which they were intermittently provided with a visual representation of the difference signal between the average activation of the salience and executive control networks, and tasked with attempting to self-regulate this signal. Our results show that, given feedback about their performance over three training sessions, participants were able to (1) learn strategies to differentially control the balance between SN and ECN activation on demand, as well as (2) successfully transfer this newly learned skill to a situation where they (a) did not receive any feedback anymore, and (b) were exposed to an acute stressor in form of the prospect of a mild electric stimulation. The current study hence constitutes an important first successful demonstration of neurofeedback training based on stress-related large-scale network balance - a novel approach that has the potential to train control over the central response to stressors in real-life and could build the foundation for future clinical interventions that aim at increasing resilience.

Neural Representation of Costs and Rewards in Decision Making

Decision making is crucial for animal survival because the choices they make based on their current situation could influence their future rewards and could have potential costs. This review summarises recent developments in decision making, discusses how rewards and costs could be encoded in the brain, and how different options are compared such that the most optimal one is chosen. The reward and cost are mainly encoded by the forebrain structures (e.g., anterior cingulate cortex, orbitofrontal cortex), and their value is updated through learning. The recent development on dopamine and the lateral habenula's role in reporting prediction errors and instructing learning will be emphasised. The importance of dopamine in powering the choice and accounting for the internal state will also be discussed. While the orbitofrontal cortex is the place where the state values are stored, the anterior cingulate cortex is more important when the environment is volatile. All of these structures compare different attributes of the task simultaneously, and the local competition of different neuronal networks allows for the selection of the most appropriate one. Therefore, the total value of the task is not encoded as a scalar quantity in the brain but, instead, as an emergent phenomenon, arising from the computation at different brain regions.

Neural and computational mechanisms of momentary fatigue and persistence in effort-based choice

From a gym workout, to deciding whether to persevere at work, many activities require us to persist in deciding that rewards are ‘worth the effort’ even as we become fatigued. However, studies examining effort-based decisions typically assume that the willingness to work is static. Here, we use computational modelling on two effort-based tasks, one behavioural and one during fMRI. We show that two hidden states of fatigue fluctuate on a moment-to-moment basis on different timescales but both reduce the willingness to exert effort for reward. The value of one state increases after effort but is ‘recoverable’ by rests, whereas a second ‘unrecoverable’ state gradually increases with work. The BOLD response in separate medial and lateral frontal sub-regions covaried with these states when making effort-based decisions, while a distinct fronto-striatal system integrated fatigue with value. These results provide a computational framework for understanding the brain mechanisms of persistence and momentary fatigue.

The willingness to exert effort into demanding tasks often declines over time through fatigue. Here the authors provide a computational account of the moment-to-moment dynamics of fatigue and its impact on effort-based choices, and reveal the neural mechanisms that underlie such computations.

Interaction of schizophrenia and chronic cannabis use on reward anticipation sensitivity

Chronic cannabis use and schizophrenia are both thought to affect reward processing. While behavioural and neural effects on reward processing have been investigated in both conditions, their interaction has not been studied, although chronic cannabis use is common among these patients. In the present study eighty-nine participants divided into four groups (control chronic cannabis users and non-users; schizophrenia patient cannabis users and non-users) performed a two-choice decision task, preceded by monetary cues (high/low reward/punishment or neutral), while being scanned using functional magnetic resonance imaging. Reward and punishment anticipation resulted in activation of regions of interest including the thalamus, striatum, amygdala and insula. Chronic cannabis use and schizophrenia had opposing effects on reward anticipation sensitivity. More specifically control users and patient non-users showed faster behavioural responses and increased activity in anterior/posterior insula for high magnitude cues compared to control non-users and patient users. The same interaction pattern was observed in the activation of the right thalamus for reward versus punishment cues. This study provided evidence for interaction of chronic cannabis use and schizophrenia on reward processing and highlights the need for future research addressing the significance of this interaction for the pathophysiology of these conditions and its clinical consequences.

A mosaic of cost-benefit control over cortico-striatal circuitry

Dopamine contributes to cognitive control through well-established effects in both the striatum and cortex. Although earlier work suggests that dopamine affects cognitive control capacity, more recent work suggests that striatal dopamine may also impact on cognitive motivation. We consider the emerging perspective that striatal dopamine boosts control by making people more sensitive to the benefits versus the costs of cognitive effort, and we discuss how this sensitivity shapes competition between controlled and prepotent actions. We propose that dopamine signaling in distinct cortico-striatal subregions mediates different types of cost-benefit tradeoffs, and also discuss mechanisms for the local control of dopamine release, enabling selectivity among cortico-striatal circuits. In so doing, we show how this cost-benefit mosaic can reconcile seemingly conflicting findings about the impact of dopamine signaling on cognitive control.

The Use of Magnetic Resonance Imaging Techniques in Assessing the Effects of Alcohol Consumption and Heavy Drinking on the Adolescent Brain: A Scoping Review Protocol

Introduction: Alcohol consumption, specifically heavy drinking during adolescence, has been shown to be accompanied by adverse structural brain changes in adolescent drinkers. This scoping review will aim to quantify and evaluate the quality of studies in which magnetic resonance imaging (MRI) techniques are used to assess regional brain deficits among adolescents who consume alcohol. Methods and analysis: This scoping review will be conducted following the Arksey and O’Malley scoping review methodology framework and will be reported using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) extension for Scoping Reviews (PRISMA-ScR) guidelines. Literature will be searched for the period January 1999 to March 2021. Two reviewers will independently screen titles/abstracts and full-texts in two consecutive screening stages. Eligible studies will be independently reviewed to ensure that inclusion criteria are met. Cohen’s Kappa (κ) will be used to calculate inter-rater agreement. A third reviewer will resolve any disagreements. The Joanna Briggs Institute (JBI) Appraisal Tools will be used for quality appraisal of the included studies. Findings will be reported by means of a narrative overview, tabular presentation of study characteristics, and quality assessment, and a thematic analysis of major themes. This scoping review has been registered with the Open Science Framework. Ethics and dissemination: Scoping reviews do not require ethical approval, however, this review forms part of a larger study that has obtained approval from the Faculty of Health and Medical Sciences, Health Research Ethics Committee at Stellenbosch University (S20/04/086). Findings will be disseminated by means of peer-reviewed publications and conferences.

Increased cognitive workload evokes greater neurovascular coupling responses in healthy young adults

Understanding how the brain allocates resources to match the demands of active neurons under physiological conditions is critically important. Increased metabolic demands of active brain regions are matched with hemodynamic responses known as neurovascular coupling (NVC). Several methods that allow noninvasive assessment of brain activity in humans detect NVC and early detection of NVC impairment may serve as an early marker of cognitive impairment. Therefore, non-invasive NVC assessments may serve as a valuable tool to detect early signs of cognitive impairment and dementia. Working memory tasks are routinely employed in the evaluation of cognitive task-evoked NVC responses. However, recent attempts that utilized functional near-infrared spectroscopy (fNIRS) or transcranial Doppler sonography (TCD) while using a similar working memory paradigm did not provide convincing evidence for the correlation of the hemodynamic variables measured by these two methods. In the current study, we aimed to compare fNIRS and TCD in their performance of differentiating NVC responses evoked by different levels of working memory workload during the same working memory task used as cognitive stimulation. Fourteen healthy young individuals were recruited for this study and performed an n-back cognitive test during TCD and fNIRS monitoring. During TCD monitoring, the middle cerebral artery (MCA) flow was bilaterally increased during the task associated with greater cognitive effort. fNIRS also detected significantly increased activation during a more challenging task in the left dorsolateral prefrontal cortex (DLPFC), and in addition, widespread activation of the medial prefrontal cortex (mPFC) was also revealed. Robust changes in prefrontal cortex hemodynamics may explain the profound change in MCA blood flow during the same cognitive task. Overall, our data support our hypothesis that both TCD and fNIRS methods can discriminate NVC evoked by higher demand tasks compared to baseline or lower demand tasks.

Changes in neural reward processing following Amplification of Positivity treatment for depression and anxiety: Preliminary findings from a randomized waitlist controlled trial

Positive valence system (PVS) deficits are increasingly recognized as important treatment targets for depression and anxiety. Emerging behavioral treatments designed to upregulate the PVS show initial promise; however, neural mechanisms underlying these approaches remain unknown. This study investigated neural reward-processing-related changes following Amplification of Positivity (AMP)-a treatment designed to enhance positive thinking, emotions and behaviors through positive activity interventions (Clinicaltrials.gov: NCT02330627). Individuals with depression and/or anxiety (N = 29) were randomized to 10 sessions of AMP (n = 16) or waitlist (WL; n = 13). Participants completed a monetary incentive delay task during fMRI at baseline and post-assessment. Hypothesis-driven region of interest (ventral striatum, insula, anterior cingulate) and exploratory whole-brain activation and connectivity analyses evaluated pre-to-post changes for AMP vs. WL when anticipating potential monetary gain or loss. No between-group brain activation changes emerged in regions of interest or whole-brain analyses. Increased neural connectivity from pre-to-post-treatment was observed in AMP vs. WL, including ventral striatum, anterior insula, and anterior cingulate connectivity with prefrontal, limbic, occipital and parietal regions-predominantly during loss anticipation. This preliminary study is the first to examine neural mechanisms of positive activity interventions in depression and anxiety and suggests that AMP may strengthen brain connectivity in reward processing, attention, and emotion regulation networks.