Mesolimbic interaction of emotional valence and reward improves memory formation

The neuroscience of active learning and direct instruction

Throughout the educational system, students experiencing active learning pedagogy perform better and fail less than those taught through direct instruction. Can this be ascribed to differences in learning from a neuroscientific perspective? This review examines mechanistic, neuroscientific evidence that might explain differences in cognitive engagement contributing to learning outcomes between these instructional approaches. In classrooms, direct instruction comprehensively describes academic content, while active learning provides structured opportunities for learners to explore, apply, and manipulate content. Synaptic plasticity and its modulation by arousal or novelty are central to all learning and both approaches. As a form of social learning, direct instruction relies upon working memory. The reinforcement learning circuit, associated agency, curiosity, and peer-to-peer social interactions combine to enhance motivation, improve retention, and build higher-order-thinking skills in active learning environments. When working memory becomes overwhelmed, additionally engaging the reinforcement learning circuit improves retention, providing an explanation for the benefits of active learning. This analysis provides a mechanistic examination of how emerging neuroscience principles might inform pedagogical choices at all educational levels.

Emotional contagion and prosocial behaviour in fish: An evolutionary and mechanistic approach

In this review, we consider the definitions and experimental approaches to emotional contagion and prosocial behaviour in mammals and explore their evolutionary conceptualisation for studying their occurrence in the evolutionarily divergent vertebrate group of ray-finned fish. We present evidence for a diverse set of fish phenotypes that meet definitional criteria for prosocial behaviour and emotional contagion and discuss conserved mechanisms that may account for some preserved social capacities in fish. Finally, we provide some considerations on how to address the question of interdependency between emotional contagion and prosocial response, highlighting the importance of recognition processes, decision-making systems, and ecological context for providing evolutionary explanations.

Untangling the threads of motivated memory: Independent influences of reward and emotion

Motivational and emotional influences on memory have been studied extensively; however, despite the link between these constructs, they have been studied in separate lines of research, with very little work examining their effects concurrently. The current study takes a novel approach to manipulate motivational and emotional influences orthogonally, and within the same task, to test their interplay on intentional memory formation. If emotion and reward motivation are tightly linked, they may rely on overlapping cognitive mechanisms, thus we would not expect emotion and reward to interact in memory. Alternatively, they could be distinct constructs and therefore would boost memory when both are included in the same experimental trial, above and beyond additive effects. To test these competing predictions, in Experiment 1, participants (n = 180) completed an old/new recognition memory task with emotional (negative, positive) and neutral words intentionally encoded with high or low reward anticipation cues. In Experiment 2, participants (n = 159) encoded emotional and neutral words with a high or low reward cue, but memory was tested with free recall using study-test blocks. The findings from both experiments converged. There were main effects of emotion and reward in generally hypothesized directions, but no evidence of an interaction between these factors. This is in line with the prediction that emotion and reward motivation are similar constructs. Their combination within a trial does not boost memory above and beyond either of these factors alone perhaps indicating these constructs have similar cognitive mechanisms.

The effect of reward-induced arousal on the success and precision of episodic memory retrieval

Moment-to-moment fluctuations in arousal can have large effects on learning and memory. For example, when neutral items are predictive of a later reward, they are often remembered better than neutral items without a reward association. This reward anticipation manipulation is thought to induce a heightened state of arousal, resulting in stronger encoding. It is unclear, however, whether these arousal-induced effects on encoding are 'all-or-none', or whether encoding precision varies from trial to trial with degree of arousal. Here, we examined whether trial-to-trial variability in reward-related pupil-linked arousal might correspond to variability in participants' long-term memory encoding precision. We tested this using a location memory paradigm in which half of the to-be-encoded neutral items were linked to later monetary reward, while the other half had no reward association. After the encoding phase, we measured immediate item location memory on a continuous scale, allowing us to assess both memory success and memory precision. We found that pre-item baseline pupil size and pupil size during item encoding were not related to subsequent memory performance. In contrast, the anticipation of instrumental reward increased pupil size, and a smaller anticipatory increase in pupil size was linked to greater subsequent memory success but not memory precision.

Factors influencing sleep-dependent consolidation: Sleep strengths memory based on encoding depth but not repetition

Sleep consolidates declarative memory after deep but not shallow incidental encoding, but little is known about this form of consolidation. One unexplored area is the extent to which the amount of exposure to incidentally encoded information affects consolidation processes. In two experiments, we manipulated the number of times information was presented. In Experiment 1, participants encoded words either one or three times in a deep or shallow incidental encoding task and completed a surprise recognition test after sleep or wake. Sleep consolidated information after deep encoding after one and three exposures, but not after shallow encoding. In Experiment 2, we explored the relationship between sleep architecture and memory after deep encoding. There was a trend for accuracy to be negatively related to N1 sleep, and reaction time to be negatively related to slow-wave sleep for words encoded once; however, the correlations did not survive corrections for multiple comparisons. These results are discussed with respect to active and passive consolidation processes.

Negative emotion reduces the discriminability of reward outcomes in the ventromedial prefrontal cortex

Reward and emotion are tightly intertwined, so there is a growing interest in mapping their interactions. However, our knowledge of these interactions in the human brain, especially during the consummatory phase of reward is limited. To address this critical gap, we conducted a functional magnetic resonance imaging study to investigate the effects of negative emotion on reward outcome processing. We employed a novel design where emotional valence (negative or neutral) indicated the type of outcome (reward or no-reward) in a choice task. We focused our functional magnetic resonance imaging analysis on the ventro-medial prefrontal cortex (vmPFC), ventral striatum and amygdala, which were frequently implicated in reward outcome processing. In these regions of interest, we performed multi-voxel pattern analysis to specifically probe how negative emotion modulates reward outcome processing. In vmPFC, using decoding analysis, we found evidence consistent with the reduced discriminability of multi-variate activity patterns of reward vs no-reward outcomes when signaled by a negative relative to a neutral image, suggesting an emotional modulation of reward processing along the plausible common value/valence dimension. These findings advance our limited understanding of the basic brain mechanisms underlying the influence of negative emotion on consummatory reward processing, with potential implications for mental disorders, particularly anxiety and depression.

Reward association impairs recognition of incidentally encoded negative information: Electrophysiological evidence

Previous studies investigating the effect of reward on emotional episodic memory have produced inconsistent results. In this study, through two experiments using event-related potentials (ERPs), we investigated the effect of reward association on the encoding and retrieval of incidentally encoded emotional information, and examined whether this effect changes over time. Participants in the two experiments were asked to discriminate the emotional valence of color images under reward or no-reward condition and incidentally encode them. Immediate (in Experiment 1) or 24-hour delayed (in Experiment 2) recognition after encoding was tested. In Experiments 1 and 2, reward (relative to no-reward) significantly improved the recognition of positive and neutral items, but significantly reduced the recognition of negative items. During encoding, the significant ERP reward effects (significantly more positive ERP amplitude for rewarded items than for non-rewarded ones) for positive and neutral images were widely distributed from 200 to 1500 ms after image onset, while those for negative stimuli occurred mainly from 200 to 500 ms. During retrieval, the significant ERP reward effects for positive and neutral items occurred in the two experiments, but the reversed ERP reward effects for negative items were found only in Experiment 1. The results of the present study suggest that reward association affects the encoding and retrieval of emotional images by enhancing memory processing efficiency of positive and neutral items, while impairing recognition of negative items, thus yielding a robust and sustained modulation over frontal/frontocentral or centroparietal/parietal areas where mechanisms of reward and emotion processing operate in conjunction.

Of ugly gains and happy losses: An event-related potential study of interactions of the intrinsic and acquired valence of emotional pictures

During the last decades, event-related potential research on the processing of intrinsic and acquired valence has made great progress, but the two dimensions rarely varied simultaneously. Only that way, however, can we investigate whether the acquisition of extrinsic valence varies with intrinsic valence and whether intrinsic and acquired valence share the same brain mechanisms. Forty-five participants performed associative learning of gains and losses, using pictures varying on intrinsic valence (positive, negative) and outcome (90 % gain, 50 %/50 %, 90 % loss). 64-channel EEG was recorded. During acquisition, one picture from each valence/outcome combination was repeatedly presented, followed by abstract outcome information (+10 ct, -10 ct) at the predefined probability. In the test phase, participants pressed buttons to earn the real gains and avoid the real losses associated with the pictures. Here, effects of outcome and/or its congruence with intrinsic valence were observed for RT, error rate, frontal theta power, posterior P2, P300, and LPP. Moreover, outcome systematically affected post-test valence and arousal ratings. During acquisition, a contingency effect (90 % > 50 %) on amplitude of a frontal negative slow wave accompanied the progress of learning, independently of outcome, valence, and congruence. The relative absence of outcome effects during acquisition suggests "cold" semantic rather than genuinely affective processing of gains and losses. However, with real gains and losses in the test phase, "hot" affective processing took place, and outcome and its congruence with intrinsic valence influenced behavior and neural processing. Finally, the data suggest both shared and distinct brain mechanisms of intrinsic and acquired valence.

A reward effect on memory retention, consolidation, and generalization?

Reward improves memory through both encoding and consolidation processes. In this preregistered study, we tested whether reward effects on memory generalize from high-rewarded items to low-rewarded but episodically related items. Fifty-nine human volunteers incidentally encoded associations between unique objects and repeated scenes. Some scenes typically yielded high reward, whereas others typically yielded low reward. Memory was tested immediately after encoding (n = 29) or the next day (n = 30). Overall, reward had only a limited influence on memory. It did not enhance consolidation and its effect did not generalize to episodically related stimuli. We thus contribute to understanding the boundary conditions of reward effects on memory.

Independent effects of emotional arousal and reward anticipation on episodic memory formation

Events that elicit emotional arousal or are associated with reward are more likely remembered. Emotional arousal activates the amygdala and the central noradrenergic system, whereas reward anticipation results in an activity in the mesocorticolimbic dopaminergic system. The activation of both pathways enhances memory formation in the hippocampus where their effects are based on similar neural substrates, e.g. tagging of active hippocampal synapses. Moreover, emotional arousal and reward anticipation both enhance attention, which can also affect memory formation. In addition, both neuromodulators interact on the cellular level. Therefore, we tested in the current functional magnetic resonance imaging study whether simultaneously occurring emotional arousal and reward anticipation might have interacting effects on memory formation. We did not find evidence for such an interaction, neither on the behavioral nor on the neural level. Our results further suggest that reward anticipation enhances memory formation rather by an increase in anticipation-related arousal-reflected in activity in the dorsal anterior cingulate cortex-and not dopaminergic midbrain activity. Accompanying behavioral experiments indicated that the effect of reward anticipation on memory is (i) caused at least to some extent by anticipating the speeded response to obtain the reward and not by the valance of the outcome and (ii) can be observed already immediately after encoding, i.e. before consolidation.

Attention- versus significance-driven memory formation: Taxonomy, neural substrates, and meta-analyses

Functional neuroimaging data on episodic memory formation have expanded rapidly over the last 30 years, which raises the need for an integrative framework. This study proposes a taxonomy of episodic memory formation to address this need. At the broadest level, the taxonomy distinguishes between attention-driven vs. significance-driven memory formation. The three subtypes of attention-driven memory formation are selection-, fluctuation-, and level-related. The three subtypes of significance-driven memory formation are novelty-, emotion-, and reward-related. Meta-analytic data indicated that attention-driven memory formation affects the functioning of the extra-medial temporal lobe more strongly than the medial temporal lobe (MTL) regions. In contrast, significance-driven memory formation affects the functioning of the MTL more strongly than the extra-MTL regions. This study proposed a model in which attention has a stronger impact on the formation of neocortical traces than hippocampus/MTL traces, whereas significance has a stronger impact on the formation of hippocampus/MTL traces than neocortical traces. Overall, the taxonomy and model provide an integrative framework in which to place diverse encoding-related findings into a proper perspective.

The interaction between reward and the task-irrelevant emotional context in memory

Reward improves task performance while the emotional contexts irrelevant to the task impair task performance. An interaction between reward and the task-irrelevant emotional context has been discovered by some studies using perceptual tasks. However, it is unclear that how memory performance would be affected by both variables. This study aimed to answer this question and explore the role of arousal induced by emotional stimuli, to which was seldomly paid attention by previous studies. We conducted two experiments with the study-test paradigm. The first difference between the experiments was the way that the emotional stimuli were presented. They were presented with the words (Experiment 1) or separately (Experiment 2). The second difference was that the manipulation of the emotional arousal was phasic (Experiment 1) or tonic (Experiment 2). Both experiments showed that the reward effect was greater in emotional context compared to the neutral context, which is not only due to the poorer memory of no reward-associated words but also the better memory of reward-associated words in emotional contexts especially in negative one. These results supported the view that emotional arousal enhanced the memory of high priority stimuli (reward-associated words) and impaired the memory of low priority stimuli (no reward-associated words).

Different effects of feedback-induced emotion and material-induced emotion on memory

The function of emotion in enhancing memory has been proven by a large number of studies. However, previous studies mainly used emotional materials to induce emotions, and far fewer studies have examined how neutral stimuli and emotional event connections affect memory. In Experiment 1, the feedback from the results was used as an emotional event to explore the impact of connected emotions on memory. In Experiment 2, emotional materials were used to induce emotions, and the effects on memory in the two studies were compared. The emotions induced by the feedback resulted in positive emotions having the strongest effects on memory, while negative emotions had the weakest memory effect. However, when the emotional materials were used, there were different outcomes: negative emotional memories were the best, and neutral memories were the worst. Based on these results, we may conclude that different emotion-inducing methods have different effects on memory and that emotionally enhanced memory is not applicable to all emotion-inducing modes.

Reward motivation influences response bias on a recognition memory task

Reward-motivated memory has been studied extensively in psychology and neuroscience. Many recognition studies follow the same type of paradigm: stimuli are cued at encoding with high or low reward values which indicate the amount the stimulus is worth if successfully recognized on a subsequent memory test. Each incorrect endorsement of a lure at retrieval is penalized with an arbitrary value between the high and low reward value, resulting in a single false alarm rate. Studies employing this type of paradigm have reported higher hit rates for high value items compared to low value items, but generally hit rate is the only measure of memory that is reported as a function of reward value. It is currently not clear what aspects of the experimental design lead to these memory effects, and other measures, like discriminability and response bias, cannot be properly calculated when there is only a single false alarm rate, but we hypothesize that these are also susceptible to motivational manipulations. To test how reward anticipation might influence memory and response bias in this type of task, we created a novel paradigm that allowed us to calculate both by associating rewards with categories (indoor vs. outdoor scenes), thus calculating separate false alarm rate as well as hit rate at each level of reward. We report results of three experiments that varied rewards and penalties for correct and error responses for the category items. In two experiments, we replicated prior findings of higher hit rates for high compared to low reward items, but consistently across three experiments, when d' was calculated, we found no difference in memory discriminability as a function of reward. Further, Experiment 1 we found that response bias was more conservative for low reward items: participants were more likely to endorse a 'new' response to low compared to high reward items. This effect was significantly reduced in Experiment 2 and eliminated in Experiment 3 when the reward-penalty structure was manipulated to reduce bias. Our findings reveal that reward motivation can influence decisional biases thought to be independent of memory processes. The amount of the reward value for correct responses and the amount of the penalty for incorrect responses should be considered when designing experimental paradigms to study motivation-cognition interactions.

Functional Connectivity within and beyond the Face Network Is Related to Reduced Discrimination of Degraded Faces in Young and Older Adults

Degrading face stimuli reduces face discrimination in both young and older adults, but the brain correlates of this decline in performance are not fully understood. We used functional magnetic resonance imaging to examine the effects of degraded face stimuli on face and nonface brain networks and tested whether these changes would predict the linear declines seen in performance. We found decreased activity in the face network (FN) and a decrease in the similarity of functional connectivity (FC) in the FN across conditions as degradation increased but no effect of age. FC in whole-brain networks also changed with increasing degradation, including increasing FC between the visual network and cognitive control networks. Older adults showed reduced modulation of this whole-brain FC pattern. The strongest predictors of within-participant decline in accuracy were changes in whole-brain network FC and FC similarity of the FN. There was no influence of age on these brain-behavior relations. These results suggest that a systems-level approach beyond the FN is required to understand the brain correlates of performance decline when faces are obscured with noise. In addition, the association between brain and behavior changes was maintained into older age, despite the dampened FC response to face degradation seen in older adults.

Regulatory Effects of Reward Anticipation and Target on Attention Processing of Emotional Stimulation

Studies suggest that reward and emotion are interdependent. However, there are discrepancies regarding the interaction between these variables. Some researchers speculate that the inconsistent findings may be due to different targets being used. Although reward and emotion both affect attention, it is not clear whether their impacts are independent. This study examined the impact of reward anticipation on emotion processing for different targets. A cue-target paradigm was used, and behavior and eye-tracking data were recorded in an emotion or sex recognition task under the conditions of reward and non-reward anticipation. The results showed that when the target was related to the emotional attribute of the stimulus, the reward promoted the processing target information, thereby generating reward-oriented attention. When the target was unrelated to the emotional attributes of the stimulus, the reward did not promote the processing target information, and at the same time, individuals had negative emotional biases toward the emotional faces. The results revealed that, in addition to affecting the attention to emotional faces independently, the target regulated the promotion of reward anticipation to emotional attention and attention bias toward negative stimuli.

The Matter of Non-Avian Reptile Sentience, and Why It "Matters" to Them: A Conceptual, Ethical and Scientific Review

The concept of sentience, how it is characterised and which non-human animals possess it have long been of contention in academic and intellectual debates. Many have argued that there is no way to empirically know that animals have conscious experiences. Yet others argue that consciousness, awareness and sentience in non-human animals can be quite obvious, and can indeed be measured empirically. Most modern declarations of animal sentience from official organisations and governments now include all vertebrate animals as sentient beings, including reptiles and fish. Some declarations also include some invertebrate species. This conceptual, ethical and scientific review first focuses on conceptual components and definitions of consciousness, awareness and sentience. It then specifically discusses how cognitive, neurobiological, ethological and comparative psychological research in non-avian reptiles over the last century has evidenced many capacities that historically were denied to this class of animals. Non-avian reptiles do indeed possess all of the necessary capacities to be declared as sentient beings, at least in the small proportion of reptile species that have actually been empirically investigated so far. It is suggested that much innovative future research will continue to uncover evidence of capabilities linked to sentience within a wide range of species, including non-avian reptiles, fish and invertebrates.

NEVER forget: negative emotional valence enhances recapitulation

A hallmark feature of episodic memory is that of "mental time travel," whereby an individual feels they have returned to a prior moment in time. Cognitive and behavioral neuroscience methods have revealed a neurobiological counterpart: Successful retrieval often is associated with reactivation of a prior brain state. We review the emerging literature on memory reactivation and recapitulation, and we describe evidence for the effects of emotion on these processes. Based on this review, we propose a new model: Negative Emotional Valence Enhances Recapitulation (NEVER). This model diverges from existing models of emotional memory in three key ways. First, it underscores the effects of emotion during retrieval. Second, it stresses the importance of sensory processing to emotional memory. Third, it emphasizes how emotional valence - whether an event is negative or positive - affects the way that information is remembered. The model specifically proposes that, as compared to positive events, negative events both trigger increased encoding of sensory detail and elicit a closer resemblance between the sensory encoding signature and the sensory retrieval signature. The model also proposes that negative valence enhances the reactivation and storage of sensory details over offline periods, leading to a greater divergence between the sensory recapitulation of negative and positive memories over time. Importantly, the model proposes that these valence-based differences occur even when events are equated for arousal, thus rendering an exclusively arousal-based theory of emotional memory insufficient. We conclude by discussing implications of the model and suggesting directions for future research to test the tenets of the model.

A Neuroeconomic Theory of Mental Time Travel

We propose a theoretical model that places attention at the center of mental time travel (MTT) ability. This theory predicts that attention promotes a memory-based process that encodes memories of unexpected events, facilitates accurate recollection of information of such events during MTT, and optimizes subsequent decision-making. This process coexists with a habitual process that governs all other events and treats them equally. Our theory demonstrates that the memory-based process is useful when the environment features novel experiences that are likely to be relevant in future decision-making, hence worth remembering accurately. By contrast, the habitual process is optimal in environments that either do not change significantly, or have a small chance of being repeated in the future. This may explain why the ability to mentally travel in time has developed differently in humans than in other species. Implications are discussed in the context of decision-making.

Goal-relevant situations facilitate memory of neutral faces

Emotional situations are typically better remembered than neutral situations, but the psychological conditions and brain mechanisms underlying this effect remain debated. Stimulus valence and affective arousal have been suggested to explain the major role of emotional stimuli in memory facilitation. However, neither valence nor arousal are sufficient affective dimensions to explain the effect of memory facilitation. Several studies showed that negative and positive details are better remembered than neutral details. However, other studies showed that neutral information encoded and coupled with arousal did not result in a memory advantage compared with neutral information not coupled with arousal. Therefore, we suggest that the fundamental affective dimension responsible for memory facilitation is goal relevance. To test this hypothesis at behavioral and neural levels, we conducted a functional magnetic resonance imaging study and used neutral faces embedded in goal-relevant or goal-irrelevant daily life situations. At the behavioral level, we found that neutral faces encountered in goal-relevant situations were better remembered than those encountered in goal-irrelevant situations. To explain this effect, we studied neural activations involved in goal-relevant processing at encoding and in subsequent neutral face recognition. At encoding, activation of emotional brain regions (anterior cingulate, ventral striatum, ventral tegmental area, and substantia nigra) was greater for processing of goal-relevant situations than for processing of goal-irrelevant situations. At the recognition phase, despite the presentation of neutral faces, brain activation involved in social processing (superior temporal sulcus) to successfully remember identities was greater for previously encountered faces in goal-relevant than in goal-irrelevant situations.

Memory Recall for High Reward Value Items Correlates With Individual Differences in White Matter Pathways Associated With Reward Processing and Fronto-Temporal Communication

When given a long list of items to remember, people typically prioritize the memorization of the most valuable items. Prior neuroimaging studies have found that cues denoting the presence of high value items can lead to increased activation of the mesolimbic dopaminergic reward circuit, including the nucleus accumbens (NAcc) and ventral tegmental area (VTA), which in turn results in up-regulation of medial temporal lobe encoding processes and better memory for the high value items. Value cues may also trigger the use of elaborative semantic encoding strategies which depend on interactions between frontal and temporal lobe structures. We used diffusion tensor imaging (DTI) to examine whether individual differences in anatomical connectivity within these circuits are associated with value-induced modulation of memory. DTI data were collected from 19 adults who also participated in an functional magnetic resonanceimaging (fMRI) study involving a value-directed memory task. In this task, subjects encoded words with arbitrarily assigned point values and completed free recall tests after each list, showing improved recall performance for high value items. Motivated by our prior fMRI finding of increased recruitment of left-lateralized semantic network regions during the encoding of high value words (Cohen et al., 2014), we predicted that the robustness of the white matter pathways connecting the ventrolateral prefrontal cortex (VLPFC) with the temporal lobe might be a determinant of recall performance for high value items. We found that the mean fractional anisotropy (FA) of each subject’s left uncinate fasciculus (UF), a fronto-temporal fiber bundle thought to play a critical role in semantic processing, correlated with the mean number of high value, but not low value, words that subjects recalled. Given prior findings on reward-induced modulation of memory, we also used probabilistic tractography to examine the white matter pathway that links the NAcc to the VTA. We found that the number of fibers projecting from left NAcc to VTA was reliably correlated with subjects’ selectivity index, a behavioral measure reflecting the degree to which recall performance was impacted by item value. Together, these findings help to elucidate the neuroanatomical pathways that support verbal memory encoding and its modulation by value.

Context and Time Matter: Effects of Emotion and Motivation on Episodic Memory Overtime

Previous studies have shown that compared with neutral cues, stimuli with positive and negative/stressful contexts or reward and punishment cues are remembered better. However, it is unclear whether the enhanced effect differs in emotion or motivation dimensions and the passage of time. We addressed these issues by manipulating different contextual cues for neutral words at different time intervals. In experiment 1, subjects were asked to learn words with picture contexts in positive, negative/stressful, and neutral valences and were tested by old/new word recognition and contextual judgment 10 min, 1 day, and 1 week later. In experiment 2, the reward and punishment motivations were manipulated by monetary cues during learning. Word recognition and contextual judgment were assessed 10 min, 1 day, 1 week, and 1 month after the study. Compared with negative and punishment conditions, the words in positive and reward contexts were recognized better at shorter intervals, which was associated with recollection process. In contrast, the words in negative and punishment contexts were recognized better at longer intervals, which was mainly associated with familiarity process. These results clarified how different dimensions of emotional and motivational contexts influence memory at short and long intervals and highlighted the role of contextual features in memory formation and consolidation.

Potential reward reduces the adverse impact of negative distractor stimuli

Knowledge about interactions between reward and negative processing is rudimentary. Here, we employed functional MRI to probe how potential reward signaled by advance cues alters aversive distractor processing during perception. Behaviorally, the influence of aversive stimuli on task performance was reduced during the reward compared to no-reward condition. In the brain, at the task phase, paralleling the observed behavioral pattern, we observed significant interactions in the anterior insula and dorsal anterior cingulate cortex, such that responses during the negative (vs neutral) condition were reduced during the reward compared to no-reward condition. Notably, negative distractor processing in the amygdala appeared to be independent of the reward manipulation. During the initial cue phase, we observed increased reward-related responses in the ventral striatum/accumbens, which were correlated with behavioral interference scores at the subsequent task phase, revealing that participants with increased reward-related responses exhibited a greater behavioral benefit of reward in reducing the adverse effect of negative images. Furthermore, during processing of reward (vs no-reward) cues, the ventral striatum exhibited stronger functional connectivity with fronto-parietal regions important for attentional control. Together, our findings contribute to the understanding of how potential reward influences attentional control and reduces negative distractor processing in the human brain.

Monetary incentives at retrieval promote recognition of involuntarily learned emotional information

Previous studies have suggested that the effects of reward on memory processes are affected by certain factors, but it remains unclear whether the effects of reward at retrieval on recognition processes are influenced by emotion. The event-related potential was used to investigate the combined effect of reward and emotion on memory retrieval and its neural mechanism. The behavioral results indicated that the reward at retrieval improved recognition performance under positive and negative emotional conditions. The event-related potential results indicated that there were significant interactions between the reward and emotion in the average amplitude during recognition, and the significant reward effects from the frontal to parietal brain areas appeared at 130-800 ms for positive pictures and at 190-800 ms for negative pictures, but there were no significant reward effects of neutral pictures; the reward effect of positive items appeared relatively earlier, starting at 130 ms, and that of negative pictures began at 190 ms. These results indicate that monetary incentives at retrieval promote recognition of involuntarily learned emotional information.

The role of value in the attentional boost effect

Focusing attention on one item typically interferes with the ability to process other information. Yet, target detection can both facilitate memory for items paired with the target (the attentional boost effect) and increase the perceived value of those items (cued approach). Because long-term memory is better for valuable items than for neutral items, we asked whether the attentional boost effect is due to changes in the perceived value of items that are paired with targets. In three experiments, participants memorised a series of briefly presented images that depicted valuable (e.g., food) or neutral (e.g., children's toys) items. Whenever an item appeared, a square flashed in its centre. Participants pressed a button if the square was a target colour but not if it was a distractor colour. Consistent with previous research, target-paired items were remembered better than distractor-paired items and were rated as more valuable. Importantly, if memory for target-paired items is enhanced because they increased in perceived value, then valuable items should have been better remembered than neutral items. However, we found no evidence that value enhanced memory for the items in this task. Thus, it is unlikely that the attentional boost effect is due to changes in perceived value.

Reward anticipation modulates the effect of stress-related increases in cortisol on episodic memory

When acute stress is experienced shortly after an event is encoded into memory, this can slow the forgetting of the study event, which is thought to reflect the effect of cortisol on consolidation. In addition, when events are encoded under conditions of high reward they tend to be remembered better than those encoded under non-rewarding conditions, and these effects are thought to reflect the operation of the dopaminergic reward system. Although both modulatory systems are believed to impact the medial temporal lobe regions critical for episodic memory, the manner, and even the extent, to which these two systems interact is currently unknown. To address this question in the current study, participants encoded words under reward or non-reward conditions, then one half of the participants were stressed using the social evaluation cold pressor task and the other half completed a non-stress control task. After a two-hour delay, all participants received a free recall and recognition memory test. There were no significant effects of stress or reward on overall memory performance. However, for the non-reward items, increases in stress-related cortisol in stressed participants were related to increases in recall and increases in recollection-based recognition responses. In contrast, for the reward items, increases in stress-related cortisol were not related to increases in memory performance. The results indicate that the stress and the reward systems interact in the way they impact episodic memory. The results are consistent with tag and capture models in the sense that cortisol reactivity can only affect non-reward items because plasticity-related products are already provided by reward anticipation.

Season-independent cognitive deficits in seasonal affective disorder and their relation to depressive symptoms

Although cognitive impairments are common in depressed individuals, it is unclear which aspects of cognition are affected and whether they represent state or trait features of depression. We here exploited a naturalistic model, namely the seasonal fluctuations in depressed status in individuals with Seasonal Affective Disorder (SAD), to study depression-related cognition, longitudinally. Twenty-nine medication-free individuals diagnosed with winter-SAD and 30 demographically matched healthy controls with no seasonality symptoms completed the Letter-number Sequencing task (LNS), the Symbol Digit Modalities Test (SDMT) and the Simple Reaction Time (SRT) twice; in summer and in winter. Compared to controls, SAD individuals showed significant season-independent impairments in tasks measuring working memory (LNS), cognitive processing speed (SDMT) and motor speed (SRT). In SAD individuals, cognitive processing speed was significantly negatively associated with the seasonal change in SAD depressive symptoms. We present novel evidence that in SAD individuals, working memory, cognitive processing- and motor speed is not only impaired in the winter but also in the summer. This suggests that certain cognitive impairments are SAD traits. Furthermore, impairments in cognitive processing speed appear to be related to depressive symptoms in SAD. Reduced processing speed may thus constitute a SAD vulnerability trait marker.

Mutual Influence of Reward Anticipation and Emotion on Brain Activity during Memory Retrieval

Previous studies on the joint effect of reward motivation and emotion on memory retrieval have obtained inconsistent results. Furthermore, whether and how any such joint effect might vary over time remains unclear too. Accordingly, using the event-related potential (ERP) measurement of high temporal resolution, our study investigates the cognitive and brain mechanisms of monetary reward and emotion affecting the retrieval processes of episodic memory. Twenty undergraduate and graduate students participated in the research, and our study’s behavioral results indicated that reward (relative to no reward) and negative emotion (relative to positive and neutral emotion) significantly improved recognition performance. The ERP results showed that there were significant interactions between monetary reward and emotion on memory retrieval, and the reward effects of positive, neutral, and negative memory occurred at varied intervals in mean amplitude. The reward effect of positive memory appeared relatively early, at 260–330 ms after the stimulus onset in the frontal-frontocentral area, at 260–500 ms in the centroparietal-parietal area and at 500–700 ms in the frontocentral area. However, the reward effects of neutral and negative memory occurred relatively later, and that of negative memory appeared at 500–700 ms in the frontocentral and centroparietal area and that of neutral memory was at 500–700 ms in the frontocentral and centroparietal-parietal area. Meanwhile, significant FN400 old/new effects were observed in the negative and rewarded positive items, and the old/new effects of negative items appeared earlier at FN400 than positive items. Also, significant late positive component (LPC) old/new effects were found in the positive, negative, and rewarded neutral items. These results suggest that, monetary reward and negative emotion significantly improved recognition performance, and there was a mutual influence between reward and emotion on brain activity during memory retrieval.

Memory Performance for Everyday Motivational and Neutral Objects Is Dissociable from Attention

Episodic memory is typically better for items coupled with monetary reward or punishment during encoding. It is yet unclear whether memory is also enhanced for everyday objects with appetitive or aversive values learned through a lifetime of experience, and to what extent episodic memory enhancement for motivational and neutral items is attributable to attention. In a first experiment, we investigated attention to everyday motivational objects using eye-tracking during free-viewing and subsequently tested episodic memory using a remember/know procedure. Attention was directed more to aversive stimuli, as evidenced by longer viewing durations, whereas recollection was higher for both appetitive and aversive objects. In the second experiment, we manipulated the visual contrast of neutral objects through changes of contrast to further dissociate attention and memory encoding. While objects presented with high visual contrast were looked at longer, recollection was best for objects presented in unmodified, medium contrast. Generalized logistic mixed models on recollection performance showed that attention as measured by eye movements did not enhance subsequent memory, while motivational value (Experiment 1) and visual contrast (Experiment 2) had quadratic effects in opposite directions. Our findings suggest that an enhancement of incidental memory encoding for appetitive items can occur without an increase in attention and, vice versa, that enhanced attention towards salient neutral objects is not necessarily associated with memory improvement. Together, our results provide evidence for a double dissociation of attention and memory effects under certain conditions.

Neural mechanisms underlying the reward-related enhancement of motivation when remembering episodic memories with high difficulty

The motivation to receive rewards enhances episodic memories, and the motivation is modulated by task difficulty. In episodic retrieval, however, functional neuroimaging evidence regarding the motivation that mediates interactions between reward and task difficulty is scarce. The present fMRI study investigated this issue. During encoding performed without fMRI, participants encoded Japanese words using either deep or shallow strategies, which led to variation in difficulty level during subsequent retrieval. During retrieval with fMRI, participants recognized the target words in either high or low monetary reward conditions. In the behavioral results, a reward-related enhancement of memory was found only when the memory retrieval was difficult, and the rewarding effect on subjective motivation was greater in the retrieval of memories with high difficulty than those with low difficulty. The fMRI data showed that reward-related increases in the activation of the substantia nigra/ventral tegmental area (SN/VTA), medial temporal lobe (MTL), dorsomedial prefrontal cortex (dmPFC), and dorsolateral prefrontal cortex (dlPFC) were greater during the retrieval of memories with high difficulty than those with low difficulty. Furthermore, reward-related enhancement of functional connectivity between the SN/VTA and MTL and between the SN/VTA and dmPFC during the retrieval of memories with high difficulty was significantly correlated with reward-related increases of retrieval accuracy and subjective motivation. The reward-related enhancement of episodic retrieval and retrieval-related motivation could be most effective when the level of retrieval difficulty is optimized. Such reward-related enhancement of memory and motivation could be modulated by a network including the reward-related SN/VTA, motivation-related dmPFC, and memory-related MTL. Hum Brain Mapp 38:3428-3443, 2017. © 2017 Wiley Periodicals, Inc.

Intrinsic monitoring of learning success facilitates memory encoding via the activation of the SN/VTA-Hippocampal loop

Humans constantly learn in the absence of explicit rewards. However, the neurobiological mechanisms supporting this type of internally-guided learning (without explicit feedback) are still unclear. Here, participants who completed a task in which no external reward/feedback was provided, exhibited enhanced fMRI-signals within the dopaminergic midbrain, hippocampus, and ventral striatum (the SN/VTA-Hippocampal loop) when successfully grasping the meaning of new-words. Importantly, new-words that were better remembered showed increased activation and enhanced functional connectivity between the midbrain, hippocampus, and ventral striatum. Moreover, enhanced emotion-related physiological measures and subjective pleasantness ratings during encoding were associated with remembered new-words after 24 hr. Furthermore, increased subjective pleasantness ratings were also related to new-words remembered after seven days. These results suggest that intrinsic—potentially reward-related—signals, triggered by self-monitoring of correct performance, can promote the storage of new information into long-term memory through the activation of the SN/VTA-Hippocampal loop, possibly via dopaminergic modulation of the midbrain.

DOI:http://dx.doi.org/10.7554/eLife.17441.001

Research shows that a reward such as money, or even simply the promise of such a reward, can boost the formation of long-term memories. However, in our everyday lives, we continually gain new knowledge and make new memories in the absence of any obvious immediate reward.

Rewards activate a network of brain regions that includes the hippocampus, which has a key role in memory, plus several areas that release the chemical messenger dopamine, which boosts memory formation. However, it was not clear whether this network of brain regions also supports learning that is driven internally rather than by external rewards or incentives.

Ripollés et al. have now tested this idea by asking thirty-six volunteers to try and learn the meaning of new words by reading pairs of sentences, all while lying down inside a brain scanner. Half of the paired sentences provided a clear and obvious meaning for the new word. As such, the volunteers were reasonably aware when they’d learned the meaning of a new word without any external feedback. This approach confirmed that the activity of the brain’s reward-memory loop did indeed increase whenever a volunteer learned a new word.

Next, outside the brain scanner, the volunteers performed the same task but this time they had to rate how engaging and enjoyable they found it after each trial. Emotional responses such as enjoyment trigger sweating, which alters the electrical activity of the skin. Ripollés et al. observed greater changes in this “electrodermal” activity when the volunteers learned words that they would go on to remember one day later, than when they learned words that they would quickly forget. The volunteers also reported greater enjoyment when learning the words that they would subsequently remember better, even after seven days.

Overall, these findings suggest that internally driven learning is in itself rewarding, and that under certain circumstances at least it can activate the brain’s reward-memory circuit. A key question for the future is whether tapping into intrinsically rewarding forms of learning might be a more effective educational strategy than relying on external feedback and incentives. This could be crucial to improving the design of educational programs – for example, in teaching literacy and foreign languages – and for improving the recovery of verbal skills lost after stroke.

DOI:http://dx.doi.org/10.7554/eLife.17441.002

Repetition suppression in the medial temporal lobe and midbrain is altered by event overlap

Repeated encounters with the same event typically lead to decreased activation in the medial temporal lobe (MTL) and dopaminergic midbrain, a phenomenon known as repetition suppression. In contrast, encountering an event that overlaps with prior experience leads to increased response in the same regions. Such increased responding is thought to reflect an associative novelty signal that promotes memory updating to resolve differences between current events and stored memories. Here, we married these ideas to test whether event overlap significantly modulates MTL and midbrain responses-even when events are repeated and expected-to promote memory updating through integration. While undergoing high-resolution functional MRI, participants were repeatedly presented with objects pairs, some of which overlapped with other, intervening pairs and some of which contained elements unique from other pairs. MTL and midbrain regions showed widespread repetition suppression for nonoverlapping pairs containing unique elements; however, the degree of repetition suppression was altered for overlapping pairs. Entorhinal cortex, perirhinal cortex (PRc), midbrain, and PRc-midbrain connectivity showed repetition-related increases across overlapping pairs. Notably, increased PRc activation for overlapping pairs tracked individual differences in the ability to reason about the relationships among pairs-our behavioral measure of memory integration. Within the hippocampus, activation increases across overlapping pairs were unique to CA₁ , consistent with its hypothesized comparator function. These findings demonstrate that event overlap engages MTL and midbrain functions traditionally implicated in novelty processing, even when overlapping events themselves are repeated. Our findings further suggest that the MTL-midbrain response to event overlap may promote integration of new content into existing memories, leading to the formation of relational memory networks that span experiences. Moreover, the results inform theories about the division of labor within MTL, demonstrating that the role of PRc in episodic encoding extends beyond familiarity processing and item-level recognition. © 2016 Wiley Periodicals, Inc.

Striatal Associative Learning Signals Are Tuned to In-groups

An important feature of adaptive social behavior is the ability to flexibly modify future actions based on the successes or failures of past experiences. The ventral striatum (VS) occupies a central role in shaping behavior by using feedback to evaluate actions and guide learning. The current studies tested whether feedback indicating the need to update social knowledge would engage the VS, thereby facilitating subsequent learning. We also examined the sensitivity of these striatal signals to the value associated with social group membership. Across two fMRI studies, participants answered questions testing their knowledge about the preferences of personally relevant social groups who were high (in-group) or low (out-group) in social value. Participants received feedback indicating whether their responses were correct or incorrect on a trial-by-trial basis. After scanning, participants were given a surprise memory test examining memory for the different types of feedback. VS activity in response to social feedback correlated with subsequent memory, specifying a role for the VS in encoding and updating social knowledge. This effect was more robust in response to in-group than out-group feedback, indicating that the VS tracks variations in social value. These results provide novel evidence of a neurobiological mechanism adaptively tuned to the motivational relevance of the surrounding social environment that focuses learning efforts on the most valuable social outcomes and triggers adjustments in behavior when necessary.

Episodic memory in normal aging and Alzheimer disease: Insights from imaging and behavioral studies

Age-related cognitive changes often include difficulties in retrieving memories, particularly those that rely on personal experiences within their temporal and spatial contexts (i.e., episodic memories). This decline may vary depending on the studied phase (i.e., encoding, storage or retrieval), according to inter-individual differences, and whether we are talking about normal or pathological (e.g., Alzheimer disease; AD) aging. Such cognitive changes are associated with different structural and functional alterations in the human neural network that underpins episodic memory. The prefrontal cortex is the first structure to be affected by age, followed by the medial temporal lobe (MTL), the parietal cortex and the cerebellum. In AD, however, the modifications occur mainly in the MTL (hippocampus and adjacent structures) before spreading to the neocortex. In this review, we will present results that attempt to characterize normal and pathological cognitive aging at multiple levels by integrating structural, behavioral, inter-individual and neuroimaging measures of episodic memory.

A new look on S-R associations: How S and R link

Humans can learn associations between stimuli and responses which allow for faster, more efficient behavior when the same response is required to the same stimulus in the future. This is called stimulus-response (S-R) priming. Perceptual representations are known to be modular and hierarchical, i.e. different brain areas represent different perceptual features and higher brain areas represent increasingly abstract properties of the stimulus. In this study we investigated how perceptually specific the stimulus in S-R priming is. In particular we wanted to test whether basic visual features play a role in the S-R associations. We used a novel stimulus: images of objects built from basic visual features. Participants performed a classification task on the objects. We found no significant effect on reaction times of switching vs. repeating perceptual features between presentations of the same object. This suggests that S-R associations involve a perceptually non-specific stimulus representation.

The response of rodents to scent marks: four broad hypotheses

This article is part of a Special Issue "Chemosignals and Reproduction". Many terrestrial mammals must be able to distinguish between the myriad of scent marks they encounter in order for them to facilitate or deter direct interactions with their scent donors. I review studies that examine how rodents, mainly meadow voles (Microtus pennsylvanicus), respond when they encounter the scent marks of conspecifics and heterospecifics, and how context, as well as the age and condition of senders and receivers, affect their responses. The review uses four broad hypotheses to discuss the response of rodents to scent marks. The four hypotheses are as follows: 1) Scent marks convey accurate information to the receiver about the sender's state and phenotype and genotype. 2) Scent marks are individually distinct. 3) The response of receivers to scent marks is flexible and would be modulated by the cognitive abilities of receivers. 4) Receivers respond to the information contained or conveyed by the scent mark in a manner that will increase their survival and fitness. The studies cited in this review show that scent marks signal accurate information about the sender's phenotype, genotype, and condition, which receivers use to distinguish among the scent marks of different conspecifics and heterospecifics, and by doing so, receivers tailor their response accordingly to increase their survival and fitness. Thus, the four broad hypotheses may serve as guide to increase our understanding of the response of receivers to scent marks and provide a conceptual framework for future research and the development of additional hypotheses.

Levodopa administration modulates striatal processing of punishment-associated items in healthy participants

RATIONALE

Appetitive and aversive processes share a number of features such as their relevance for action and learning. On a neural level, reward and its predictors are associated with increased firing of dopaminergic neurons, whereas punishment processing has been linked to the serotonergic system and to decreases in dopamine transmission. Recent data indicate, however, that the dopaminergic system also responds to aversive stimuli and associated actions.

OBJECTIVES

In this pharmacological functional magnetic resonance imaging study, we investigated the contribution of the dopaminergic system to reward and punishment processing in humans.

METHODS

Two groups of participants received either placebo or the dopamine precursor levodopa and were scanned during alternating reward and punishment anticipation blocks.

RESULTS

Levodopa administration increased striatal activations for cues presented in punishment blocks. In an interaction with individual personality scores, levodopa also enhanced striatal activation for punishment-predictive compared with neutral cues in participants scoring higher on the novelty-seeking dimension.

CONCLUSIONS

These data support recent indications that dopamine contributes to punishment processing and suggest that the novelty-seeking trait is a measure of susceptibility to drug effects on motivation. These findings are also consistent with the possibility of an inverted U-shaped response function of dopamine in the striatum, suggesting an optimal level of dopamine release for motivational processing.

Motivated Memories: Effects of Reward and Recollection in the Core Recollection Network and Beyond

fMRI was employed to assess whether the neural correlates of accurate source memory are modulated by the reward value of recollected information. Study items comprised pictures of objects, each paired with a depiction of 1 of 2 coins. The reward value of the coins ($2.00 vs. $0.02) was disclosed after study. At test, a source memory procedure was employed in which subjects discriminated between studied and unstudied objects and, for objects judged studied, indicated the identity of the coin paired with the object at study. Correct judgments earned a reward corresponding to the value of the coin, whereas incorrect judgments were penalized. No regions were identified where the magnitude of recollection effects was modulated by reward. Exclusive effects of source accuracy were evident in the hippocampus. Different striatal sub-regions demonstrated exclusive recollection effects, exclusive reward effects, and overlap between the 2 effects. The left angular gyrus and medial prefrontal cortex were additively responsive to source accuracy and the reward. The findings suggest that reward value and recollection success are conjointly but independently represented in at least 2 cortical regions and that striatal retrieval success effects cannot be accounted for in terms of a single construct, such as goal satisfaction.

Neural correlates of preparatory and regulatory control over positive and negative emotion

This study used functional magnetic resonance imaging to investigate brain activation during preparatory and regulatory control while participants (N = 24) were instructed either to simply view or decrease their emotional response to, pleasant, neutral or unpleasant pictures. A main effect of emotional valence on brain activity was found in the right precentral gyrus, with greater activation during positive than negative emotion regulation. A main effect of regulation phase was evident in the bilateral anterior prefrontal cortex (PFC), precuneus, posterior cingulate cortex, right putamen and temporal and occipital lobes, with greater activity in these regions during preparatory than regulatory control. A valence X regulation interaction was evident in regions of ventromedial PFC and anterior cingulate cortex, reflecting greater activation while regulating negative than positive emotion, but only during active emotion regulation (not preparation). Conjunction analyses revealed common brain regions involved in differing types of emotion regulation including selected areas of left lateral PFC, inferior parietal lobe, temporal lobe, right cerebellum and bilateral dorsomedial PFC. The right lateral PFC was additionally activated during the modulation of both positive and negative valence. Findings demonstrate significant modulation of brain activity during both preparation for, and active regulation of positive and negative emotional states.

Dopaminergic basis of salience dysregulation in psychosis

Disrupted salience processing is proposed as central in linking dysregulated dopamine function with psychotic symptoms. Several strands of evidence are now converging in support of this model. Animal studies show that midbrain dopamine neurons are activated by unexpected salient events. In psychotic patients, neurochemical studies have confirmed subcortical striatal dysregulation of dopaminergic neurotransmission, whereas functional magnetic resonance imaging (fMRI) studies of salience tasks have located alterations in prefrontal and striatal dopaminergic projection fields. At the clinical level, this may account for the altered sense of meaning and significance that predates the onset of psychosis. This review draws these different strands of evidence together in support of an emerging understanding of how dopamine dysregulation may lead to aberrant salience and psychotic symptoms.