Neural correlates underlying the effect of reward value on recognition memory

Responsible remembering: The role of metacognition, forgetting, attention, and retrieval in adaptive memory

In our everyday lives, we must remember important information, especially if there are consequences for forgetting. In this review, I discuss recent work on responsible remembering: the strategic and effortful prioritization of important information with consequences for forgetting. Thus far, research regarding responsible remembering has revealed several key factors and mechanisms that work together to enhance memory for important information that will continue to be refined: the identification and selection of what to remember (metacognitive reflectivity), the forgetting of less important information to facilitate memory for items that do need to be remembered (responsible forgetting), the functional prioritization of attention at the expense of competing factors (responsible attention), and the selective recall of important information via efficient retrieval strategies (responsible retrieval). Together, these functions form a cohesive system that aims to selectively prioritize, encode, and recall information that is deemed important based on its anticipated utility or the consequences of forgetting, and considering the importance of information may be a critical memory adaptation as we age. Specifically, if younger and older adults learn to self-assess and prioritize important information that has negative consequences if forgotten, engage in strategic forgetting, efficiently allocate their attentional resources, and utilize effective retrieval operations, memory for said important information can be enhanced.

The role of attention and verbal rehearsal in remembering more valuable item-colour binding

Selectively remembering more valuable information can improve memory efficiency. Such value effects have been observed on long-term memory for item-colour binding, but the possible contributory factors are unclear. The current study explored contributions from attention (Experiment 1) and verbal rehearsal (Experiment 2). Across two experiments, memory was superior for item-colour bindings that were associated with high (relative to low) point values at encoding, both in an immediate test and a delayed re-test. When availability of attentional resources was reduced during encoding, value only influenced immediate and not delayed memory (Experiment 1). This indicates that a transient value effect can be obtained with little attentional resources, but attentional resources are involved in creating a longer lasting effect. When articulatory suppression was implemented during encoding (Experiment 2), value effects were somewhat reduced in the immediate test and abolished in the delayed re-test, suggesting a role for verbal rehearsal in value effects on item-colour binding memory. These patterns of value effects did not interact with encoding presentation format (i.e., sequential vs. simultaneous presentation of objects). Together, these results suggest that attentional resources and verbal rehearsal both contribute to value effects on item-colour binding memory, with varying impacts on the durability of these effects.

Improving memory through choice and deliberation in decision-making: Evidence from ERPs

The goal of decision-making is to select one option and disregard the others. However, deliberation can also create a memory association between the chosen and unchosen options. This study aims to investigate how choice and deliberation affect the memory of postdecision options and the underlying mechanisms. Using event-related potentials (ERPs), we examined item recognition (Experiment 1) and associative recognition (Experiment 2) following certain and uncertain decisions. In Experiment 1, items that were chosen in certain decisions were remembered better than unchosen items. There was no difference between chosen and unchosen items in uncertain decisions. Moreover, a late recollection-related LPC (a late positive component) old/new effect was larger for chosen items than unchosen items in certain decisions. The early familiarity-related FN400 and the late recollection-related LPC old/new effects were significant for chosen and unchosen items in uncertain decisions. In Experiment 2, there was no difference in performance on associative memory. A FN400 old/new effect (an index of integration) in certain or uncertain decisions was not observed. Although significant LPC old/new effects were found in both certain and uncertain decisions, no difference was found between them. These results propose that decision-making can enhance item memory performance through two distinct processes: value and elaboration. Elaboration involves focusing on the details within items rather than integrating items into a cohesive whole.

In vivo structural connectivity of the reward system along the hippocampal long axis

Recent work has identified a critical role for the hippocampus in reward-sensitive behaviors, including motivated memory, reinforcement learning, and decision-making. Animal histology and human functional neuroimaging have shown that brain regions involved in reward processing and motivation are more interconnected with the ventral/anterior hippocampus. However, direct evidence examining gradients of structural connectivity between reward regions and the hippocampus in humans is lacking. The present study used diffusion MRI (dMRI) and probabilistic tractography to quantify the structural connectivity of the hippocampus with key reward processing regions in vivo. Using a large sample of subjects (N = 628) from the human connectome dMRI data release, we found that connectivity profiles with the hippocampus varied widely between different regions of the reward circuit. While the dopaminergic midbrain (ventral tegmental area) showed stronger connectivity with the anterior versus posterior hippocampus, the ventromedial prefrontal cortex showed stronger connectivity with the posterior hippocampus. The limbic (ventral) striatum demonstrated a more homogeneous connectivity profile along the hippocampal long axis. This is the first study to generate a probabilistic atlas of the hippocampal structural connectivity with reward-related networks, which is essential to investigating how these circuits contribute to normative adaptive behavior and maladaptive behaviors in psychiatric illness. These findings describe nuanced structural connectivity that sets the foundation to better understand how the hippocampus influences reward-guided behavior in humans.

Confidence judgments interfere with perceptual decision making

Determining one's confidence in a decision is a vital part of decision-making. Traditionally, psychological experiments have assessed a person's confidence by eliciting confidence judgments. The notion that such judgments can be elicited without impacting the accuracy of the decision has recently been challenged by several studies which have shown reactivity effects-either an increase or decrease in decision accuracy when confidence judgments are elicited. Evidence for the direction of reactivity effects has, however, been decidedly mixed. Here, we report three studies designed to specifically make reactivity effects more prominent by eliciting confidence judgment contemporaneously with perceptual decisions. We show that confidence judgments elicited contemporaneously produce an impairment in decision accuracy, this suggests that confidence judgments may rely on a partially distinct set of cues/evidence than the primary perceptual decision and, additionally, challenges the continued use of confidence ratings as an unobtrusive measure of metacognition.

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.

The interactive effect of external rewards and self-determined choice on memory

Both external motivational incentives (e.g., monetary reward) and internal motivational incentives (e.g., self-determined choice) have been found to promote memory, but much less is known about how these two types of incentives interact with each other to affect memory. The current study (N = 108) examined how performance-dependent monetary rewards affected the role of self-determined choice in memory performance, also known as the choice effect. Using a modified and better controlled version of the choice paradigm and manipulating levels of reward, we demonstrated an interactive effect between monetary reward and self-determined choice on 1-day delayed memory performance. Specifically, the choice effect on memory decreased when we introduced the performance-dependent external rewards. These results are discussed in terms of understanding how external and internal motivators interact to impact learning and memory.

Can neural correlates of encoding explain the context dependence of reward-enhanced memory?

Selective encoding can be studied by manipulating how valuable it is for participants to remember specific stimuli, for instance, by varying the monetary reward participants receive for recalling a particular stimulus in a subsequent memory test. It would be reasonable for participants to strategically attend more to high-reward items compared to low-reward items in mixed list contexts, but to attend both types of items equally in pure list contexts, where all items are of equal value. Reward-enhanced memory may be driven by automatic dopaminergic interactions between reward circuitry and the hippocampus and thus be insensitive to list context; or it may be driven by meta-cognitive strategies, and thus context-dependent. We contrasted these alternatives by manipulating list composition and tracked selective encoding through multiple EEG measures of attention and rehearsal. Behavioral results were context-dependent, such that recall of high-reward items was increased only in mixed lists. This result and aspects of the recall dynamics confirm predictions of the eCMR (emotional Context Maintenance and Retrieval) model. The power of ssVEPs was lower for high-reward items regardless of list composition, suggesting decreased visual processing of high-reward stimuli and that ssVEPs may index the modulation of context-to-item associations predicted by eCMR. By contrast, reward modulated the amplitude of Late Positive Potential and Frontal Slow Wave only in mixed lists. Taken together, the results provide evidence that reward-enhanced memory is caused by an interplay between strategic processes applied when high- and low-reward items compete for cognitive resources during encoding and context-dependent mechanisms operating during recall.

Reward advantage over punishment for incentivizing visual working memory

The prospects of gaining reward and avoiding punishment widely influence human behavior. Despite of numerous attempts to investigate the influence of motivational signals on working memory (WM), whether the valence and the magnitude of motivational signals interactively influence WM performance remains unclear. To investigate this, the present study used a free-recall working memory task with EEG recording to compare the effect of incentive valence (reward or punishment), as well as the magnitude of incentives on visual WM. Behavioral results revealed that the presence of incentive signals improved WM precision when compared with no-incentive condition, and compared with punishing cues, rewarding cues led to greater facilitation in WM precision, as well as confidence ratings afterward. Moreover, event related potential (ERP) results suggested that compared with punishment, reward led to an earlier latency of late positive component (LPC), a larger amplitude of contingent negative variation (CNV) during the expectation period, and a larger P300 amplitude during the sample and delay periods. Furthermore, reward advantage over punishment in behavioral and neural results were correlated, such that individuals with larger CNV difference between reward and punishment conditions also report greater distinction in confidence ratings between the two conditions. In sum, our results demonstrate what and how rewarding cues cause more beneficial effects than punishing cues when incentivizing visual WM.

Strong but Fragmented Memory of a Stressful Episode

While it is commonly assumed that stressful events are vividly remembered, it remains largely unknown whether all aspects of memory for a stressful episode are enhanced. In this preregistered study, we tested whether stress enhances later remembering of individual elements of a stressful episode at the cost of impaired processing of the association between these elements. Therefore, male and female participants (N = 122) underwent a stressful (or control) episode during which they encoded a series of stimuli. To investigate stress effects on the memory for individual events and the links between these, we used temporal sequence effects in recognition memory tested 24 h after encoding. Specifically, we tested whether stress would affect the memory enhancement for a target item if this is preceded by another item that also preceded the target during encoding (recognition priming). Our results showed that participants recalled single events encoded under stress better than those encoded under nonstressful conditions, but were less able to leverage the temporal sequence of events encoded under stress to cue memory at delayed recall, reflected in reduced memory for items preceded by the item that preceded them also during encoding. Functional near-infrared spectroscopy further revealed that encoding under stress was accompanied by opposite changes in inferotemporal and dorsolateral prefrontal areas. Together, our data suggest that acute stress induces a mode of memory formation that results in strong but less integrated memories.

Instructed motivational states bias reinforcement learning and memory formation

Motivation influences goals, decisions, and memory formation. Imperative motivation links urgent goals to actions, narrowing the focus of attention and memory. Conversely, interrogative motivation integrates goals over time and space, supporting rich memory encoding for flexible future use. We manipulated motivational states via cover stories for a reinforcement learning task: The imperative group imagined executing a museum heist, whereas the interrogative group imagined planning a future heist. Participants repeatedly chose among four doors, representing different museum rooms, to sample trial-unique paintings with variable rewards (later converted to bonus payments). The next day, participants performed a surprise memory test. Crucially, only the cover stories differed between the imperative and interrogative groups; the reinforcement learning task was identical, and all participants had the same expectations about how and when bonus payments would be awarded. In an initial sample and a preregistered replication, we demonstrated that imperative motivation increased exploitation during reinforcement learning. Conversely, interrogative motivation increased directed (but not random) exploration, despite the cost to participants' earnings. At test, the interrogative group was more accurate at recognizing paintings and recalling associated values. In the interrogative group, higher value paintings were more likely to be remembered; imperative motivation disrupted this effect of reward modulating memory. Overall, we demonstrate that a prelearning motivational manipulation can bias learning and memory, bearing implications for education, behavior change, clinical interventions, and communication.

Establishing a causal role for left ventrolateral prefrontal cortex in value-directed memory encoding with high-definition transcranial direct current stimulation

One critical approach for promoting the efficiency of memory is to adopt selective encoding strategies to prioritize more valuable information. Past neuroimaging studies have shown that value-directed modulation of verbal memory depends heavily on the engagement of left-lateralized semantic processing regions, particularly in the ventrolateral prefrontal cortex (VLPFC). In the present study, we used high-definition transcranial direct current stimulation (HD-tDCS) to seek evidence for a causal role of left VLPFC in supporting the memory advantage for high-value items. Three groups of healthy young adult participants were presented with lists of words to remember, with each word accompanied by an arbitrarily assigned point value. During the first session, all participants received sham stimulation as they encoded five lists of 30 words each. Two of these lists were immediately tested with free recall, with feedback given to allow participants to develop metacognitive insight and strategies to maximize their point total. The second session had the exact same structure as the first, but the groups differed in whether they received continued sham stimulation (N = 22) or anodal stimulation of the left VLPFC (N = 21) or right VLPFC (N = 20). Those lists not tested with immediate recall were tested with recognition judgments after a one-day delay. Since no brain stimulation was applied during this Day 2 test, any performance differences can be attributed to the effects of stimulation on Day 1 encoding processes. Anodal stimulation of left VLPFC significantly boosted participants' memory encoding selectivity. In comparison, no such effect was seen in participants who received right VLPFC or sham stimulation. Estimates of recollection- and familiarity-based responding revealed that left VLPFC stimulation specifically amplified the effects of item value on recollection. These results demonstrate a causal role for left VLPFC in the implementation of selective value-directed encoding strategies, putatively by boosting deep semantic processing of high-value words. Our findings also provide further evidence on the hemispheric lateralization of value-directed verbal memory encoding.

Value-directed memory selectivity relies on goal-directed knowledge of value structure prior to encoding in young and older adults

People are generally able to selectively attend and remember high-value over low-value information. Here, we investigated whether young and older adults would display typical value-based memory selectivity effects for to-be-learned item-value associations when goal-directed information about the meaning of associated values was presented before and after encoding. In two experiments, both young and older adults were presented with one (Experiment 1) or multiple (Experiment 2) lists of words that were arbitrarily paired with different numerical values (e.g., "door-8") or font colors (e.g., "door" presented in red), which indicated each word's value. In Experiment 1, participants were told that the numerical value indicated the relative importance of each item either before they studied the list (preencoding), after they studied it (postencoding), or not at all (no value control instructions). Older adults were significantly more selective in the preencoding condition relative to the other conditions, whereas younger adults were not selective in any condition on this single-list (numerical) value task of Experiment 1. In Experiment 2, young and older adults were tested on four additional lists of both pre- and postencoding trials each after studying and recalling four lists of words without any value instructions. Results from Experiment 2 revealed that both young and older adults selectively prioritized high-value words on the preencoding trials, but not on postencoding trials, on this color-based categorical (low-medium-high) value task. The present study highlights a critical role of goal-directed knowledge of value-based instructions prior to encoding to facilitate typically observed value-directed memory selectivity for important information. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Midbrain-Hippocampus Structural Connectivity Selectively Predicts Motivated Memory Encoding

Motivation is a powerful driver of learning and memory. Functional MRI studies show that interactions among the dopaminergic midbrain substantia nigra/ventral tegmental area (SN/VTA), hippocampus, and nucleus accumbens (NAc) are critical for motivated memory encoding. However, it is not known whether these effects are transient and purely functional, or whether individual differences in the structure of this circuit underlie motivated memory encoding. To quantify individual differences in structure, diffusion-weighted MRI and probabilistic tractography were used to quantify SN/VTA-striatum and SN/VTA-hippocampus pathways associated with motivated memory encoding in humans. Male and female participants completed a motivated source memory paradigm. During encoding, words were randomly assigned to one of three conditions, reward ($1.00), control ($0.00), or punishment (-$1.00). During retrieval, participants were asked to retrieve item and source information of the previously studied words and were rewarded or penalized according to their performance. Source memory for words assigned to both reward and punishment conditions was greater than those for control words, but there were no differences in item memory based on value. Anatomically, probabilistic tractography results revealed a heterogeneous, topological arrangement of the SN/VTA. Tract density measures of SN/VTA-hippocampus pathways were positively correlated with individual differences in reward-and-punishment-modulated memory performance, whereas density of SN/VTA-striatum pathways showed no association. This novel finding suggests that pathways emerging from the human SV/VTA are anatomically separable and functionally heterogeneous. Individual differences in structural connectivity of the dopaminergic hippocampus-VTA loop are selectively associated with motivated memory encoding.SIGNIFICANCE STATEMENT Functional MRI studies show that interactions among the SN/VTA, hippocampus, and NAc are critical for motivated memory encoding. This has led to competing theories that posit either SN/VTA-NAc reward prediction errors or SN/VTA-hippocampus signals underlie motivated memory encoding. Additionally, it is not known whether these effects are transient and purely functional or whether individual differences in the structure of these circuits underlie motivated memory encoding. Using diffusion-weighted MRI and probabilistic tractography, we show that tract density measures of SN/VTA-hippocampus pathways are positively correlated with motivated memory performance, whereas density of SN/VTA-striatum pathways show no association. This finding suggests that anatomic individual differences of the dopaminergic hippocampus-VTA loop are selectively associated with motivated memory encoding.

The Effects of Reward on Associative Memory Depend on Unitization Depths

Previous studies have found that reward effect is stronger for more difficult to retrieve items, but whether this effect holds true for the associative memory remains unclear too. We investigated the effects and neural mechanisms of the different unitization depths and reward sets on encoding associative memory using event-related potentials (ERPs), which were recorded through a Neuroscan system with a 64-channel electrode cap according to the international 10-20 system, and five electrodes (Fz, FCz, Cz, CPz, and Pz) were selected for analysis. Thirty healthy college students took part in this study. During encoding, participants were carried out two encoding tasks, a congruity-judgment task with high unitization and a color-judgment task with low unitization, with half of the items rewarded. The test phase was conducted immediately after the encoding phase. The results for false alarm rates and Prs (i.e., hit rates for old pairs minus false alarm rates for new pairs) in relational retrieval revealed that the reward differences in the color-judgment task were greater than those in the congruity-judgment task. The ERP results further showed significant reward effects (i.e., the reward significantly improved the average amplitudes compared to no reward) at P300 (300-500 ms) and LPP (500-800 ms) in the color-judgment task both for intact and rearranged items, and the reward effects at LPP (electrodes Fz, FCz, Cz, CPz, and Pz) were distributed more widely than the reward effects at P300 (electrodes Fz and FCz) in the color-judgment task. These results suggest that reward provided a greater boost when retrieving associative memory of low unitized items.

The Impact of Error-Consequence Severity on Cue Processing in Importance-Biased Prospective Memory

Prospective memory (PM) enables people to remember to complete important tasks in the future. Failing to do so can result in consequences of varying severity. Here, we investigated how PM error-consequence severity impacts the neural processing of relevant cues for triggering PM and the ramification of that processing on the associated prospective task performance. Participants role-played a cafeteria worker serving lunches to fictitious students and had to remember to deliver an alternative lunch to students (as PM cues) who would otherwise experience a moderate or severe aversive reaction. Scalp-recorded, event-related potential (ERP) measures showed that the early-latency frontal positivity, reflecting the perception-based neural responses to previously learned stimuli, did not differ between the severe versus moderate PM cues. In contrast, the longer-latency parietal positivity, thought to reflect full PM cue recognition and post-retrieval processes, was elicited earlier by the severe than the moderate PM cues. This faster instantiation of the parietal positivity to the severe-consequence PM cues was then followed by faster and more accurate behavioral responses. These findings indicate how the relative importance of a PM can be neurally instantiated in the form of enhanced and faster PM-cue recognition and processing and culminate into better PM.

Selective memory disrupted in intra-modal dual-task encoding conditions

Given natural memory limitations, people can generally attend to and remember high-value over low-value information even when cognitive resources are depleted in older age and under divided attention during encoding, representing an important form of cognitive control. In the current study, we examined whether tasks requiring overlapping processing resources may impair the ability to selectively encode information in dual-task conditions. Participants in the divided-attention conditions of Experiment 1 completed auditory tone-distractor tasks that required them to discriminate between tones of different pitches (audio-nonspatial) or auditory channels (audio-spatial), while studying items in different locations in a grid (visual-spatial) differing in reward value. Results indicated that, while reducing overall memory accuracy, neither cross-modal auditory distractor task influenced participants' ability to selectively encode high-value items relative to a full attention condition, suggesting maintained cognitive control. Participants in Experiment 2 studied the same important visual-spatial information while completing demanding color (visual-nonspatial) or pattern (visual-spatial) discrimination tasks during study. While the cross-modal visual-nonspatial task did not influence memory selectivity, the intra-modal visual-spatial secondary task eliminated participants' sensitivity to item value. These results add novel evidence of conditions of impaired cognitive control, suggesting that the effectiveness of top-down, selective encoding processes is attenuated when concurrent tasks rely on overlapping processing resources.

Memory and Reward-Based Learning: A Value-Directed Remembering Perspective

The ability to prioritize valuable information is critical for the efficient use of memory in daily life. When information is important, we engage more effective encoding mechanisms that can better support retrieval. Here, we describe a dual-mechanism framework of value-directed remembering in which both strategic and automatic processes lead to differential encoding of valuable information. Strategic processes rely on metacognitive awareness of effective deep encoding strategies that allow younger and healthy older adults to selectively remember important information. In contrast, some high-value information may also be encoded automatically in the absence of intention to remember, but this may be more impaired in older age. These different mechanisms are subserved by different neural substrates, with left-hemisphere semantic processing regions active during the strategic encoding of high-value items, and automatic enhancement of encoding of high-value items may be supported by activation of midbrain dopaminergic projections to the hippocampal region. Expected final online publication date for the Annual Review of Psychology, Volume 73 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Alpha oscillatory power decreases are associated with better memory for higher valued information

Items associated with high value are often better remembered. Value may increase attention toward item in context associations. Alpha oscillations (8-13 Hz) are thought to underlie attention and their observation may reveal the role attention plays in value-based memory. In the current study, EEG is used to record brain activity while participants (n = 30) completed a source recognition memory task where items were associated with either high or low value backgrounds to determine whether greater attentional resources are deployed when encoding high value information. Participants demonstrated better memory for objects associated with high value backgrounds. Alpha oscillatory power in occipital/temporal brain regions exhibited greater desynchronization when encoding objects associated with high value that were later successfully recalled compared to those associated with low value. In addition, beta oscillatory power in midfrontal brain regions exhibited greater desynchronization during successful recall of high value objects compared to low value objects. Together these results suggest that more attentional resources are used to encode information that is associated with high value, which increases the likelihood of later successful memory recall.

Adaptive Memory: Independent Effects of Survival Processing and Reward Motivation on Memory

Humans preferentially remember information processed for their survival relevance, a memorial benefit known as the survival processing effect. Memory is also biased towards information associated with the prospect of reward. Given the adaptiveness of these effects, they may depend on similar mechanisms. We tested whether motivation drives both effects, with reward incentives that are known to boost extrinsic motivation and survival processing perhaps stimulating intrinsic motivation. Accordingly, we manipulated survival processing and reward incentive independently during an incidental-encoding task in which participants chose between pairs of words concerning their relevance for a scenario, and examined the effects on encoding event-related potentials (ERP) activity and later performance on a surprise recall test. We hypothesized that if survival processing fosters intrinsic motivation, it should reduce the beneficial effects of extrinsic motivation (reward incentive). In contrast to this prediction, we found that reward incentive and survival processing independently improved memory and that the P300, a measure of lower-level cognitive resource allocation, was increased by reward incentive independent of survival processing. Further, survival processing and reward incentive independently increased the frontal slow wave (FSW), a measure of higher-level elaboration. These findings suggest that while survival processing and reward incentive may both increase encoding elaboration, the memory-enhancing effect of survival processing does not depend on increased intrinsic motivation. Additionally, we replicated a recent finding whereby the survival processing effect generalizes to a choice-based encoding task and further showed that the beneficial effect of choice on memory likely does not interact with either survival processing or reward.