Effects of active exploration on novelty-related declarative memory enhancement

Contextual novelty detection and novelty-related memory enhancement in amnestic mild cognitive impairment

INTRODUCTION

Though novelty processing plays a critical role in memory function, little is known about how it influences learning in memory-impaired populations, such as amnestic Mild Cognitive Impairment (aMCI).

METHODS

21 aMCI patients and 22 age- and education-matched healthy older participants performed two tasks-(i) an oddball paradigm where fractals that were often repeated (60 % of the stimuli), less frequently repeated (20 %), or novel (presented once each) were shown to assess novelty preference (longer viewing time for novel than familiar stimuli), and (ii) a Von Restorff paradigm assessing novelty-related effects on memory. Participants studied 22 lists of 10 words. Among these lists, 18 contained an isolated word different from the others by its distinctive aspect, here the font size (90-point, 120-point or 150-point against 60-point for non-isolated words). The remaining four were control lists without isolated words. After studying each list, participants freely recalled the maximum words possible.

RESULTS

For the oddball task, a group-by-stimulus type ANOVA on median viewing times revealed a significant effect of stimulus type, but not of group. Both groups spent more time on novel stimuli. For the Von Restorff task, both aMCI and healthy controls recalled the isolated words (presented in 120-point or 150-point, but not 90-point) better than others (excluding primacy and recency effects). Novelty-related memory benefit-gain factor-was computed as the difference between the recall scores for isolated and other words. A group-by-font size ANOVA on gain factors revealed no group effect, nor interaction, suggesting that aMCI patients benefited from novelty, alike controls.

CONCLUSION

Novelty preference and the boosting effect of isolation-related novelty on subsequent recall seem preserved despite impaired episodic memory in aMCI patients. This is discussed in the light of contemporary divergent theories regarding the relationship between novelty and memory, as either being independent or parts of a continuum.

Novelty-induced memory boosts in humans: The when and how

Novel information potentially signals danger or reward and behavioral and psychophysiological studies have suggested that the brain prioritizes its processing. Some effects of novelty even go beyond the stimulus itself. Studies in animals have robustly shown that exposure to novel stimulation can promote memory for information presented before or after this exposure. Research regarding effects of novelty on memory in humans is lagging, but in the last few years, several studies have emerged that suggest that memory-facilitating effects of novelty also exist in humans. Here, we provide a comprehensive overview of these studies. We identified several factors that have been shown to influence whether novelty promotes memory or not, including the timing between the novel experience and the learning events, the involvement with the novel material, and population characteristics (such as clinical diagnosis or age). Finally, we link the behavioral findings to potential neurobiological mechanisms and discuss the relevance of specific findings in light of potential clinical and educational applications that could leverage novelty to improve memory.

Enriched learning: behavior, brain, and computation

The presence of complementary information across multiple sensory or motor modalities during learning, referred to as multimodal enrichment, can markedly benefit learning outcomes. Why is this? Here, we integrate cognitive, neuroscientific, and computational approaches to understanding the effectiveness of enrichment and discuss recent neuroscience findings indicating that crossmodal responses in sensory and motor brain regions causally contribute to the behavioral benefits of enrichment. The findings provide novel evidence for multimodal theories of enriched learning, challenge assumptions of longstanding cognitive theories, and provide counterevidence to unimodal neurobiologically inspired theories. Enriched educational methods are likely effective not only because they may engage greater levels of attention or deeper levels of processing, but also because multimodal interactions in the brain can enhance learning and memory.

Novel immersive virtual reality experiences do not produce retroactive memory benefits for unrelated material

The experience of novelty can enhance memory for information that occurs close in time, even if not directly related to the experience-a phenomenon called "behavioural tagging." For example, an animal exposed to a novel spatial environment shows improved memory for other information presented previously. This has been linked to neurochemical modulations induced by novelty, which affect consolidation of memories for experiences that were encoded around the same time. Neurophysiological research in animals has shown that novelty benefits weakly encoded but not strongly encoded information. However, a benefit that is selective to weak memories seems difficult to reconcile with studies in humans that have reported that novelty improves recollection, but not familiarity. One possibility is that the novelty increases activity in hippocampus, which is also associated with processes that enable recollection. This is consistent with another prediction of behavioural tagging theory, namely that novelty only enhances consolidation of information that converges on the same neuronal population. However, no study has directly explored the relationship between encoding strength and retrieval quality (recollection versus familiarity). We examined the effects of exposure to a novel immersive virtual reality environment on memory for words presented immediately beforehand, under either deep or shallow encoding tasks, and by testing both recall memory immediately, and recognition memory with remember/know instructions the next day. However, Bayes factors showed no evidence to support the behavioural tagging predictions: that novelty would improve memory, particularly for shallowly encoded words, and this improvement would differentially affect familiarity versus recollection.

Effects of exploring a novel environment on memory across the lifespan

Exploration of a novel environment has been shown to promote memory formation in healthy adults. Studies in animals have suggested that such novelty-induced memory boosts are mediated by hippocampal dopamine. The dopaminergic system is known to develop and deteriorate over the lifespan, but so far, the effects of novelty on memory across the lifespan have not yet been investigated. In the current study, we had children, adolescents, younger, and older adults (n = 439) explore novel and previously familiarized virtual environments to pinpoint the effects of spatial novelty on declarative memory in humans across different age groups. After exploration, words were presented while participants performed a deep or shallow encoding task. Incidental memory was quantified in a surprise test. Results showed that participants in the deep encoding condition remembered more words than those in the shallow condition, while novelty did not influence this effect. Interestingly, however, children, adolescents and younger adults benefitted from exploring a novel compared to a familiar environment as evidenced by better word recall, while these effects were absent in older adults. Our findings suggest that the beneficial effects of novelty on memory follow the deterioration of neural pathways involved in novelty-related processes across the lifespan.

Novelty exposure induces stronger sensorimotor representations during a manual adaptation task

Active exploration of novel spatial environments enhances memory for subsequently presented explicit, declarative information in humans. These effects have been attributed to novelty promoting dopamine release via mesolimbic dopaminergic pathways in the brain. As procedural motor learning has been linked to dopamine as well, we predict that novelty effects extend to this domain. To test this hypothesis, the present study examined whether spatial novelty exploration benefits subsequent sensorimotor adaptation. Participants explored either two different virtual environments (i.e., novelty condition; n = 210) or two identical environments (i.e., familiar condition; n = 253). They then performed a manual adaptation task in which they had to adapt joystick movements to a visual perturbation. We assessed the rate of adaptation following the introduction of this perturbation, and the rate of deadaptation following its removal. While results showed reliable adaptation patterns and similar adaptation rates across both conditions, individuals in the novelty condition showed slower deadaptation. This suggests that exposure to spatial novelty induced stronger sensorimotor representations during adaptation, potentially through novelty-induced dopaminergic effects in mesocortical and/or nigrostriatal pathways. Novelty exposure may be employed to promote motor learning on tasks that require precision movements in altered sensory contexts, for example, in astronauts moving in microgravity or patients with impaired motor processing.

A bias toward the unknown: individual and environmental factors influencing exploratory behavior

With limited resources, exploring new opportunities is crucial for survival. Exploring novel options, however, comes at the cost of uncertainty. Therefore, there is a trade‐off between exploiting options with a known beneficial outcome and exploring novel options with a potentially higher gain. Computational models have suggested that novelty may promote exploratory behavior by inducing a so‐called novelty bonus through reward‐related processes. So far, few studies have provided behavioral evidence for such a novelty bonus. In this study, we aimed to investigate whether spatial novelty can stimulate exploratory behavior (Experiment 1), and whether age, novelty‐seeking, and reduced action radius or social interactions due to COVID‐19 restrictions influenced the exploration–exploitation trade‐off (Experiment 2). In both experiments, we employed a novel paradigm in which participants made binary decisions between food items, while on rare trials, a surprise option was presented. Results from Experiment 1 are in line with a novelty bonus, with spatial novelty promoting exploratory behavior. In Experiment 2, we found that exploratory behavior declined with age, high novelty seekers made more exploratory choices than low novelty seekers, and participants with a smaller action radius made fewer exploratory choices. These findings are consistent with previous findings in animals and predictions from computational models.

Novelty processing associated with neural beta oscillations improves recognition memory in young and older adults

Novelty anticipation activates the mesolimbic system and promotes subsequent long-term memory in younger adults. Importantly, mesolimbic structures typically degenerate with age, which might reduce positive effects of novelty anticipation. Here, we used electroencephalography in combination with an established paradigm in healthy young (19-33 years old, n = 28) and older (53-84, n = 27) humans. Colored cues predicted the subsequent presentation of either a novel or previously familiarized image (75% cue validity). On the subsequent day, recognition memory for the novel images was tested. Behaviorally, novelty anticipation improved recollection-based but not familiarity-based recognition memory in both groups, and this effect was more pronounced in older subjects. Furthermore, novelty and familiarity cues increased theta (4-8 Hz) and decreased alpha/beta power (9-20 Hz); at outcome, expected novel and familiar images both increased beta power (13-25 Hz). Finally, a subsequent memory effect for expected novel images was associated with increases in beta power independent of age. Together, novelty anticipation drives hippocampus-dependent long-term recognition memory across the life span, and this effect appears to be related to neural beta oscillations.

The Hippocampal Horizon: Constructing and Segmenting Experience for Episodic Memory

How do we recollect specific events that have occurred during continuous ongoing experience? There is converging evidence from non-human animals that spatially modulated cellular activity of the hippocampal formation supports the construction of ongoing events. On the other hand, recent human oriented event cognition models have outlined that our experience is segmented into discrete units, and that such segmentation can operate on shorter or longer timescales. Here, we describe a unification of how these dynamic physiological mechanisms of the hippocampus relate to ongoing externally and internally driven event segmentation, facilitating the demarcation of specific moments during experience. Our cross-species interdisciplinary approach offers a novel perspective in the way we construct and remember specific events, leading to the generation of many new hypotheses for future research.

Anticipation of novel environments enhances memory for incidental information

Novelty is a potent driver of learning, but little is known about whether anticipation of novelty can enhance memory for incidental information. Here, participants incidentally encountered objects while they actively navigated toward novel or previously familiarized virtual rooms. Across immediate and delayed surprise memory tests, participants showed superior recollection for incidental objects encountered while anticipating novel as compared with familiarized rooms. Furthermore, memory for incidental objects correlated positively with between-participants average curiosity about novel rooms but negatively with within-participants trial-specific curiosity. Our findings contribute to the growing literature on how salient processes impact memory for incidental material.