Learning & memory最新文献

The statistical study of human memory requires large-scale experiments, involving many stimulus conditions and test subjects. While this approach has proven to be quite fruitful for meaningless material such as random lists of words, naturalistic stimuli, like narratives, have until now resisted such a large-scale study, due to the quantity of manual labor required to design and analyze such experiments. In this work, we develop a pipeline that uses large language models (LLMs) both to design naturalistic narrative stimuli for large-scale recall and recognition memory experiments, as well as to analyze the results. We performed online memory experiments with a large number of participants and collected recognition and recall data for narratives of different sizes. We found that both recall and recognition performance scale linearly with narrative length; however, for longer narratives, people tend to summarize the content rather than recalling precise details. To investigate the role of narrative comprehension in memory, we repeated these experiments using scrambled versions of the narratives. Although recall performance declined significantly, recognition remained largely unaffected. Recalls in this condition seem to follow the original narrative order rather than the actual scrambled presentation, pointing to a contextual reconstruction of the story in memory. Finally, using LLM text embeddings, we construct a simple measure for each clause based on semantic similarity to the whole narrative, that shows a strong correlation with recall probability. Overall, our work demonstrates the power of LLMs in accessing new regimes in the study of human memory, as well as suggesting novel psychologically informed benchmarks for LLM performance.

Partial reinforcement schedules, wherein a conditioned stimulus (CS) is intermittently paired with an unconditioned stimulus (US) during associative learning, have been widely studied and found to affect the extinction and recall of learned behaviors. Notably, behaviors conditioned under partial (as opposed to consistent) reinforcement are more resistant to extinction, an effect known as the partial reinforcement extinction effect (PREE). The present study initially aimed to examine the effects of partial reinforcement on the acquisition and recall of fear extinction (FE) when altering the contextual environment. However, our systematic investigation of partial reinforcement using C57BL/6J mice challenges the well-established PREE within the domain of FE learning. Across multiple experimental setups altering CS duration, US intensity, and reinforcement schedules, we consistently found no significant impact of partial reinforcement on the acquisition, consolidation, or recall of FE. Mice exhibited similar patterns of extinction and spontaneous recovery of conditioned fear responses regardless of reinforcement schedule. These findings suggest that partial reinforcement during fear acquisition may not confer resistance to extinction of conditioned freezing, challenging the established understanding of the PREE and prompting a reexamination of how reinforcement schedules affect learning and memory of fear-related behaviors.

While motivation typically enhances memory, some studies show that, in certain contexts, motivation associated with rewards can impair memory. Goal states associated with motivation can impact attention, which in turn influences what information is encoded and later remembered. There is limited research on how different incentive contexts, which manipulate attentional orientation to memoranda, lead to either reward-motivated memory enhancements or impairments in item and relational memory. Here, we test how different reward-motivated states may narrow or broaden attention with downstream consequences on memoranda. In study 1, giving participants a rewarded timed goal during visual search impaired both their item and relational memory relative to un-timed participants who were simply told that they would be rewarded for searching regardless of speed (despite having equated time). In study 2, we show that giving participants an elaborative goal after visual search completion remediates item and relational memory deficits in the Feedback group. Finally, in study 3, we show that elaborative processing of target items during visual search resulted in reward-motivated memory benefits for the item, but not relational memory for the context in which the item was encoded. Together, these findings support a model where the goal-relevant alterations in attentional breadth to reward may ultimately filter what information is remembered or forgotten.

How does negative affect spread through existing memories? Whereas many studies have investigated generalization of learned threat responses across perceptual and semantic dimensions, little attention has been given to the possibility that Pavlovian threat responses may spread beyond what is directly learned to previously encoded memories that overlap in content. Here, we increased the demand on associative memory in a modified sensory preconditioning task to investigate this. First, participants encoded 40 unique episodes, each consisting of two neutral stimuli. On the following day, one of each pair was newly associated with either an aversive or a neutral stimulus. Another day later, both stimuli of the original memories were found to trigger enhanced pupil dilation if one was indirectly linked to an aversive stimulus. This effect was independent of whether the associations encoded on day 1 were accurately retained on the day of testing, and confined to trials on which the indirectly associated stimulus was consciously brought to mind, suggesting the formation of a link that directly connects preconditioned stimuli to subsequently learned aversive outcomes. The present study demonstrates that the human defensive system is remarkably adept at quickly anticipating threat based on information acquired over separate events, and gives a first glimpse into the associative structures that enable this ability.

Emotional events hold a privileged place in our memories, differing in accuracy and structure from memories for neutral experiences. Although much work has focused on the pronounced differences in memory for negative experiences, there is growing evidence that positive events may lead to more holistic, or integrated, memories. However, it is unclear whether these affect-driven changes in memory structure, which have been found in highly controlled laboratory environments, extend to real-world episodic memories. We ran experiments that assessed memory for experiences created in the laboratory (Experiment 1) and, using smartphones, memories for everyday experiences (Experiment 2). We complement these design innovations with a novel analysis approach to model memory accuracy and integration in both settings. Consistent with past findings, emotional events were subjectively remembered more strongly. These studies also revealed that features of more positive events were indeed more integrated within memory, both in the laboratory and the real world. These effects were specific to participants' emotional responses to the events during encoding rather than general emotional states at the time of retrieval, and reflected a general increase in integration between multiple memory features. Together, these results demonstrate robust differences in memory for positive events, introduce a novel measure of memory integration, and highlight the importance of assessing the impact of emotion on memory beyond the laboratory.

Agency beliefs influence how humans learn from different contexts and outcomes. Research demonstrates that stressors, such as exposure to early-life adversity (ELA), are associated with both agency beliefs and learning, but how these processes interact remains unclear. The current study investigated whether exposure to ELA influences agency and interacts with reinforcement learning in adults. Replicating prior behavioral and computational work, ELA resulted in decreased learning, while increased adversity severity was associated with decreased latent agency beliefs. These findings suggest that exposure to adversity in childhood has a nuanced impact on reinforcement learning and agency beliefs in adulthood.

Social isolation is a risk factor for cognitive impairment. Adolescents may be particularly vulnerable to these effects, because they are in a critical period of development marked by significant physical, hormonal, and social changes. However, it is unclear if the effects of social isolation on learning and memory are similar in both sexes or if they persist into adulthood after a period of recovery. We socially isolated male and female 129Sv/Ev mice throughout adolescence (postnatal days 29-56), provided a 2-week resocialization recovery period, and then tested spatial learning and cognitive flexibility in the active place avoidance task. After behavioral testing, mice were injected with 5'-bromo-2'-deoxyuridine (BrdU) so that lasting effects of social isolation on cell proliferation in the dentate gyrus could be examined. Tissue was also stained for doublecortin (DCX). We found that in males, isolation led to a modest impairment in the rate of initial spatial learning, whereas in females, initial learning was unaffected. However, when the location of the shock zone was switched during the conflict variant of the task, cognitive flexibility was impaired in females only. Similarly, social isolation reduced cell proliferation and the number of immature neurons in the ventral dentate gyrus only in females. Together, these findings indicate that social isolation during adolescence differentially impairs spatial processing in males and females, with effects that persist into adulthood.

Stressful and emotionally arousing experiences induce the release of noradrenergic and glucocorticoid hormones that synergistically strengthen memories but differentially regulate qualitative aspects of memory. This highlights the need for sophisticated behavioral tasks that allow for the assessment of memory quality. The dual-event inhibitory avoidance task for rats is such a behavioral task designed to evaluate both the strength and specificity of memory. The noradrenergic stimulant yohimbine given systemically immediately after the training session was found to enhance both the strength and specificity of memory, whereas the glucocorticoid corticosterone induced a generalized strengthening of memory. As mice are the preferred species for targeted gene and neural circuit manipulations, we here aimed to set up the dual-event inhibitory avoidance task for mice, and to replicate the effects of systemic yohimbine and corticosterone administration on memory strength and specificity. Whereas noninjected control mice efficiently acquired the task and selectively avoided the test context previously associated with footshock, the introduction of posttraining intraperitoneal injections induced testing order effects and substantially increased variability both within groups and across experiments, precluding a thorough investigation of stress hormone effects on memory specificity. Thus, whereas the dual-event inhibitory avoidance task can be used to test the specificity of memory in mice, our findings indicate that intraperitoneal injections impact performance. Therefore, this task is less suitable to assess stress hormone effects on memory specificity in mice.

Chronic stress typically leads to deficits in fear extinction. However, when a delay occurs from the end of chronic stress and the start of fear conditioning (a "recovery"), rats show improved context-cue discrimination, compared to recently stressed rats or nonstressed rats. The infralimbic cortex (IL) is important for fear extinction and undergoes neuronal remodeling after chronic stress ends, which could drive improved context-cue discrimination. Here, glutamatergic IL neurons of Sprague-Dawley male rats were targeted for inhibition using inhibitory designer receptors exclusively activated by designer drugs (DREADDs) and daily injections of clozapine N-oxide (CNO) during a 21-day recovery period from chronic stress. Histological verification confirmed DREADDs in the IL with some spread to nearby medial prefrontal cortex (PFC) regions. CNO administration was then discontinued before fear conditioning started and behavioral testing thereafter so that behavioral assessments occurred without neuronal inhibition. Fear conditioning involved presenting male rats with three tone-foot shock pairings on 1 day, which was followed by 2 days of 15 tone-alone extinction sessions. Daily and repeated inhibition of mainly IL neurons during the 21-day recovery period did not disrupt fear learning or fear extinction in all groups (controls, stressed rats without a recovery, and stressed rats with a recovery). However, chronically stressed rats given a recovery and with DREADD activation showed impaired spontaneous recovery, indicating a failure to form a tone-foot shock association. The findings show that daily inhibition of mainly IL neurons prior to fear conditioning and extinction depends upon the changes that occur during the recovery period following the end of chronic stress.