Unique effects of sedatives, dissociatives, psychedelics, stimulants, and cannabinoids on episodic memory: A review and reanalysis of acute drug effects on recollection, familiarity, and metamemory.

Despite distinct classes of psychoactive drugs producing putatively unique states of consciousness, there is surprising overlap in terms of their effects on episodic memory and cognition more generally. Episodic memory is supported by multiple subprocesses that have been mostly overlooked in psychopharmacology and could differentiate drug classes. Here, we reanalyzed episodic memory confidence ratings from 10 previously published data sets (28 drug conditions total) using signal detection models to estimate two conscious states involved in episodic memory and one consciously controlled metacognitive process of memory: autonoetic retrieval of specific details (recollection), noetic recognition absent of retrieved details (familiarity), and retrospective introspection of memory decisions (metamemory). Sedatives, dissociatives, psychedelics, stimulants, and cannabinoids had unique patterns of effects on these mnemonic processes dependent on whether they impacted encoding, consolidation, or retrieval (the formation, stabilization, and access to memory traces, respectively). Sedatives at encoding reliably impaired both recollection and familiarity but at consolidation enhanced recollection. Dissociatives and cannabinoids at encoding impaired recollection but less reliably impaired familiarity, and cannabinoids at retrieval increased false recollections. These drug-induced encoding impairments occasionally came with metamemory enhancements, perhaps because of less interstimulus interference. Psychedelics at encoding impaired recollection but tended to enhance familiarity and did not impact metamemory. Stimulants at encoding enhanced metamemory, at consolidation impaired metamemory, and at retrieval enhanced familiarity and metamemory. These findings allude to mechanisms underlying the idiosyncratic phenomena of drugs, such as blackouts from sedatives and presque vu from psychedelics. Finally, these findings converge on a model in which memory quantity and stability influence metamemory. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The acute effects of psychoactive drugs on emotional episodic memory encoding, consolidation, and retrieval: A comprehensive review.

Psychoactive drugs modulate learning and emotional processes in ways that could impact their recreational and medical use. Recent work has revealed how drugs impact different stages of processing emotional episodic memories, specifically encoding (forming memories), consolidation (stabilizing memories), and retrieval (accessing memories). Drugs administered before encoding may preferentially impair (e.g., GABAA sedatives including alcohol and benzodiazepines, Δ9-tetrahydrocannabinol or THC, ketamine), enhance (e.g., dextroamphetamine and dextromethamphetamine), or both impair and enhance (i.e., ± 3,4-methylenedioxymethylamphetamine or MDMA) emotionally negative and positive compared to neutral memories. GABAA sedatives administered immediately post-encoding (during consolidation) can preferentially enhance emotional memories, though this selectivity may decline or even reverse (i.e., preferential enhancement of neutral memories) as the delay between encoding and retrieval increases. Finally, retrieving memories under the effects of THC, dextroamphetamine, MDMA, and perhaps GABAA sedatives distorts memory, with potentially greater selectively for emotional (especially positive) memories. We review these effects, propose neural mechanisms, discuss methodological considerations for future work, and speculate how drug effects on emotional episodic memory may contribute to drug use and abuse.

Foreign language reduces false memories by increasing memory monitoring.

People have false memories that distort their recollection of past events. Language is an important source of such memories, from providing false inferences to outright misinformation. Here we investigate the impact of using a native or foreign language on bilinguals' susceptibility to false memories. Although language has been argued to impact false memories in multiple ways, our study was inspired by recent work in the decision-making literature, which leads to the novel hypothesis that foreign language encourages people to engage in careful memory monitoring that could reduce false memories. This hypothesis contrasts with a processing load account, which predicts that a foreign language would increase false memories because it is naturally more difficult to process information in a foreign language. We tested these hypotheses using two false memory tasks. Using the DRM task, Experiment 1 found that individuals were more accurate in identifying false memories when using their foreign language compared with their native tongue, consistent with the memory monitoring hypothesis. Using the misinformation task, Experiment 2 found that processing misleading information in one's foreign language eliminated false memories, again supporting the hypothesis that a foreign language increases the use of memory monitoring. These findings support a monitoring hypothesis that has been overlooked in prior studies on bilingualism and false memory, with implications for billions of people who regularly use a foreign language. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Impact of stereotype threat on brain activity during memory tasks in older adults.

We report the first neuroimaging experiment to investigate the impact of explicitly activating aging stereotypes (i.e., stereotype threat) on brain activity during cognitive tasks. Cognitively normal older adults read about aging stereotypes or a control passage prior to taking episodic memory, working memory, and a non-demanding control task during fMRI. At the group level, stereotype activation did not impact cognitive performance or measures sensitive to stress and anxiety (physiological or self-report), but like prior work, highly educated and retired adults exhibited greater stereotype effects on episodic memory. At the neural level, stereotype activation did not impact brain activity in executive control or emotional regulation regions previously linked to stereotype threat effects in younger adults, suggesting that stereotype threat operates differently in older adults. Instead, on each task, the stereotype group showed more brain activity than the control group in parietal midline regions (e.g., precuneus, posterior cingulate). Although activity in these regions can arise from many processes, they have previously been associated with self-referential thinking and error-prevention focus, and in our study, brain activity in these regions was associated with slower responses and lower false alarm errors on the episodic memory task. Collectively, these findings are more consistent with the regulatory fit hypothesis than an executive control interference hypothesis of stereotype threat effects in older adults, whereby older adults adopt an error-prevention mindset in response to explicit stereotype threat.

The effect of feedback and recollection rejection instructions on the development of memory monitoring and accuracy.

Recollection rejection (a form of memory monitoring) involves rejecting false details on the basis of remembering true details (recall to reject), thereby increasing memory accuracy. This study examined how recollection rejection instructions and feedback affect memory accuracy and false recognition in 5-year-olds, 6- and 7-year-olds, 8- and 9-year-olds, and adults. Participants (N = 336) completed three study-test phases. Instructions and item-level feedback were manipulated during the first two phases, with the third phase including a test containing no instructions or feedback to evaluate learning effects. As predicted, in the younger children, as compared with the older children and adults, we found reduced accuracy scores (hits to studied items minus false alarms to related lures), reduced recollection rejection to related lures, and increased false recognition scores. We also found that, in the third phase, prior feedback reduced false recognition scores, potentially by improving monitoring, and typical developmental differences in false recognition were eliminated. However, there were mixed findings of instructions and feedback, and in some conditions these interventions harmed memory. These findings provide initial evidence that combining instructions and feedback with repeated task practice may improve monitoring effectiveness, but additional work is needed on how these factors improve and sometimes harm performance in young children.

Creating emotional false recollections: Perceptual recombination and conceptual fluency mechanisms.

We investigated the impact of 2 hypothetical mechanisms of episodic memory reconstruction-perceptual recombination and conceptual fluency-on objectively measured recollection accuracy and false recollections of neutral and emotional stimuli. Participants encoded negative, neutral, and positive pictures depicting objects and scenes (i.e., target pictures), each accompanied with a descriptive verbal label (e.g., "boy crying at funeral," "wooden basket on floor," "four chimpanzees laughing together"). Next, they encoded fragmented pictures of some of the scenes they did and did not earlier see (perceptual misinformation), or they received multiple presentations of the corresponding verbal labels (conceptual misinformation). Recollection of target pictures was then tested, using labels as retrieval cues. We had three key findings in each of two experiments. First, as in our prior work, both perceptual and conceptual misinformation significantly increased false recollection judgments of nonstudied pictures, including high-confidence errors. These effects implicate perceptual recombination and conceptual fluency mechanisms. Second, these misinformation effects generalized across all emotional categories, implicating separable roles of these two mechanisms on emotional recollections. Finally, conceptual misinformation was less likely to influence negative than neutral recollection errors, providing new evidence that emotion can improve retrieval monitoring accuracy and reduce false memories based on conceptual fluency (i.e., an emotional distinctiveness heuristic). (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Δ9-Tetrahydrocannabinol During Encoding Impairs Perceptual Details yet Spares Context Effects on Episodic Memory.

BACKGROUND: With the growing acceptance of cannabis use, it is crucial to understand the drug's effects on episodic memory accuracy and distortion. We investigated the impact of the administration of Δ9-tetrahydrocannabinol (THC), the main psychoactive constituent of cannabis, on a context-based memory illusion. METHODS: In a double-blind, placebo-controlled, within-subjects design, healthy infrequent cannabis users (N = 24) memorized object pictures that were superimposed over scenes (e.g., gray cat on beach) after pretreatment with placebo or THC (15 mg oral). Two days later under sober conditions, memory for the object pictures was tested by asking participants to discriminate between previously seen objects or perceptually similar lures (e.g., different gray cat). Context reinstatement was manipulated by presenting objects on their original or different scenes (e.g., beach or forest). RESULTS: THC impaired memory for perceptual details of objects compared with placebo, and the context illusion was obtained in each condition: context reinstatement increased high-confidence false recognition along with correct recognition of previously seen objects. Although THC did not interact with these context effects overall, post hoc analyses showed that THC magnified the context illusion when objects were semantically congruent with their encoding contexts but abolished the context illusion when objects were incongruent with their encoding contexts. CONCLUSIONS: These results are consistent with the hypothesis that THC impairs the encoding of specific object information more than item-context associations. As a result, THC may spare the distorting effects of context reinstatement on memory. In fact, THC may increase these distorting effects under conditions when objects are semantically congruent with context.

Activating Aging Stereotypes Increases Source Recollection Confusions in Older Adults: Effect at Encoding but Not Retrieval.

OBJECTIVES: Activating aging stereotypes can impair older adult performance on episodic memory tasks, an effect attributed to stereotype threat. Here, we report the first study comparing the effects of explicitly activating aging stereotypes at encoding versus retrieval on recollection accuracy in older adults. METHOD: During the encoding phase, older adults made semantic judgments about words, and during the retrieval phase, they had to recollect these judgments. To manipulate stereotype activation, participants read about aging-related decline (stereotype condition) or an aging-neutral passage (control condition), either before encoding or after encoding but before retrieval. We also assessed stereotype effects on metacognitive beliefs and two secondary tasks (working memory, general knowledge) administered after the recollection task. RESULTS: Stereotype activation at encoding, but not retrieval, significantly increased recollection confusion scores compared to the control condition. Stereotype activation also increased self-reports of cognitive decline with aging, but it did not reliably impact task-related metacognitive assessments or accuracy on the secondary tasks. DISCUSSION: Explicitly activating aging stereotypes at encoding increases the likelihood of false recollection in older adults, potentially by diminishing encoding processes. Stereotype activation also influenced global metacognitive assessments, but this effect may be unrelated to the effect of stereotypes on recollection accuracy.

Alcohol and pharmacologically similar sedatives impair encoding and facilitate consolidation of both recollection and familiarity in episodic memory.

Alcohol and other pharmacologically similar sedatives (i.e., GABAA positive allosteric modulators or PAMs) impair the encoding of new episodic memories but retroactively facilitate the consolidation of recently encoded memories. These effects are consistent for recollection (i.e., the retrieval of details) but some mixed results have been reported for familiarity (i.e., a feeling of knowing a stimulus was presented). Here, with dual-process models, we reanalyzed prior work testing the effects of GABAA PAMs at encoding or consolidation. Contrary to previous conclusions, we show that GABAA PAMs at encoding consistently impair both recollection and familiarity when an independence correction is applied to familiarity-based responses. These findings were further confirmed and extended in a dual-process signal detection analysis of a recent study on the effects of alcohol during encoding or consolidation: Alcohol at encoding impaired both recollection and familiarity, whereas alcohol at consolidation enhanced both recollection and familiarity. These findings speak to the ability of alcohol and other GABAA PAMs to induce 'blackouts,' highlighting the importance of dual-process approaches when analyzing drug manipulations at different phases of episodic memory.

Does tDCS over prefrontal cortex improve episodic memory retrieval? Potential importance of time of day.

We report 4 experiments aiming to replicate and extend the finding that anodal transcranial direct current stimulation (tDCS) over dorsolateral prefrontal cortex after encoding and just prior to retrieval improves accuracy on an episodic recollection task. Our first 3 experiments failed to replicate the tDCS effect in planned analyses, but post-hoc analyses uncovered tDCS effects on recollection accuracy during morning sessions. To further investigate, Experiment 4 randomly assigned participants to morning or afternoon sessions. As predicted, tDCS (compared to sham stimulation) improved recollection accuracy in the morning. We hypothesize that tDCS effects are easier to detect during nonoptimal cognitive processing times (e.g., mornings for younger adults). Importantly, we found both significant and null tDCS results across our experiments, indicating that more research is needed to determine the extent that anodal tDCS to left prefrontal cortex reliably improves recollection accuracy at different stimulation times.

Δ9-Tetrahydrocannabinol at Retrieval Drives False Recollection of Neutral and Emotional Memories.

BACKGROUND: It is well established that the main psychoactive constituent of cannabis, Δ9-tetrahydrocannabinol (THC), impairs episodic memory encoding and modulates emotional processing, but little is known about the impact of THC during the retrieval of emotional episodic memories. With the rise of cannabis to treat medical conditions, including those characterized by emotional and episodic memory disturbances, there is an urgent need to determine the effects of THC on memory accuracy and distortion. Here, we report the first study investigating the effects of THC during retrieval of neutral and emotional episodic memories. METHODS: Using a double-blind, placebo-controlled, within-subjects design, healthy volunteers (N = 23) viewed negative, neutral, and positive pictures (emotional memory task) and lists of semantically related words (false memory task). Forty-eight hours later, participants ingested a capsule containing either THC (15 mg) or placebo and completed tasks to test their memories for the previously studied pictures and words. RESULTS: THC during retrieval did not reduce the number of correct responses to studied items. Instead, it robustly increased false recollection on both the emotional memory and false memory tasks. This effect was found for both neutral and emotional items. CONCLUSIONS: These findings show that THC has adverse effects during memory retrieval, distorting both neutral and emotional memories. Coupled with THC's known effects during encoding, these new retrieval findings are important in light of the spreading acceptance of cannabis.

The Dark Side of Context: Context Reinstatement Can Distort Memory.

It is widely assumed that context reinstatement benefits memory, but our experiments revealed that context reinstatement can systematically distort memory. Participants viewed pictures of objects superimposed over scenes, and we later tested their ability to differentiate these old objects from similar new objects. Context reinstatement was manipulated by presenting objects on the reinstated or switched scene at test. Not only did context reinstatement increase correct recognition of old objects, but it also consistently increased incorrect recognition of similar objects as old ones. This false recognition effect was robust, as it was found in several experiments, occurred after both immediate and delayed testing, and persisted with high confidence even after participants were warned to avoid the distorting effects of context. To explain this memory illusion, we propose that context reinstatement increases the likelihood of confusing conceptual and perceptual information, potentially in medial temporal brain regions that integrate this information.

MDMA Impairs Both the Encoding and Retrieval of Emotional Recollections.

The psychoactive drug ±3,4-methylenedioxymethamphetamine (MDMA) is increasingly used for its perceived emotional effects (eg, prosociality, empathy, psychotherapy), but surprisingly little research has been aimed at identifying the effect of the drug on emotional episodic memory in humans. Here, we report the first double-blind placebo-controlled study to examine the effects of MDMA on emotional memory separately during encoding and retrieval in healthy participants. Participants viewed emotionally negative, neutral, and positive pictures and their labels. Forty-eight hours later, they were given cued recollection and recognition memory tests designed to assess recollection and familiarity for the studied pictures. Participants were randomly assigned to one of three groups who received MDMA (1 mg/kg) either during encoding (Encoding group; N=20), retrieval (Retrieval group; N=20), or neither (Placebo group; N=20). Although MDMA administered at either phase did not affect overall memory accuracy, it did alter the recollection of details associated specifically with emotional memories as estimated using a dual process signal detection analysis of confidence judgments and subjective 'remember' judgments. In the Encoding group, MDMA reduced recollection estimates for negative and positive pictures but had little to no effect on neutral items or familiarity estimates. There was evidence for similar trends in the Retrieval group. These findings indicate that MDMA attenuates the encoding and retrieval of salient details from emotional events, consistent with the idea that its potential therapeutic effects for treating posttraumatic stress disorder are related to altering emotional memory.

Effects of feedback and test practice on recollection and retrieval monitoring: comparing first graders, third graders, and adults.

We tested the effects of repeated testing and feedback on recollection accuracy in first graders, third graders, and adults. All participants studied a list of words and pictures, and then took three recollection tests, with each test probing different words and pictures from the earlier study phase. On the first and third tests no feedback was given, whereas on the second test, some subjects received item-level feedback throughout the recollection test. Recollection confusion scores declined across successive tests in all age groups. However, explicit feedback did not improve recollection accuracy or reduce recollection confusions in any age group. We also found that all age groups were able to use picture recollections in a disqualifying monitoring strategy without task experience or feedback. As a whole, these findings suggest that children and adults can use some aspects of retrieval monitoring without feedback or practice, whereas other aspects of retrieval monitoring can benefit from test practice in children and adults. We discuss the potential roles of metacognitive learning and unintended social feedback on these test practice effects.

Children's Use of Memory Editing Strategies to Reject Source Misinformation.

This is the first reported study of children's use of two metacognitive strategies, recollection rejection and diagnostic monitoring, to reject misinformation. Recollection rejection involves the retrieval of details that disqualify an event, whereas diagnostic monitoring involves the failure to retrieve expected details. First (n = 56, age 7 years) and third graders (n = 52, age 9 years) witnessed a staged classroom interaction involving common and bizarre accidents, were presented with misinformation about the source of these events, and took a memory test. Both age groups used recollection rejection, but third graders were more effective. There was little evidence that diagnostic monitoring influenced responses for bizarre events, potentially because these events were not sufficiently bizarre in the context of the stereotype induction.

Stereotypes, Warnings, and Identity-Related Variables Influence Older Adults' Susceptibility to Associative False Memory Errors.

Background and Objectives: Activating ageist stereotypes can impair older adults' ability to remember information. This effect has been shown to be strongest for older adults who possess certain characteristics (e.g., young-old, highly educated). The present study extended this line of research to investigate the relationship between stereotyping and false memory susceptibility in older adults. Research Design and Methods: We first presented older adults with lists of associated words in an incidental learning paradigm. Afterward, we manipulated whether participants were presented with stereotypes about aging and whether they were given warnings about the associative nature of the lists. Participants then completed a yes/no recognition test and answered demographic questions. Results: Older adults in the stereotyped group were more likely to falsely recognize non-presented theme words than older adults in the control group. Further, those who were highly educated and/or retired were most likely to experience this false memory susceptibility. Discussion and Implications: Similar to the research on veridical memory, these findings suggest that the effects of ageist stereotyping on older adults' false memory susceptibility may be best understood in terms of the individual differences that older adults possess. Identifying the types of people who are at risk of experiencing stereotype threat is an important step toward helping older adults avoid memory impairment in the presence of common stereotypes.

Reduced interference from memory testing: A postretrieval monitoring account.

Initial learning can interfere with subsequent learning (proactive interference [PI]), but recent work indicates initial testing can reduce PI. Here, we tested 2 alternative hypotheses of this effect: Does testing reduce PI by constraining retrieval to the target list, or by facilitating a postretrieval monitoring process? Participants first studied 4 lists of unrelated words. The study-only group performed a distractor task following each list, whereas the tested group recalled each list. After these initial lists, both groups studied and were tested on a final list. Replicating prior work, the tested group recalled more of the final list items and had fewer prior-list intrusions than the study-only group (i.e., initial testing reduced subsequent PI). To test the 2-alternative hypotheses, Experiment 1 used a modified recall test for the final list, whereby participants were asked to recall the final list of words and also report any items from prior lists that inadvertently came to mind. Contrary to the constrained retrieval hypothesis, initial testing did not reduce the number of prior list items that came to mind, but consistent with the postretrieval monitoring hypothesis, testing increased the likelihood that the intrusions would be correctly attributed to prior lists. Experiments 2 and 3 further tested the postretrieval monitoring hypothesis by testing the final list twice. According to the hypothesis, testing all of the lists should render prior testing nondiagnostic of list membership, thereby impairing retrieval monitoring in the test group and minimizing its ability to reduce PI. This prediction was confirmed. (PsycINFO Database Record

Effect of Alcohol on Encoding and Consolidation of Memory for Alcohol-Related Images.

BACKGROUND: Drug and alcohol abusers develop strong memories for drug-related stimuli. Preclinical studies suggest that such memories are a result of drug actions on reward pathways, which facilitate learning about drug-related stimuli. However, few controlled studies have investigated how drugs affect memory for drug-related stimuli in humans. METHODS: The current study examined the direct effect of alcohol on memory for images of alcohol-related or neutral beverages. Participants received alcohol (0.8 g/kg) either before viewing visual images (encoding condition; n = 20) or immediately after viewing them (consolidation condition; n = 20). A third group received placebo both before and after viewing the images (control condition; n = 19). Memory retrieval was tested exactly 48 hours later, in a drug-free state. RESULTS: Alcohol impaired memory in the encoding condition and enhanced memory in the consolidation condition, but these effects did not differ for alcohol-related and neutral beverage stimuli. However, in the encoding condition, participants who experienced greater alcohol-induced stimulation exhibited better memory for alcohol-related, but not neutral beverage stimuli. CONCLUSIONS: These findings suggest that individual differences in sensitivity to the positive, rewarding effects of alcohol are associated with greater propensity to remember alcohol-related stimuli encountered while intoxicated. As such, stimulant responders may form stronger memory associations with alcohol-related stimuli, which might then influence their drinking behavior.

Two mechanisms of constructive recollection: Perceptual recombination and conceptual fluency.

Recollection is constructive and prone to distortion, but the mechanisms through which recollections can become embellished with rich yet illusory details are still debated. According to the conceptual fluency hypothesis, abstract semantic or conceptual activation increases the familiarity of a nonstudied event, causing one to falsely attribute imagined features to actual perception. In contrast, according to the perceptual recombination hypothesis, details from actually perceived events are partially recollected and become erroneously bound to a nonstudied event, again causing a detailed yet false recollection. Here, we report the first experiments aimed at disentangling these 2 mechanisms. Participants imagined pictures of common objects, and then they saw an actual picture of some of the imagined objects. We next presented misinformation associated with these studied items, designed to increase conceptual fluency (i.e., semantically related words) or perceptual recombination (i.e., perceptually similar picture fragments). Finally, we tested recollection for the originally seen pictures using verbal labels as retrieval cues. Consistent with conceptual fluency, processing-related words increased false recollection of pictures that were never seen, and consistent with perceptual recombination, processing picture fragments further increased false recollection. We also found that conceptual fluency was more short-lived than perceptual recombination, further dissociating these 2 mechanisms. These experiments provide strong evidence that conceptual fluency and perceptual recombination independently contribute to the constructive aspects of recollection. (PsycINFO Database Record

Acute Effects of Alcohol on Encoding and Consolidation of Memory for Emotional Stimuli.

OBJECTIVE: Acute doses of alcohol impair memory when administered before encoding of emotionally neutral stimuli but enhance memory when administered immediately after encoding, potentially by affecting memory consolidation. Here, we examined whether alcohol produces similar biphasic effects on memory for positive or negative emotional stimuli. METHOD: The current study examined memory for emotional stimuli after alcohol (0.8 g/kg) was administered either before stimulus viewing (encoding group; n = 20) or immediately following stimulus viewing (consolidation group; n = 20). A third group received placebo both before and after stimulus viewing (control group; n = 19). Participants viewed the stimuli on one day, and their retrieval was assessed exactly 48 hours later, when they performed a surprise cued recollection and recognition test of the stimuli in a drug-free state. RESULTS: As in previous studies, alcohol administered before encoding impaired memory accuracy, whereas alcohol administered after encoding enhanced memory accuracy. Critically, alcohol effects on cued recollection depended on the valence of the emotional stimuli: Its memory-impairing effects during encoding were greatest for emotional stimuli, whereas its memory-enhancing effects during consolidation were greatest for emotionally neutral stimuli. Effects of alcohol on recognition were not related to stimulus valence. CONCLUSIONS: This study extends previous findings with memory for neutral stimuli, showing that alcohol differentially affects the encoding and consolidation of memory for emotional stimuli. These effects of alcohol on memory for emotionally salient material may contribute to the development of alcohol-related problems, perhaps by dampening memory for adverse consequences of alcohol consumption.