Does alcohol affect memory for emotional and non-emotional experiences in different ways?

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.

Alcohol-Induced Retrograde Facilitation?

Somewhat counterintuitively, alcohol consumption following learning of new information has been shown to enhance performance on a delayed subsequent memory test. This phenomenon has become known as the retrograde facilitation effect (Parker et al., 1981). Although conceptually replicated repeatedly, serious methodological problems are associated with most previous demonstrations of retrograde facilitation. Moreover, two potential explanations have been proposed, the interference and the consolidation hypothesis. So far, empirical evidence for and against both hypotheses is inconclusive (Wixted, 2004). To scrutinize the existence of the effect, we conducted a pre-registered replication that avoided common methodological pitfalls. In addition, we used Küpper-Tetzel and Erdfelder's (2012) multinomial processing tree (MPT) model to disentangle encoding, maintenance, and retrieval contributions to memory performance. With a total sample size of N = 93, we found no evidence for retrograde facilitation in overall cued or free recall of previously presented word pairs. In line with this, MPT analyses also showed no reliable difference in maintenance probabilities. However, MPT analyses revealed a robust alcohol advantage in retrieval. We conclude that alcohol-induced retrograde facilitation might exist and be driven by an underlying retrieval benefit. Future research is needed to investigate potential moderators and mediators of the effect explicitly.

Loss and Frontal Striatal Reactivities Characterize Alcohol Use Severity and Rule-Breaking Behavior in Young Adult Drinkers

BACKGROUND

Alcohol misuse is associated with externalizing behaviors, including rule breaking. Studies have implicated altered reward processing in externalizing behaviors and alcohol misuse. Here, we investigated whether reward or punishment reactivity more significantly influenced alcohol use severity and rule-breaking behavior in young adult drinkers.

METHODS

We curated data from the Human Connectome Project and identified 181 binge (132 men) and 288 nonbinge (97 men) drinkers performing a gambling task during brain imaging. Alcohol use severity was quantified by the first principal component of principal-component analysis of all drinking measures. We analyzed the imaging data using published routines and evaluated the results at a corrected threshold. We examined the interrelationship between imaging and clinical metrics with mediation and path analyses.

RESULTS

Compared with nonbingers, bingers showed more severe rule-breaking behavior and responded significantly faster during post-loss than during post-win trials. Compared with nonbingers, bingers demonstrated greater inferior/middle frontal gyrus and cerebellum activations in loss-predominating blocks but no differences in regional responses to win-predominating blocks, relative to an interblock baseline. The right caudate body showed loss reactivity that was positively correlated with the rule-breaking score. No regional responses to wins were significantly correlated with the rule-breaking score. Mediation and path analyses demonstrated significant models with inferior/middle frontal gyrus and caudate reactivity to loss interrelating rule breaking and alcohol use severity.

CONCLUSIONS

Punishment rather than reward reactivity was associated with alcohol use severity and rule breaking in young adults. The findings highlight the roles of negative emotions in psychological models of externalizing behaviors and alcohol misuse.

Interoceptive signaling in alcohol cognitive biases: Role of family history and alliesthetic components

The role of interoceptive signals in the development of cognitive biases for drug-related cues has been hypothesized in the past; however, experimental evidence is lacking. This report examined the relationship between physiological responses and memories for alcohol cues. Participants (n = 158) were categorized as having either a positive or negative family history of alcohol use disorder (AUD). They were assigned to an alcohol, placebo, or control beverage condition to which they were blinded. All participants were presented with alcohol, neutral, and emotional cues. Heart rate variability (HRV) at 0.1 Hz, as an index of viscero-afferent reactivity, and in the high-frequency range was measured during picture-cue exposure. Participants then completed free recall and repetition priming tasks to assess memories for previously presented stimuli. Participants with a positive family history (FHP) for AUD who received an alcohol beverage displayed a positive relationship between 0.1 Hz HRV and free recall. This effect was specific to alcohol cues, highlighting the relevance of physiological signals in the development of alcohol cognitive biases. These results support the hypothesis of a coordinated brain-body interaction in the development of drug-related behaviors. FHP as an AUD risk factor may increase the mapping of physiological responses onto cognitive biases for alcohol cues. Increased ratings of subjective intoxication dampened this relationship, suggesting that perceived bodily states may modulate incentive salience processes. This report provides novel evidence for the involvement of interoceptive signals in addictive processes, setting a precedent for the exploration of brain-body interactions in the study of alcohol cognitive biases.

The effect of acute alcohol consumption on meal memory and subsequent food intake: Two laboratory experiments

Altering the quality of episodic meal memories has been shown to affect subsequent food intake. Acute alcohol consumption disrupts memory formation and produces short-term overeating. In two studies, we investigated whether alcohol consumption can affect meal-related memories and later food intake. Study 1 (N = 60, 50% male) investigated how consumption of an alcoholic drink (0.5 g/kg) prior to consumption of a lunch meal affected meal memory of that lunch, and later food intake, compared with a placebo-alcohol. Findings revealed that alcohol consumption did not impair meal memory, and did not affect subsequent food intake. Study 2 (N = 72, 50% male) investigated whether, due to alcohol's retrograde facilitation effect (the enhancement of recall due to reduced interference at the point of exposure) consuming alcohol after consumption of a lunch meal could enhance meal memory, compared with when consumed before a lunch meal (both a dosage of 0.6 g/kg), and compared with consumption of a soft drink. Contrary to prediction, alcohol consumed after a lunch meal did not significantly increase meal memory. But, certain types of meal memory were impaired when alcohol was consumed before the meal, compared with consumption of a soft drink. Subsequent food intake did not differ between conditions. Taken together, findings suggest that alcohol intoxication can impair some forms of meal memory recall, likely due to disruption of memory formation during the encoding phase. However, there was no evidence that this impairment contributes towards alcohol-induced overeating.

Alcohol Intoxication and Cognition: Implications on Mechanisms and Therapeutic Strategies

Binge alcohol drinking is highly prevalent in young adults and results in 30% deaths per year in young males. Binge alcohol drinking or acute alcohol intoxication is a risk factor for developing alcohol use disorder (AUD). Three FDA approved drugs are currently in use as therapy for AUD; however, all of them have contra-indications and limitations. Structural brain imaging studies in alcoholics have shown defects in the brain regions involved in memory, cognition and emotional processing. Positron emission tomography (PET) using radiotracers (e.g., 18FDG) and measuring brain glucose metabolism have demonstrated diagnostic and prognostic utility in evaluating patients with cognitive impairment. Using PET imaging, only a few exclusive human studies have addressed the relationship between alcohol intoxication and cognition. Those studies indicate that alcohol intoxication causes reduction in brain activity. Consistent with prior findings, a recent study by us showed that acute alcohol intoxication reduced brain activity in the cortical and subcortical regions including the temporal lobe consisting the hippocampus. Additionally, we have observed a strong correlation between reduction in metabolic activity and spatial cognition impairment in the hippocampus after binge alcohol exposure. We have also demonstrated the involvement of a stress response protein, cold inducible RNA binding protein (CIRP), as a potential mechanistic mediator in acute alcohol intoxication. In this review, we will first discuss in detail prior human PET imaging studies on alcohol intoxication as well as our recent study on acute alcohol intoxication, and review the existing literature on potential mechanisms of acute alcohol intoxication-induced cognitive impairment and therapeutic strategies to mitigate these impairments. Finally, we will highlight the importance of studying brain regions as part of a brain network in delineating the mechanism of acute alcohol intoxication-induced cognitive impairment to aid in the development of therapeutics for such indication.

Acute alcohol and cognition: Remembering what it causes us to forget

Addiction has been conceptualized as a specific form of memory that appropriates typically adaptive neural mechanisms of learning to produce the progressive spiral of drug-seeking and drug-taking behavior, perpetuating the path to addiction through aberrant processes of drug-related learning and memory. From that perspective, to understand the development of alcohol use disorders, it is critical to identify how a single exposure to alcohol enters into or alters the processes of learning and memory, so that involvement of and changes in neuroplasticity processes responsible for learning and memory can be identified early. This review characterizes the effects produced by acute alcohol intoxication as a function of brain region and memory neurocircuitry. In general, exposure to ethanol doses that produce intoxicating effects causes consistent impairments in learning and memory processes mediated by specific brain circuitry, whereas lower doses either have no effect or produce a facilitation of memory under certain task conditions. Therefore, acute ethanol does not produce a global impairment of learning and memory, and can actually facilitate particular types of memory, perhaps particular types of memory that facilitate the development of excessive alcohol use. In addition, the effects on cognition are dependent on brain region, task demands, dose received, pharmacokinetics, and tolerance. Additionally, we explore the underlying alterations in neurophysiology produced by acute alcohol exposure that help to explain these changes in cognition and highlight future directions for research. Through understanding the impact that acute alcohol intoxication has on cognition, the preliminary changes potentially causing a problematic addiction memory can better be identified.

Altered oscillatory brain dynamics of emotional processing in young binge drinkers

Heavy episodic drinking, also termed binge drinking, is commonly practiced by young adults. It is accompanied by a range of cognitive, affective, and social problems, but the neural dynamics underlying changes in emotional functions is poorly understood. To investigate the behavioral and brain indices of affective processing as a function of binge drinking, young, healthy participants (23.3 ± 3.3 years) were assigned to two groups (n = 32 each) based on their drinking habits. Binge drinking (BD) participants reported drinking heavily with at least five binge episodes in the last 6 months, whereas light drinkers (LD) reported no more than one binge episode in the last 6 months. Participants provided subjective ratings of emotionally evocative images with negative, positive, erotic, and neutral themes mostly selected from the International Affective Picture System (IAPS). Electroencephalography (EEG) signal was recorded with a 64-channel system and analyzed in theta frequency band (4-7 Hz) with Morlet wavelets. Subjective ratings of the IAPS pictures were equivalent across both groups. However, affective modulation of event-related theta power both during early appraisal and later integrative processing stages was attenuated in BD, particularly those engaging in high-intensity drinking. These findings suggest that binge drinking is associated with altered neurophysiological indices of affective functions that are reflected in lower theta responsivity to emotions. The blunted long-range cortico-cortical and corticolimbic integration is consistent with compromised affective functions in alcohol use disorder. These findings may have implications for diagnostic and intervention strategies in heavy alcohol users.

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., GABA_A 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 GABA_A PAMs at encoding or consolidation. Contrary to previous conclusions, we show that GABA_A 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 GABA_A PAMs to induce 'blackouts,' highlighting the importance of dual-process approaches when analyzing drug manipulations at different phases of episodic memory.

Latent growth classes of alcohol-related blackouts over the first 2 years of college

Alcohol-related blackouts are common among college student drinkers. The present study extends prior work by examining latent growth classes of blackouts and several predictors of class membership. Participants (N = 709 college drinkers) completed a baseline survey at college entry and biweekly online assessments throughout freshman and sophomore years. Results revealed 5 latent growth class trajectories, reflecting varying experiences of blackouts at the beginning of college and differential change in blackouts over time. The largest class represented a relatively low-risk group (low decrease; 47.3%) characterized by endorsement of no or very low likelihood of blackouts, and decreasing likelihood of blackouts over time. Another decreasing risk group (high decrease; 11.1%) initially reported a high proportion of blackouts and had the steepest decrease in blackout risk over time. A small percentage showed consistently high likelihood of blackouts over time (high stable; 4.1%). The remaining 2 groups were distinguished by relatively moderate (moderate stable; 14.9%) and lower (low stable; 22.6%) likelihood of blackouts, which remained stable over time. Comparisons between classes revealed that students with greater perceived peer drinking, perceived peer approval of drinking, and enhancement motives upon entry to college tended to be in higher risk groups with consistent experiences of blackouts over time, whereas blackout likelihood decreased over time for students with greater conformity motives. Findings suggest that precollege preventive interventions may be strengthened by considering not only factors related to current risk for blackouts and other alcohol-related consequences, but also those factors related to persistence of these behaviors over time. (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.

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.

The sensitivity of laboratory tests assessing driving related skills to dose-related impairment of alcohol: A literature review

Laboratory tests assessing driving related skills can be useful as initial screening tools to assess potential drug induced impairment as part of a standardized behavioural assessment. Unfortunately, consensus about which laboratory tests should be included to reliably assess drug induced impairment has not yet been reached. The aim of the present review was to evaluate the sensitivity of laboratory tests to the dose dependent effects of alcohol, as a benchmark, on performance parameters. In total, 179 experimental studies were included. Results show that a cued go/no-go task and a divided attention test with primary tracking and secondary visual search were consistently sensitive to the impairing effects at medium and high blood alcohol concentrations. Driving performance assessed in a simulator was less sensitive to the effects of alcohol as compared to naturalistic, on-the-road driving. In conclusion, replicating results of several potentially useful tests and their predictive validity of actual driving impairment should deserve further research. In addition, driving simulators should be validated and compared head to head to naturalistic driving in order to increase construct validity.

Drinkers' memory bias for alcohol picture cues in explicit and implicit memory tasks

BACKGROUND

Alcohol cues can bias attention and elicit emotional reactions, especially in drinkers. Yet, little is known about how alcohol cues affect explicit and implicit memory processes, and how memory for alcohol cues is affected by acute alcohol intoxication.

METHODS

Young adult participants (N=161) were randomly assigned to alcohol, placebo, or control beverage conditions. Following beverage consumption, they were shown neutral, emotional and alcohol-related pictures cues. Participants then completed free recall and repetition priming tasks to test explicit and implicit memory, respectively, for picture cues. Average blood alcohol concentration for the alcohol group was 74±13mg/dl when memory testing began. Two mixed linear model analyses were conducted to examine the effects of beverage condition, picture cue type, and their interaction on explicit and implicit memory.

RESULTS

Picture cue type and beverage condition each significantly affected explicit recall of picture cues, whereas only picture cue type significantly influenced repetition priming. Individuals in the alcohol condition recalled significantly fewer pictures than those in other conditions, regardless of cue type. Both free recall and repetition priming were greater for emotional and alcohol-related cues compared to neutral picture cues. No interaction effects were detected.

CONCLUSIONS

Young adult drinkers showed enhanced explicit and implicit memory processing of alcohol cues compared to emotionally neutral cues. This enhanced processing for alcohol cues was on par with that seen for positive emotional cues. Acute alcohol intoxication did not alter this preferential memory processing for alcohol cues over neutral cues.

Selective effects of acute alcohol intake on the prospective and retrospective components of a prospective-memory task with emotional targets

RATIONALE

Prospective memory involves remembering to do something in the future and has a prospective component (remembering that something must be done) and a retrospective component (remembering what must be done and when it must be done). Initial studies reported an impairment in prospective-memory performance due to acute alcohol consumption. Retrospective-memory studies demonstrated that alcohol effects vary depending on the emotionality of the information that needs to be learned.

OBJECTIVES

The aim of the present study was to investigate possible differential effects of a mild acute alcohol dose (0.4 g/kg) on the prospective and retrospective components of prospective memory depending on cue valence.

METHOD

Seventy-five participants were allocated to an alcohol or placebo group and performed a prospective-memory task in which prospective-memory cue valence was manipulated (negative, neutral, positive). The multinomial model of event-based prospective memory (Smith and Bayen 2004) was used to measure alcohol and valence effects on the two prospective-memory components separately.

RESULTS

Overall, no main effect of alcohol or valence on prospective-memory performance occurred. However, model-based analyses demonstrated a significantly higher retrospective component for positive compared with negative cues in the placebo group. In the alcohol group, the prospective component was weaker for negative than for neutral cues and the retrospective component was stronger for positive than for neutral cues. Group comparisons showed that the alcohol group had a significantly lower prospective component for negative cues and a lower retrospective component for neutral cues.

CONCLUSION

This is the first study to demonstrate selective alcohol effects on prospective-memory components depending on prospective-memory cue valence.

Extinction learning is slower, weaker and less context specific after alcohol

Alcohol is frequently involved in psychological trauma and often used by individuals to reduce fear and anxiety. We examined the effects of alcohol on fear acquisition and extinction within a virtual environment. Healthy volunteers were administered alcohol (0.4 g/kg) or placebo and underwent acquisition and extinction from different viewpoints of a virtual courtyard, in which the conditioned stimulus, paired with a mild electric shock, was centrally located. Participants returned the following day to test fear recall from both viewpoints of the courtyard. Skin conductance responses were recorded as an index of conditioned fear. Successful fear acquisition under alcohol contrasted with impaired extinction learning evidenced by persistent conditioned responses (Experiment 1). Participants’ impairments in extinction under alcohol correlated with impairments in remembering object-locations in the courtyard seen from one viewpoint when tested from the other viewpoint. Alcohol-induced extinction impairments were overcome by increasing the number of extinction trials (Experiment 2). However, a test of fear recall the next day showed persistent fear in the alcohol group across both viewpoints. Thus, alcohol impaired extinction rather than acquisition of fear, suggesting that extinction is more dependent than acquisition on alcohol-sensitive representations of spatial context. Overall, extinction learning under alcohol was slower, weaker and less context-specific, resulting in persistent fear at test that generalized to the extinction viewpoint. The selective effect on extinction suggests an effect of alcohol on prefrontal involvement, while the reduced context-specificity implicates the hippocampus. These findings have important implications for the use of alcohol by individuals with clinical anxiety disorders.

Effects of acute methamphetamine on emotional memory formation in humans: encoding vs consolidation

Understanding how stimulant drugs affect memory is important for understanding their addictive potential. Here we examined the effects of acute d-methamphetamine (METH), administered either before (encoding phase) or immediately after (consolidation phase) study on memory for emotional and neutral images in healthy humans. Young adult volunteers (N = 60) were randomly assigned to either an encoding group (N = 29) or a consolidation group (N = 31). Across three experimental sessions, they received placebo and two doses of METH (10, 20 mg) either 45 min before (encoding) or immediately after (consolidation) viewing pictures of emotionally positive, neutral, and negative scenes. Memory for the pictures was tested two days later, under drug-free conditions. Half of the sample reported sleep disturbances following the high dose of METH, which affected their memory performance. Therefore, participants were classified as poor sleepers (less than 6 hours; n = 29) or adequate sleepers (6 or more hours; n = 31) prior to analyses. For adequate sleepers, METH (20 mg) administered before encoding significantly improved memory accuracy relative to placebo, especially for emotional (positive and negative), compared to neutral, stimuli. For poor sleepers in the encoding group, METH impaired memory. METH did not affect memory in the consolidation group regardless of sleep quality. These results extend previous findings showing that METH can enhance memory for salient emotional stimuli but only if it is present at the time of study, where it can affect both encoding and consolidation. METH does not appear to facilitate consolidation if administered after encoding. The study also demonstrates the important role of sleep in memory studies.

Acute ethanol withdrawal impairs contextual learning and enhances cued learning

BACKGROUND

Alcohol affects many of the brain regions and neural processes that support learning and memory, and these effects are thought to underlie, at least in part, the development of addiction. Although much work has been done regarding the effects of alcohol intoxication on learning and memory, little is known about the effects of acute withdrawal from a single alcohol exposure.

METHODS

We assess the effects of acute ethanol withdrawal (6 hours postinjection with 4 g/kg ethanol) on 2 forms of fear conditioning (delay and trace fear conditioning) in C57BL/6J and DBA/2J mice. The influence of a number of experimental parameters (pre- and post training withdrawal exposure; foreground/background processing; training strength; and nonassociative effects) is also investigated.

RESULTS

Acute ethanol withdrawal during training had a bidirectional effect on fear-conditioned responses, decreasing contextual responses and increasing cued responses. These effects were apparent for both trace and delay conditioning in DBA/2J mice and for trace conditioning in C57BL/6J mice; however, C57BL/6J mice were selectively resistant to the effects of acute withdrawal on delay cued responses.

CONCLUSIONS

Our results show that acute withdrawal from a single, initial ethanol exposure is sufficient to alter long-term learning in mice. In addition, the differences between the strains and conditioning paradigms used suggest that specific learning processes can be differentially affected by acute withdrawal in a manner that is distinct from the reported effects of both alcohol intoxication and withdrawal following chronic alcohol exposure. Thus, our results suggest a unique effect of acute alcohol withdrawal on learning and memory processes.

Men's Intentions to Have Sex With a New Partner: Sexual and Emotional Responding, Alcohol, and Condoms

Findings regarding the relation between alcohol and intentions to have sex have been mixed, and little research has examined the role of condom availability on intentions to have sex. Sexual and emotional responding may influence subsequent sexual decisions. Thus, a better understanding of sexual and emotional responding combined with situational factors such as condom presence could help explain the discrepancies in findings regarding alcohol's effect on intentions to have sex. The effects of alcohol and condom presence on men's intentions to have sex were examined using an experimental paradigm involving an alcohol administration study and a second-person eroticized scenario. The effects of sexual and emotional responding were also examined in relation to intentions to have sex. It was found that alcohol increased positive mood, which was associated with higher intentions to have sex. In addition, condom presence was directly associated with higher intentions to have sex. More sexual desire was related to increased likelihood of sexual intentions. These findings increase understanding of mechanisms underlying the relation between alcohol and intentions to have sex.

Memory for drug-related visual stimuli in young adult, cocaine-dependent polydrug users

BACKGROUND AND OBJECTIVES

Implicit (unconscious) and explicit (conscious) memory associations with drugs have been examined primarily using verbal cues. However, drug seeking, drug use behaviors, and relapse in chronic cocaine and other drug users are frequently triggered by viewing substance-related visual cues in the environment. We thus examined implicit and explicit memory for drug picture cues to understand the relative extent to which conscious and unconscious memory facilitation of visual drug cues occurs during cocaine dependence.

METHODS

Memory for drug-related and neutral picture cues was assessed in 14 inpatient cocaine-dependent polydrug users and a comparison group of 21 young adults with limited drug experience (n = 35). Participants completed picture cue exposure, free recall and recognition tasks to assess explicit memory, and a repetition priming task to assess implicit memory.

RESULTS

Drug cues, compared to neutral cues, were better explicitly recalled and implicitly primed, and especially so in the cocaine group. In contrast, neutral cues were better explicitly recognized, and especially in the control group.

CONCLUSION

Certain forms of explicit and implicit memory for drug cues were enhanced in cocaine users compared to controls when memory was tested a short time following cue exposure. Enhanced unconscious memory processing of drug cues in chronic cocaine users may be a behavioral manifestation of heightened drug cue salience that supports drug seeking and taking. There may be value in expanding intervention techniques to utilize cocaine users' implicit memory system.

Alpha 2B adrenoceptor genotype moderates effect of reboxetine on negative emotional memory bias in healthy volunteers

Evidence suggests that emotional memory plays a role in the pathophysiology of depression/anxiety disorders. Noradrenaline crucially modulates emotional memory. Genetic variants involved in noradrenergic signaling contribute to individual differences in emotional memory and vulnerability to psychopathology. A functional deletion polymorphism in the α-2B adrenoceptor gene (ADRA2B) has been linked to emotional memory and post-traumatic stress disorder. The noradrenaline reuptake inhibitor reboxetine attenuates enhanced memory for negative stimuli in healthy and depressed individuals. We examined whether the effect of reboxetine on emotional memory in healthy individuals would be moderated by ADRA2B genotype. ADRA2B deletion carriers demonstrated enhanced emotional memory for negative stimuli compared with deletion noncarriers, consistent with prior studies. Reboxetine attenuated enhanced memory for negative stimuli in deletion noncarriers but had no significant effect in deletion carriers. This is the first demonstration of genetic variation influencing antidepressant drug effects on emotional processing in healthy humans.

Memory for emotional picture cues during acute alcohol intoxication

OBJECTIVE

Memory affects behavior by allowing events to be anticipated and goals to be planned based on previous experiences. Emotional memory, in particular, is thought to play a central role in behavior in general and in drinking behavior in particular. Alcohol intoxication has been shown to disrupt intentional, conscious memory, but not unintentional, implicit memory for neutral stimuli; however, its effects on emotional memory are not well understood. This study examined whether alcohol intoxication affected memory for emotionally valenced stimuli by testing explicit recall and implicit repetition priming of emotional picture cues.

METHOD

Participants were 36 young adults (21-24 years old, 16 women) who received an alcohol, placebo, or no-alcohol beverage. Both cue exposure and memory testing occurred after beverage consumption (i.e., during intoxication for the alcohol group).

RESULTS

Alcohol intoxication impaired explicit recall of all cue types but did not impair implicit repetition priming. Emotionally negative and positive cues were more often recalled compared with neutral cues across all beverage groups, and emotionally negative cues demonstrated more priming than emotionally positive or neutral cues in all beverage groups.

CONCLUSIONS

Alcohol intoxication disrupted effortful recall of all cues, although the relative memory advantage of emotionally valenced over-neutral stimuli remained even after drinking. The effects of alcohol on unintentional memory priming were not statistically significant, but the effects of emotionally negative cues were. Further research is needed to better understand alcohol intoxication and emotional valence effects on memory processes during implicit memory tasks and the possibility that negative mood facilitates memory priming of negative emotional stimuli.

Pre-encoding administration of amphetamine or THC preferentially modulates emotional memory in humans

RATIONALE

Many addictive drugs are known to have effects on learning and memory, and these effects could motivate future drug use. Specifically, addictive drugs may affect memory of emotional events and experiences in ways that are attractive to some users. However, few studies have investigated the effects of addictive drugs on emotional memory in humans.

OBJECTIVES

This study examined the effects of the memory-enhancing drug dextroamphetamine (AMP) and the memory-impairing drug Δ(9)-tetrahydrocannabinol (THC) on emotional memory in healthy volunteers.

METHODS

Participants completed three experimental sessions across which they received capsules containing placebo and two doses of either AMP (10 and 20 mg; N = 25) or THC (7.5 and 15 mg; N = 25) before viewing pictures of positive (pleasant), neutral, and negative (unpleasant) scenes. Memory for the pictures was assessed 2 days later, under drug-free conditions.

RESULTS

Relative to placebo, memory for emotional pictures was improved by AMP and impaired by THC, but neither drug significantly affected memory for unemotional pictures. Positive memory biases were not observed with either drug, and there was no indication that the drugs' memory effects were directly related to their subjective or physiological effects alone.

CONCLUSIONS

This study provides the first clear evidence that stimulant drugs can preferentially strengthen, and cannabinoids can preferentially impair, memory for emotional events in humans. Although addictive drugs do not appear to positively bias memory, the possibility remains that these drugs' effects on emotional memory could influence drug use among certain individuals.

Effects of delta-9-tetrahydrocannabinol on evaluation of emotional images

There is growing evidence that drugs of abuse alter processing of emotional information in ways that could be attractive to users. Our recent report that Δ⁹-tetrahydrocannabinol (THC) diminishes amygdalar activation in response to threat-related faces suggests that THC may modify evaluation of emotionally-salient, particularly negative or threatening, stimuli. In this study, we examined the effects of acute THC on evaluation of emotional images. Healthy volunteers received two doses of THC (7.5 and 15 mg; p.o.) and placebo across separate sessions before performing tasks assessing facial emotion recognition and emotional responses to pictures of emotional scenes. THC significantly impaired recognition of facial fear and anger, but it only marginally impaired recognition of sadness and happiness. The drug did not consistently affect ratings of emotional scenes. THC's effects on emotional evaluation were not clearly related to its mood-altering effects. These results support our previous work, and show that THC reduces perception of facial threat. Nevertheless, THC does not appear to positively bias evaluation of emotional stimuli in general.

Functional biomarkers for the acute effects of alcohol on the central nervous system in healthy volunteers

The central nervous system (CNS) effects of acute alcohol administration have been frequently assessed. Such studies often use a wide range of methods to study each of these effects. Unfortunately, the sensitivity of these tests has not completely been ascertained. A literature search was performed to recognize the most useful tests (or biomarkers) for identifying the acute CNS effects of alcohol in healthy volunteers. All tests were grouped in clusters and functional domains. Afterwards, the effect of alcohol administration on these tests was scored as improvement, impairment or as no effect. Furthermore, dose-response relationships were established. A total number of 218 studies, describing 342 different tests (or test variants) were evaluated. Alcohol affected a wide range of CNS domains. Divided attention, focused attention, visuo-motor control and scales of feeling high and of subjective drug effects were identified as the most sensitive functional biomarkers for the acute CNS effects of alcohol. The large number of CNS tests that are used to determine the effects of alcohol interferes with the identification of the most sensitive ones and of drug-response relationships. Our results may be helpful in selecting rational biomarkers for studies investigating the acute CNS effects of alcohol or for future alcohol- interaction studies.

Retrograde facilitation of verbal memory by trihexyphenidyl in healthy elderly with and without the APOE epsilon4 allele

Retrograde facilitation (RF) of information learned prior to acute oral administration of trihexyphenidyl, a preferential muscarinic M1 receptor antagonist which impairs new learning, was studied in 24 healthy elderly subjects. The relationship between the RF induced by this anticholinergic drug and the APOE epsilon4 allele was also examined. Acute adverse performance effects of trihexyphenidyl (1- and 2mg) were determined using the Buschke Selective Reminding Test administered pre-drug and at 1, 2.5, and 5h post-drug. Recall of pre-drug words at the end of the fifth hour neuropsychological assessment (end-of-session recall) was of primary interest. Words studied before drug administration were better recalled following 2mg trihexyphenidyl compared to placebo, and this RF effect was not affected by the APOE epsilon4 allele. Better recall of pre-drug words following 2-mg trihexyphenidyl was associated with a greater amnestic effect of this dose. Our findings demonstrated that RF induced by trihexyphenidyl was related to anterograde amnestic effects of the drug and resulted in part from drug-induced reduction of retroactive interference.

Drinking and future thinking: acute effects of alcohol on prospective memory and future simulation

BACKGROUND

It has recently been shown that acute alcohol globally impairs 'prospective memory' (PM)-remembering to do something in the future (Leitz et al. in Psychopharmacology 205:379-387, 2009). In healthy, sober individuals, simulating future events at encoding enhances PM performance.

AIMS

We therefore aimed to determine if future event simulation could attenuate the impairing effects of acute alcohol on PM.

METHODS

Using a double-blind independent group design, 32 healthy volunteers were administered a 0.6-g/kg dose of ethanol or matched placebo. PM performance was assessed using a behavioural task, the 'Virtual Week', which was adapted to enable future event simulation in both remote and recent contexts. Episodic memory was indexed with a source memory task and planning with the Tower of London task.

RESULTS

We replicated the finding of Leitz et al. that acute alcohol consumption impairs prospective memory for event-based tasks. Future event simulation significantly improved PM performance on these tasks and eliminated the PM deficit caused by acute alcohol consumption.

CONCLUSIONS

This is the first evidence that future event simulation can overcome alcohol-induced deficits in prospective memory and may have important clinical implications for the rehabilitation of chronic alcohol users.

Global impairment of prospective memory following acute alcohol

RATIONALE

Whilst the deleterious effects of alcohol on retrospective remembering have been widely documented, no study has yet objectively determined alcohol's effects on prospective memory (PM)--remembering to do something in the future.

OBJECTIVES

With this aim, the present study determined the acute effects of alcohol upon PM using a laboratory measure that simulates the PM tasks in everyday life--'Virtual Week'--both (a) in its standard form with regular, irregular, event-based and time-based PM tasks; and (b) an adapted version which enabled exploration of how future event simulation at encoding impacted upon subsequent PM.

METHODS

Forty healthy volunteers were administered 0.6 g/kg ethanol or a matched placebo in a double-blind fashion and completed the two versions of Virtual Week along with prose recall (to tap retrospective memory) and an executive function task.

RESULTS

Alcohol acutely produced global impairments across all (regular, irregular, event-based and time-based) PM tasks. It also produced impairments of episodic memory which positively correlated with PM performance of irregular tasks. Future-event simulation tended to enhance PM in the placebo but not in the alcohol group.

CONCLUSIONS

These findings on an objective measure of PM suggest that 4-5 units of alcohol will compromise PM abilities in everyday life.

Acute effects of alcohol on the development of intrusive memories

RATIONALE

Post-traumatic stress disorder is characterised by repeated intrusive imagery of the traumatic event. Despite alcohol's impairing effect on memory and frequent involvement in real-life trauma, virtually nothing is known of the interaction between alcohol and trauma memory.

OBJECTIVE

We aimed to investigate the acute alcohol effects on spontaneous memories following a trauma film as well as explicit memory for the film.

METHODS

Utilising an independent-group double-blind design, 48 healthy volunteers were randomly allocated to receive alcohol of 0.4 or 0.8 g/kg or a matched placebo drink. A stressful film was viewed post-drink. Skin conductance was monitored throughout and mood and dissociative symptoms were indexed. Volunteers recorded their spontaneous memories of the film daily in an online diary over the following week. Their explicit memory for both gist and details of the film was tested on day 7.

RESULTS

Intriguingly, an inverted 'U' alcohol dose-response was observed on intrusive memories with a low dose of alcohol increasing memory intrusions while a high dose decreased intrusions. In contrast, explicit memory performance after 7 days showed a linear dose-response effect of alcohol with both recall and recognition decreasing as dose increased.

CONCLUSIONS

These findings highlight a striking differential pattern of alcohol's effects on spontaneous memories as compared with explicit memories. Alcohol's effect on spontaneous memories may reflect a dose-dependent impairment of two separate memory systems integral to the processing of different aspects of a traumatic event.

Effects of ethanol on encoding, consolidation, and expression of extinction following contextual fear conditioning

Studies of contextual fear conditioning have found that ethanol administered prior to a conditioning session impairs the conditioned freezing response during a test session the next day. The present experiments examined the effects of ethanol on extinction, the loss of conditioned responding that occurs as the animal learns that a previously conditioned context no longer signals shock. Ethanol (1.5 g/kg) administered prior to single (Experiment 1) or multiple (Experiment 2) extinction sessions impaired extinction. Ethanol administered prior to a test session disrupted the expression of freezing after extinction (Experiments 3-5). There was some evidence that ethanol served as an internal stimulus signaling the operation of conditioning or extinction contingencies (Experiments 4-5). In Experiment 6, postsession injections of 1.5 g/kg ethanol had no effect on extinction with brief (3 min) or long (24 min) exposures to the context, but injections of 3 g/kg after long exposures impaired extinction. Together, these results indicate that ethanol affects extinction by acting on multiple learning and performance processes, including attention, memory encoding, and memory expression.

Paradoxical facilitatory effect of low-dose alcohol consumption on memory mediated by NMDA receptors

Epidemiological studies have suggested a negative correlation between alcohol intake and Alzheimer's disease. In vitro, ethanol negatively modulates NMDA receptor function. We hypothesized that chronic moderate alcohol intake leads to improved memory via adaptive responses in the expression of NMDA receptors and downstream signaling. We fed liquid diets containing no, moderate, or high amounts of ethanol to control and matched rats with hippocampal knock-down of the NR1 subunit. Rats with increased hippocampal NR1 expression were also generated to determine whether they had a phenotype similar to that of ethanol-fed animals. We found that moderate ethanol intake improved memory, increased NR1 expression, and changed some aspects of neurotrophin signaling. NR1 knock-down prevented ethanol's facilitatory effects, whereas hippocampal NR1 overexpression mimicked the effect of chronic low-dose ethanol intake on memory. In contrast, high-dose ethanol reduced neurogenesis, inhibited NR2B expression, and impaired visual memory. In conclusion, adaptive changes in hippocampal NMDA receptor expression may contribute to the positive effects of ethanol on cognition.

Intact Preference Conditioning in Acute Intoxication Despite Deficient Declarative Knowledge and Working Memory

BACKGROUND

The impact of alcohol on implicit, emotional learning is not well understood, partly because family history, drug use, and task demands influence these processes. The conditioned pattern preference (CPP) task provides a more ecologically valid means to investigate implicit cognition in the lab because it has low demand awareness and relies on learning to associate nonverbal cues with reward.

METHODS

This study examined the effects of acute alcohol intoxication on implicit learning using the CPP task in 83 intoxicated and 69 sober young adults. Information on individual drug use, family history, impulsivity, and alcohol expectancies was also collected.

RESULTS

Alcohol intoxication affected explicit, but not implicit learning on the CPP task. In addition, participants who reported a positive family history of addiction (FH+) or individual recreational drug use did not exhibit a preference for cues previously paired with reward.

CONCLUSIONS

Preference formation on the CPP task recruits motivational neurocircuitry, an effect that is unaltered by alcohol. Group differences in implicit emotional learning on this task may represent neurocognitive differences in individuals at risk for addiction.

The effect of alcohol and repetition at encoding on implicit and explicit false memories

RATIONALE

Alcohol impairs explicit memory, whilst leaving implicit memory relatively intact. Less is known about its effects on false memories.

AIM

The present study examines the effects of alcohol on explicit and implicit false memories using study list repetition as a tool for modulating learning at encoding.

METHODS

Thirty-two participants were given either an alcohol (0.6 g/kg) or placebo beverage before undergoing an encoding phase consisting of 10 lists of nine associated words (veridical items). Each list was associated to a word, which was not presented at encoding (semantically associated non-studied lure; critical item), serving as the measure for false memory. Half of the lists were presented once, and half were repeated three times. The next day, participants underwent an implicit (stem completion and post hoc awareness measurements), and an explicit (free recall) task.

RESULTS

Alcohol decreased veridical and false explicit memory for singularly presented lists compared to placebo; no group difference existed for repeated lists. Implicit veridical memory was not affected by alcohol. Awareness memory measures demonstrated in placebo participants an increased ability with repetition in rejecting false memories. The reverse was found in intoxicated participants who with repetition accepted more false memories.

CONCLUSION

Alcohol appears to decrease semantic activation leading to a decline in false memories. Increased learning with repetition, which increases the rejection of false memories under placebo, is reversed under alcohol leading to a decrease in rejection of false memories. The latter effect of alcohol may be due to its ability to impair monitoring processes established at encoding.

Brain catalase mediates potentiation of social recognition memory produced by ethanol in mice

The involvement of catalase in ethanol-induced locomotion has been clearly proven. However, studies addressing the role of this enzyme in the effects that ethanol exerts on memory are lacking. In the present study, the social recognition test (SRT) was used to evaluate ethanol effects on memory. In this test, the reduction in investigation time of a juvenile conspecific, when this social stimulus is presented for the second time, is considered a reliable index of memory. Exploration ratios (ER) were calculated to evaluate the recognition capacity of mice. Ethanol (0.0, 0.5, 1.0 or 1.5g/kg, i.p.) was administered immediately after the first juvenile presentation, and 2h later the juvenile was re-exposed to the adult. Additionally, adult mice received aminotriazole (AT) or sodium azide (two catalase inhibitors) 5h or 30 min before juvenile presentation, respectively. Ethanol (1.0 and 1.5g/kg) was able to reduce ER, indicating an improving effect on memory. This improvement was prevented by either AT or sodium azide pre-treatment. However, neither AT nor sodium azide attenuated the memory-enhancing capacity of NMDA or nicotine, suggesting a specific interaction between catalase inhibitors and ethanol in their effects on memory. The present results suggest that brain catalase activity could mediate the memory-enhancing capacity of ethanol and add further support to the idea that this enzyme mediates some of the psychopharmacological effects produced by ethanol.