Retrograde enhancement by alcohol of delayed free recall performance

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.

Acute and residual mood and cognitive performance of young adults following smoked cannabis

OBJECTIVES

To examine acute and residual mood and cognitive performance in young adult regular cannabis users following smoked cannabis.

METHODS

Ninety-one healthy young adults completed this double-blind, placebo-controlled, parallel-groups study. Participants were randomized to receive active (12.5% THC) or placebo cannabis with a 2:1 allocation ratio, and mood [Profile of Mood States (POMS)] and cognitive performance [Hopkins Verbal Learning Test - Revised (HVLT-R), Digit Symbol Substitution Test (DSST), Continuous Performance Test (CPT), grooved pegboard (GPB)] were assessed before and 1, 24, and 48 (h) after smoking cannabis ad libitum. High and Low THC groups were based on blood THC concentrations.

RESULTS

One hour after smoking cannabis, compared to Placebo, in both the High and Low THC groups, there were increases in POMS Arousal and Positive Mood, and in the High THC group only, increases in Confusion, Friendliness, and Elation, and a decrease in Fatigue. Increases in Friendliness and Elation in the High THC group remained significant for 24 h. The only significant acute effect of cannabis on cognition was a decrease in the percent of words retained in the HVLT-R in the High THC group compared to Placebo (mean difference = 15.8%, 95% CI = 3.6-28.0%, p = 0.006). Unexpectedly, compared to Placebo, both the High and Low THC groups improved in DSST performance at 48 h (p ≤ 0.016).

CONCLUSIONS

Under the present experimental conditions, in young regular cannabis users, smoking cannabis ad libitum had significant effects on mood, some of which persisted 24 h later, yet minimal effects on cognition, and no evidence of residual cognitive impairment.

Improved memory for information learnt before alcohol use in social drinkers tested in a naturalistic setting

Alcohol is known to facilitate memory if given after learning information in the laboratory; we aimed to investigate whether this effect can be found when alcohol is consumed in a naturalistic setting. Eighty-eight social drinkers were randomly allocated to either an alcohol self-dosing or a sober condition. The study assessed both retrograde facilitation and alcohol induced memory impairment using two independent tasks. In the retrograde task, participants learnt information in their own homes, and then consumed alcohol ad libitum. Participants then undertook an anterograde memory task of alcohol impairment when intoxicated. Both memory tasks were completed again the following day. Mean amount of alcohol consumed was 82.59 grams over the evening. For the retrograde task, as predicted, both conditions exhibited similar performance on the memory task immediately following learning (before intoxication) yet performance was better when tested the morning after encoding in the alcohol condition only. The anterograde task did not reveal significant differences in memory performance post-drinking. Units of alcohol drunk were positively correlated with the amount of retrograde facilitation the following morning. These findings demonstrate the retrograde facilitation effect in a naturalistic setting, and found it to be related to the self-administered grams of alcohol.

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.

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.

The influence of blood alcohol concentrations of around 0.03% on neuropsychological functions--a double-blind, placebo-controlled investigation

There is a general agreement that blood alcohol concentrations (BACs) of about 0.05% result in impairment of the ability to drive. This fact has been supported by means of experiments. In addition, there are only a few studies to date investigating low BACs. The present study aims to investigate the extent and quality of cognitive changes in low BACs of around 0.03%. Sixteen healthy male subjects were examined in a double-blind, placebo-controlled study. During the trials the BAC was regulated to about 0.03%. As part of the study a record was made of the general level of intelligence, subjective impairments, possible depressive symptoms, general ability to perform, vigilance, divided attention, response times and performance of memory. Statistical analysis took place using the two-period crossover design. Verbal intelligence, general performance, vigilance (optical stimuli), divided attention, vigilance towards acoustic stimuli and the general response time to acoustic and visual-acoustic sequential stimuli, and memory were not impaired significantly by a BAC of around 0.03%. The total response and motor response time to optical stimuli as well as decision time about sequential optical stimuli were, however, significantly changed for BACs of around 0.03%. In conclusion, the present results show that already in BACs of around 0.03%, particular cognitive functions which rely on perception and processing of visual information, are significantly impaired. This was evident in the more complex and urgent tasks.

Alcohol's dissociation of implicit and explicit memory processes: implications of a parallel distributed processing model of semantic priming

Alcohol's dissociation of implicit (unintentional) and explicit (intentional) memory processes in social drinkers was examined. It was hypothesized that an alcohol challenge would lower the percentage of words recalled and result in more retroactive interference in explicit recall tasks but would not lengthen reaction time in an implicit semantic priming task involving highly semantically similar words. Men and women completed all memory tasks in each of 2 counterbalanced sessions (alcohol challenge vs. no-alcohol) separated by 1 week. Alcohol significantly degraded processing in both explicit memory tasks, yet implicit semantic priming remained intact. A parallel distributed processing model that simulates semantic memory is presented. When this system is strongly activated, it does not appear to be altered during moderate alcohol intoxication.

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

Alcohol has been shown to have both impairing and facilitating effects on memory, depending on the sequencing of learning and ingestion of the drug. Its effects on memory for emotional material, however, have not been shown reliably. The current experiment sought to investigate the effects of alcohol on later recall of emotional and neutral events experienced before and after alcohol drinking. Using an incidental-learning paradigm, alcohol (0.65 g/kg) or placebo was administered in a double-blind randomized design to 34 participants, between two learning phases in which they viewed and rated positive, negative and neutral images. The drug's effects on memory were assessed in a surprise test of free recall. In addition, impact of alcohol on ratings of mood states, and of valence and arousal that the pictures evoked, was examined. Alcohol facilitated memory for material seen before, and impaired memory for material seen after, its administration. Furthermore, under alcohol, emotional images in the first set were more recalled over neutral than in the second set, indicating a higher retrograde facilitation for emotional than for neutral material. Alcohol improved positive mood states but had no effect on negative mood states. Evaluation of pictures with regard to valence showed an increase of the ratings for the positive and neutral images after alcohol and a decrease after placebo. No drug effects were found for arousal ratings. Whether a picture was likely to be remembered or not (tested only for set 2) was dependent on the intensity of the arousal but not of the valence that the picture evoked in the participants. Pictures that were rated high in arousal were also remembered better, and this effect was irrespective of alcohol or placebo ingestion. These data have shown that alcohol elicits retrograde facilitation and anterograde impairment for emotional materials. Furthermore, these data demonstrate that alcohol selectively facilitates memories for emotional events experienced before administration, and suggest a possible explanation for the reinforcing effects of drinking.

The Psychology and Neuroscience of Forgetting

Traditional theories of forgetting are wedded to the notion that cue-overload interference procedures (often involving the A-B, A-C list-learning paradigm) capture the most important elements of forgetting in everyday life. However, findings from a century of work in psychology, psychopharmacology, and neuroscience converge on the notion that such procedures may pertain mainly to forgetting in the laboratory and that everyday forgetting is attributable to an altogether different form of interference. According to this idea, recently formed memories that have not yet had a chance to consolidate are vulnerable to the interfering force of mental activity and memory formation (even if the interfering activity is not similar to the previously learned material). This account helps to explain why sleep, alcohol, and benzodiazepines all improve memory for a recently learned list, and it is consistent with recent work on the variables that affect the induction and maintenance of long-term potentiation in the hippocampus.

Effects of post-training ethanol and group housing upon memory of an appetitive task in mice

It has been shown that post-training ethanol's facilitating effects upon memory disappeared if the mice were kept isolated after training. Since ethanol-treated mice were attacked by their cagemates, it has been hypothesized that the improved retention induced by ethanol resulted from an interaction between ethanol and group housing which added aversive information to training. To investigate the correctness of this interpretation, ethanol effects upon memory of an appetitive task were studied. C57BL/6J mice (isolated the day before training) were individually trained to find a cheese pellet placed in a corner of an open-field. Mice were injected intraperitoneally immediately after training with saline, 0.5, 1.5, or 2.0 g/kg of ethanol. They were then returned to their home cage and left alone, with another mouse, or with five other mice for 2 h after training. All mice were tested 24 h later for retention. Reductions in the number of pellet approaches or in the latency to eat the pellet were taken as measures of learning. Post-training ethanol disrupted retention of the appetitive task in a dose-related manner. Moreover disruption was greater in mice group housed after training. The results support the hypothesis that ethanol's post-training facilitating effects upon aversive memory may be due to added aversive information to the stimulus complex, rather than, or in addition, to enhanced storage of memory traces.

Effects of alcohol and white noise on recall of relevant and irrelevant task components

This study examined the effects of arousal, induced by alcohol and white noise, on the free recall of intentionally learned words and incidentally learned word-locations, in the presence or absence of word-order cues. The Activation-Deactivation Adjective Check List, a self-report measure of arousal showed that noise affected the tension dimension of arousal, whereas the moderate alcohol dose primarily affected the energy dimension of arousal. That the low dose exerted an arousing effect was evidenced by an increase in tension but only when combined with noise. When word-order was randomized over trials, noise improved word-recall and counteracted the deleterious effect of the moderate alcohol dose. When order remained fixed, however, the moderate dose impaired recall, and at that dose recall was worse under noise. Location-recall was impaired by the moderate dose, and it was superior when word-order remained fixed. It was concluded that recall was influenced by arousal mechanisms and that perceived task demand and consequent effort were possible factors contributing to the obtained effects.

Benzodiazepine receptor ligands: tools for memory research in clinical pharmacology

In order to study the time course of amnesic effects of the benzodiazepine hypnotic lormetazepam, and their reversal by the benzodiazepine antagonist Ro 15-1788, a combined visual and auditory memory test was developed, which was designed to allow repeated assessments. Immediate recall as well as delayed free recall and recognition (1 h after drug) were investigated before and after intravenous lormetazepam (0.02 mg/kg) followed 15 min later by intravenous Ro 15-1788 (0.03 mg/kg) or placebo. A third group received placebo followed by Ro 15-1788. Results are based on ten subjects per treatment group and are compared with an age-matched control population (n = 20) without treatment. Immediate and delayed recall as well as recognition in both visual and auditory tests were impaired abruptly after intravenous lormetazepam. These effects were reversed instantaneously after Ro 15-1788, which had no marked effect on these parameters when given alone. Ratings by visual analog scales (1 h after drug administration) indicated concomitant sedation and impaired concentration after lormetazepam, which was attenuated by Ro 15-1788. By itself, Ro 15-1788 had no effect on these measures. Interestingly, the performance in delayed free recall of the visual memory test was significantly enhanced in the lormetazepam group prior to administration. Our results suggest that impaired acquisition of new information after lormetazepam is benzodiazepine receptor mediated and may be associated with a drug-induced enhancement of retrieval of information acquired before lormetazepam administration.

Post-learning ethanol effects on a water-finding task in rats

Ethanol's post-training facilitation of memory was examined using a latent learning paradigm known as the "water-finding task." Rats were assigned to one of two ethanol groups (E0.75 g/kg or E1.5 g/kg) or to a control group (saline) and individually placed in a novel open field containing a drinking tube. Following this exposure, subjects were immediately administered intraperitoneal (IP) injections of either the saline or ethanol and 48 hours later, re-introduced to the field. Initial latencies to contact the tube each time were recorded. A linear regression analysis of trial 2 latencies regressed onto trial 1 latencies indicated a statistically significant effect of ethanol on the relation between initial and subsequent latencies. Though the control rats' trial 2 latencies were completely random with respect to their previous speeds (rSAL = -0.07), the ethanol rats' trial 2 latencies were positively correlated with initial speeds (rE0.75 = 0.35, rE1.5 = 0.67). These results suggest that under conditions of post-training ethanol, trial 2 behavior is more similar to, or controlled by, trial 1 behavior and are consistent with the argument that, under certain training and testing contexts, ethanol can come to exert control over a response's recurrence.

The amnesic action of benzodiazepines in man

A qualitative description of the amnesia produced by the benzodiazepines in man is presented. The benzodiazepines exert their greatest effects in tests of long-term episodic memory in which they cause a dose-related impairment in the acquisition of new information, do not appear to affect retention and may facilitate retrieval. Benzodiazepines do not appear to impair semantic memory or the acquisition of skills. Although state-dependent learning may be observed with benzodiazepine treatment it is a small effect and cannot account for most of the observed impairments. The amnesia appears to be characteristic of all benzodiazepines and may be related to the sedative action of these compounds but evidence on the latter point is inconclusive. The importance of the amnesic action in a population of clinically anxious outpatients taking benzodiazepines over an extended period remains to be investigated. The benzodiazepines may provide the cognitive psychologist with a useful tool to investigate the mechanisms of normal memory.