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

Hazy memories in the courtroom: A review of alcohol and other drug effects on false memory and suggestibility

Alcohol and other psychoactive drugs are oftentimes implicated in legal cases. A pertinent question herein is whether such substances might adversely affect testimonies of victims, eyewitnesses, or suspects by propelling the formation of false memory and increasing susceptibility to suggestion. In the current review, we amassed all available evidence on the effects of intoxication on false memory formation and suggestibility, including the substances alcohol, benzodiazepines, cannabis, stimulants, hallucinogens, and antipsychotics. Our review indicated that alcohol and cannabis under certain conditions increased the susceptibility to false memories and/or suggestion with effect sizes ranging from medium to large. When intoxicated during an event, alcohol is most likely to increase this susceptibility at high intoxication levels or after a delay, whereas cannabis exerts detrimental effects during acute intoxication but not necessarily once sober. For other substances, ecologically valid research separating different memory phases is needed. Overall, differences between substances regarding false memory effects exist, suggesting that a nuanced approach is needed when dealing with intoxicated individuals in a legal context.

Improving intoxicated witness recall with the Enhanced Cognitive Interview

RATIONALE

Witnesses and victims typically provide the central leads in police investigations, yet statistics from past research indicates in many instances these individuals are intoxicated.

OBJECTIVES

To date, however, no research has looked at how best to interview such witnesses to maximise the amount of accurate information they recall.

METHODS

In the present research, whilst on a night out, participants watched a videoed theft whilst either sober or moderately (MBAC = 0.05%) or severely (MBAC = 0.14%) intoxicated. A week later, in a different location, participants were interviewed using either the Enhanced Cognitive (ECI) or Structured Interview.

RESULTS

The ECI was found to improve the recall accuracy and completeness of witness accounts across all three drinking conditions. However, no significant interaction was indicated between alcohol and interview condition.

CONCLUSIONS

The study findings are discussed in terms of their real-world value in aiding police officers to elicit as complete and as accurate an account as possible from intoxicated witnesses.

Autobiographical memory compromise in individuals with alcohol use disorders: Towards implications for psychotherapy research

It has been found that Autobiographical memory (i.e., memory for personal experiences and facts about the self) are not properly maintained in people with alcohol-use disorders (AUD). The present paper offers a comprehensive overview of findings regarding the consequences of AUD on autobiographical memory. More specifically, we offer a theoretical model (the AMAUD Autobiographical Memory and Alcohol Use Disorders model) according to which chronic alcohol consumption compromises emotion regulation as well as executive control, which maintains the construction of autobiographical memory. Compromises in emotional regulation and executive functioning can be linked to a weak aspiration to construct detailed memories (i.e., autobiographical overgenerality), compromises of subjective reliving, anterograde amnesia, negative self-defining memories, and a difficulty to mentally project oneself forward in time to generate complex autobiographical representations and self-images. By gathering cognitive and clinical aspects of autobiographical decline in AUD, this model constitutes a theoretical foundation that may lead to a better understanding of this decline. Different clinical perspectives are proposed for developing personalized autobiographical memory rehabilitation programs for individuals with AUD.

Acute alcohol effects on explicit and implicit motivation to drink alcohol in socially drinking adolescents

Alcohol-related cues can evoke explicit and implicit motivation to drink alcohol. Concerning the links between explicit and implicit motivation, there are mixed findings. Therefore, we investigated both concepts in 51 healthy 18- to 19-year-old males, who are less affected by neuropsychological deficits in decision-making that are attributed to previous alcohol exposure than older participants. In a randomized crossover design, adolescents were infused with either alcohol or placebo. Self-ratings of alcohol desire, thirst, well-being and alcohol effects comprised our explicit measures of motivation. To measure implicit motivation, we used money and drink stimuli in a Pavlovian conditioning (Pc) task and an Approach-Avoidance Task (AAT). Alcohol administration increased explicit motivation to drink alcohol, reduced Pc choices of alcoholic drink-conditioned stimuli, but had no effect on the AAT. This combination of results might be explained by differences between goal-directed and habitual behavior or a temporary reduction in rewarding outcome expectancies. Further, there was no association between our measures of motivation to drink alcohol, indicating that both self-reported motivation to drink and implicit approach tendencies may independently contribute to adolescents' actual alcohol intake. Correlations between Alcohol Use Disorders Identification Test (AUDIT) scores and our measures of motivation to drink alcohol suggest that interventions should target high-risk adolescents after alcohol intake. Clinical trials: Project 4: Acute Effects of Alcohol on Learning and Habitization in Healthy Young Adults (LeAD_P4); NCT01858818; https://clinicaltrials.gov/ct2/show/NCT01858818.

Autobiographical Memory Deficits in Alcohol-Dependent Patients with Short- and Long-Term Abstinence

BACKGROUND

Autobiographical memory (AM) enables the storage and retrieval of life experiences that allow individuals to build their sense of identity. Several AM impairments have been described in patients with alcohol abuse disorders without assessing whether such deficits can be recovered. This cross-sectional study aimed to identify whether the semantic (SAM) and episodic (EAM) dimensions of AM are affected in individuals with alcohol dependence after short-term abstinence (STA) or long-term abstinence (LTA). A second aim of this study was to examine the factors that could disrupt the efficiency of semantic and episodic AM (the impact of depression severity, cognitive functions, recent or early traumatic events, and drinking history variables).

METHODS

After clinical and cognitive evaluations (alcohol consumption, depression, anxiety, IQ, memory performance), AM was assessed with the Autobiographical Memory Interview in patients with recent (between 4 and 6 weeks) and longer (at least 6 months) abstinence. Participants were asked to retrieve the number and nature of traumatic or painful life experiences in recent or early life periods (using the Childhood Traumatic Events Scale).

RESULTS

The 2 abstinent groups had lower global EAM and SAM scores than the control group. These scores were comparable for both abstinent groups. For childhood events, no significant differences were observed in SAM for both groups compared with control participants. For early adulthood and recent events, both STA and LTA groups had lower scores on both SAM and EAM. Moreover, there was a negative correlation between the length of substance consumption and SAM scores.

CONCLUSIONS

This study highlighted a specific AM disorder in both episodic and semantic dimensions. These deficits remained after 6 months of abstinence. This AM impairment may be explained by compromised encoding and consolidation of memories during bouts of drinking.

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.

Relations Between Cognitive Abilities, Drinking Characteristics, and Emotional Recognition in Alcohol Dependence: A Preliminary Exploration

BACKGROUND

Alcohol dependence is characterized by wide-ranging cognitive impairments, but also by emotional facial expressions (EFEs) recognition deficits. Although they play a crucial role both in the development and in the maintenance of the disease, cognitive and emotional disorders have up to now been mostly explored separately. As a result, not much is known regarding their interactions. This study thus aims at exploring the relations between cognition and emotion in alcohol dependence, and more specifically between cognitive performance, drinking characteristics, and EFE recognition.

METHODS

About 26 recently detoxified alcohol-dependent individuals and 26 matched controls were tested for cognitive abilities (by means of a standardized neuropsychological battery) and for EFE recognition.

RESULTS

Alcohol-dependent individuals simultaneously presented altered performances for executive abilities and EFE recognition (particularly for disgust recognition). Moreover, a regression analysis showed that EFE performance was centrally related to episodic memory and cognitive flexibility.

CONCLUSIONS

These results clarify the relations between EFE recognition, cognitive abilities, and drinking characteristics in alcohol dependence and clearly suggest that cognitive factors should be taken into account in future studies exploring emotional processes in alcohol dependence. Specific cognitive programs should be developed to rehabilitate cognitive and emotional abilities simultaneously.

Inert gas narcosis disrupts encoding but not retrieval of long term memory

Exposure to increased ambient pressure causes inert gas narcosis of which one symptom is long-term memory (LTM) impairment. Narcosis is posited to impair LTM by disrupting information encoding, retrieval (self-guided search), or both. The effect of narcosis on the encoding and retrieval of LTM was investigated by testing the effect of learning-recall pressure and levels of processing (LoP) on the free-recall of word lists in divers underwater. All participants (n=60) took part in four conditions in which words were learnt and then recalled at either low pressure (1.4-1.9atm/4-9msw) or high pressure (4.4-5.0atm/34-40msw), as manipulated by changes in depth underwater: low-low (LL), low-high(LH), high-high (HH), and high-low (HL). In addition, participants were assigned to either a deep or shallow processing condition, using LoP methodology. Free-recall memory ability was significantly impaired only when words were initially learned at high pressure (HH & HL conditions). When words were learned at low pressure and then recalled at low pressure (LL condition) or high pressure (LH condition) free-recall was not impaired. Although numerically superior in several conditions, deeper processing failed to significantly improve free-recall ability in any of the learning-recall conditions. This pattern of results support the hypothesis that narcosis disrupts encoding of information into LTM, while retrieval appears to be unaffected. These findings are discussed in relation to similar effects reported by some memory impairing drugs and the practical implications for workers in pressurised environments.

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.

Event-Related Theta Power during Lexical-Semantic Retrieval and Decision Conflict is Modulated by Alcohol Intoxication: Anatomically Constrained MEG

Language processing is commonly characterized by an event-related increase in theta power (4-7 Hz) in scalp EEG. Oscillatory brain dynamics underlying alcohol's effects on language are poorly understood despite impairments on verbal tasks. To investigate how moderate alcohol intoxication modulates event-related theta activity during visual word processing, healthy social drinkers (N = 22, 11 females) participated in both alcohol (0.6 g/kg ethanol for men, 0.55 g/kg for women) and placebo conditions in a counterbalanced design. They performed a double-duty lexical decision task as they detected real words among non-words. An additional requirement to respond to all real words that also referred to animals induced response conflict. High density whole-head MEG signals and midline scalp EEG data were decomposed for each trial with Morlet wavelets. Each person's reconstructed cortical surface was used to constrain noise-normalized distributed minimum norm inverse solutions for theta frequencies. Alcohol intoxication increased reaction time and marginally affected accuracy. The overall spatio-temporal pattern is consistent with the left-lateralized fronto-temporal activation observed in language studies applying time-domain analysis. Event-related theta power was sensitive to the two functions manipulated by the task. First, theta estimated to the left-lateralized fronto-temporal areas reflected lexical-semantic retrieval, indicating that this measure is well suited for investigating the neural basis of language functions. While alcohol attenuated theta power overall, it was particularly deleterious to semantic retrieval since it reduced theta to real words but not pseudowords. Second, a highly overlapping prefrontal network comprising lateral prefrontal and anterior cingulate cortex was sensitive to decision conflict and was also affected by intoxication, in agreement with previous studies indicating that executive functions are especially vulnerable to alcohol intoxication.

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.

fMRI BOLD response of high-risk college students (Part 2): during memory priming of alcohol, marijuana and polydrug picture cues

AIMS

This study examined brain activity using functional magnetic resonance imaging (fMRI) and reaction time (RT) during an implicit repetition priming memory task involving alcohol, polydrug, marijuana and emotional picture cues.

METHODS

Participants were 5 male and 5 female high-risk college students who had just participated in a cue exposure study (Ray et al., this issue). fMRI and RT data were collected while participants made decisions about previously seen and new picture cues.

RESULTS

Both behavioral RT and brain imaging data revealed strong memory priming for drug and alcohol cues. Neurologically, a repetition priming effect (suppression in neural activity for repeated cues) was observed in response to alcohol cues in the left prefrontal, bilateral occipital, and bilateral occipitotemporal regions, as well as right insula and right precuneus (Z ranged from 3.03 to 3.31 P < 0.05). Polydrug cues elicited priming in the occipital and temporal areas, and marijuana cues in the occipital area.

CONCLUSIONS

Prefrontal and insular cortex involvement both in reactivity to alcohol cues (Ray et al., this issue) and subsequent implicit memory processing of these cues, as found in this study, suggests their potential role in the maintenance of high-risk alcohol use behaviors.

Gender differences in acute alcohol effects on self-regulation of arousal in response to emotional and alcohol-related picture cues

Basic mechanisms through which men and women self-regulate arousal have received little attention in human experimental addiction research, although stress-response-dampening and craving theories suggest an important role of emotional arousal in motivating alcohol use. This study examined gender differences in the effects of acute alcohol intoxication on psychophysiological and self-reported arousal in response to emotionally negative, positive, and neutral, and alcohol-related, picture cues. Thirty-six social drinkers (16 women) were randomly assigned to an alcohol, placebo, or control beverage group and exposed to picture cues every 10 s (0.1 Hz presentation frequency). Psychophysiological arousal was assessed via a 0.1-Hz heart rate variability (HRV) index. A statistically significant beverage group-by-gender interaction effect on psychophysiological, but not self-reported, arousal was found. The 0.1-Hz HRV responses to picture cues were suppressed by alcohol only in men. This gender-specific suppression pattern did not differ significantly across picture cue types. There were no significant gender differences in the placebo or control group. Greater dampening of arousal by alcohol intoxication in men, compared with women, may contribute to men's greater tendency to use alcohol to cope with stress.

The effects of energy drinks alone and with alcohol on neuropsychological functioning

OBJECTIVE

Caffeinated energy drinks-alone or with alcohol-are heavily marketed to young adults, many of whom believe that caffeine counteracts some negative effects of alcohol intoxication. While the effects of caffeine and alcohol have been widely investigated, few studies have examined neuropsychological performance after consumption of a beverage containing both ingredients.

METHODS

In a double-blind, placebo-controlled design, 27 non-caffeine-deprived female participants were randomly assigned to consume a caffeinated energy drink alone, one containing alcohol, or a non-alcoholic, non-caffeinated control beverage. Pre- and post-test assessments were conducted using alternate forms of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS).

RESULTS

Participants who consumed the energy drink plus alcohol evidenced significantly lower post-test performance on a global score of neuropsychological status. Specifically, deficits were found in both visuospatial/constructional and language performance scores. While participants who consumed the caffeinated beverage alone trended toward improved attention scores, neuropsychological status did not show meaningful changes from the pre- to post-test.

CONCLUSIONS

Consumption of an energy drink containing 6% alcohol by volume negatively influenced performance on a global measure of cognitive functioning.

Acute alcohol effects on repetition priming and word recognition memory with equivalent memory cues

Acute alcohol intoxication effects on memory were examined using a recollection-based word recognition memory task and a repetition priming task of memory for the same information without explicit reference to the study context. Memory cues were equivalent across tasks; encoding was manipulated by varying the frequency of occurrence (FOC) of words in the study lists. Twenty-two female and male social drinkers (age 21-24 years) completed equivalent versions of the memory tasks in two counterbalanced sessions (alcohol challenge, no-alcohol). Alcohol and the FOC manipulation affected recollection-based memory processing, but not repetition priming. Results supported alcohol's dissociative effects on memory systems.

Memory encoding and retrieval on the ascending and descending limbs of the blood alcohol concentration curve

RATIONALE

Little is known about acute effects of alcohol on memory encoding and retrieval on different limbs (ascending and descending) of the blood alcohol concentration (BAC) curve.

OBJECTIVES

This extensive experiment was designed to examine alcohol's effects on memory encoding and retrieval throughout a protracted drinking episode.

METHODS

In a 9-h session, male participants consumed either alcohol (1 ml/kg) or placebo (n = 32/32) over a period of 90 min and learned various materials in different memory tasks before, during, and after consuming the drinks, while their BAC levels were monitored. A week later, in a similar session, they were tested on learned materials before, during, and after drinking. Mood was assessed throughout both sessions.

RESULTS

Alcohol impaired recall of words more than recognition, and cued recall most severely. Perceptual priming and picture recognition were not affected by alcohol. Alcohol impaired encoding in cued recall, recognition of completed word fragments, and free recall regardless of limb, but impaired retrieval in word recognition only during the ascending BAC. Alcohol increased negative mood on the descending limb during the first session, and on the ascending limb during the second session.

CONCLUSIONS

Under naturalistic drinking conditions, alcohol's effects on memory depend on task, memory process, and limb of the BAC curve. The differential effects of alcohol on retrieval during the ascending and descending limbs demonstrate the importance of examining the differential effects on the two limbs.