Frontal deficits in alcoholism: An ERP study

Eye Tracking Studies Exploring Cognitive and Affective Processes among Alcohol Drinkers: a Systematic Review and Perspectives

Acute alcohol intoxication and alcohol use disorders are characterized by a wide range of psychological and cerebral impairments, which have been widely explored using neuropsychological and neuroscientific techniques. Eye tracking has recently emerged as an innovative tool to renew this exploration, as eye movements offer complementary information on the processes underlying perceptive, attentional, memory or executive abilities. Building on this, the present systematic and critical literature review provides a comprehensive overview of eye tracking studies exploring cognitive and affective processes among alcohol drinkers. Using PRISMA guidelines, 36 papers that measured eye movements among alcohol drinkers were extracted from three databases (PsycINFO, PubMed, Scopus). They were assessed for methodological quality using a standardized procedure, and categorized based on the main cognitive function measured, namely perceptive abilities, attentional bias, executive function, emotion and prevention/intervention. Eye tracking indexes showed that alcohol-related disorders are related to: (1) a stable pattern of basic eye movement impairments, particularly during alcohol intoxication; (2) a robust attentional bias, indexed by increased dwell times for alcohol-related stimuli; (3) a reduced inhibitory control on saccadic movements; (4) an increased pupillary reactivity to visual stimuli, regardless of their emotional content; (5) a limited visual attention to prevention messages. Perspectives for future research are proposed, notably encouraging the exploration of eye movements in severe alcohol use disorders and the establishment of methodological gold standards for eye tracking measures in this field.

A case-comparison study of executive functions in alcohol-dependent adults with maternal history of alcoholism

Introduction

As executive dysfunctions frequently accompany alcohol dependence, we suggest that reports of executive dysfunction in alcoholics are actually due, in some case to a maternal history of alcohol misuse (MHA+). A history of maternal alcohol dependence increases the risk for prenatal alcohol exposure to unborn children. These exposures likely contribute to executive dysfunction in adult alcoholics. To assess this problem, we propose a case-comparison study of alcohol-dependent subjects with and without a MHA.

Methods

Ten alcohol-dependent subjects, with a maternal history of alcoholism (MHA) and paternal history of alcoholism (PHA), were matched with 10 alcohol-dependent people with only a paternal history of alcoholism (PHA). Executive functions (cancellation, Stroop, and trail-making A and B tests) and the presence of a history of three mental disorders (attention deficit hyperactivity disorder, violent behavior while intoxicated, and suicidal behavior) were evaluated in both populations.

Results

Alcohol-dependent subjects with MHA showed a significant alteration in executive functions and significantly more disorders related to these functions than PHA subjects. The major measures of executive functioning deficit are duration on task accomplishment in all tests. Rates of ADHD and suicidality were found to be higher in MHA patients compared to the controls.

Conclusion

A history of MHA, because of the high risk of PAE (in spite of the potential confounding factors such as environment) must be scrupulously documented when evaluating mental and cognitive disorders in a general population of alcoholics to ensure a better identification of these disorders. It would be helpful to replicate the study with more subjects.

Alcohol and nicotine co-Administration during pregnancy and lactation periods alters sensory discrimination of adult NMRI mice offspring

The present study investigated the impacts of alcohol, nicotine, and their co-administration during pregnancy and lactation on sensory information processing including visual, tactile, and auditory discrimination in adult NMRI mice offspring. Pregnant mice were injected with saline or 20% alcohol (3 g/kg), or nicotine (1 mg/kg) or their co-administration alcohol+nicotine, intraperitoneally until the end of lactation. The offspring were separated from their mothers after lactation period on postnatal day (PND) 28. The locomotor activity, novel object recognition-dependent on visual system (NOR-VS), novel texture discrimination- dependent on somatosensory system (NTR-SS), and acoustic startle reflex were evaluated in PND90. The results revealed no statistical significance for locomotor activity of alcohol, nicotine, and co-administration alcohol+nicotine groups compared to the saline group in the open field task. The results, however, showed a significant decline in the ability of novel object discrimination in the nicotine and co-administration alcohol + nicotine groups compared to the saline group (P < 0.05) in the NOR-VS task. In the NTR-SS and acoustic startle reflex tasks, texture discrimination and the prepulse inhibition abilities in the offspring administered with nicotine and alcohol alone were reduced when compared to the saline group. Also, co-administration of alcohol+nicotine groups showed a decline in the aforementioned tests compared to the saline group (P <0.05). Administration of alcohol and nicotine during fetal and postpartum development disrupts sensory processing of inputs of visual, tactile, and auditory systems in adult mice.

Light social drinkers are more distracted by irrelevant information from an induced attentional bias than heavy social drinkers

It is well established that alcoholics and heavy social drinkers show a bias of attention towards alcohol-related items. Previous research suggests that there is a shared foundation of attentional bias, which is linked to attentional control settings. Specifically, attentional bias relates to a persistent selection of a Feature Search Mode which prioritises attentional bias-related information for selection and processing. However, no research has yet examined the effect of pre-existing biases on the development of an additional attentional bias. This paper seeks to discover how pre-existing biases affect the formation of a new, additional attentional bias. Twenty-five heavy and 25 light social drinkers, with and without a pre-existing bias to alcohol-related items, respectively, had an attentional bias towards the colour green induced via an information sheet. They then completed a series of one-shot change detection tasks. In the critical task, green items were present but task-irrelevant. Irrelevant green items caused significantly more interference for light than heavy social drinkers. This somewhat counter intuitive result is likely due to heavy drinkers having more experience in exerting cognitive control over attentional biases, something not previously observed in investigations of the effects of holding an attentional bias. Our findings demonstrate for the first time that an established attentional bias significantly modulates future behaviour.

An event-related potential study of spatial working memory in binge drinking college students

This study used event-related potentials (ERPs) and a modified spatial 2-back task to investigate spatial working memory in binge drinking (BD) college students. Based on the Korean version of the Alcohol Use Disorder Identification Test (AUDIT-K) and Alcohol Use Questionnaire (AUQ) scores, participants were assigned into BD (n = 25) and non-BD (n = 25) groups. The modified spatial 2-back task includes congruent, incongruent, and lure conditions and participants are required to respond as rapidly and accurately as possible to the congruent stimuli but not to the incongruent and lure stimuli. The BD and non-BD groups exhibited comparable performances on the spatial 2-back task but the BD group showed significantly larger P3 amplitudes than the non-BD group. Additionally, the non-BD group showed larger P3 amplitudes in response to the congruent stimuli compared to the incongruent and lure stimuli whereas the P3 amplitudes in the BD group did not differ significantly among the three conditions. These results indicate that the BD individuals exerted greater effort to maintain performance levels comparable to non-BD individuals and that they were less efficient in differentiating or allocating attentional resources between relevant and irrelevant information.

Failure to utilize feedback during explicit decision-making task in alcohol-dependent patients

BACKGROUND

Patients who are diagnosed with alcohol-dependent syndrome (ADS) are shown to have neuropsychological deficits, especially executive function (EF) deficits. Among the EFs, decision-making is one such function which has consistently been shown to be impaired in people who are dependent on alcohol, compared to controls. Decision-making in this population is usually assessed with gambling-type tasks. However, some of these tasks are ambiguous, work on chance factors, rarely match with real-life gambling situations, and/or involve nonconscious mechanisms.

MATERIALS AND METHODS

The current study compared 26 male patients with ADS (P-ADS) with equal number of their nonalcohol-dependent male siblings on sensation seeking and explicit gambling task (EGT). EGT is similar to the Iowa gambling task in administration, but varies from it as it involves a single outcome and provides unambiguous, explicit, and continuous feedback for the participants.

RESULTS AND CONCLUSION

The results did not show any significant relationship between decision-making variables and sensation seeking. However, despite unambiguous, explicit, and continuous feedback, patients showed significantly poor decision-making as compared to the siblings of the P-ADS group. This study throws light on why people who are addicted to alcohol have difficulties in decision-making, despite knowing the adverse effects.

Heritability and molecular-genetic basis of the P3 event-related brain potential: a genome-wide association study

P3 amplitude is a candidate endophenotype for disinhibitory psychopathology, psychosis, and other disorders. The present study is a comprehensive analysis of the behavioral- and molecular-genetic basis of P3 amplitude and a P3 genetic factor score in a large community sample (N = 4,211) of adolescent twins and their parents, genotyped for 527,829 single nucleotide polymorphisms (SNPs). Biometric models indicated that as much as 65% of the variance in each measure was due to additive genes. All SNPs in aggregate accounted for approximately 40% to 50% of the heritable variance. However, analyses of individual SNPs did not yield any significant associations. Analyses of individual genes did not confirm previous associations between P3 amplitude and candidate genes but did yield a novel association with myelin expression factor 2 (MYEF2). Main effects of individual variants may be too small to be detected by GWAS without larger samples.

Binge drinking and cognitive impairment in young people

AIMS AND OBJECTIVES

To investigate the links between the binge pattern of drinking and the development of cognitive impairment in young adults in the UK. To determine from the findings whether cognitive impairment is an additional public health concern manifesting from this form of alcohol misuse and its relevance to nursing practice.

BACKGROUND

Young adults in the UK are participating in binge drinking; a 'harmful' form of alcohol misuse. Morbidity and mortality associated with alcohol misuse is already a public health concern.

DESIGN

Literature review.

METHOD

Multiple database searches were undertaken, which revealed three case-control studies. The studies all investigated the binge pattern of drinking as well as meeting the following inclusion criteria; primary research published from 2005 onwards, used a human sample, participants were aged 18 to 24 and cognitive function was tested.

RESULTS

The quantitative data found cognitive impairment present in young adult binge drinkers, specifically in regions of the frontal lobe, temporal lobe and hippocampus. Individually the studies did not pose strong enough evidence to generalise findings. However, collectively the core findings along with previous studies can validate the link between binge drinking and cognitive impairment.

CONCLUSION

Nurse-led alcohol misuse screening and brief intervention is the most effective public health prevention strategy. It is important for nurses to keep abreast of current evidence to better inform their practice and the information they provide to their service users. This review emphasises the need for nurses to routinely screen young adults and address the associated risk to cognitive function when participating in harmful drinking.

Auditory event-related potentials (P3) and cognitive changes induced by frontal direct current stimulation in alcoholics according to Lesch alcoholism typology

Frontal lobe dysfunction is a hallmark of alcohol dependence. Recent studies have shown that a simple but powerful technique of cortical modulation--transcranial direct current stimulation (tDCS)--can induce significant cognitive changes. We therefore aimed to assess the clinical and electrophysiological (as indexed by P3) effects of tDCS of left dorsolateral prefrontal cortex (DLPFC) in different types of alcoholic patients according to Lesch's typology. We enrolled 49 alcoholic subjects, aged between 18 and 75 yr, during the subacute abstinence period to participate in this study. Subjects underwent event-related potential (ERP) registration of alcohol-related and neutral sounds before, during and after active tDCS (1 mA, 35 cm², during 10 min) or sham procedure in a counterbalanced and randomized order. Frontal assessment battery (FAB) and five items of the Obsessive Compulsive Drinking Scale were applied at the beginning and at the end of each experimental session. ERP analysis showed an increase in the mean amplitude of P3 associated with alcohol-related sounds after tDCS. This effect was not seen for neutral sounds. This change was more pronounced in Lesch IV alcoholics. Secondary exploratory analysis showed a significant improvement of FAB performance after active tDCS compared to sham tDCS in Lesch IV alcoholics only. We showed clinical and electrophysiological evidence of tDCS-induced frontal activity enhancement that was specific for Lesch IV alcoholics. Given that frontal dysfunction may contribute to the loss of control over drinking behaviour, local increase in frontal activity induced by tDCS might have a beneficial clinical impact in the future.

Acute effects of alcohol on the human brain: diffusion tensor imaging study

BACKGROUND AND PURPOSE

DTI can provide information about brain ultrastructure by quantifying water diffusion. Our objective was to assess the value of DTI in detecting the acute effects of alcohol on healthy human brains.

MATERIALS AND METHODS

Sixteen healthy volunteers were studied with conventional MR imaging and DTI before and 0.5, 1, 2, and 3 hours after the initiation of acute alcohol administration. Two DTI parameters, FA and ADC, were measured in the frontal lobe, internal capsule, external capsule, precentral gyrus, postcentral gyrus, thalamus, middle cerebellar peduncle, and brain stem. BrACs were measured at each time point after drinking to estimate BACs.

RESULTS

No abnormalities were found by conventional MR imaging at any time point in all subjects. ADC values of the frontal lobe, thalamus, and middle cerebellar peduncle were significantly reduced, reaching a minimum value at 1 or 2 hours, and FA values of the frontal lobe were significantly increased, reaching a maximal value at 0.5 hour in both doses. BrAC (BAC) was significantly increased to reach a peak at 0.5 hour in both doses and decreased gradually.

CONCLUSIONS

DTI can detect changes in brains after acute alcohol consumption that are not detectable by conventional MR imaging. The frontal lobe, thalamus, and middle cerebellar peduncle are more vulnerable to the effects of acute alcohol consumption. DTI is more effective than BrAC or BAC for the detection of alcohol-induced changes on the human brain.

Delayed transition from ambiguous to risky decision making in alcohol dependence during Iowa Gambling Task

It has been demonstrated that alcohol-dependent patients exhibit decision-making deficits, particularly, hypersensitivity to reward and executive dysfunction. Yet, how the impaired motivational process and executive dysfunction in the patients affect decisions under ambiguity and risk with different degrees of uncertainty is little known. To investigate the neuropsychological origin of the impaired decision making under uncertainty in alcohol dependence, we administered the Iowa Gambling Task (IGT), Game of Dice Task (GDT) and Wisconsin Card Sorting Test (WCST) to 23 alcohol-dependent patients and 21 healthy subjects, and calculated the correlations between the task performances. We found that the patients showed poor performance in all three tasks compared with the healthy subjects. Moreover, correlations between performances on the GDT and the later trials of the IGT were delayed in alcohol-dependent patients when compared with healthy subjects. There is also a significant correlation between performances of earlier trials of the IGT and the WCST in the patients. These findings suggest that executive dysfunction in alcohol-dependent patients hampers appropriate estimation of probability distributions of possible alternatives, leading to a delayed transition from ambiguous to risky conditions in the Iowa Gambling Task.

Chronic alcoholism: insights from neurophysiology

INTRODUCTION

Increasing knowledge of the anatomical structures and cellular processes underlying psychiatric disorders may help bridge the gap between clinical signs and basic physiological processes. Accordingly, considerable insight has been gained in recent years into a common psychiatric condition, i.e., chronic alcoholism.

MATERIAL AND METHODS

We reviewed various physiological parameters that are altered in chronic alcoholic patients compared to healthy individuals--continuous electroencephalogram, oculomotor measures, cognitive event-related potentials and event-related oscillations--to identify links between these physiological parameters, altered cognitive processes and specific clinical symptoms.

RESULTS

Alcoholic patients display: (1) high beta and theta power in the resting electroencephalogram, suggesting hyperarousal of their central nervous system; (2) abnormalities in smooth pursuit eye movements, in saccadic inhibition during antisaccade tasks, and in prepulse inhibition, suggesting disturbed attention modulation and abnormal patterns of prefrontal activation that may stem from the same prefrontal "inhibitory" cortical dysfunction; (3) decreased amplitude for cognitive event-related potentials situated along the continuum of information-processing, suggesting that alcoholism is associated with neurophysiological deficits at the level of the sensory cortex and not only disturbances involving associative cortices and limbic structures; and (4) decreased theta, gamma and delta oscillations, suggesting cognitive disinhibition at a functional level.

DISCUSSION

The heterogeneity of alcoholic disorders in terms of symptomatology, course and outcome is the result of various pathophysiological processes that physiological parameters may help to define. These alterations may be related to precise cognitive processes that could be easily monitored neurophysiologically in order to create more homogeneous subgroups of alcoholic individuals.

The acute effect of low-dose alcohol on working memory during mental arithmetic: II. Changes of nonlinear and linear EEG-complexity in the theta band, heart rate and electrodermal activity

OBJECTIVE AND HYPOTHESIS

Nonlinear and linear methods of EEG-complexity analysis and autonomic measures were used to characterize processes accompanying performance in a mental arithmetic task challenged by low ("social") alcohol doses. It was expected that alcohol in such doses will dampen changes of task-related EEG-synchronization in the theta band, and those of heart rate and electrodermal activity (EDA).

METHODS

In the mental arithmetic task addition and working memory, effort was required. The EEG, ECG and EDA were recorded in 5 conditions: task, placebo-task, low dose-task (0.2 g/kg alcohol), high dose-task (0.4 g/kg alcohol). Omega-complexity and synchronization likelihood (SL) were computed of the theta band of the EEG.

RESULTS

Task-related decrease of the Omega-complexity and increase of the SL was found in the theta frequency band. Following alcohol consumption, these changes did not develop as seen especially for SL in the anterior area, although the significant effects were elicited by task performance. Conspicuous task-evoked increases were observed for ECG and EDA which were even more enhanced by alcohol.

CONCLUSIONS

Task-induced significant changes of the Omega-complexity and that of SL indicate increased synchrony in the theta band, probably corresponding to working memory effort. Both of these measures proved to be sensitive for the effect of low alcohol dose although these alcohol-elicited changes were not statistically significant. Task-induced heart rate and EDA increases were further intensified by alcohol probably indicating its activating effect on these autonomic measures in the dose range studied.

Binge drinking in young adults: Data, definitions, and determinants

Binge drinking is an increasingly important topic in alcohol research, but the field lacks empirical cohesion and definitional precision. The present review summarizes findings and viewpoints from the scientific binge-drinking literature. Epidemiological studies quantify the seriousness of alcohol-related problems arising from binge drinking, with a growing incidence reported in college-age men over the last 2 years. Experimental studies have found neurocognitive deficits for frontal lobe processing and working memory operations in binge-drinking compared with nonbinge alcohol drinkers. The findings are organized with the goals of providing a useful binge-drinking definition in the context of the empirical results. Theoretical implications are discussed on how binge drinking may alter neurophysiological and neurocognitive function.

Prefrontal cortex volumes in adolescents with alcohol use disorders: unique gender effects

BACKGROUND

Adolescents with alcohol use disorders (AUD) have shown smaller prefrontal cortex (PFC) volumes compared with healthy controls; however, differences may have been due to comorbid disorders. This study examined PFC volumes in male and female adolescents with AUD who did not meet criteria for comorbid mood or attention disorders.

METHODS

Participants were adolescents aged 15 to 17 who met criteria for AUD (n = 14), and demographically similar healthy controls (n = 17). Exclusions included any history of a psychiatric or neurologic disorder other than AUD or conduct disorder. Magnetic resonance imaging scans occurred after at least 5 days of abstinence from alcohol or drugs. Overall PFC volumes and white matter PFC volumes were compared between groups.

RESULTS

After controlling for conduct disorder, gender, and intracranial volume, AUD teens demonstrated marginally smaller anterior ventral PFC volumes (p = 0.09) than controls, and significant interactions between group and gender were observed (p < 0.001 to p < 0.03). Compared with same-gender controls, females with AUD demonstrated smaller PFC volumes, while males with AUD had larger PFC volumes. The same pattern was observed for PFC white matter volumes.

CONCLUSIONS

Consistent with adult literature, alcohol use during adolescence is associated with prefrontal volume abnormalities, including white matter differences. However, adolescents with AUD demonstrated gender-specific morphometric patterns. Thus, it is possible that gender may moderate the impact of adolescent alcohol use on prefrontal neurodevelopment, and the neurodevelopmental trajectories of heavy drinking boys and girls should be evaluated separately in longitudinal studies.

P3 components of the event-related potential and marijuana dependence in Southwest California Indians

Native Americans have some of the highest rates of marijuana use and abuse, yet neurobiological measures associated with addiction to marijuana in this population remain unknown. The present investigation evaluated associations between the P350 and P450 components of the event-related potential (ERP) elicited by affective stimuli, and marijuana dependence in a population of Southwest California (SWC) Indian adults. Three hundred and seventeen participants with a mean age of 30 years who were free of major Axis I and psychiatric diagnoses and antisocial personality disorder were categorized as: (1) no marijuana use disorders or other drug dependence diagnoses; (2) marijuana dependence and no other drug dependence diagnoses; and (3) marijuana dependence and other drug dependence diagnoses. ERPs were collected using a facial discrimination task that generated a late positive component with two peaks at approximately P350 and P450 milliseconds. Multivariate analyses of variance was used to detect associations between the two component peaks and the three participant groups taking into consideration age, gender and the presence of a lifetime diagnosis of alcohol dependence. Increases in the latency of both the P350 and P450 component peaks were found to be associated with the diagnosis of marijuana dependence and marijuana dependence co-morbid with other drug dependence. Women appeared to be more impacted than men are. A diagnosis of marijuana dependence was not associated with any changes in late component amplitudes. Taken together these studies suggest that marijuana dependence may be associated with delays in the evaluation and identification of emotional stimuli in SWC Indians.

P3 components and adolescent binge drinking in Southwest California Indians

In adolescence, consuming a large number of drinks over a short interval of time (e.g. binging) is not an uncommon occurrence. Since adolescence is an important neurodevelopmental period, the effect of binge drinking on brain and behavior has become a significant health concern. The present study evaluated event-related potentials (ERPs) in young adult Southwest California Indians who had a history of binge drinking during their adolescence. One hundred twenty five participants who were currently 18-25 yrs of age who were free of Axis I psychiatric diagnoses were categorized as: 1) reporting no binge drinking during adolescence (>5 drinks per occasion before age 18) or drug dependence diagnoses 2) reporting binge drinking during adolescence with no drug dependence diagnoses 3) reporting binge drinking during adolescence and drug dependence diagnoses. ERPs were collected using a facial discrimination task. Adolescent alcohol and drug exposure was found to be associated with decreases in the latency of an early P3 component (P350). Decreases in a later component amplitude (P450) were also found in young adults exposed to alcohol, and those exposed to alcohol and drugs. However, that finding appears to be a combined result of predisposing factors such as family history of alcoholism and presence of other externalizing diagnoses. Taken together these preliminary studies suggests that adolescent binge drinking may result in a decreases in P3 component latencies and amplitudes perhaps reflecting a loss or delay in the development of inhibitory brain systems.

A Ser9Gly polymorphism in the dopamine D3 receptor gene (DRD3) and event-related P300 potentials

An important reason for the interest in P300 event-related potentials are findings in patients with psychiatric disorders like schizophrenia or alcoholism in which attenuations of the P300 amplitude are common findings. The P300 wave has been suggested to be a promising endophenotype for genetic research since attenuations of the amplitude and latency can be observed not only in patients but also in relatives. In parallel, the search for genes involved in the pathogenesis of psychiatric disorders has revealed for both, schizophrenia and alcoholism an association with a DRD3 Ser9Gly polymorphism in a number of studies. In the present study, we have investigated 124 unrelated healthy subjects of German descent and have found diminished parietal and increased frontal P300 amplitudes in Gly9 homozygotes in comparison to Ser9 carriers. This finding suggests a possible role of the DRD3 receptor gene in the interindividual variation of P300 amplitudes. Further studies should address the direct role of the DRD3 Ser9Gly polymorphism in attenuated P300 amplitudes in psychiatric disorders like schizophrenia or alcoholism.

Set-shifting and selective attentional impairment in alcoholism and its relation with drinking variables

BACKGROUND

Individuals with chronic alcoholism show impairments in visual scanning, set-shifting and response inhibition abilities.

AIM

To study the relationship between performance on tests of set-shifting and selective attention, and alcohol intake variables (duration of dependence, amount of alcohol intake, and duration of abstinence during the past year).

METHODS

In this cross-sectional, controlled study, inpatients from a tertiary care centre were selected. Thirty patients with alcohol dependence and 15 age-, sex- and education-matched normal controls were administered the Trail Making Test (TMT) and Stroop test to assess visual scanning, set-shifting and response inhibition abilities. The data were analysed using the chi(2) test, t test and ANOVA with post-hoc analysis.

RESULTS

The patient group performed poorly on all measures of the tests. The duration of dependence and the amount of alcohol intake (during the past 1 year) were not found to significantly affect the performance on the 2 tests. The duration of abstinence during the past 1 year was significantly related to performance on the Stroop test with patients having a longer duration of abstinence showing lesser impairment.

CONCLUSION

Patients with a fewer number of days of alcohol intake during the past 1 year show relatively better visual scanning, set-shifting and response inhibition abilities.

Quantitative trait locus-specific genotype x alcoholism interaction on linkage for evoked electroencephalogram oscillations

We explored the evidence for a quantitative trait locus (QTL)-specific genotype × alcoholism interaction for an evoked electroencephalogram theta band oscillation (ERP) phenotype on a region of chromosome 7 in participants of the US Collaborative Study on the Genetics of Alcoholism. Among 901 participants with both genotype and phenotype data available, we performed variance component linkage analysis (SOLAR version 2.1.2) in the full sample and stratified by DSM-III-R and Feighner-definite alcoholism categories. The heritability of the ERP phenotype after adjusting for age and sex effects in the combined sample and in the alcoholism classification sub-groups ranged from 40% to 66%. Linkage on chromosome 7 was identified at 158 cM (LOD = 3.8) in the full sample and at 108 in the non-alcoholic subgroup (LOD = 3.1). Further, we detected QTL-specific genotype × alcoholism interaction at these loci. This work demonstrates the importance of considering the complexity of common complex traits in our search for genes that predispose to alcoholism.