P3 scalp topography to target and novel visual stimuli in children of alcoholics

Deficient Event-Related Theta Oscillations in Individuals at Risk for Alcoholism: A Study of Reward Processing and Impulsivity Features

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. Event-related oscillations (EROs) have been used to effectively measure brain (dys)function during cognitive tasks in individuals with alcoholism and related disorders and in those at risk to develop these disorders. The current study examines ERO theta power during reward processing as well as impulsivity in adolescent and young adult subjects at high risk for alcoholism.

METHODS

EROs were recorded during a monetary gambling task (MGT) in 12-25 years old participants (N = 1821; males = 48%) from high risk alcoholic families (HR, N = 1534) and comparison low risk community families (LR, N = 287) from the Collaborative Study on the Genetics of Alcoholism (COGA). Impulsivity scores and prevalence of externalizing diagnoses were also compared between LR and HR groups.

RESULTS

HR offspring showed lower theta power and decreased current source density (CSD) activity than LR offspring during loss and gain conditions. Younger males had higher theta power than younger females in both groups, while the older HR females showed more theta power than older HR males. Younger subjects showed higher theta power than older subjects in each comparison. Differences in topography (i.e., frontalization) between groups were also observed. Further, HR subjects across gender had higher impulsivity scores and increased prevalence of externalizing disorders compared to LR subjects.

CONCLUSIONS

As theta power during reward processing is found to be lower not only in alcoholics, but also in HR subjects, it is proposed that reduced reward-related theta power, in addition to impulsivity and externalizing features, may be related in a predisposition to develop alcoholism and related disorders.

Reward processing deficits and impulsivity in high-risk offspring of alcoholics: A study of event-related potentials during a monetary gambling task

BACKGROUND

Individuals at high risk to develop alcoholism often manifest neurocognitive deficits as well as increased impulsivity. The goal of the present study is to elucidate reward processing deficits, externalizing disorders, and impulsivity as elicited by electrophysiological, clinical and behavioral measures in subjects at high risk for alcoholism from families densely affected by alcoholism in the context of brain maturation across age groups and gender.

METHODS

Event-related potentials (ERPs) and current source density (CSD) during a monetary gambling task (MGT) were measured in 12-25 year old offspring (N=1864) of families in the Collaborative Study on the Genetics of Alcoholism (COGA) Prospective study; the high risk (HR, N=1569) subjects were from families densely affected with alcoholism and the low risk (LR, N=295) subjects were from community families. Externalizing disorders and impulsivity scores were also compared between LR and HR groups.

RESULTS

HR offspring from older (16-25 years) male and younger (12-15 years) female subgroups showed lower P3 amplitude than LR subjects. The amplitude decrement was most prominent in HR males during the loss condition. Overall, P3 amplitude increase at anterior sites and decrease at posterior areas were seen in older compared to younger subjects, suggesting frontalization during brain maturation. The HR subgroups also exhibited hypofrontality manifested as weaker CSD activity during both loss and gain conditions at frontal regions. Further, the HR subjects had higher impulsivity scores and increased prevalence of externalizing disorders. P3 amplitudes during the gain condition were negatively correlated with impulsivity scores.

CONCLUSIONS

Older male and younger female HR offspring, compared to their LR counterparts, manifested reward processing deficits as indexed by lower P3 amplitude and weaker CSD activity, along with higher prevalence of externalizing disorders and higher impulsivity scores.

SIGNIFICANCE

Reward related P3 is a valuable measure reflecting neurocognitive dysfunction in subjects at risk for alcoholism, as well as to characterize reward processing and brain maturation across gender and age group.

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.

In search of biomarkers in psychiatry: EEG-based measures of brain function

Current clinical parameters used for diagnosis and phenotypic definitions of psychopathology are both highly variable and subjective. Intensive research efforts for specific and sensitive biological markers, or biomarkers, for psychopathology as objective alternatives to the current paradigm are ongoing. While biomarker research in psychiatry has focused largely on functional neuroimaging methods for identifying the neural functions that associate with psychopathology, scalp electroencephalography (EEG) has been viewed, historically, as offering little specific brain source information, as scalp appearance is only loosely correlated to its brain source dynamics. However, ongoing advances in signal processing of EEG data can now deliver functional EEG brain-imaging with distinctly improved spatial, as well as fine temporal, resolution. One computational approach proving particularly useful for EEG cortical brain imaging is independent component analysis (ICA). ICA decomposition can be used to identify distinct cortical source activities that are sensitive and specific to the pathophysiology of psychiatric disorders. Given its practical research advantages, relatively low cost, and ease of use, EEG-imaging is now both feasible and attractive, in particular for studies involving the large samples required by genetically informative designs to characterize causal pathways to psychopathology. The completely non-invasive nature of EEG data acquisition, coupled with ongoing advances in dry, wireless, and wearable EEG technology, makes EEG-imaging increasingly attractive and appropriate for psychiatric research, including the study of developmentally young samples. Applied to large genetically and developmentally informative samples, EEG imaging can advance the search for robust diagnostic biomarkers and phenotypes in psychiatry.

Multifactorial determinants of target and novelty-evoked P300 amplitudes in children of addicted parents

Background

Although P300 amplitude reductions constitute a persistent finding in children of addicted parents, relatively little is known about the specificity of this finding. The major aim of this study was to investigate the association between parental rearing, adverse life events, stress-reactivity, substance use and psychopathology on the one hand, and P300 amplitude in response to both target and novel distracter stimuli on the other hand. Moreover, we assessed whether risk group status (i.e., having a parental history of Substance Use Disorders [SUD]) uniquely contributed to P300 amplitude variation above and beyond these other variables.

Methods

Event-related potentials were recorded in high-risk adolescents with a parental history of SUD (HR;n=80) and normal-risk controls (NR;n=100) while performing a visual Novelty Oddball paradigm. Stress-evoked cortisol levels were assessed and parenting, life adversities, substance use and psychopathology were examined by using self-reports.

Results

HR adolescents displayed smaller P300 amplitudes in response to novel- and to target stimuli than NR controls, while the latter only approached significance. Interestingly, the effect of having a parental history of SUD on target-P300 disappeared when all other variables were taken into account. Externalizing problem behavior was a powerful predictor of target-P300. In contrast, risk group status uniquely predicted novelty-P300 amplitude reductions above and beyond all other factors.

Conclusion

Overall, the present findings suggest that the P300 amplitude reduction to novel stimuli might be a more specific endophenotype for SUD than the target-P300 amplitude. This pattern of results underscores the importance of conducting multifactorial assessments when examining important cognitive processes in at-risk adolescents.

The P300 event-related brain potential as a neurobiological endophenotype for substance use disorders: a meta-analytic investigation

Endophenotypes are intermediate phenotypes on the putative causal pathway from genotype to phenotype and can aid in discovering the genetic etiology of a disorder. There are currently very few suitable endophenotypes available for substance use disorders (SUD). The amplitude of the P300 event-related brain potential is a possible candidate. The present study determined whether the P300 amplitude fulfils two fundamental criteria for an endophenotype: (1) an association with the disorder (disease marker), and (2) presence in unaffected biological relatives of those who have the disorder (vulnerability marker). For this purpose, two separate meta-analyses were performed. Meta-analysis 1 investigated the P300 amplitude in relation to SUD in 39 studies and Meta-analysis 2 investigated P300 amplitude in relation to a family history (FH+) of SUD in 35 studies. The findings indicate that a reduced P300 amplitude is significantly associated with SUD (d=0.51) and, though to a lesser extent, with a FH+ of SUD (d=0.28). As a disease maker, the association between reduced P300 amplitude and SUD is significantly larger for participants that were exclusively recruited from treatment facilities (d=0.67) than by other methods (i.e., community samples and family studies; d=0.45 and 0.32, respectively), and larger for abstinent SUD patients (d=0.71) than for current substance users (d=0.37). Furthermore, in contrast to FH+ males, a P300 amplitude reduction seems not to be present in FH+ females (d=-0.07). Taken together, these results suggest that P300 amplitude reduction can be both a useful disease and vulnerability marker and is a promising neurobiological endophenotype for SUD, though only in males. Implications and future directions are discussed.

Event-related potentials during visual target detection in treatment-naïve active alcoholics

BACKGROUND

Reduced P3b event-related potentials (ERP) amplitude during visual target detection in alcoholics is a robust phenomenon. However, this finding is based primarily on samples of treated alcoholics, who comprise only about 25% of alcoholics. We studied visual target detection in a treatment-naïve alcohol-dependent sample (TNAD) versus age and gender comparable nonalcoholic controls (NAC) to investigate whether reduced P3 amplitudes generalize to TNAD.

METHODS

EEGs were recorded from 74 TNAD and 63 age and gender comparable NAC during visual target detection. ANOVA was applied at midline electrodes to amplitudes and latencies of N2 and P3 ERP components during target and rare nontarget conditions.

RESULTS

Treatment-naïve alcohol-dependent subjects had a modestly lower P3b amplitude (p=0.05) and a more robustly lower N2b amplitude (p=0.29). In the target condition, TNAD showed a significant reduction in P3b amplitude and a larger reduction in N2b amplitude, with these phenomena being independent of each other. Latencies to P3b, N2b, and P3a were earlier in TNAD than NAC, with this effect correlating with our reported effect of better attention in TNAD versus NAC.

CONCLUSION

The significant reduction in P3b amplitude in TNAD suggests that this phenomenon is present in TNAD, but dramatically smaller than that observed in treated samples (we reported an effect over 5 times as large in treated long-term abstinent alcoholics). The N2b amplitude reduction (not present in long-term abstinent alcoholics) may reflect the effects of active alcohol abuse. Finally, the shorter latencies of these components in TNAD is associated with better scores on tests of attention and may reflect compensatory attentional effort in the context of active drinking.

Auditory and visual novelty processing in normally-developing Kenyan children

OBJECTIVE

The aim of this study was to describe the normative development of the electrophysiological response to auditory and visual novelty in children living in rural Kenya.

METHODS

We examined event-related potentials (ERPs) elicited by novel auditory and visual stimuli in 178 normally-developing children aged 4-12 years (86 boys, mean 6.7 years, SD 1.8 years and 92 girls, mean 6.6 years, SD 1.5 years) who were living in rural Kenya.

RESULTS

The latency of early components (auditory P1 and visual N170) decreased with age and their amplitudes also tended to decrease with age. The changes in longer-latency components (Auditory N2, P3a and visual Nc, P3a) were more modality-specific; the N2 amplitude to novel stimuli decreased with age and the auditory P3a increased in both latency and amplitude with age. The Nc amplitude decreased with age while visual P3a amplitude tended to increase, though not linearly.

CONCLUSIONS

The changes in the timing and magnitude of early-latency ERPs likely reflect brain maturational processes. The age-related changes to auditory stimuli generally occurred later than those to visual stimuli suggesting that visual processing matures faster than auditory processing.

SIGNIFICANCE

ERPs may be used to assess children's cognitive development in rural areas of Africa.

Event-related oscillations versus event-related potentials in a P300 task as biomarkers for alcoholism

OBJECTIVE

It has been proposed that event-related oscillation (ERO) measures of EEG activity recorded in P300 tasks provide more powerful biomarkers of alcoholism than event-related potential (ERP) measures. This study examines this question in a group of long-term abstinent alcoholics (LTAAs).

METHODS

EEGs were recorded on 48 LTAAs and 48 age and gender-matched nonalcoholic controls (NACs) during the performance of a 3-condition visual target detection task. The event-related data were analyzed to extract ERP amplitude measures and total and evoked ERO power measures. Data were analyzed using multivariate analysis of covariance to determine the contributions of ERO versus ERP measures to discriminate between the LTAA versus NAC groups.

RESULTS

The LTAA group showed significantly lower evoked delta ERO power and total delta and theta ERO power compared to the control group. The evoked and total ERO power measures provide an alternative (but not more powerful) representation of the group difference than does P3b amplitude. There was a weak suggestion that nonphase-locked theta ERO power (which contributes to total ERO power) might provide independent discriminatory information.

CONCLUSIONS

Reduced evoked ERO power in the response to target stimuli provided an alternative and comparable representation of the reduced P3b amplitude in LTAA. This is not surprising as the evoked ERO power measures are derived from time-frequency representations of the ERP waveform. Induced theta oscillations might provide independent discriminatory information beyond ERP amplitude measures, but separate analysis of the event-related nonphase-locked activity is required to investigate this further.

Cognitive Event-Related Potentials and Alcoholism

The discipline of neuropsychiatry tries to bridge the gap between neurology and psychiatry in order to gain insight into the biological bases of psychiatric disorders. A principal tool is electrophysiological assessments, as, for instance, event-related potentials (ERPs). In this paper, we will review the current main findings concerning the status of cognitive ERPs in a specific psychiatric disease, i.e., chronic alcoholism. First, delayed P300 latency and reduced P300 amplitude are a common and robust finding in chronic alcoholics. Our aim will be to insert this empirical finding into the growing knowledge of molecular actions of alcohol and genetic patterns of alcohol dependence together with a more precise identification of alcohol-influenced neuronal and psychopathological processes. We will show how this may help us to reach a better understanding of this pathology. Second, an important set of data also pointed out that earlier ERP components, such as the N100, the mismatch negativity (MMN), the P100, and the N170, were also affected by chronic consumption of alcohol. Therefore, as the entire information-processing system seemed to be altered, these results deserved to be discussed, at least concerning their main clinical implications. Finally, although long term consequences of alcohol abuse have been extensively described, little is known about the detrimental effect on neural and cognitive processes of massive alcohol intake over a short period of time (e.g., binge drinking). Recent data on this new and challenging issue will be outlined.

Deviant P300 amplitude development in males is associated with paternal externalizing psychopathology

Boys at risk for alcoholism show deviant P300 amplitude development. Genetic influences on P300, however, are related to a range of externalizing disorders. This study examined whether P300 development from adolescence to early adulthood differed between groups varying in severity of paternal externalizing. Parietal P300 was assessed during the "rotated heads" task on up to 3 times between the ages of 17 and 24 years. Participants were divided into 3 paternal externalizing groups: (a) severe (father has adult antisocial behavior), (b) intermediate (father has alcohol dependence but not a more severe disorder), and (c) low (father has no externalizing disorders or substance treatment and is not extreme in alcohol use). Mixed models were used to evaluate linear change in amplitude. P300 decreased with age. The severe-risk group had smaller P300 initially and changed less with time than did the low-risk group. The intermediate-risk group did not differ significantly from the low-risk group, but differed marginally from the severe-risk males. Externalizing and early-onset substance disorders in the sons were associated with smaller initial values of P300. Measures of deviant P300 development may be vulnerability markers for externalizing psychopathology.

Genetic contribution to the P3 in young and middle-aged adults

Previous studies in young and adolescent twins suggested substantial genetic contributions to the amplitude and latency of the P3 evoked by targets in an oddball paradigm. Here we examined whether these findings can be generalized to adult samples. A total of 651 twins and siblings from 292 families participated in a visual oddball task. In half of the subjects the age centered around 26 (young adult cohort), in the other half the age centered around 49 (middle-aged adult cohort). P3 peak amplitude and latency were scored for 3 midline leads Pz, Cz, and Fz. No cohort differences in heritability were found. P3 amplitude (approximately 50%) and latency (approximately 45%) were moderately heritable for the 3 leads. A single genetic factor influenced latency at all electrodes, suggesting a single P3 timing mechanism. Specific genetic factors influenced amplitude at each lead, suggesting local modulation of the P3 once triggered. Genetic analysis of the full event-related potential waveform showed that P3 heritability barely changes from about 100 ms before to 100 ms after the peak. Age differences are restricted to differences in means and variances, but the proportion of genetic variance as part of the total variance of midline P3 amplitude and latency does not change from young to middle-aged adulthood.

Application of electroencephalography to the study of cognitive and brain functions in schizophrenia

The electroencephalogram (EEG) recorded from the human scalp is widely used to study cognitive and brain functions in schizophrenia. Current research efforts are primarily devoted to the assessment of event-related potentials (ERPs) and event-related oscillations (EROs), extracted from the ongoing EEG, in patients with schizophrenia and in clinically unaffected individuals who, due to their family history and current mental status, are at high risk for developing schizophrenia. In this article, we discuss the potential usefulness of ERPs and EROs as genetic vulnerability markers, as pathophysiological markers, and as markers of possible ongoing progressive cognitive and cortical deterioration in schizophrenia. Our main purpose is to illustrate that these neurophysiological measures can offer valuable quantitative biological markers of basic pathophysiological mechanisms and cognitive dysfunctions in schizophrenia, yet they may not be specific to current psychiatry's diagnosis and classification. These biological markers can provide unique information on the nature and extent of cognitive and brain dysfunction in schizophrenia. Moreover, they can be utilized to gain deeper theoretical insights into illness etiology and pathophysiology and may lead to improvements in early detection and more effective and targeted treatment of schizophrenia. We conclude by addressing several key methodological, conceptual, and interpretative issues involved in this research field and by suggesting future research directions.

Impaired Emotional Facial Expression Recognition in Alcohol Dependence: Do These Deficits Persist With Midterm Abstinence?

BACKGROUND

Emotional facial expression (EFE) decoding has been repetitively shown to be impaired in alcoholic inpatients. The present study aimed to replicate and extend previous findings on EFE recognition deficits in alcoholism.

METHODS

Alcoholic and control participants' performances were compared on an EFE decoding task with a transversal and a longitudinal design. More specifically, 49 alcoholic individuals were recruited at a long-stay postdetoxification treatment center at the third or fourth week of their detoxification process. Twenty-two of them [abstinent alcoholic participants (AA)] were met at the end of their hospitalization process, 2 months later. The 27 remaining patients [dropping alcoholic participants(AD)] dropped out from treatment before the second meeting. A control group (C) of 22 participants was constituted, and assessed twice with the same average time as AA between the 2 assessments. The 3 groups were similar regarding age, sex, and education level. Participants were presented at both times with an EFE decoding test consisting of 16 photographs depicting EFE of happiness, anger, disgust, and sadness.

RESULTS

The results corroborated previous findings highlighting more EFE decoding deficits in alcoholic participants compared with control participants, with no improvement after 3 months of abstinence. Transversal analyses further evidenced more EFE decoding difficulties in AD than in AA compared with controls.

CONCLUSIONS

EFE decoding deficits in alcoholism persist with midterm abstinence. Alcoholic patients who dropped from treatment had the worst EFE decoding performance at baseline. Emotional facial expression decoding deficit could have a prognostic value in alcohol dependence.

Reduced Frontal Lobe Activity in Subjects With High Impulsivity and Alcoholism

OBJECTIVE

Impulsivity is an important characteristic of many psychiatric disorders, including substance-related disorders. These disinhibitory disorders have a similar underlying genetic diathesis, with each disorder representing a different expression of the same underlying genetic liability. This study assessed whether there is a relationship between impulsivity and alcohol dependence, and their correlations with P3 (P300) amplitude, a proposed endophenotype of alcoholism.

METHODS

Healthy control subjects (n=58) and subjects with DSM-IV diagnosis of alcohol dependence (n=57) were assessed with a visual oddball task. Event-Related Potentials (ERPs) were recorded from 61 scalp electrodes and P3 amplitudes measured. Barratt Impulsiveness Scale (BIS), version 11, was used to evaluate impulsivity. Source localization of P3 was computed using low-resolution brain electromagnetic tomography (LORETA).

RESULTS

Alcoholic subjects manifested reductions in target P3 amplitudes (p<0.0001). Using LORETA, significantly reduced activation was mapped in the cingulate, medial, and superior frontal regions in alcoholic subjects and highly impulsive subjects. Alcoholic subjects had significantly higher scores on the BIS (p<0.0001) than nonalcoholic individuals. There were significant negative correlations between total scores on BIS and P3 amplitude (r=-0.274, p=0.003, on Pz; r=-0.250, p=0.007, on Cz).

CONCLUSIONS

Our results demonstrate a strong frontal focus of reduced activation during processing of visual targets in alcoholic subjects and individuals with higher impulsivity. The findings suggest that impulsivity may be an important factor that underlies the pathogenesis of alcohol dependence. Studies are underway to examine the relationship between impulsivity and ERPs in offspring of alcoholic subjects, and to identify genes associated with the underlying predisposition involved in disinhibitory disorders.

Delta and theta oscillations as risk markers in adolescent offspring of alcoholics

BACKGROUND

Visual P300 is consistently lower in alcohol-dependent individuals, their offspring and subjects at risk. Delta and theta event-related oscillations (ERO) are the major contributors to the P300 signal. The total and evoked power in delta and theta bands in the 300 to 700 ms post-stimulus window (corresponding to the zone of P300 maxima) was compared between adolescent offspring of alcoholics (high-risk) and age-matched normal controls (low-risk), to assess the utility of the risk markers.

METHODS

EEG was recorded during the performance of a visual oddball task. The S-transform algorithm decomposed the EEG signals into different frequency bands and the group differences in total and evoked power in the oscillatory responses during the P300 time window (300 to 700 ms) were analyzed using a multivariate design. Similar analysis was performed on P300 peak amplitude for the target.

RESULTS

The high-risk group showed significantly lower parietal post-stimulus evoked and total power in the delta band for targets. A decrease in total power was seen centrally and parietally in the theta band. The P300 peak amplitude in the parietal electrodes was also significantly lower in the high-risk group.

CONCLUSIONS

The decreased total theta power and total and evoked delta power for visual targets in high risk individuals may serve as an endophenotypic marker in the development of alcoholism and other disinhibitory disorders. The differences seen between the offspring of alcoholics and controls may have a cholinergic basis. The ERO measures appear to be more robust than the P300 amplitude in differentiating the groups.

Visual P300s in long-term abstinent chronic alcoholics

BACKGROUND

Evidence of reduced P3b amplitudes in chronic alcoholics and individuals at risk for developing alcoholism suggest that the P3b may be an endophenotypic marker for alcoholism. If this is the case, then long-term abstinent alcoholics (LTAAs) should exhibit reduced P3b amplitudes. Thus far, P3b studies on chronic alcoholics have focused primarily on samples with relatively short-term abstinence (less than 15 months). This study examines the amplitude and latency of the P3b and P3a event-related brain electrical components in LTAAs compared with normal controls (NCs) and whether these measures are related to alcohol use and other subject variables.

METHODS

Electroencephalographs (EEGs) were recorded on 48 LTAAs (mean abstinence=6.7 years) compared with 48 age-matched and gender-matched NCs during a visual P300 experiment consisting of standard, target, and rare nontarget conditions. This paradigm elicited the P3b (target condition) and the P3a (rare nontarget condition) components.

RESULTS

Long-term abstinent alcoholics had reduced P3b amplitudes and increased P3b latencies in comparison with NCs. Long-term abstinent alcoholics also exhibited delayed P3a components, but no P3a amplitude reductions. Alcohol use variables, a family history of alcohol problems, and the duration of alcohol abstinence were not associated with any amplitude or latency variables.

CONCLUSIONS

Even after very prolonged abstinence, reduced P3b amplitudes are present in chronic alcoholics and are not associated with any family history or alcohol use variables. These results provide equivocal support for reduced P3b amplitude being an endophenotypic marker for alcoholism, but are also consistent with P3b being affected by a threshold of alcohol abuse, with the effect not resolving over long periods of abstinence.

Evoked gamma band response in male adolescent subjects at high risk for alcoholism during a visual oddball task

This study investigates early evoked gamma band activity in male adolescent subjects at high risk for alcoholism (HR; n=68) and normal controls (LR; n=27) during a visual oddball task. A time-frequency representation method was applied to EEG data in order to obtain stimulus related early evoked (phase-locked) gamma band activity (29-45 Hz) and was analyzed within a 0-150 ms time window range. Significant reduction of the early evoked gamma band response in the frontal and parietal regions during target stimulus processing was observed in HR subjects compared to LR subjects. Additionally, the HR group showed less differentiation between target and non-target stimuli in both frontal and parietal regions compared to the LR group, indicating difficulty in early stimulus processing, probably due to a dysfunctional frontoparietal attentional network. The results indicate that the deficient early evoked gamma band response may precede the development of alcoholism and could be a potential endophenotypic marker of alcoholism risk.

Association of DRD4 exon III polymorphism with auditory P300 amplitude in 8-year-old children

OBJECTIVES

The present study was designed to investigate the association between the DRD4 genotype and auditory P300 amplitudes in a high-risk community sample.

METHODS

ERPs were elicited in 197 eight-year-olds (98 boys, 99 girls) using a passive and an active oddball task. Auditory stimuli of 60 dB HL were presented binaurally at 1000 (standard stimulus) and 2000 Hz (target stimulus), at a relative frequency ratio of 80:20. Two trial blocks of 250 stimuli each were collected. P300 amplitudes were analyzed from Fz, Cz and Pz. DNA was genotyped for the DRD4 exon III polymorphism.

RESULTS

A pattern of significant interactions of the DRD4 genotype with gender and experimental conditions was obtained. In both the active and the passive task, boys with at least one copy of the DRD4 7-repeat allele displayed significantly lower P300 amplitudes during the second trial block than boys carrying other alleles.

CONCLUSIONS

This finding provides further evidence supporting a role of P300 amplitude reduction as an endophenotype for disinhibited psychopathology.

The utility of neurophysiological markers in the study of alcoholism

OBJECTIVE

This review attempts to differentiate neuroelectric measures (electroencephalogram (EEG), event-related potentials (ERPs) and event-related oscillations (EROs)) related to acute and chronic effects of alcohol on the brain from those that reflect underlying deficits related to the predisposition to develop alcoholism and related disorders. The utility of these neuroelectric measures as endophenotypes for psychiatric genetics is evaluated.

METHODS

This article reviews the main findings of EEG and ERP abnormalities in alcoholics, offspring of alcoholics at high risk to develop alcoholism and the electrophysiological effects of alcohol on high risk compared to low-risk offspring. It highlights findings using EROs, a fast developing tool in examining brain function and cognition. It also reviews evidence of genetic findings related to these electrophysiological measures and their relationship to clinical diagnosis.

RESULTS

Many of these abnormal neuroelectric measures are under genetic control, may precede the development of alcoholism, and may be markers of a predisposition toward the development of a spectrum of disinhibitory conditions including alcoholism. Genetic loci underlying some neuroelectic measures that involve neurotransmitter systems of the brain have been identified.

CONCLUSIONS

Quantitative neuroelectric measures (EEG, ERPs, EROs) provide valuable endophenotypes in the study of genetic risk to develop alcoholism and related disorders.

SIGNIFICANCE

Genetic studies of neuroelectric endophenotypes offer a powerful strategy for identifying susceptibility genes for developing psychiatric disorders, and provide novel insights into etiological factors.

Spatial-anatomical mapping of NoGo-P3 in the offspring of alcoholics: evidence of cognitive and neural disinhibition as a risk for alcoholism

OBJECTIVE

The concept of disinhibition as a behavioral and biological trait has been considered to be involved in the etiology of alcoholism and its co-existing disorders. The magnitude and functional mapping of event-related potential P3(00) components were analyzed, in order to examine the possible response inhibition deficits in the offspring of alcoholics.

METHODS

The P3 components were compared between 50 offspring of alcoholics (OA) and a matched normal control group (NC) using a visual Go/NoGo task. The low-resolution electromagnetic tomography (LORETA) was used to analyze the functional brain mapping between groups.

RESULTS

The results indicated that the OA group manifested decreased P3 amplitude during the NoGo but not the Go condition compared to the NC group. The voxel-by-voxel analysis in LORETA showed group differences at several brain regions including prefrontal areas during the processing of NoGo but not Go signals.

CONCLUSIONS

The decreased NoGo-P3 suggests that cognitive and neural disinhibition in offspring of alcoholics may serve as a neurocognitive index for a phenotypic marker in the development of alcoholism and related disorders.

SIGNIFICANCE

Dysfunctional neural and response inhibition in the offspring of alcoholics perhaps provides an endophenotypic marker of risk for the development of alcoholism and related disorders.

Characterization of N200 and P300: selected studies of the Event-Related Potential

The Event-Related Potential (ERP) is a time-locked measure of electrical activity of the cerebral surface representing a distinct phase of cortical processing. Two components of the ERP which bear special importance to stimulus evaluation, selective attention, and conscious discrimination in humans are the P300 positivity and N200 negativity, appearing 300 ms and 200 ms post-stimulus, respectively. With the rapid proliferation of high-density EEG methods, and interdisciplinary interest in its application as a prognostic, diagnostic, and investigative tool, an understanding of the underpinnings of P300 and N200 physiology may support its application to both the basic neuroscience and clinical medical settings. The authors present a synthesis of current understanding of these two deflections in both normal and pathological states.

Alcoholism risk, tobacco smoking, and P300 event-related potential

OBJECTIVE

The P300 event-related potential (ERP) is sometimes larger for individuals at low- compared to high-risk for alcoholism. These effects are inconsistent, and how P300 is affected by tobacco smoking in the context of alcoholism risk is unknown. The present study used P300 to examine the inter-relationship between alcoholism heritability and smoking status.

METHODS

P300 was elicited with a visual discrimination task from young adults at low- and high-risk for alcoholism. Half of the subjects in each risk category reported that they did not smoke cigarettes, and the other half reported that they smoked regularly, with equal numbers of male and female subjects assessed. ERPs were recorded, and subjects were instructed to respond only to an infrequently presented target stimulus that occurred in a series of standard and distracter stimuli.

RESULTS

P300 amplitude from the target stimuli was larger for the low-risk compared to high-risk subjects overall. However, smoking status demonstrated even stronger effects, with non-smokers producing consistently larger component amplitudes than smokers and accounting for more variance than alcoholism risk. These group factors also significantly affected P300 scalp topography. No reliable alcoholism risk or smoking group effects were obtained for the ERPs from the other stimuli.

CONCLUSIONS

The findings suggest that P300 measures of alcoholism risk in young adults are moderated by smoking status. Theoretical implications are discussed.

Gene-environment interplay in alcoholism and other substance abuse disorders: expressions of heritability and factors influencing vulnerability

Factors that confer predisposition and vulnerability for alcoholism and other substance abuse disorders may be described usefully within the gene-environment interplay framework. Thus, it is postulated that heritability provides a major contribution not only to alcohol but also to other substances of abuse. Studies of evoked potential amplitude reduction have provided a highly suitable and testable method for the assessment of both environmentally-determined and heritable characteristics pertaining to substance use and dependence. The different personal attributes that may co-exist with parental influence or exist in a shared, monozygotic relationship contribute to the final expression of addiction. In this connection, it appears that personality disorders are highly prevalent co-morbid conditions among addicted individuals, and, this co-morbidity is likely to be accounted for by multiple complex etiological relationships, not least in adolescent individuals. Co-morbidity associated with deficient executive functioning may be observed too in alcohol-related aggressiveness and crimes of violence. The successful intervention into alcohol dependence and craving brought about by baclofen in both human and animal studies elucidates glutamatergic mechanisms in alcoholism whereas the role of the dopamine transporter, in conjunction with both the noradrenergic and serotonergic transporters, are implicated in cocaine dependence and craving. The role of the cannabinoids in ontogeny through an influence upon the expression of key genes for the development of neurotransmitter systems must be considered. Finally, the particular form of behaviour/characteristic outcome due to childhood circumstance may lie with biological, gene-based determinants, for example individual characteristics of monoamine oxidase (MAO) activity levels, thereby rendering simple predictive measures both redundant and misguiding.

Alcoholism risk and the P300 event-related brain potential: Modality, task, and gender effects

The P300 event related potential (ERP) was elicited from young adults at low- (LR) and high-risk (HR) for alcoholism (n = 24/risk group), with equal numbers of male and female subjects employed. The effects of stimulus modality, task difficulty, and gender were assessed with analogous auditory and visual paradigms (tone location/head rotation and tone matching/shape matching). Although task performance was generally comparable across risk groups, LR subjects produced smaller P300 amplitudes than HR subjects for the visual matching tasks. No consistent risk group P300 latency effects were obtained. Gender, task difficulty, and scalp topography differentially modulated the risk group outcomes across paradigms. These findings suggest that P300 amplitude reflects risk-for-alcoholism in male and female young adults, but the specific task conditions and electrode location affect the strength of risk group differences.

Auditory P3 in female alcoholics

BACKGROUND

The P3 (P300) has been considered to be a phenotypical marker of the risk for alcoholism. Although reductions in visual P3 in male and female alcoholics have been replicated, studies of auditory target P3 have been inconsistent. Our objective was to study the magnitude of auditory P3 reduction in female alcoholics and to establish the association between P3 reduction and alcoholism while taking into account comorbid depression and psychoactive drug dependence. The characteristics of P3 reduction were further examined by studying the reduction in family history-positive and -negative individuals.

METHODS

Auditory target P3s recorded from 61 scalp electrodes in female alcoholics (n = 71) were compared with P3s from female controls (n = 159) ranging in age from 18 to 50 years. The amplitudes and latencies were statistically analyzed, by using repeated-measures ANOVA, in six regional electrode arrays and at representative electrode sites, with age and comorbid depression as covariates. The effects of family density and clinical variables such as depression and drug dependence were also examined with correlation analysis.

RESULTS

Alcoholic women had significantly lower P3 amplitudes in all six regions and at midline electrode sites. The reductions were not associated with comorbid depression, as shown by low correlations and similar P3 amplitudes at Pz in female alcoholics with and without depression. The P3 amplitudes in women with a high family density were smaller than those in women with a low family density of alcohol dependence. Drug dependency did not influence P3 amplitude, as shown by similar responses in drug-dependent and non-drug-dependent alcoholic women.

CONCLUSIONS

These findings highlight the significance of P3 reductions associated with alcoholism in women, independently of comorbid depression. Family density effects further support the evidence that these findings are heritable. These results suggest that P3 can be considered as a phenotypical marker of vulnerability to alcoholism in women.

Substance use disorders, externalizing psychopathology, and P300 event-related potential amplitude

We hypothesize the existence of an inherited predisposition for a spectrum of behaviors and traits characterized by behavioral disinhibition. This externalizing spectrum includes childhood disruptive disorders, antisocial behavior, substance use disorders, personality traits related to behavioral undercontrol, and the precocious expression of problem behavior. We further hypothesize that a genetically influenced central nervous system diathesis underlies this spectrum and is reflected in reduced P300 amplitude in a visual oddball event-related potential task. A review of evidence bearing on the model is derived from findings from the Minnesota Twin Family Study, a population-based, longitudinal investigation of twin youth. These findings indicate that the collection of attributes related to behavioral disinhibition is familial, heritable, and interrelated. Evidence supporting P3 amplitude reduction (P3-AR) as an index of genetic vulnerability for this externalizing spectrum includes its association with (a) familial risk for substance use and antisocial personality disorders, (b) diagnoses of childhood disruptive disorders and substance use disorders, (c) early onset of undersocialized behavior, and (d) quantitative phenotypes related to externalizing problems. In addition, the development of substance use disorders over a 3-year period is associated with P3-AR measured prior to their expression. These findings suggest that P3-AR indexes one aspect of the genetic diathesis for a spectrum of externalizing problem behavior.

Linkage and linkage disequilibrium mapping of ERP and EEG phenotypes

Linkage analyses of highly heritable electrophysiological phenotypes (EEG, ERP) that can potentially identify individuals at risk for alcoholism were performed on a large sample of families with a high density of alcohol dependence as part of the Collaborative Study on the Genetics of Alcoholism (COGA); these genetic findings are summarized. Quantitative trait loci (QTLs) were identified for several ERP characteristics (P300, N100, N400) and for the beta frequencies of the EEG where we report linkage and linkage disequilibrium at a GABA(A) receptor gene on chromosome 4. Genetic analyses of ERPs suggest that several regions of the human genome contain genetic loci related to the generation of N100, N400 and P300, which are possible candidate loci underlying the functional organization of human neuroelectric activity. The advent of genomics and proteomics and a fuller understanding of gene regulation, will open new horizons on the critical electrical events so essential for human brain function.

P300 amplitude in adolescent twins discordant and concordant for alcohol use disorders

The sons of alcoholics have repeatedly been found to have reduced P300 amplitude. Further, quantitative behavioral genetic and molecular genetic studies indicating a genetic influence on P300 amplitude have fueled speculation that this component may be a biological vulnerability marker for alcoholism. To further explore this possibility, we examined P300 in adolescent twin pairs from an epidemiological sample who were (a) discordant for alcohol abuse/dependence, (b) concordant for alcohol abuse/dependence, or (c) concordant for the absence of alcohol abuse/dependence and other relevant disorders. For discordant pairs, the alcohol abusing/dependent twins' amplitude did not differ from that of non-alcoholic co-twins. Pairs free of psychopathology had greater amplitudes than both alcoholism discordant and concordant pairs. P300 amplitude was more similar in monozygotic than dizygotic discordant pairs, suggesting a genetic influence on P300 amplitude in this group. The findings are consistent with P300 amplitude being a marker of vulnerability to alcohol use disorders.

Visual P3 findings in Mission Indian youth: relationship to family history of alcohol dependence and behavioral problems

Native Americans have some of the highest rates of alcohol abuse and dependence, yet risk factors for problem drinking remain relatively unknown. The amplitude of the P3 component of the event-related potential (ERP) has been suggested to be an index of 'vulnerability to alcoholism', especially when it is elicited by visual tasks in younger individuals. Visual P3 tasks, however, have not been previously investigated in Native American youth. One hundred and four Mission Indian youth between the ages of 7 and 13 years participated in the study. ERPs were collected using two visual target paradigms: a facial discrimination and an estimation of line orientation task. Analyses of covariance revealed that participants with a first degree family history of alcoholism had lower P3 component amplitudes in frontal leads to the facial discrimination task. Lower P3 amplitudes, in posterior areas, were found in the line discrimination task in children who scored above the 75th percentile in delinquent behaviors on the Achenbach Child Behavior Checklist. These findings are consistent with investigations in non-Indian populations demonstrating that the late positive component of the event related potential is sensitive to both familial history of alcohol dependence as well as personal history of externalizing behaviors.

Neuroelectrical signs of selective attention to color in boys with attention-deficit hyperactivity disorder

In order to gain insight into the functional and macroanatomical loci of visual selective processing deficits that may be basic to attention-deficit hyperactivity disorder (ADHD), the present study examined multi-channel event-related potentials (ERPs) recorded from 7- to 11-year-old boys clinically diagnosed as having ADHD (n=24) and age-matched healthy control boys (n=24) while they performed a visual (color) selective attention task. The spatio-temporal dynamics of several ERP components related to attention to color were characterized using topographic profile analysis, topographic mapping of the ERP and associated scalp current density distributions, and spatio-temporal source potential modeling. Boys with ADHD showed a lower target hit rate, a higher false-alarm rate, and a lower perceptual sensitivity than controls. Also, whereas color attention induced in the ERPs from controls a characteristic early frontally maximal selection positivity (FSP), ADHD boys displayed little or no FSP. Similarly, ADHD boys manifested P3b amplitude decrements that were partially lateralized (i.e., maximal at left temporal scalp locations) as well as affected by maturation. These results indicate that ADHD boys suffer from deficits at both relatively early (sensory) and late (semantic) levels of visual selective information processing. The data also support the hypothesis that the visual selective processing deficits observed in the ADHD boys originate from deficits in the strength of activation of a neural network comprising prefrontal and occipito-temporal brain regions. This network seems to be actively engaged during attention to color and may contain the major intracerebral generating sources of the associated scalp-recorded ERP components.

Auditory P3a deficits in male subjects at high risk for alcoholism

BACKGROUND

Substantial evidence indicates that alcoholism is biologically mediated by a genetic predisposition. As the decreased P300 (P3b) event-related brain potential component does not recover with prolonged abstinence, it is unlikely to be related to drinking history but is more likely to be genetically influenced. This is supported by findings that P3b amplitudes are reduced in subjects at high-risk compared to low-risk for alcoholism. Although there are few studies of P3a in HR subjects, lower P3a amplitudes have been reported with a novel nontarget stimulus paradigm, as well as with a difficult three-stimulus visual paradigm. Using a similar three-tone auditory paradigm in which the discriminability between the target and standard tone is difficult, the P3a component can also be reliably elicited with a rare nontarget perceptually distinct stimulus. This technique was employed in young adult subjects at low-risk and high-risk for alcoholism.

METHODS

A total of 17 low-risk and 24 high-risk male subjects were employed as subjects in an auditory paradigm that yielded a large amplitude P3a with a centro-frontal maximum to the nontarget and a robust low amplitude prolonged P3b with a parietal maximum amplitude to the target stimulus. Current source density maps were derived to assess topographic differences between low-risk and high-risk subjects.

RESULTS

The high-risk group manifested significantly lower P3a amplitudes than the low-risk group at the frontal electrodes to rare nontarget stimuli. High-risk subjects also demonstrated a more disorganized current source density map for P3a compared to low-risk subjects.

CONCLUSIONS

The reduction of P3a in the high-risk group may be due to cortical dysfunction including the frontal and prefrontal cortex. The lower P3a amplitude coupled with more disorganized current source density maps suggest inefficient brain functioning in high-risk subjects.

Middle-latency auditory evoked potentials in children at high risk for alcoholism

PURPOSE

In the course of a high-risk study for alcoholism, the middle-latency auditory evoked potentials (MAEPs) of children of alcoholics were explored.

MATERIAL AND METHODS

A series of auditory clicks (0.1 ms, 60 dB SL, 1.1/s) were used to record the Pa and Pb peaks of the MAEPs in 15 children of alcoholics with a multigenerational family history of alcoholism, and 17 control subjects, ranging from 10 to 14 years of age.

RESULTS

The latency of Pb was shorter in the high-risk than in the control group, and there was also a significant risk group by age interaction on Pa latency. The amplitude of Pa was smaller in the children of alcoholics.

CONCLUSIONS

The characteristics of the MAEPs of the high-risk subjects did not match the pattern of abnormalities previously observed in chronic alcoholics, which are supposed to be a consequence of the neurotoxic effects of ethanol. Nonetheless, the results showed significant differences in MAEPs between children of alcoholics and controls, pointing to an anomalous pattern of information transmission from thalamus to cortex that should be further analyzed using larger samples in a broader age range.

Attention and selection in the growing child: views derived from developmental psychophysiology

Our understanding of developmental changes in attentional selection in the growing child has been advanced substantially by the results of (a relatively small number of) studies undertaken from a psychophysiological perspective. The basic outcome of these studies is that, in attentional filtering as well as selective set (the two basic paradigms in attention research), the processes necessary for attentional selection are in essence available even to the young child; however, the speed and efficiency of these processes tends to increase as the child grows into an adolescent. Under optimal conditions, filtering is performed at early stages of information processing, but less optimal stimulus characteristics and task requirements may induce a shift in the locus of selection to later processing stages for young children whereas older individuals are better able to preserve their early locus of selection. When early selection is constrained, young children are substantially more sensitive to the adverse effects of response competition. In selective set, sub-optimal conditions lead not so much to a shift in locus of selection processes, but to a shift in the age at which asymptote efficiency is attained. We have proposed hierarchical regression analysis as a useful technique to examine whether age-related differences in attention effects, as observed in specific ERP components and in RT, are reflections of an age effect on a single source of attentional selection or of separate sources that each contribute uniquely to the developmental trends seen in (attention effects on) RT. Re-analyses of existing data demonstrated that (again depending on task specifics) many but not all of the different component processes involved in attentional selection contributed unique variance to the age-related changes in attention effects.

Event-related brain potentials in response to novel sounds in dementia

OBJECTIVE

Non-target, deviant stimuli generate an earlier latency, front-central novelty P3, whereas correctly detected task-relevant stimuli generate a parietal maximal target P3. We examined whether the P3 component to novel stimuli is affected by dementing processes, and is therefore useful for distinguishing Alzheimer's type dementia (AD) from vascular dementia (VD).

METHODS

We recorded ERPs to task-relevant stimuli (target P3) and novel task-irrelevant stimuli (novelty P3) in an auditory oddball task in AD (n = 16), VD (n = 16), and age-matched controls (n = 18). The amplitude, latency, and scalp topography of target and novelty P3 were compared among 3 groups using ANOVA. The relationship between P3 measures and intelligence scores were evaluated by correlation analysis.

RESULTS

The amplitude, latency and scalp topography of the target P3 were comparably affected by both AD and VD. However, the amplitude of the novelty P3 was markedly reduced in VD, but not in AD, and the scalp topographics were different in the 3 groups. The amplitude was maximal at frontal sites in controls, at central sites in AD, and at parietal sites in VD. The target P3 latency was prolonged in both AD and VD, whereas the novelty P3 latency was only prolonged in VD. AD was discriminated satisfactorily from VD by using the novelty amplitude at Cz and the ratio of the amplitudes at Fz and Pz as independent variables.

CONCLUSIONS

These results suggest that the response to novel stimuli is differentially affected by dementia with degenerative and vascular etiology.

What is inherited in the predisposition toward alcoholism? A proposed model

BACKGROUND

The etiological factors associated with the predisposition to develop alcohol dependence remain largely unknown. In recent years, neurophysiological anomalies have been identified in young and adult offspring of alcoholic probands. These neuroelectric features have been replicated in several laboratories across many different countries and are observed in male and female alcoholics and some of their relatives and offspring. Moreover, these electrophysiological abnormalities are heritable and predictive of future alcohol abuse or dependence.

METHODS

A model is presented which hypothesizes that the genetic predisposition to develop alcoholism involves an initial state of central nervous system (CNS) disinhibition/hyperexcitability. We propose that the event-related brain potential (ERP) anomalies reflect CNS disinhibition. This homeostatic imbalance results in excess levels of CNS excitability which are temporarily alleviated by the ingestion of alcohol. It is hypothesized that this hyperexcitability is heritable, and is critically involved in the predisposition toward alcoholism and the development of dependence. A brief review of the relevant literature is presented.

RESULTS

Neurophysiological, neurochemical, and genetic evidence support the proposed model. In addition, strikingly similar observations between animal research and the human condition are identified. Finally, it is asserted that the proposed model is primarily biological in nature, and therefore does not account for the entire clinical variance.

CONCLUSION

A putative CNS homeostatic imbalance is noted as a critical state of hyperexcitability. This hyperexcitability represents a parsimonious model of what is inherited in the predisposition to develop alcoholism. It is our hope that this model will have heuristic value, resulting in the elucidation of etiological factors involved in alcohol dependence.