A functional MRI study of visual oddball: evidence for frontoparietal dysfunction in subjects at risk for alcoholism

Attending to rare stimuli interspersed among repetitive frequent stimuli produces a positive scalp potential at 300 to 600 ms after the target stimulus onset; this potential is known as the P300 wave. Although there is clear evidence of low visual P300 in subjects at high risk (HR) for developing alcoholism, the functional neuroanatomical correlates have not been studied. Functional and high-resolution anatomical magnetic resonance images were collected during the performance of a visual oddball task, from six control (low risk-LR) subjects with high P300s and eight HR subjects with low P300s. All the HR subjects were offspring of male alcoholics. The data were analyzed using a randomization-based statistical method that accounts for multiple comparisons, requires no assumptions about the noise structure of the data, and does not require spatial or temporal smoothing. Target counts showed that all subjects performed the task comparably. Analysis of the functional magnetic resonance imaging (fMRI) data revealed two areas with significantly lower activation in the HR group when compared to the LR group: the bilateral inferior parietal lobule (BA 40), and the bilateral inferior frontal gyrus (BA 44). Inferior parietal lobule showed significantly lower activation in the HR group in contrast to the LR group, and inferior frontal gyrus was not activated in the HR group but was only activated in the LR group. This finding indicates that a dysfunctional frontoparietal circuit may underlie the low P300 responses seen in HR subjects. This perhaps implies a deficiency in the rehearsal component of the working memory system.

P300 and genetic risk for schizophrenia

BACKGROUND

We assessed the suitability of event-related potential frontal and temporoparietal P300 changes as intermediate phenotypes in genetic studies of schizophrenia. We applied a principal component analysis approach based on the notion that P300 abnormalities in siblings of schizophrenic patients may involve a widespread network of relatively weak cortical generators and because an earlier, smaller study that used a topographic analysis of covariance model did not show that localized P300 changes predict risk for schizophrenia.

METHODS

P300 changes in 66 schizophrenic patients, 115 healthy siblings of schizophrenic patients, and 89 unrelated controls were studied during a standard auditory oddball paradigm. Principal components were calculated across electrodes, revealing frontal and temporoparietal components for latency and amplitude, respectively. For the frontal and temporoparietal P300 amplitude and latency components, the intraclass correlations (ICCs) between sib-pairs (pairs of unaffected siblings and schizophrenic index patients) and the relative risk ratios (lambda) were determined.

RESULTS

Compared with controls, schizophrenic patients and their unaffected siblings showed significant reductions in the temporoparietal P300 amplitude component. Both groups were also characterized by a significantly higher frontal P300 amplitude component. Significant ICCs and increased relative risk ratios were found for the frontal (ICCU = 0.18; P =.04; lambda = 3.4) and temporoparietal (ICCU = 0.24; P =.01; lambda = 1.7) P300 amplitude components.

CONCLUSIONS

Temporoparietal P300 amplitude reduction and frontal P300 amplitude increase seem to be quantitative phenotypes associated with increased risk of schizophrenia. Both measures may be useful for increasing the statistical power of genetic studies of schizophrenia.

Clinical phenotypes associated with DISC1, a candidate gene for schizophrenia

Genetic factors play an important part in the development of schizophrenia and bipolar disorder, and linkage analyses in families have successfully identified several chromosomal regions containing candidate genes. A single large pedigree has been described in which schizophrenia and depression segregate with a balanced chromosomal translocation involving the long arm of chromosome 1 and the short arm of chromosome 11. The gene named DISC1, disrupted at the chromosome 1 breakpoint, is a novel candidate gene that may have a role in the pathogenesis of schizophrenia. The cellular location and function of the protein coded by DISC1 is currently being investigated. The phenotype associated with DISC1 in the t (1;11) translocation family includes schizophrenia, schizoaffective disorder, recurrent major depression and bipolar disorder. Hence this locus is one of several now reported apparently showing linkage to both schizophrenia and bipolar disorder. The study of intermediate phenotypes or "endophenotypes" may clarify the relations between phenotype and genotype. Auditory event related potentials are EEG based physiological measures widely studied in schizophrenia. In particular the cognitive evoked potential, the P300 response generated during an "odd-ball" two-tone discrimination task consistently shows reduced amplitude in schizophrenia compared to controls. In members of the family with the t (1;11) translocation, P300 amplitude was reduced in relatives who carried the translocation compared to relatives with a normal karyotype. Furthermore the amplitude reduction was independent of the presence or absence of symptoms because asymptomatic translocation carriers showed similar P300 amplitude reduction as was found in translocation carriers who were diagnosed with schizophrenia, bipolar disorder or unipolar depression. The results confirm that subjects with schizophrenia who carry the t (1;11) translocation have similar phenotype to unrelated subjects with schizophrenia and a normal karyotype. Furthermore P300 amplitude may be a useful intermediate phenotype detecting the neuropathology of schizophrenia in "at risk" individuals even in the absence of clinical symptoms.

Differential associations of sex and D2 dopamine receptor (DRD2) genotype with negative affect and other substance abuse risk markers in children of alcoholics

Children of alcoholics have increased risk for substance abuse problems. Self-medication of negative affect may be one developmental path to future substance abuse. Because the 146 young (adolescent) children of alcoholics in the current sample had not used enough abused substances to study substance use directly, the relation of substance abuse risk markers to negative affect was assessed. Because the D2 dopamine receptor (DRD2) A1 allele has been associated with alcoholism and other substance use disorders, negative affect, measured by the Beck Depression Inventory (BDI), was determined in four groups of children: boys and girls with the A1+ allele (A1A1 and A1A2 genotypes) and with the A1- allele (A2A2 genotype). The other risk markers were stress, low amplitude of the P300 evoked potential, poor visuospatial functioning, novelty seeking (NS), and harm avoidance (HA). Stress was correlated with BDI scores in all groups. In contrast, low P300 was associated with BDI scores only in boys with the A1+ allele (P = .04), NS was associated with BDI scores only in girls with the A1+ allele (P = .02), and HA was associated with BDI scores only in boys with the A1- allele (P = .01). In addition, boys with the A1+ allele had lower BDI (P = .05) and HA (P = .005) scores than the respective scores for boys with the A1- allele. Girls with the A1- allele had lower HA scores compared with scores for boys with the A1- allele (P = .02). Girls with the A1+ allele had lower visuospatial functioning than that of boys with the A1+ allele (P<.001). Results indicate that both sex and DRD2 genotype modify associations between negative affect and other substance abuse risk markers.

Association analysis for dopamine D3 receptor, dopamine D4 receptor and dopamine transporter genetic polymorphisms and P300 event-related potentials for normal young females

OBJECTIVE

It has been demonstrated that the P300 components, a positive event-related potential, are heritable and are influenced by dopaminergic activity. We tested the genetic effects of the dopaminergic system in P300 components by association study.

METHODS

In a sample population consisting of 120 normal young Han-Chinese females, we explored the association between the P300 components, and, the genetic polymorphisms including the dopamine D3 receptor (serine-to-glycine polymorphism in exon I), the dopamine D4 receptor (variable number tandem repeat polymorphism in exon III), and the dopamine transporter (variable number tandem repeat polymorphism in promoter region).

RESULTS

No associations were demonstrated between the polymorphisms of these three genes and the P300 components.

CONCLUSIONS

Our negative findings suggest that these genetic polymorphisms do not play a major role in the modulation of P300 event-related potentials.

Association analysis of two dopamine D2 receptor gene polymorphisms and p300 event-related potential in depressive patients

Previous Western studies have demonstrated an association between the dopamine D2 receptor (DRD2) TaqI A polymorphism and components of P300 event-related potential. This finding was not replicated in our previous study of a sample of normal young Chinese females, however. In the current study of 105 patients diagnosed with major depression, we have further explored the association between the P300 components, and, the DRD2 TaqI A polymorphism and another functional DRD2 -141Cins/Del polymorphism. The results demonstrate that neither polymorphism is associated with P300 amplitude or latency, even after gender analysis. We suggest that these two DRD2 polymorphisms have no major effects on P300 components for the Chinese population. The association between the DRD2 polymorphism and P300 components may depend on ethnicity, the psychiatric state of the subjects, or the investigative paradigms used.

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.

Genetic sources of covariation among P3(00) and online performance variables in a delayed-response working memory task

Genetic and environmental sources of covariation among the P3(00) and online performance elicited in a delayed-response working memory task, and psychometric IQ assessed by the multidimensional aptitude battery, were examined in an adolescent twin sample. An association between frontal P3 latency and task performance (phenotypic r=-0.33; genotypic r=-0.49) was indicated, with genes (i.e. twin status) accounting for a large part of the covariation (>70%). In contrast, genes influencing P3 amplitude mediated only a small part (2%) of the total genetic variation in task performance. While task performance mediated 15% of the total genetic variation in IQ (phenotypic r=0.22; genotypic r=0.39) there was no association between P3 latency and IQ or P3 amplitude with IQ. The findings provide some insight into the inter-relationships among psychophysiological, performance and psychometric measures of cognitive ability, and provide support for a levels-of-processing genetic model of cognition where genes act on specific sub-components of cognitive processes.

Twin and family studies of the human electroencephalogram: a review and a meta-analysis

Electrophysiological measures may be useful markers of the genetic underpinnings of complex behavior and psychopathology. Twin and family studies have been used to estimate the genetic contribution to the individual differences in a variety of electrophysiological measures. These studies are briefly reviewed here and published twin correlations from a number of studies with comparable methodology were selected for structural equation meta-analyses. For electroencephalographic (EEG) alpha power (11 twin groups) the heritability estimates in each of the single studies were high (averaged 79%), but it was not possible to equate the twin correlations across studies in the meta-analysis. In contrast, combining the data on alpha peak frequency (five twin groups) revealed a 'meta'-heritability of 81% (95% CI: 76-84%). Aggregating the twin correlations of five twin studies on the P300, the estimated meta-heritability is 60% (95% CI: 54-65%) for P300 amplitude and 51% (95% CI: 43-58%) for P300 latency. It is concluded that genomic variation contributes significantly to individual differences in all EEG and event related potential (ERP) measures studied to date.

The relationship between two intermediate phenotypes for alcoholism: low voltage alpha EEG and low P300 ERP amplitude

OBJECTIVE

There is considerable evidence that the amplitude of the heritable P300 event-related potential (ERP) is reduced in alcoholics and their alcohol-naive children. Low voltage alpha (LVA), a heritable resting electroencephalogram (EEG) trait present in 7-14% of the population, has been shown to be associated with alcoholism and anxiety disorders. A few studies have demonstrated a modest correlation between pre-stimulus alpha power and P300 amplitude. We aimed to test this finding in community volunteers, hypothesizing that LVA would be associated with low P300 amplitude.

METHOD

Digitized resting EEG was recorded at the central parietal site (Pz) from 85 male and 113 female community volunteers (120 unrelated). ERPs were elicited at Pz by auditory and visual oddball paradigms. All participants were interviewed with the Schedule for Affective Disorders, Lifetime Version (SADS-L) and assigned blind-rated psychiatric diagnoses according to the American Psychiatric Association DSM-III-R criteria.

RESULTS

LVA participants (including alcoholics and nonalcoholics) had significantly lower auditory and visual P300 amplitudes. Absolute alpha power was modestly correlated with auditory and visual P300 amplitude and was associated with 9.4% and 4.6% of the variance, respectively.

CONCLUSIONS

The association between LVA and low P300 amplitude, two distinct electrophysiological traits, suggests that, at least in individuals with the LVA trait, some aspects of resting, unstimulated brain activity and activated brain function in the form of attentional response may be fundamentally related.

P3 event-related potential amplitude and the risk for disinhibitory disorders in adolescent boys

BACKGROUND

The children of parents who abuse alcohol typically show reduced amplitude of the P3 event-related potential wave. We determined if this effect was present in a population-based sample of older adolescent boys, whether it was associated with paternal antisocial personality and drug use, and whether it appeared in youth with childhood externalizing and substance use disorders.

METHODS

A statewide sample of 502 male youth, identified from Minnesota birth records as members of twin pairs, had their P3 amplitude measured, using a visual oddball paradigm when they were approximately 17 years old. Structured clinical interviews covering attention-deficit/hyperactivity disorder, conduct disorder, oppositional defiant disorder, antisocial personality disorder, and substance use disorders were administered in person to the youth and his parents at the time of the P3 assessment and again to the youth 3 years later.

RESULTS

Reduced P3 was associated with disorders and paternal risk for disorders, reflecting a behavioral disinhibition spectrum that included attention-deficit/hyperactivity disorder, oppositional defiant disorder, conduct disorder, antisocial personality disorder, alcoholism, nicotine dependence, and illicit drug abuse and dependence. Reduced P3 at age 17 predicted the development of substance use disorders at age 20. Most effect sizes associated with these group differences exceeded 0.70, indicating medium to moderately large group differences. Maternal alcoholism and substance use during pregnancy were unrelated to P3 amplitude in offspring.

CONCLUSION

Small amplitude P3 may indicate genetic risk for a dimension of disinhibiting psychiatric disorders, including childhood externalizing, adult antisocial personality disorder, and substance use disorders.

Neurodevelopmental patterns of visual P3b in association with familial risk for alcohol dependence and childhood diagnosis

BACKGROUND

The P3b component of the event-related potential (ERP) has frequently been reported to be reduced in children and adolescents at high risk for developing alcoholism relative to control children and adolescents without familial loading for alcohol dependence. P300 amplitude changes during development for all children. Previously it has been shown that high-risk offspring display a pattern in which the amplitude is lower at age 8 with a smaller rate of change during adolescence.

METHODS

Admixture analysis was applied to data obtained for those children and adolescents having five or more annual assessments of ERPs to determine if multiple P3b growth patterns exist. The P3b amplitude patterns obtained were related to risk status, concurrent presence of childhood psychopathology (internalizing or externalizing), and age of onset to develop a diagnosis.

RESULTS

A pattern characterized by lower P3b amplitude at study entry and a slower rate of change during child and adolescent development (pattern 3) was most often associated with high-risk status in boys and high-risk status in combination with the presence of a childhood diagnosis in girls. Pattern 3 was significantly related to the overall presence of childhood psychopathology (internalizing or externalizing) and to the presence of an Axis I diagnosis at young adult follow-up.

CONCLUSIONS

The developmental pattern previously described for offspring at high risk for developing alcoholism because of their familial/genetic background was confirmed. Admixture analysis has refined this observation and suggests that among all children and adolescents tested, three developmental patterns can be identified, one of which is most often seen in association with male high-risk children and adolescents.

Auditory event-related brain potentials in parents of children with specific language impairment

Auditory event-related brain potentials evoked in response to tone stimuli and to speech stimuli were recorded in a group of parents of children with specific language-impairment and a group of parents of normally speaking children. The parents of the language-impaired children showed longer P3 latencies than the parental control group in the speech task requiring a phonological discrimination, but did not differ from the controls in the linguistically non-demanding tone discrimination task. The longer P3 latency was associated with a positive parental history of language delay. There were no group differences concerning the N1 component in any of the tasks. The findings indicate that parents of children with specific language impairment show signs of deficient late-stage perceptual higher order linguistic processing, whereas the earlier central sensory detection stage of the phonological information is no different from the controls. Our observations are particularly interesting with regard to a study of the children of these two parental groups, where the language-impaired children showed longer P3 latencies than controls in both a tone task and a speech task, whereas there were no differences between the children concerning the N1 component. We propose that deficient late-stage auditory higher order perceptual processing as indexed by the longer P3 latency to speech stimuli observed both in children with specific language-impairment and in their parents may represent a constitutional trait, contributing to the language acquisition difficulties in these children.

Genetic influence on the variance in P3 amplitude and latency

The P3(00) event-related potential (ERP) component is widely used as a measure of cognitive functioning and provides a sensitive electrophysiological index of the attentional and working memory demands of a task. This study investigated what proportion of the variance in the amplitude and latency of the P3, elicited in a delayed response working memory task, could be attributed to genetic factors. In 335 adolescent twin pairs and 48 siblings, the amplitude and latency of the P3 were examined at frontal, central, and parietal sites. Additive genetic factors accounted for 48% to 61% of the variance in P3 amplitude. Approximately one-third of the genetic variation at frontal sites was mediated by a common genetic factor that also influenced the genetic variation at parietal and central sites. Familial resemblance in P3 latency was due to genetic influence that accounted for 44% to 50% of the variance. Genetic covariance in P3 latency across sites was substantial, with a large part of the variance found at parietal, central, and frontal sites attributed to a common genetic factor. The findings provide further evidence that the P3 is a promising phenotype of neural activity of the brain and has the potential to be used in linkage and association analysis in the search for quantitative trait loci (QTLs) influencing cognition.

Stability of genetic and environmental influences on P300 amplitude: a longitudinal study in adolescent twins

This study examined the stability of genetic and environmental influences on individual differences in P300 amplitude during adolescence. The P300 component is an event-related brain potential (ERP) that has attracted much attention as a biological marker for disturbed cognitive processing in psychopathology. Understanding the genetics of this biological marker may contribute to understanding the genetics of the associated psychopathologies. In a group of 213 adolescent twin pairs, the P300 component was measured twice, the first time at age 16 and the second time 18 months later. A large part of the variance of the P300 amplitude could be explained by familial factors, with estimates ranging from 30% to 81%. Whether the familial resemblance was due to genetic or shared environmental factors depended on sex. For males, genetic factors explained familial resemblance in P300 amplitude, but for females such resemblance was likely due to shared environmental factors. The phenotypic stability of the P300 amplitude from 16 to 18 years was high in both sexes, and stability could be attributed largely to the same familial factors. There was no evidence that new familial influences emerged at age 18.

Genetic correlation between the P300 event-related brain potential and the EEG power spectrum

Previous studies have demonstrated moderate heritability of the P300 component of event-related brain potentials (ERPs) and high heritability of background electroencephalogram (EEG) power spectrum. However, it is unclear whether EEG and ERPs are influenced by common or independent genetic factors. This study examined phenotypic and genetic correlations between EEG spectral power and P300 amplitude using data from 206 Dutch twin pairs, age 16 years. Multivariate genetic models (Cholesky decomposition) were fitted to the observed twin covariances using Mx software. In males, genetic correlations between P300 and EEG power measures were high (0.54-0.74); 30% of the total P300 variance could be explained by genetic factors influencing EEG delta power and 26% by P300-specific genetic factors (total heritability 56%). In females, 45% of P300 variance could be attributed to familial influences that were shared with the EEG. However, it was not possible to distinguish between the genetic versus shared environmental factors, consistent with previous analysis of P300 in this sample (van Beijsterveldt et al., 1998). The results suggest that a substantial proportion of genetic influences on P300 amplitude can be explained by strong heritability of slow EEG rhythms contributing to P300.

Association analysis for dopamine D2 receptor Taq1 polymorphism with P300 event-related potential for normal young females

P300 has been demonstrated abnormal for a variety of neuropsychiatric disorders, and heritability has been proposed. We analyzed the event-related potentials for three DRD2 genotype groups in 134 normal young females. The results demonstrate that there is no association for DRD2 genotype and P300 components. Our negative findings in normal subjects suggest association demonstrated for P300 latency and the DRD2 allele may be disease dependent.

Description of the Genetic Analysis Workshop 11 Collaborative Study on the Genetics of Alcoholism

Problem 1 of Genetic Analysis Workshop 11 consists of data from a family study of the genetics of alcoholism and related traits contributed by the six centers making up the National Institute for Alcohol Abuse and Alcoholism sponsored by the Collaborative Study on the Genetics of Alcoholism (COGA). The family data included 1,214 members of 105 pedigrees ascertained for having three or more individuals affected with alcoholism. Data available to workshop participants included clinical phenotypes, personality measures, smoking behavior, event-related potentials, platelet monamine oxidase B activity, and a genome scan of 296 markers.

Visual P300 and the self-directedness scale of the Temperament and Character Inventory

Reduced amplitude of the P300 event-related brain potential has been associated with several psychopathological conditions and is thought to represent brain dysfunction in such conditions. Predisposition to personality disorders and psychopathology in general is also associated with low scores on the self-directedness (SD) scale of the Temperament and Character Inventory. The present preliminary study investigated the relationship between amplitudes of P300 elicited by rare target stimuli in a visual oddball task and SD scores in 58 healthy participants. P300 was found to be significantly reduced in subjects with low SD, as supported by correlational analysis and by comparison of groups formed on the basis of SD scores. This finding may be relevant to prior findings indicating reduced P300 amplitudes in a variety of psychopathological conditions and suggests that a common vulnerability factor, reflected in the low SD personality scores, may contribute to the P300 reduction in psychiatric populations.

[The P300 component of evoked potentials in the evaluation of schizophrenia: new evidence and future visions]

OBJECTIVE

To analyze the character as pathophysiological marker of the P300 component in the evaluation of schizophrenic illness. We therefore review clinical and neuropsychological evidence of studies in which this was used as a tool for evaluation to reach a diagnosis.

DEVELOPMENT

The P300 component is useful for studying not only cognitive processes but also the physiopathology of complex disorders such as schizophrenia. This component reflects the state of functions of attention control and memory, both necessary for final evaluation of a stimulus. These cognitive functions become altered in schizophrenic illness, as is shown by abnormality in the generation of the P300 component. We review the most relevant results, which permit characterization of the many features of schizophrenia from genetic, symptom, morphology and neuropsychological studies in which the P300 component is particularly relevant. Similarly, we analyze current controversies due to the great heterogeneity of methodology and the nature of the illness itself.

CONCLUSIONS

Current understanding allows us to establish that the P300 is a biological marker of relevant aspects of schizophrenia such as the genetic risk of suffering a psychotic episode, determine the type and gravity of the symptoms of the disease, as well as the degree of structural deterioration of the patient. The P300 component is sensitive to the effect of different neuroleptic drugs, on both the symptoms and neuropsychological functions of the patient. These findings let us suggest the P300 component as a valid marker for the evaluation of schizophrenia and the neuropsychological processes.

P300 event-related potential amplitude as an endophenotype of alcoholism--evidence from the collaborative study on the genetics of alcoholism

There is substantial information supporting the role of genetic factors in the susceptibility for alcohol dependence. However, the identification of specific genes that contribute to this predisposition has proven elusive, although several theoretically relevant candidates, e.g. DRD2 or 5-HT(1B), have been considered. The difficulty in identifying specific genes may be related to the clinical heterogeneity of the disorder resulting in a poorly defined phenotype for genetic analysis. An alternative approach to the use of a diagnostic phenotype for identifying alcoholism susceptibility genes may lie in the examination of the neurobiological correlates of the disorder, the so-called endophenotypes. One possible endophenotype of alcohol dependence may be related to the P300 waveform of the event-related brain potential (ERP). Using data obtained from the Collaborative Study on the Genetics of Alcoholism (COGA), a multi-site family-based study, the utility of P300 amplitude as an endophentype was examined. Differences in P300 amplitude were found between alcoholics and nonalcoholics, between unaffected relatives of alcoholics and relatives of controls, as well as between unaffected offspring of alcoholic fathers and offspring of controls. A genetic analysis indicated that attributes of the P(3) ERP waveform are heritable, and a quantitative trait locus analysis found linkage to several chromosomal regions. These data provide significant support for P300 as an endophenotype for alcohol dependence.

P300 in family studies of schizophrenia: review and critique

The published studies using P300 event-related potential (ERP) as a vulnerability marker in schizophrenia have been summarized and reviewed. Several factors across sibling, offspring, and familial studies appear to contribute to the variegated findings with respect to the utility of P300 as a vulnerability marker for schizophrenia. These include how subject samples are defined in terms of their genetic loading for schizophrenia, sample size, ERP methodology, and the relationship of P300 measures to neuropsychological test outcomes. It was concluded that the P300 holds promise as a vulnerability marker for schizophrenia, if used in conjunction with other neuroimaging and neuropsychological testing methods.

Lateralized P3 deficit in schizotypal personality disorder

BACKGROUND

Reduced, left-lateralized P3 amplitude has been reported in several studies focusing on electrophysiologic function in schizophrenia. Also, several lines of evidence suggest a similarity between schizophrenia and schizotypal personality disorder (SPD). This study was undertaken to determine the replicability of our previous finding of a left-lateralized P3 amplitude deficit in SPD.

METHODS

We recorded event-related potentials in 21 SPD and 18 normal control subjects in an auditory "oddball" P3 paradigm.

RESULTS

In the SPD subjects, but not in the control subjects, there was lower P3 amplitude at T3 compared with T4.

CONCLUSIONS

These results are similar to the ones in our previous work and further support the presence of a left-lateralized P3 deficit in SPD.