Linkage of eye movement dysfunction to chromosome 6p in schizophrenia: additional evidence

Pseudoneurotic Symptoms in the Schizophrenia Spectrum: A Longitudinal Study of Their Relation to Psychopathology and Clinical Outcomes

BACKGROUND AND HYPOTHESIS

Nonpsychotic symptoms (depression, anxiety, obsessions, etc.) are frequent in schizophrenia-spectrum disorders and are usually conceptualized as comorbidity or transdiagnostic symptoms. However, in twentieth century foundational psychopathological literature, many nonpsychotic symptoms with specific phenomenology (here termed pseudoneurotic symptoms) were considered relatively typical of schizophrenia. In this prospective study, we investigated potential associations of pseudoneurotic symptoms with diagnostic status, functional outcome as well as psychopathological dimensions of schizophrenia.

STUDY DESIGN

First-admitted patients (N = 121) diagnosed with non-affective psychosis, schizotypal disorder, or other mental illness were examined at initial hospitalization and 5 years later with a comprehensive assessment of psychopathology. Informed by the literature, we constructed scales targeting pseudoneurotic symptoms and other, more general, nonpsychotic symptoms.

STUDY RESULTS

Pseudoneurotic symptoms aggregated in schizophrenia-spectrum groups compared to other mental illnesses and occurred at similar levels at baseline and follow-up. They longitudinally predicted poorer social and occupational functioning in schizophrenia-spectrum patients over a 5-year-period but not transition to schizophrenia-spectrum disorders from other mental illnesses. Finally, the level of pseudoneurotic symptoms correlated with disorder of basic self at both assessments and with positive and negative symptoms at follow-up. The scale targeting general nonpsychotic symptoms did not show this pattern of associations.

CONCLUSIONS

The study supports that a group of nonpsychotic symptoms, ie, pseudoneurotic symptoms, are associated with schizophrenia-spectrum disorders and linked with temporally stable psychopathology, particularly disorder of the basic self. Their prospective association with social and occupational functioning needs replication.

Pseudoneurotic symptoms in the schizophrenia spectrum: An empirical study

BACKGROUND

Nonpsychotic symptoms (depression, anxiety, obsessions etc.) are frequent in schizophrenia-spectrum disorders. Twentieth century foundational psychopathological literature claimed that certain nonpsychotic symptoms (here termed pseudoneurotic symptoms) are relatively closely linked with the schizophrenia-spectrum, despite descriptive overlap with symptoms of other diagnoses. In this study, we investigated the association of pseudoneurotic and other nonpsychotic symptoms with the schizophrenia-spectrum as well as a hypothesis about an association of pseudoneurotic symptoms with disorder of basic self.

METHODS

The sample (N = 226) comprised patients with non-affective psychosis (N = 119), schizotypal personality disorder (N = 51) and other mental illness (N = 56), who were examined with a comprehensive assessment of lifetime psychopathology. Informed by the literature, we constructed scales targeting pseudoneurotic symptoms and other, more general, nonpsychotic symptoms.

RESULTS

Pseudoneurotic symptoms aggregated significantly in schizophrenia-spectrum disorders with an Area under the receiver operating characteristic curve of 0.84 (SE 0.03) for classifying patients with schizophrenia-spectrum disorders versus other mental illness. Patients with non-affective psychosis scored slightly, but significantly, higher on the scale targeting general nonpsychotic symptomatology than the other groups. In multiple regression analysis, pseudoneurotic symptoms were predicted by general nonpsychotic symptoms, disorders of basic self, and negative symptoms but not positive symptoms.

CONCLUSION

The study supports that certain neurotic-like symptoms with specific descriptive features (pseudoneurotic symptoms) are associated with schizophrenia-spectrum disorders. It suggests that pseudoneurotic symptoms are linked with temporally stable schizophrenia psychopathology (disorder of basic self and negative symptoms).

Disordered Selfhood in Schizophrenia and the Examination of Anomalous Self-Experience: Accumulated Evidence and Experience

Disordered selfhood in schizophrenia was rediscovered at the turn of the millennium. In 2005, Psychopathology published the psychometric instrument, the Examination of Anomalous Self-Experience (EASE). In this article, we summarize the historical background of the creation of the EASE, explicate the notion of the disorder of basic or minimal self with the help of phenomenological philosophy, and provide a brief description of clinical manifestations targeted by the EASE. We also present our personal experience using and teaching the EASE and summarize the empirical evidence obtained so far. We conclude that the basic self-disorder represents a crucial phenotype of schizophrenia spectrum disorders and that this phenotype offers a potential avenue to empirical pathogenetic research and psychotherapeutic treatment.

Formal Thought Disorder and Self-Disorder: An Empirical Study

Background: Formal thought disorder was constitutively linked to the original concept of schizophrenia and has since been one of central features supporting its diagnosis. Bleuler considered formal thought disorder as a fundamental symptom of schizophrenia among other fundamental symptoms, including ego disorders. The contemporary concept of self-disorder represents a more developed, nuanced, and systematic approach to disturbances of self-experience than the Bleulerian concept of ego disorders. As fundamental symptoms, on Bleuler's account, are persistently present in every case, an association between these symptoms could be expected. The purpose of this study was to examine the association between self-disorder and formal thought disorder. Methods: A sample of 94 diagnostically heterogeneous patients was examined for formal thought disorder using clinical rating and a proverb test. The proverb test was analyzed for two different aspects of formal thought disorder: literal responses and bizarre responses. The sample was comprehensively assessed for psychopathology, including self-disorder as measured with the Examination of Anomalous Self-Experience scale. Results: The patients, who provided bizarre responses, had a higher level of self-disorder, more negative symptoms, lower level of social functioning, and lower level of intelligence. Bizarre answers aggregated in patients diagnosed within the schizophrenia spectrum compared with patients outside the schizophrenia spectrum. We found moderate correlations between the two measures of formal thought disorder (clinically rated and bizarre responses) and self-disorder (0.454 [p < 0.01] and 0.328 [p < 0.01]). Literal responses did not differ between diagnostic groups and also did not correlate with bizarre responses. Specificity of bizarre responses for a diagnosis within schizophrenia spectrum was 86.89%, whereas sensitivity was 40.85%. Conclusion: The close relation between formal thought disorder and self-disorder further adds to the notion of self-disorder as a unifying psychopathological core beneath the apparently heterogeneous symptoms of schizophrenia.

Exploring schizophrenia spectrum psychopathology in borderline personality disorder

We have previously argued that the current borderline personality disorder (BPD) diagnosis is over-inclusive and clinically and conceptually impossible to distinguish from the schizophrenia spectrum disorders. This study involves 30 patients clinically diagnosed with BPD as their main diagnosis by three BPD dedicated outpatient treatment facilities in Denmark. The patients underwent a careful and time-consuming psychiatric evaluation involving several senior level clinical psychiatrists and researchers and a comprehensive battery of psychopathological scales. The study found that the vast majority of patients (67% in DSM-5 and 77% in ICD-10) in fact met the criteria for a schizophrenia spectrum disorder, i.e., schizophrenia (20%) or schizotypal (personality) disorder (SPD). The schizophrenia spectrum group scored significantly higher on the level of disorders of core self as measured by the Examination of Anomalous Self-Experiences Scale (EASE). The BPD criterion of "identity disturbance" was significantly correlated with the mean total score of EASE. These findings are discussed in the light of changes from prototypical to polythetic diagnostic systems. We argue that the original prototypes/gestalts informing the creation of BPD and SPD have gone into oblivion during the evolution of polythetic criteria.

Differential-diagnostic confusion and non-specificity of affective symptoms and anxiety: An empirical study of first-admission patients

In everyday clinical work, psychiatrists encounter patients who present with symptoms spanning several diagnostic categories, e.g., showing signs of a psychosis, depression, and anxiety. This raises the critical question of which symptoms hold precedence over other and, by extension, which diagnosis is the right diagnosis. ICD-10 and DSM-5 do not provide unambiguous answers to this question and therefore psychiatry remains exposed to diagnostic disagreement with consequences for treatment and research. We explored symptom distribution in a sample of 98 first-admission psychiatric patients. We extracted and categorized singular symptoms into symptom domains: anxiety, mania, delusions, hallucinations, first-rank symptoms, and negative symptoms. Most symptoms were seen in most disorders. We found symptoms of depression and anxiety in almost all patients. Thus, just counting symptoms do not seem to be a valid way to make diagnoses. We elaborately discuss these issues in the context of the differential-diagnosis between schizophrenia and depression. Finally, we suggest that a combination of a criteria- and Gestalt-based approach to diagnosing mental disorders may contribute to counteract some of the current differential-diagnostic confusion.

Social Life in the Schizophrenia Spectrum: A Phenomenological Study of Five Patients

BACKGROUND

Social difficulties are a hallmark of schizophrenia spectrum conditions, yet their background and exact nature remain contested. Previous pivotal studies on chronically ill patients have suggested that a position of "positive withdrawal" is associated with a decreased tendency to rehospitalization. This concept designates an essentially withdrawn but not negatively experienced position balanced by elements relating the individual to the social world.

OBJECTIVES

To explore a less ill subgroup of schizophrenia spectrum patients' ways of navigating the social world and examine potential links to anomalous self-experiences by applying key insights from phenomenology and anthropology.

METHOD

The present study was part of a 5-year follow-up on a group of first-admission schizophrenia spectrum patients. From this sample of 48 patients, 5 were selected for qualitative evaluation following the principles of thematic analysis.

RESULTS

A "positively withdrawn" position characterizes a wider group of patients than originally reported. Further, we identified a preference for partaking in social activities in particular circumstances with clearly circumscribed goals or social roles and rules. This alleviated social discomfort and helped patients stay embedded in a social milieu. All patients experienced high levels of self-disorders.

CONCLUSIONS

We suggest that certain aspects of social impairment may, in fact, reflect meaningful compensatory mechanisms, and argue that this conceptualization of social difficulties is relevant to various psychotherapeutic interventions.

Self-disorders in schizophrenia-spectrum disorders: a 5-year follow-up study

Self-disorders have been hypothesized to be an underlying and trait-like core feature of schizophrenia-spectrum disorders and a certain degree of temporal stability of self-disorders would therefore be expected. The aim of the study was to examine the persistence of self-disorders measured by the Examination of Anomalous Self Experiences over a time span of 5 years. 48 patients with schizophrenia-spectrum disorders were thoroughly assessed for psychopathology at baseline and 5 years later. Self-disorders were assessed by the Examination of Anomalous Self Experiences. The level of self-disorders was same at the two occasions for the full Examination of Anomalous Self Disorders and for four out of the five domains. For one domain, the level of self-disorders increased slightly from baseline to follow-up. The correlations between baseline and follow-up were moderate. 9 out of the 13 most-frequently rated items at baseline showed equal frequencies at follow-up. The baseline level of self-disorders predicted global symptomatic, but not functional outcome. Self-disorders measured by the Examination of Anomalous Self Experiences show a high level of temporal persistence over 5 years and predict symptomatic outcome.

Genome-wide association studies of smooth pursuit and antisaccade eye movements in psychotic disorders: findings from the B-SNIP study

Eye movement deviations, particularly deficits of initial sensorimotor processing and sustained pursuit maintenance, and antisaccade inhibition errors, are established intermediate phenotypes for psychotic disorders. We here studied eye movement measures of 849 participants from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) study (schizophrenia N=230, schizoaffective disorder N=155, psychotic bipolar disorder N=206 and healthy controls N=258) as quantitative phenotypes in relation to genetic data, while controlling for genetically derived ancestry measures, age and sex. A mixed-modeling genome-wide association studies approach was used including ~4.4 million genotypes (PsychChip and 1000 Genomes imputation). Across participants, sensorimotor processing at pursuit initiation was significantly associated with a single nucleotide polymorphism in IPO8 (12p11.21, P=8 × 10-11), whereas suggestive associations with sustained pursuit maintenance were identified with SNPs in SH3GL2 (9p22.2, P=3 × 10-8). In participants of predominantly African ancestry, sensorimotor processing was also significantly associated with SNPs in PCDH12 (5q31.3, P=1.6 × 10-10), and suggestive associations were observed with NRSN1 (6p22.3, P=5.4 × 10-8) and LMO7 (13q22.2, P=7.3x10-8), whereas antisaccade error rate was significantly associated with a non-coding region at chromosome 7 (P=6.5 × 10-9). Exploratory pathway analyses revealed associations with nervous system development and function for 40 top genes with sensorimotor processing and pursuit maintenance (P=4.9 × 10-2-9.8 × 10-4). Our findings suggest novel patterns of genetic variation relevant for brain systems subserving eye movement control known to be impaired in psychotic disorders. They include genes involved in nuclear trafficking and gene silencing (IPO8), fast axonal guidance and synaptic specificity (PCDH12), transduction of nerve signals (NRSN1), retinal degeneration (LMO7), synaptic glutamate release (SH3GL2), and broader nervous system development and function.

Exploring social cognition in schizophrenia

The aim of the study was to compare social cognition between groups of patients diagnosed with schizophrenia and healthy controls and to replicate two previous studies using tests of social cognition that may be particularly sensitive to social cognitive deficits in schizophrenia. Thirty-eight first-admitted patients with schizophrenia and 38 healthy controls solved 11 "imaginary conversation (i.e., theory of mind)" items, 10 "psychological understanding" items, and 10 "practical understanding" items. Statistical tests were made of unadjusted and adjusted group differences in models adjusting for intelligence and neuropsychological test performance. Healthy controls performed better than patients on all types of social cognitive tests, particularly on "psychological understanding." However, after adjusting for intelligence and neuropsychological test performance, all group differences became nonsignificant. When intelligence and global cognitive functioning is taken into account, schizophrenia patients and healthy controls perform similarly on social cognitive tests.

EASE: Examination of Anomalous Self-Experience

Skala EASE jest listą objawów do częściowo ustrukturalizowanego fenomenologicznego badania subiektywnych lub empirycznych nieprawidłowości (anomalii), które można uznać za zaburzenia podstawowej, „minimalnej” samoświadomości. EASE opracowana została na podstawie samoopisów otrzymanych od pacjentów chorujących na zaburzenia ze spektrum schizofrenii. Skala ma duże znaczenie dla opisu, diagnozy oraz diagnozy różnicowej zaburzeń ze spektrum schizofrenii. Prezentowana wersja zawiera istotne szczegółowe kwestie dotyczące zbierania wywiadu oraz opisy objawów psychopatologicznych (Podręcznik), arkusz wyników (Aneks A), listę pozostałych pozycji Skali stosowanych w czasie wywiadu (Aneks B) oraz porównawczą listę pozycji EASE/BSABS (Bonner Skala für die Beurteilung von Basissymptomen, Bońska Skala do Oceny Objawów Podstawowych) (Aneks C).

Temporal persistence of anomalous self-experience: A 5years follow-up

BACKGROUND

The concept of self-disorders in schizophrenia has gained substantial interest and it has now been established empirically that self-disorders aggregate in schizophrenia-spectrum disorders but not in other mental disorders or in healthy controls. Yet, the issue of temporal persistence has not been addressed.

AIM

The aim of this study is to examine the temporal persistence of self-disorders.

METHODS

96 first admission patients were thoroughly assessed for psychopathology including SD at baseline and again 5years later. We created a 25-item self-disorder scale which was used both at baseline and follow-up to assess self-disorders. The scale was a pre-cursor of the later published EASE-scale. Additionally, we examined the development of positive and negative syndromes and of the Global Assessment of Functioning (GAF).

RESULTS

There was a high correlation between self-disorders at baseline and at follow-up, and the majority of the items in self-disorders scale showed equal proportions between baseline and follow-up.

CONCLUSION

Self-disturbances showed a high level of persistence at 5-year follow-up.

Eye Movement in Unipolar and Bipolar Depression: A Systematic Review of the Literature

BACKGROUND

The analysis of eye movements (EM) by eye-tracking has been carried out for several decades to investigate mood regulation, emotional information processing, and psychomotor disturbances in depressive disorders.

METHOD

A systematic review of all English language PubMed articles using the terms "saccadic eye movements" OR "eye-tracking" AND "depression" OR "bipolar disorders" was conducted using PRISMA guidelines. The aim of this review was to characterize the specific alterations of EM in unipolar and bipolar depression.

RESULTS

Findings regarding psychomotor disturbance showed an increase in reaction time in prosaccade and antisaccade tasks in both unipolar and bipolar disorders. In both disorders, patients have been reported to have an attraction for negative emotions, especially for negative pictures in unipolar and threatening images in bipolar disorder. However, the pattern could change with aging, elderly unipolar patients disengaging key features of sad and neutral stimuli. METHODological limitations generally include small sample sizes with mixed unipolar and bipolar depressed patients.

CONCLUSION

Eye movement analysis can be used to discriminate patients with depressive disorders from controls, as well as patients with bipolar disorder from patients with unipolar depression. General knowledge concerning psychomotor alterations and affective regulation strategies associated with each disorder can also be gained thanks to the analysis. Future directions for research on eye movement and depression are proposed in this review.

Linkage and whole genome sequencing identify a locus on 6q25-26 for formal thought disorder and implicate MEF2A regulation

Formal thought disorder is a major feature of schizophrenia and other psychotic disorders. It is heritable, found in healthy relatives of patients with schizophrenia and other mental disorders but knowledge of specific genetic factors is lacking. The aim of this study was to search for biologically relevant high-risk variants. Formal thought disorder was assessed in participants in the Copenhagen Schizophrenia Linkage Study (N=236), a unique high-risk family study comprised of six large pedigrees. Microsatellite linkage analysis of formal thought disorder was performed and subsequent haplotype analysis of the implicated region using phased microsatellite and SNP genotypes. Whole genome sequencing (N=3) was used in the attempt to identify causative variants in the linkage region. Linkage analysis of formal thought disorder resulted in a single peak at chromosome 6(q26-q27) centred on marker D6S1277, with a maximum LOD score of 4.0. Phasing and fine mapping of the linkage peak identified a 5.5Mb haplotype (chr6:162242322-167753547, hg18) in 31 individuals, all belonging to the same pedigree sharing the haplotype from a common ancestor. The haplotype segregated with increased total thought disorder index score (P=4.9 × 10(-5)) and qualitatively severe forms of thought disturbances. Whole genome sequencing identified a novel nucleotide deletion (chr6:164377205 AG>A, hg18) predicted to disrupt the potential binding of the transcription factor MEF2A. The MEF2A binding site is located between two genes previously reported to associate with schizophrenia, QKI (HGNC:21100) and PDE10A (HGNC:8772). The findings are consistent with MEF2A deregulation conferring risk of formal thought disorder.

Exploring rationality in schizophrenia

BACKGROUND

Empirical studies of rationality (syllogisms) in patients with schizophrenia have obtained different results. One study found that patients reason more logically if the syllogism is presented through an unusual content.

AIMS

To explore syllogism-based rationality in schizophrenia.

METHOD

Thirty-eight first-admitted patients with schizophrenia and 38 healthy controls solved 29 syllogisms that varied in presentation content (ordinary v. unusual) and validity (valid v. invalid). Statistical tests were made of unadjusted and adjusted group differences in models adjusting for intelligence and neuropsychological test performance.

RESULTS

Controls outperformed patients on all syllogism types, but the difference between the two groups was only significant for valid syllogisms presented with unusual content. However, when adjusting for intelligence and neuropsychological test performance, all group differences became non-significant.

CONCLUSIONS

When taking intelligence and neuropsychological performance into account, patients with schizophrenia and controls perform similarly on syllogism tests of rationality.

DECLARATION OF INTEREST

None.

COPYRIGHT AND USAGE

© The Royal College of Psychiatrists 2015. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) licence.

Self-Disorders, Neurocognition and Rationality in Schizophrenia: A Preliminary Study

BACKGROUND/AIMS

Although the very idea that the generative disorder in schizophrenia is a disturbance of the self is as old as the schizophrenia concept itself, empirical studies have only recently emerged, documenting that anomalous self-experiences (i.e. self-disorders, SDs) aggregate in schizophrenia spectrum disorders but not in other mental disorders. The aim of this study is to explore potential associations between SDs, neurocognitive performance, rationality and IQ in patients with schizophrenia.

METHODS

The sample comprises 31 patients diagnosed with schizophrenia (DSM-IV). All patients underwent comprehensive evaluation. SDs were assessed with the Examination of Anomalous Self-Experience scale. Neurocognitive performance was measured with 4 PC-implemented subtests from the Cambridge Neuropsychological Test Automated Battery. Rationality was measured using syllogism tests. The IQ was indexed by a summary score of 4 IST-2000-R computerized subtests.

RESULTS

No correlation was found between SDs and neurocognitive performance or between SDs and IQ. SDs were found to correlate with rationality. Neurocognitive performance correlated with rationality, and both correlated with IQ, respectively.

CONCLUSIONS

The lack of correlation between SDs and neurocognitive performance is consistent with the results from the only previous study exploring this issue, suggesting that SDs depict something essential to schizophrenia, whereas neurocognitive impairment does not. The correlation between SDs and rationality indicates that the syllogism tests reflect something central for schizophrenia, but the result needs further corroboration from larger, empirical studies.

Self-disorders and the schizophrenia spectrum: a study of 100 first hospital admissions

INTRODUCTION

Self-disorders (SD) have been described as a core feature of schizophrenia both in classical and recent psychopathological literature. However, the specificity of SD for the schizophrenia spectrum disorders has never been demonstrated in a diagnostically heterogeneous sample, nor has the concurrent validity of SD been examined.

AIM

(1) To examine the specificity of Examination of Anomalous Self-Experiences (EASE) measured SD to the schizophrenia spectrum disorder in first contact inpatients, (2) to explore the internal consistency and factorial structure of the EASE, (3) to assess the concurrent validity of SD by exploring correlations between SD and the canonical psychopathological dimensions of schizophrenia, (4) to explore relations of SD to intelligence, sociodemographic, and extrinsic illness characteristics.

METHODS

A total of 100 consecutive first admission patients underwent a comprehensive psychopathological examination and an assessment of SD with the EASE scale. The diagnostic distribution of the EASE scores was tested with ANOVA, whereas the relations between the EASE scores and other symptomatic dimensions of schizophrenia were tested with Spearman's rho. A potential factorial structure and the internal consistency of the EASE scale were also examined.

RESULTS

SD aggregated significantly in the schizophrenia spectrum disorders, with no differences between schizophrenia and schizotypal disorders. EASE scores correlated moderately with canonical psychopathological dimensions of schizophrenia. Factor analysis of the EASE disclosed only one factor and the internal consistency of the EASE was excellent.

CONCLUSIONS

SD aggregate selectively in the schizophrenia spectrum disorders, with similar levels in schizophrenia and schizotypy. The study lends validity to the view of SD as an experiential vulnerability phenotype of the schizophrenia spectrum disorders.

Disordered self in the schizophrenia spectrum: a clinical and research perspective

This article explores the phenomenological and empirical rediscovery of anomalous self-experience as a core feature of the schizophrenia spectrum disorders and presents the current status of research in this field. Historically, a disordered self was considered to be a constitutive phenotype of schizophrenia. Although the notion of a disordered self has continued to appear occasionally over the years-mainly in the phenomenologically or psychodynamically oriented literature-this notion was usually considered as a theoretical construct rather than as referring to concretely lived anomalous experiences. Empirical research on the disorders of self-experience in schizophrenia can be traced back to the US-Denmark psychopathological collaboration in the well-known adoption and high-risk studies, which aimed at identifying trait or phenotypic vulnerability features. This research was later followed by clinical work with first-admission schizophrenia patients. We offer clinical descriptions of anomalous self-experience and outline the phenomenological structures of subjectivity that are needed for grasping the nature of these anomalous experiential phenomena. What appears to underlie these experiences is an instability of the first-person perspective that threatens the basic experience of being a self-coinciding, embodied, demarcated, and persisting subject of awareness. We summarize a series of empirical studies targeting self-experience in schizophrenia performed prior to and after the construction of a phenomenologically oriented psychometric instrument for assessing anomalies of self-experience, the Examination of Anomalous Self-Experience (EASE). These empirical studies support the classic clinical intuition that anomalous self-experiences form a central phenotype of schizophrenia. Implications for diagnosis and research are briefly discussed.

Smooth pursuit eye movement, prepulse inhibition, and auditory paired stimuli processing endophenotypes across the schizophrenia-bipolar disorder psychosis dimension

BACKGROUND

This study examined smooth pursuit eye movement (SPEM), prepulse inhibition (PPI), and auditory event-related potentials (ERP) to paired stimuli as putative endophenotypes of psychosis across the schizophrenia-bipolar disorder dimension.

METHODS

Sixty-four schizophrenia probands (SZP), 40 psychotic bipolar I disorder probands (BDP), 31 relatives of SZP (SZR), 26 relatives of BDP (BDR), and 53 healthy controls (HC) were tested. Standard clinical characterization, SPEM, PPI, and ERP measures were administered.

RESULTS

There were no differences between either SZP and BDP or SZR and BDR on any of the SPEM, PPI, or ERP measure. Compared with HC, SZP and BDP had lower SPEM maintenance and predictive pursuit gain and ERP theta/alpha and beta magnitudes to the initial stimulus. PPI did not differ between the psychosis probands and HC. Compared with HC, SZR and BDR had lower predictive pursuit gain and ERP theta/alpha and beta magnitudes to the first stimulus with differences ranging from a significant to a trend level. Neither active symptoms severity nor concomitant medications were associated with neurophysiological outcomes. SPEM, PPI, and ERP scores had low intercorrelations.

CONCLUSION

These findings support SPEM predictive pursuit and lower frequency auditory ERP activity in a paired stimuli paradigm as putative endophenotypes of psychosis common to SZ and BD probands and relatives. PPI did not differ between the psychosis probands and HC. Future studies in larger scale psychosis family samples targeting putative psychosis endophenotypes and underlying molecular and genetic mediators may aid in the development of biology-based diagnostic definitions.

Non-Mendelian etiologic factors in neuropsychiatric illness: pleiotropy, epigenetics, and convergence

The target article by Charney on behavior genetics/genomics discusses how numerous molecular factors can inform heritability estimations and genetic association studies. These factors find application in the search for genes for behavioral phenotypes, including neuropsychiatric disorders. We elaborate upon how single causal factors can generate multiple phenotypes, and discuss how multiple causal factors may converge on common neurodevelopmental mechanisms.

Assessing the diagnostic validity of a structured psychiatric interview in a first-admission hospital sample

The use of structured psychiatric interviews performed by non-clinicians is frequent for research purposes and is becoming increasingly common in clini-cal practice. The validity of such interviews has rarely been evaluated empirically. In this study of a sample of 100 diagnostically heterogeneous, first-admitted inpatients, the results of an assessment with the Structured Clinical Interview for DSM-IV (SCID), yielding a DSM-IV diagnosis and performed by a trained non-clinician, were compared with a consensus lifetime best diagnostic estimate (DSM-IV) by two experienced research clinicians, based on multiple sources of information, which included videotaped comprehensive semi-structured narrative interviews. The overall kappa agreement was 0.18. The sensitivity and specificity for the diagnosis of schizophrenia by SCID were 19% and 100%, respectively. It is concluded that structured interviews performed by non-clinicians are not recommendable for clinical work and should only be used in research with certain precautions. It is suggested that a revival of systematic theoretical and practical training in psychopathology is an obvious way forward in order to improve the validity and therapeutic utility of psychiatric diagnosis.

Self-experience in the early phases of schizophrenia: 5-year follow-up of the Copenhagen Prodromal Study

Despite the avalanche of empirical data on prodromal/"at risk" conditions, the essential aspects of the vulnerability to the schizophrenia spectrum remain largely unaddressed. We report here the results of the Copenhagen Schizophrenia Prodromal Study, a prospective, observational study of first admission patients in putative state of beginning psychosis (N=151) with a follow-up length of 60 months. At follow-up, the rate of conversion to schizophrenia spectrum diagnosis was 37%, whereas the conversion rate from schizotypal disorder to schizophrenia was 25%. High levels of perplexity and self-disorders baseline scores yielded the best prediction of the subsequent development of schizophrenia spectrum disorders. Escalating transitions within the spectrum (i.e., from schizotypal disorder to schizophrenia) were not associated to any candidate psychopathological predictor.

The silent side of the spectrum: schizotypy and the schizotaxic self

The identification of individuals carrying unexpressed genetic liability to schizophrenia is crucial for both etiological research and clinical risk stratification. Subclinical psychopathological features detectable in the nonpsychotic part of the schizophrenia spectrum could improve the delineation of informative vulnerability phenotypes. Inspired by Meehl's schizotaxia-schizotypy heuristic model, we tested anomalous subjective experiences (self-disorders, SDs) as a candidate vulnerability phenotype in a sample of nonpsychotic, genetically high-risk subjects. A total of 218 unaffected members of 6 extended multiplex families (assessed between 1989 and 1999 during the Copenhagen Schizophrenia Linkage Study) were stratified into 4 groups of increasing psychopathological expressivity: no mental illness (NMI), no mental illness with schizotypal traits (NMI-ST), personality disorders not fulfilling other personality disorders (OPDs), and schizotypal personality disorder (SPD). We tested the distribution of SDs among the subgroups, the effect of SDs on the risk of belonging to the different subgroups, and the effect of experimental grouping and concomitant psychopathology (ie, negative symptoms (NSs) and subpsychotic formal thought disorder [FTD]) on the chances of experiencing SDs. SDs distribution followed an incremental pattern from NMI to SPD. SDs were associated with a markedly increased risk of NMI-ST, OPDs, or SPD. The odds of SDs increased as a function of the diagnostic category assignment, independently of sociodemographics and concomitant subclinical psychopathology (NSs and FTD). The results support SDs as an expression of schizotaxic vulnerability and indicate a multidimensional model of schizotypy--characterized by SDs, NSs, FTD--as a promising heuristic construct to address liability phenotypes in genetically high-risk studies.

Contribution of nonprimate animal models in understanding the etiology of schizophrenia

Schizophrenia is a severe psychiatric disorder that is characterized by positive and negative symptoms and cognitive impairments. The etiology of the disorder is complex, and it is thought to follow a multifactorial threshold model of inheritance with genetic and neurodevelop mental contributions to risk. Human studies are particularly useful in capturing the richness of the phenotype, but they are often limited to the use of correlational approaches. By assessing behavioural abnormalities in both humans and rodents, nonprimate animal models of schizophrenia provide unique insight into the etiology and mechanisms of the disorder. This review discusses the phenomenology and etiology of schizophrenia and the contribution of current nonprimate animal models with an emphasis on how research with models of neuro transmitter dysregulation, environmental risk factors, neurodevelopmental disruption and genetic risk factors can complement the literature on schizophrenia in humans.

Looking at the schizophrenia spectrum through the prism of self-disorders: an empirical study

Nonpsychotic anomalies of subjective experience were emphasized in both classic literature and phenomenological psychiatry as essential clinical features of schizophrenia. However, only in recent years, their topicality with respect to the construct validity of the concept of the schizophrenia spectrum has been explicitly acknowledged, mainly as a consequence of the increasing focus on early detection and prevention of psychosis. The current study tested the hypothesis of a specific aggregation of self-disorders (SDs, various anomalies of self-awareness) in schizophrenia-spectrum conditions, comparing different diagnostic groups; 305 subjects, previously assessed in the Copenhagen Schizophrenia Linkage Study, were grouped into 4 experimental samples, according to their Diagnostic and Statistical Manual of Mental Disorders (Third Edition Revised) main diagnosis: schizophrenia, (n = 29), schizotypal personality disorder (n = 61), other mental illness not belonging to the schizophrenia spectrum (n = 112), and no mental illness (n = 103). The effect of diagnostic grouping on the level of SDs was explored via general linear model and logistic regression. The diagnosis of schizophrenia and schizotypy predicted higher levels of SDs, and SDs scores were significantly different between spectrum and nonspectrum samples; the likelihood of experiencing SDs increased as well with the diagnostic severity. The findings support the assumption that SDs are a discriminant psychopathological feature of the schizophrenia spectrum and suggest their incorporation to strengthen its construct validity, with potential benefit for both early detection and pathogenetic research.

Rethinking the genetic basis for comorbidity of schizophrenia and type 2 diabetes

The co-occurrence of schizophrenia (SCZ) and type 2 diabetes mellitus (T2D) has been well documented. This review article focuses on the hypothesis that the co-occurrence of SCZ and T2D may be, at least in part, driven by shared genetic factors. Previous genetic studies of T2D and SCZ evidence have disclosed a number of overlapped risk loci. However, the putative common genetic factors for SCZ and T2D remain inconclusive due to inconsistent findings. A systemic review of methods of identifying genetic loci contributing to the comorbidity link between SCZ and T2D is hence needed. In the current review article, we have discussed several different approaches to localizing the shared susceptibility genes for these two diseases. To begin with, one could start with probing the gene involved in both glucose and dopamine metabolisms. Additionally, hypothesis-free genome-wide association studies (GWAS) may provide more clues to the common genetic basis for these two diseases. Genetic similarities inferred from GWAS may shed some light on the genetic mechanism underlying the comorbidity link between SCZ and T2D. Meanwhile, endophenotypes (e.g., adiponectin level in T2D and working memory in SCZ) may serve as alternative phenotypes that are more directly influenced by genes than target diseases. Hence, endophenotypes of these diseases may be more tractable to identification. To summarize, novel approaches are needed to dissect the complex genetic basis of the comorbidity of SCZ and T2D.

A unifying hypothesis of schizophrenia: abnormal immune system development may help explain roles of prenatal hazards, post-pubertal onset, stress, genes, climate, infections, and brain dysfunction

We propose a unifying hypothesis of schizophrenia to help reconcile findings from many different disciplines. This hypothesis proposes that schizophrenia often involves pre- or perinatal exposure to adverse factors that produce a latent immune vulnerability. When this vulnerability is manifested, beginning around puberty with changes in immune function and involution of the thymus, individuals become more susceptible to infections and immune dysfunctions that contribute to schizophrenia. Our hypothesis suggests theoretical bridges between different lines of evidence on schizophrenia and offers explanations for many puzzling findings about schizophrenia. For example, the hypothesis helps account for why schizophrenia patients tend to have had increased exposure to neurotropic infections, but most individuals with such exposure do not develop schizophrenia, and why prenatal hardships increase risk for schizophrenia, but the onset of symptoms typically does not occur until after puberty. The hypothesis also explains another paradox: lower socioeconomic status and poor prenatal care increase risk for schizophrenia at the same geographic site, but international comparisons indicate that countries with higher per capita incomes and better prenatal care actually tend to have higher schizophrenia prevalences. As the hypothesis predicts, (1) prenatal adversity, which increases risk for schizophrenia, also impairs post-pubertal immune competence, (2) schizophrenia patients experience elevated morbidity from infectious and auto-immune diseases, (3) genetic and environmental risk factors for schizophrenia increase vulnerability to these diseases, (4) factors that exacerbate schizophrenic symptoms also tend to impair immune function, (5) many anti-psychotic medications combat infection, (6) effects of early infections may not appear until after puberty, when they can produce neurologic and psychiatric symptoms, and (7) immune dysfunctions, such as imbalances of pro- and anti-inflammatory cytokines, may contribute to the onset of psychotic symptoms and the progressive loss of brain tissue in schizophrenia. The disruptive effects of prenatal adversity on the development of the immune system may often combine with adverse effects on prenatal brain development to produce schizophrenia. This paper focuses on the adverse immune system effects, because effects on the brain have been extensively discussed in neurodevelopmental theories of schizophrenia. We propose new tests of scientific predictions. We also point out potential clinical implications of the hypothesis; for example, individuals with schizophrenia may often have underlying infections or immune dysfunctions, such as imbalances in inflammatory cytokines, that contribute to the illness. This possibility could be tested experimentally--e.g., by clinical trials in which patients' exposure to infection is reduced or immune function is normalized.

Genetics and intermediate phenotypes of the schizophrenia--bipolar disorder boundary

Categorization of psychotic illnesses into schizophrenic and affective psychoses remains an ongoing controversy. Although Kraepelinian subtyping of psychosis was historically beneficial, modern genetic and neurophysiological studies do not support dichotomous conceptualization of psychosis. Evidence suggests that schizophrenia and bipolar disorder rather present a clinical continuum with partially overlapping symptom dimensions, neurophysiology, genetics and treatment responses. Recent large scale genetic studies have produced inconsistent findings and exposed an urgent need for re-thinking phenomenology-based approach in psychiatric research. Epidemiological, linkage and molecular genetic studies, as well as studies in intermediate phenotypes (neurocognitive, neurophysiological and anatomical imaging) in schizophrenia and bipolar disorders are reviewed in order to support a dimensional conceptualization of psychosis. Overlapping and unique genetic and intermediate phenotypic signatures of the two psychoses are comprehensively recapitulated. Alternative strategies which may be implicated into genetic research are discussed.

Neuregulin-1 genotypes and eye movements in schizophrenia

Neuregulin-1 (NRG-1) is a putative susceptibility gene for schizophrenia but the neurocognitive processes that may involve NRG-1 in schizophrenia are unknown. Deficits in antisaccade (AS) and smooth pursuit eye movements (SPEM) are promising endophenotypes, which may be associated with brain dysfunctions underlying the pathophysiology of schizophrenia. The aim of this study was to investigate the associations of NRG-1 genotypes with AS and SPEM in schizophrenia patients and healthy controls. Patients (N = 113) and controls (N = 106) were genotyped for two NRG-1 single nucleotide polymorphisms (SNPs); SNP8NRG222662, a surrogate marker for the originally described Icelandic NRG-1 risk haplotype, and SNP8NRG243177, which has recently been associated with individual differences in brain function. Subjects underwent infrared oculographic assessment of AS and SPEM. The study replicates previous findings of impaired AS and SPEM performance in schizophrenia patients (all P < 0.005; all d = 0.5-1.5). SNP8NRG243177 risk allele carriers had marginally increased variability of AS spatial error (P = 0.050, d = 0.3), but there were no significant genotype effects on other eye movement variables and no significant diagnosis-by-genotype interactions. Generally, risk allele carriers (G allele for SNP8NRG222662 and T allele for SNP8NRG243177) had numerically worse performance than non-carriers on most AS and SPEM variables. The results do not suggest that NRG-1 genotype significantly affects AS and SPEM task performance. However, the power of the sample to identify small effects is limited and the possibility of a type II error must be kept in mind. Larger samples may be needed to reliably investigate such gene effects on oculomotor endophenotypes.

Eye tracking dysfunction in schizophrenia: characterization and pathophysiology

Eye tracking dysfunction (ETD) is one of the most widely replicated behavioral deficits in schizophrenia and is over-represented in clinically unaffected first-degree relatives of schizophrenia patients. Here, we provide an overview of research relevant to the characterization and pathophysiology of this impairment. Deficits are most robust in the maintenance phase of pursuit, particularly during the tracking of predictable target movement. Impairments are also found in pursuit initiation and correlate with performance on tests of motion processing, implicating early sensory processing of motion signals. Taken together, the evidence suggests that ETD involves higher-order structures, including the frontal eye fields, which adjust the gain of the pursuit response to visual and anticipated target movement, as well as early parts of the pursuit pathway, including motion areas (the middle temporal area and the adjacent medial superior temporal area). Broader application of localizing behavioral paradigms in patient and family studies would be advantageous for refining the eye tracking phenotype for genetic studies.

COMT val(158)met genotype and smooth pursuit eye movements in schizophrenia

The association between the catechol-O-methyltransferase (COMT) val(158)met polymorphism (rs4680) and smooth pursuit eye movements (SPEM) was investigated in 110 schizophrenia patients and 96 controls. Patients had lower steady-state pursuit gain and made more frequent saccades than controls. Genotype was not associated with schizophrenia or SPEM, in either group or the combined sample. SPEM deficits in schizophrenia appear to be determined by genotypes other than rs4680, although the study may have lacked power to detect small effects.

The power of linkage analysis of a disease-related endophenotype using asymmetrically ascertained sib pairs

A linkage study of a qualitative disease endophenotype in a sample of sib pairs, consisting of one disease affected proband and one sibling is considered. The linkage statistic compares marker allele sharing with the proband in siblings with an abnormal endophenotype to siblings with the normal endophenotype. Expressions for the distribution of this linkage statistic, in terms of the recombination fraction are derived and (1) the genetic parameter values (allele frequency and endophenotype and disease penetrance) and (2) the abnormal endophenotype rates in the population and in classes of relatives of disease affected probands. It is then shown that when either the disease or the abnormal endophenotype has additive penetrance, the expressions simplify to a monotonic function of the difference between abnormal endophenotype rates in siblings and in the population. Thought disorder is considered as a putative schizophrenia endophenotype. Forty sets of genetic parameter values that correspond to the known prevalence values for thought disorder in schizophrenic patients, siblings of schizophrenics and the general population are evaluated. For these genetic parameter values, numerical results show that the test statistic has>70% power (α = 0.0001) in general with a sample of 200 or more proband-sibling pairs to detect the linkage between a marker (θ = 0.01), and a locus pleiotropic for schizophrenia and thought disorder.

Effects of second-generation antipsychotic medication on smooth pursuit performance in antipsychotic-naive schizophrenia

CONTEXT

Analyses of smooth pursuit eye movement parameters in patients with schizophrenia provide information about the integrity of neural networks mediating motion perception, sensorimotor transformation, and cognitive processes such as prediction. Although pursuit eye tracking deficits have been widely reported in schizophrenia, the integrity of discrete components of pursuit responses and the effect of second-generation antipsychotic medication on them are not well established.

OBJECTIVE

To examine different components of smooth pursuit performance in antipsychotic-naive patients with schizophrenia before and after treatment with second-generation antipsychotic medication.

DESIGN, SETTING, AND PARTICIPANTS

Thirty-three antipsychotic-naive patients with schizophrenia performed 3 different smooth pursuit paradigms designed to evaluate specific components of the pursuit response. All of the patients were retested after 6 weeks of treatment with risperidone or olanzapine. Testing was also performed with 39 matched healthy individuals. Thirteen patients and 21 healthy participants were retested after 26 and 52 weeks.

MAIN OUTCOME MEASURES

Pursuit initiation, maintenance gain (ratio of eye velocity over target velocity), and frequency of catch-up saccades during pursuit maintenance.

RESULTS

Prior to treatment, pursuit gain when tracking less predictable ramp targets tended to be reduced, latency of pursuit initiation was speeded, and catch-up saccade frequency was increased during predictive pursuit. After antipsychotic treatment initiation, pursuit gain decreased with ramp targets, indicating treatment-emergent impairments in sensorimotor processing. No changes were observed for predictive pursuit. Exploratory analyses in the subgroup with follow-up to 1 year revealed that these effects continued through long-term follow-up with some partial normalization at 1 year. Deficits were unrelated to drug dosage and clinical ratings.

CONCLUSIONS

Impaired sensorimotor function was observed after initiation of second-generation antipsychotic medications, which may be explained by their serotonergic antagonism of brainstem sensorimotor systems. Predictive mechanisms supported by frontostriatal-cerebellar circuitry were not affected by treatment initiation and appear able to compensate for treatment-emergent sensorimotor impairments during predictive tracking.

Eye movement dysfunction in first-degree relatives of patients with schizophrenia: a meta-analytic evaluation of candidate endophenotypes

Several forms of eye movement dysfunction (EMD) are regarded as promising candidate endophenotypes of schizophrenia. Discrepancies in individual study results have led to inconsistent conclusions regarding particular aspects of EMD in relatives of schizophrenia patients. To quantitatively evaluate and compare the candidacy of smooth pursuit, saccade and fixation deficits in first-degree biological relatives, we conducted a set of meta-analytic investigations. Among 18 measures of EMD, memory-guided saccade accuracy and error rate, global smooth pursuit dysfunction, intrusive saccades during fixation, antisaccade error rate and smooth pursuit closed-loop gain emerged as best differentiating relatives from controls (standardized mean differences ranged from .46 to .66), with no significant differences among these measures. Anticipatory saccades, but no other smooth pursuit component measures were also increased in relatives. Visually-guided reflexive saccades were largely normal. Moderator analyses examining design characteristics revealed few variables affecting the magnitude of the meta-analytically observed effects. Moderate effect sizes of relatives v. controls in selective aspects of EMD supports their endophenotype potential. Future work should focus on facilitating endophenotype utility through attention to heterogeneity of EMD performance, relationships among forms of EMD, and application in molecular genetics studies.

The evolution of drug development in schizophrenia: past issues and future opportunities

Schizophrenia is a disease syndrome with major public health implications. The primary advance in pharmacotherapeutics was in 1952 with the introduction of antipsychotic medications (ie, chlorpromazine, dopamine D2 antagonism). Barriers to progress have been substantial, but many will be subject to rapid change based on current knowledge. There are attractive psychopathology indications for drug discovery (eg, impaired cognition and negative symptoms), and drugs with efficacy in these domains may have application across a number of disease classes. These pathologies are observed prior to psychosis raising the possibility of very early intervention and secondary prevention. Success in drug discovery for cognition and negative symptom pathologies may bring forth issues in ethics as the potential for enhancing normal function is explored.

Finding suitable phenotypes for genetic studies of schizophrenia: heritability and segregation analysis

BACKGROUND

Schizophrenia is a highly heritable and complex disorder. Multiple genes are likely to be involved, complicating genetic research into the etiology of this disorder. Intermediate phenotypes or endophenotypes may facilitate genetic research if they display a simpler mode of transmission than schizophrenia itself, i.e., if they reflect more closely the underlying genetic effects.

METHODS

Twenty-five multigenerational families with multiple members affected with schizophrenia (180 subjects) were administered an extensive neuropsychological, psychophysiological, and personality test battery. Familial correlations were calculated to select heritable traits. Subsequent heritability analysis followed by commingling and segregation analysis were performed to unravel the pattern of transmission and to estimate heritability.

RESULTS

Five traits, including sensorimotor gating, openness, verbal fluency, early visual perception, and spatial working memory, showed moderate familial correlations. Heritability estimates for these traits ranged from 37% to 54%. A major gene model resembling dominant transmission was found for both sensorimotor gating and openness. Verbal fluency, early visual perception, and spatial working memory may be accounted for by polygenic, multifactorial, or environmental effects.

CONCLUSIONS

Only 2 of 13 candidate endophenotypes showed a simple mode of transmission useful for successful application in molecular genetic research: sensorimotor gating and openness. To our knowledge, this is the first study to investigate the pattern of transmission for these traits.

Approaches for unraveling the joint genetic determinants of schizophrenia and bipolar disorder

Since Emil Kraepelin proposed in 1919 that dementia praecox (schizophrenia) be differentiated from manic depression (bipolar disorder), the concept of nosological dichotomy has greatly influenced the diagnosis, treatment, and research of pathogenesis of these 2 disorders. However, this concept has recently been challenged by increasing evidence showing biological overlap between schizophrenia and bipolar disorder. This article reviews some of the previous evidence for phenomenological and molecular overlaps between these 2 disorders. We then discuss approaches for examining shared etiological mechanisms with a concentration on genetic factors. We have put a particular emphasis on incorporating the concept of endophenotypes in research of shared genetic liability for these 2 disorders.

Neurophysiological endophenotypes across bipolar and schizophrenia psychosis

The search for liability genes of the world's 2 major psychotic disorders, schizophrenia and bipolar disorder I (BP-I), has been extremely difficult even though evidence suggests that both are highly heritable. This difficulty is due to the complex and multifactorial nature of these disorders. They encompass several intermediate phenotypes, some overlapping across the 2 psychotic disorders that jointly and/or interactively produce the clinical manifestations. Research of the past few decades has identified several neurophysiological deficits in schizophrenia that frequently occur before the onset of psychosis. These include abnormalities in smooth pursuit eye movements, P50 sensory gating, prepulse inhibition, P300, mismatch negativity, and neural synchrony. Evidence suggests that many of these physiological deficits are distinct from each other. They are stable, mostly independent of symptom state and medications (with some exceptions) and are also observed in non-ill relatives. This suggests a familial and perhaps genetic nature. Some deficits are also observed in the BP-I probands and to a lesser extent their relatives. These deficits in physiological measures may represent the intermediate phenotypes that index small effects of genes (and/or environmental factors). The use of these measures in genetic studies may help the hunt for psychosis liability genes and clarify the extent to which the 2 major psychotic disorders share etio-pathophysiology. In spite of the rich body of work describing these neurophysiological measures in psychotic disorders, challenges remain: Many of the neurophysiological phenotypes are still relatively complex and are associated with low heritability estimates. Further refinement of these physiological phenotypes is needed that could identify specific underlying physiological deficits and thereby improve their heritability estimates. The extent to which these neurophysiological deficits are unique or overlap across BP-I and schizophrenia is unclear. And finally, the clinical and functional consequences of the neurophysiological deficits both in the probands and their relatives are not well described.

Schizophrenia endophenotypes as treatment targets

Schizophrenia is a complex disorder that encompasses several clinical symptom domains and functional impairments. Existing treatments are meager, effective only against positive symptoms without benefiting negative symptoms and functional impairments. The drug discovery process has focused mostly on targeting D2 dopamine receptors. This followed the serendipitous discovery of the antipsychotic effects of chlorpromazine in the 1950s and, more recently, clozapine. There is a need to identify novel mechanisms in order to discover novel drugs that are effective against each of the symptom clusters and functional impairments associated with the illness. Neurophysiological studies in schizophrenia over the past 3 decades have identified several brain deficits that are stable, using valid animal models that are related to the etiology of the disorder. Many of these deficits are distinct and heritable; these are called endophenotypes. Many have well-characterized neurobiology and may therefore provide molecular targets for drug development. In addition, these endophenotypes help reduce the heterogeneity by identifying homogeneous subgroups of patients with similar pathophysiology, symptoms and functional deficits. Clinical trials of drugs, whose development is based on an endophenotype, will have enhanced statistical power when the trial is carried out in an appropriate cohort of subjects using outcome measures related to the corresponding endophenotype. Furthermore, genes that are associated with these endophenotypes are beginning to be identified. These findings will identify novel molecular targets for drug development with treatment implications for clinical symptom complex and functional deficits marked by the endophenotype. As endophenotypes are present during childhood and adolescence, novel drugs that are developed on the basis of this subgroup could have implications for preventive strategies in schizophrenia.

No association evidence between schizophrenia and dystrobrevin-binding protein 1 (DTNBP1) in Taiwanese families

Several linkage studies have shown significant linkage of schizophrenia to chromosome 6p region, which includes the positional candidate genes, Dystrobrevin-binding protein 1 (DTNBP1). The aim was to examine the association evidence of the candidate gene in 693 Taiwanese families with at least two affected siblings of schizophrenia. We genotyped nine SNPs of this gene with average intermarker distance of 17 kb. Intermarker linkage disequilibrium was calculated with GOLD. Single locus and haplotype association analyses were performed with TRANSMIT program. We found no significant association between schizophrenia and DTNBP1 either through single locus or haplotype analyses. We failed to replicate the association evidence between DTNBP1 and schizophrenia and this gene may not play a major role in the etiology of schizophrenia in this Taiwanese family sample.

Which perspectives can endophenotypes and biological markers offer in the early recognition of schizophrenia?

The early recognition of schizophrenia seems crucial; various studies relate a longer duration-of-untreated-psychosis to a worse prognosis. We give an overview over common psychopathological early recognition instruments (BSABS, CAARMS, SIPS, IRAOS, ERIraos). However, many clinical symptoms of prodromal schizophrenia stages are not sufficiently specific. Thus we review recent contributions of neuroimaging and electrophysiological as well as genetic studies: which new diagnostic perspectives offer endophenotypes (such as P300, P50 sensory gating, MMN, smooth pursuit eye movements; indicating a specific genetic vulnerability) together with a better understanding of schizophrenic pathophysiology (state-dependent biological markers, e.g. aggravated motor neurological soft signs during psychosis) in prodromal schizophrenia when still ambiguous clinical symptoms are present. Several examples (e.g. from COMT polymorphisms to working memory deficits) illustrate more specific underlying neuronal mechanisms behind behavioural symptoms. This way, a characteristic pattern of disturbed cerebral maturation might be distinguished in order to complement clinical instruments of early schizophrenia detection.

Different extraretinal neuronal mechanisms of smooth pursuit eye movements in schizophrenia: An fMRI study

Smooth pursuit eye movements (SPEM) are necessary to follow slowly moving targets while maintaining foveal fixation. In about 50% of schizophrenic patients SPEM velocity is reduced. In this study we were interested in identifying the cortical mechanisms associated with extraretinal processing of SPEM in schizophrenic patients. During condition A, patients and healthy subjects had to pursue a constantly visible target (10 degrees /s). During condition B the target was blanked out for 1000 ms while subjects were instructed to continue SPEM. Eye movement data were assessed during scanning sessions by a limbus tracker. During condition A, reduced SPEM velocity in patients was associated with reduced activation of the right ventral premotor cortex and increased activation of the left dorsolateral prefrontal cortex, the right thalamus and the Crus II of the left cerebellar hemisphere. During condition B, SPEM velocity was reduced to a similar extent in both groups. While in patients a decrease in activation was observed in the right cerebellar area VIIIA, the activation of the right anterior cingulate, the right superior temporal cortex, and the bilateral frontal eye fields was increased. The results implicate that schizophrenic patients employ different strategies during SPEM both with and without target blanking than healthy subjects. These strategies predominantly involve extraretinal mechanisms.

Trait vs. State Markers for Schizophrenia: Identification and Characterization through Visual Processes

One central issue in schizophrenia research is to identify and characterize behavioral and biological markers that are intrinsic to the complex psychiatric disorder and that can serve as targets for detection, treatment, and prevention. A trait marker represents the properties of the behavioral and biological processes that play an antecedent, possibly causal, role in the pathophysiology of the psychiatric disorder, whereas a state marker reflects the status of clinical manifestations in patients. Certain visual functions, while deficient in schizophrenia, may be independent of psychosis. The question of what types of visual functions can serve as trait or state markers is beginning to be understood. Examining clinically unaffected relatives of schizophrenia patients and patients with bipolar disorder can provide information about the relationship between a schizophrenic disposition and visual response traits. In this effort, researchers found that motion integration is dysfunctional in schizophrenia patients but not in their relatives or bipolar patients, whereas motion discrimination is dysfunctional in schizophrenia patients and their relatives, but not in bipolar patients. By synthesizing these findings, this review suggests that distinguishing enduring trait markers from transient state markers for schizophrenia through visual processes is helpful for developing neurobiologically and psychologically based intervention strategies.

Psychosis pathways converge via D2high dopamine receptors

The objective of this review is to identify a target or biomarker of altered neurochemical sensitivity that is common to the many animal models of human psychoses associated with street drugs, brain injury, steroid use, birth injury, and gene alterations. Psychosis in humans can be caused by amphetamine, phencyclidine, steroids, ethanol, and brain lesions such as hippocampal, cortical, and entorhinal lesions. Strikingly, all of these drugs and lesions in rats lead to dopamine supersensitivity and increase the high-affinity states of dopamine D2 receptors, or D2High, by 200-400% in striata. Similar supersensitivity and D2High elevations occur in rats born by Caesarian section and in rats treated with corticosterone or antipsychotics such as reserpine, risperidone, haloperidol, olanzapine, quetiapine, and clozapine, with the latter two inducing elevated D2High states less than that caused by haloperidol or olanzapine. Mice born with gene knockouts of some possible schizophrenia susceptibility genes are dopamine supersensitive, and their striata reveal markedly elevated D2High states; suchgenes include dopamine-beta-hydroxylase, dopamine D4 receptors, G protein receptor kinase 6, tyrosine hydroxylase, catechol-O-methyltransferase, the trace amine-1 receptor, regulator of G protein signaling RGS9, and the RIIbeta form of cAMP-dependent protein kinase (PKA). Striata from mice that are not dopamine supersensitive did not reveal elevated D2High states; these include mice with knockouts of adenosine A2A receptors, glycogen synthase kinase GSK3beta, metabotropic glutamate receptor 5, dopamine D1 or D3 receptors, histamine H1, H2, or H3 receptors, and rats treated with ketanserin or aD1 antagonist. The evidence suggests that there are multiple pathways that convergetoelevate the D2High state in brain regions and that this elevation may elicit psychosis. This proposition is supported by the dopamine supersensitivity that is a common feature of schizophrenia and that also occurs in many types of genetically altered, drug-altered, and lesion-altered animals. Dopamine supersensitivity, in turn, correlates with D2High states. The finding that all antipsychotics, traditional and recent ones, act on D2High dopamine receptors further supports the proposition.

Subtyping schizophrenia: implications for genetic research

Phenotypic variability and likely extensive genetic heterogeneity have been confounding the search for the causes of schizophrenia since the inception of the diagnostic category. The inconsistent results of genetic linkage and association studies using the diagnostic category as the sole schizophrenia phenotype suggest that the current broad concept of schizophrenia does not demarcate a homogeneous disease entity. Approaches involving subtyping and stratification by covariates to reduce heterogeneity have been successful in the genetic study of other complex disorders, but rarely applied in schizophrenia research. This article reviews past and present attempts at delineating schizophrenia subtypes based on clinical features, statistically derived measures, putative genetic indicators, and intermediate phenotypes, highlighting the potential utility of multidomain neurocognitive endophenotypes.

Genetics of human brain oscillations

In the last three decades, much emphasis has been placed on neural oscillations in vitro, in vivo, as well as in the human brain. These brain oscillations have been studied extensively in the resting electroencephalogram (EEG), as well as in the underlying evoked oscillations that make up the event-related potentials (ERPs). There are several approaches to elucidate the possible mechanisms of these brain oscillations. One approach is to look at the neurophysiology and neurochemistry involved in generating and modulating these oscillations. Another more recent approach is to examine the genetic underpinnings of these neural oscillations. It is proposed that the genetic underpinnings of these oscillations are likely to stem from regulatory genes which control the neurochemical processes of the brain, and therefore influence neural function. Genetic analyses of human brain oscillations may identify genetic loci underlying the functional organization of human neuroelectric activity. Brain oscillations represent important correlates of human information processing and cognition. They represent highly heritable traits that are less complex and more proximal to gene function than either diagnostic labels or traditional cognitive measures. Therefore these oscillations may be utilized as phenotypes of cognition and as valuable tools for the understanding of some complex genetic disorders. Genetic loci that have been recently identified regarding both resting and evoked brain oscillations involving the GABAergic and cholinergic neurotransmitter systems of the brain are discussed. It is concluded that 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.

Anomalous subjective experience among first-admitted schizophrenia spectrum patients: empirical investigation

Our research group has for several years conducted philosophically informed, phenomenological-empirical studies of morbid alterations of conscious experience (subjectivity) in schizophrenia (Sz) and its spectrum of disorders. Some of these experiential alterations constitute, in our view, the vulnerability markers to Sz--indicators that are intrinsic to this disorder and which were historically considered as constituting the phenotypic anchor of the very concept and the diagnostic validity of Sz spectrum disorders. In a more pragmatic clinical context, these indicators, considered here as symptoms, may be potentially effective for early differential diagnosis. In this study, 151 consecutive first-admitted patients (with bipolar, melancholic and organic patients excluded) diagnosed according to the ICD-10, were evaluated on a number of expressive and experiential psychopathological dimensions, with special emphasis on the experiences of perplexity, disorders of self-awareness, perceptual disorders and anomalous bodily experiences. The a priori scales derived from the item pool of a slightly modified OPCRIT and BSABS were used for analyses. Sz and schizotypal disorder scored equally on the subjective dimensions, suggesting a basic phenomenological affinity of these disorders. In contrast, anomalies of subjective experience were clearly more pronounced among the patients within, as compared to those outside the Sz spectrum.

Relationship between class I and II HLA antigens in schizophrenia and eye movement disturbances: a preliminary study

The region coding human leukocyte antigen (HLA) on chromosome 6q21 was shown to be associated with both the vulnerability to schizophrenia and presence of eye movement disturbances (EMD). The aim of this preliminary study was to investigate how individual class I and II HLA antigens in schizophrenic patients may be related to schizophrenia and to the intensity of two kinds of EMD: fixation and smooth pursuit. The incidence of HLA antigens was compared between 40 schizophrenic patients (17 male, 23 female) and 198 healthy control subjects (112 male, 86 female). In schizophrenic patients, the intensity of EMD assessed by infrared reflectometry and quantified on a scale from 0 to 3 was correlated with the incidence of HLA antigens. A number of differences regarding HLA antigens were found between schizophrenic patients and healthy subjects. Significant correlation was also obtained between some EMD and a number of HLA antigens. Antigens A24 and A28 were found to occur in different frequencies in schizophrenic patients and healthy control subjects. They also correlated with EMD on the fixation and smooth pursuit tests. The results obtained show an association between HLA antigens and EMD as an endophenotypic marker of schizophrenia, and may add to other findings on susceptibility loci for schizophrenia on chromosome 6p21. A limitation of this study is a small number of investigated patients with schizophrenia.