Endophenotyping schizotypy: a prelude to genetic studies within the schizophrenia spectrum

Schizotypal traits and their relationship to reading abilities in healthy adults

Schizotypal traits (i.e., personality characteristics that range from mild eccentricities to more pronounced schizophrenia-like perceptions, thought patterns, and behaviours) have been associated with a variety of cognitive impairments, including difficulties in language processing. Although these difficulties span several aspects of language (e.g., semantic processing, verbal fluency, visual word recognition), it is unclear whether reading abilities are also affected. Thus, the current study employed the Schizotypal Personality Questionnaire (SPQ) - Brief (Raine and Benishay, 1995) to examine how schizotypal traits impact both word-level and text-level reading skills (using a battery of standardized assessments) in a sample of healthy young adults. We found some evidence that higher schizotypal traits, specifically, increased Disorganized factor scores (reflecting aberrant thinking, communication patterns, and behaviour), were associated with reduced word-level reading abilities. However, this finding did not remain significant after correcting for multiple comparisons. Overall, our study suggests that reading may be another aspect of language affected by schizotypal traits, although additional research (with greater power) is needed to further explore and confirm this finding.

Comparison of executive functions in individuals with high and low levels of schizotypal trait

The dimensional approach to Schizotypal Personality Disorder (SPD) indicates that SPD includes a constellation of maladaptive personality traits on a continuum with general personality functioning. This study aimed to compare executive functions (EFs) in low and high-level schizotypal individuals. Using a convenient sampling method, we recruited 120 individuals, from which 30 individuals with high schizotypal trait levels (fourth quartile) and 30 participants with lower schizotypal trait levels (first quartile) were selected based on their scores on the schizotypal personality disorder questionnaire. Then, participants from the two groups were administered the Corsi Block-Tapping Test (CBTT), Wisconsin Card Sorting Test (WCST), and Continuance Performance Test (CPT). The results indicated individuals with higher schizotypy trait levels performed significantly poorer in tasks measuring working-visual-spatial memory, cognitive flexibility, sustained attention, and response inhibition. This pattern of results indicated that EF dysfunctions in individuals with higher schizotypy trait levels would cause significant disturbances in multiple areas of life. The practical implications of the findings are further discussed.

Comparative Analysis of Dopaminergic and Cholinergic Mechanisms of Sensory and Sensorimotor Gating in Healthy Individuals and in Patients With Schizophrenia

Sensory and sensorimotor gating provide the early processing of information under conditions of rapid presentation of multiple stimuli. Gating deficiency is observed in various psychopathologies, in particular, in schizophrenia. However, there is also a significant proportion of people in the general population with low filtration rates who do not show any noticeable cognitive decline. The review article presents a comparative analysis of existing data on the peculiarities of cholinergic and dopaminergic mechanisms associated with lowering gating in healthy individuals and in patients with schizophrenia. The differences in gating mechanisms in cohorts of healthy individuals and those with schizophrenia are discussed.

No influence of sex on the relationship between schizotypy factors and executive control across the schizophrenia spectrum

Sex differences in symptoms and executive control across schizophrenia spectrum disorders (SSD) are consistently reported. Similarly, these findings of sex differences are also observed in schizotypy, that is, schizophrenia-like features occurring in healthy individuals in the absence of a clinical diagnosis. This study aimed to examine the relationships between performance on three major domains of executive control: performance monitoring, response inhibition, and cognitive set-shifting, and schizotypy factor scores in both SSD patients and healthy controls (HCs), and whether sex moderated any relationships observed. A total of 111 (67 males and 44 females) patients with SSD and 258 (129 males and 129 females) HCs were included in this study. Schizotypal personality traits (in both SSD and HC) was assessed using the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE). Executive control performance was assessed using seven tasks. Stepwise linear regressions revealed that performance on cognitive set-shifting tasks was significantly associated with the introvertive anhedonia, cognitive disorganisation, and unusual experiences subscales of the O-LIFE. When sex was examined as a moderator, it was not a significant moderator of any of the relationships between cognitive set-shifting tasks and schizotypy factors. The results suggest that independent of sex, cognitive set-shifting ability is associated to an increased vulnerability to schizotypal personality traits, although performance monitoring and response inhibition did not.

A Developmental Study of Mirror-Gazing-Induced Anomalous Self-Experiences and Self-Reported Schizotypy from 7 to 28 Years of Age

INTRODUCTION

The mirror-gazing task (MGT) is an experimental paradigm inducing anomalous perceptions and anomalous experiences of self-face (ASEs) in the general population, ranging from changes in light and color, to face deformation, to experiencing one's specular image as another identity. Subclinical ASEs have been related to the emergence of the risk for developing psychotic disorders, and inducing such states in the general population could shed light on the factors underlying interindividual differences in proneness to these phenomena. We aimed to examine the influence of schizotypal personality traits on proneness to experiencing induced ASEs from a developmental perspective, from childhood to adulthood.

METHODS

Two hundred and sixteen children, adolescents, and young adults participated in the MGT, and their schizotypal personality traits were assessed with the Schizotypal Personality Questionnaire. Statistical analyses assessed the relationship between schizotypy dimensions and induced ASEs, and we further tested their dynamic relationship as function of age (from childhood to adulthood).

RESULTS

Results confirmed the developmental trajectory of the different schizotypy dimensions, with scores peaking during adolescence, and proneness to induced ASEs seemed to follow a similar developmental trajectory. Moreover, positive (p = 0.001) and disorganized (p = 0.004) dimensions were found to contribute to the proneness to experiencing induced ASEs. Finally, the developmental model showed that positive schizotypy (p = 0.035) uniquely distinguished between experiencing other-identity phenomena between childhood and adulthood.

CONCLUSION

This study has the potential to inform research on early detection of psychosis through a developmental approach and links the concept of schizotypy with processes of perceptual self-distortions.

Bifactor Structure of the Schizotypal Personality Questionnaire Across the Schizotypy Spectrum

Despite widespread use in schizophrenia-spectrum research, uncertainty remains around an empirically supported and theoretically meaningful factor structure of the Schizotypal Personality Questionnaire (SPQ). Current identified structures are limited by reliance on exclusively nonclinical samples. The current study compared factor structures of the SPQ in a sample of 335 nonpsychiatric individuals, 292 schizotypy-spectrum individuals (schizophrenia, schizoaffective disorder, or schizotypal personality disorder), and the combined group (N = 627). Unidimensional, correlated, and hierarchical models were assessed in addition to a bifactor model, wherein subscales load simultaneously onto a general factor and a specific factor. The best-fitting model across samples was a two-specific factor bifactor model, consistent with the nine symptom dimensions of schizotypy as primarily a direct manifestation of a unitary construct. Such findings, for the first time demonstrated in a clinical sample, have broad implications for transdiagnostic approaches, including reifying schizotypy as a construct underlying diverse manifestations of phenomenology across a wide range of severity.

Neurophysiological substrates of configural face perception in schizotypy

Face perception is a highly developed function of the human visual system. Previous studies of event-related potentials (ERPs) have identified a face-selective ERP component (negative peak at about 170 ms after stimulus onset, N170) in healthy participants. In contrast, patients with schizophrenia exhibit reduced amplitude of the N170, which may represent a pathological deficit in the neurophysiology of face perception. Interestingly, healthy humans with schizophrenia-like experiences (schizotypy) also exhibit abnormal processing of face perception. Yet, it has remained unknown how schizotypy in healthy humans is associated with the neurophysiological substrates of face perception. Here, we recruited 35 healthy participants and assessed their schizotypy by the magical ideation rating scale. We used high-density electroencephalography to obtain ERPs elicited by a set of Mooney faces (face and non-face visual stimuli). We investigated median and mean reaction times and visual ERP components in response to the stimuli. We observed a significant difference in N170 amplitude between the two face-stimulus conditions and found that the measured schizotypy scores were significantly correlated with both reaction times and N170 amplitude in response to the face stimuli across all participants. Our results thus support the model of schizotypy as a manifestation of a continuum between healthy individuals and patients with schizophrenia, where the N170 impairment serves as a biomarker for the degree of pathology along this continuum.

Contrasting characteristic behaviours among common laboratory mouse strains

Mice are widely used to model wide-ranging human neurological disorders, from development to degenerative pathophysiology. Behavioural and molecular characteristics of these mouse models are influenced by the genetic background of each strain. Among the most commonly used strains, the inbred C57BL/6J, BALB/c, CBA and 129SvEv lines and the CD1 outbred line are particularly predominant. Despite their prevalence, comparative performance of these strains on many standard behavioural tests commonly used to assess neurological conditions remains diffusely and indirectly accessible in the literature. Given that independent studies may be conducted with mice of differing genetic backgrounds, any variation in characteristic behavioural responses of specific strains should be delineated in order to properly interpret results among studies. Thus, in the present study, we aimed to characterize these commonly used mice strains through several standard behavioural tests. Here, we found that animals from different genetic background strains exhibited varying behavioural patterns when assessed for sociability/novelty, memory function, and negative behaviours like despair and stress calls. These results suggest that genetic variation among strains may be responsible-in part-for strain-specific behavioural phenotypes and potential predisposition to some neurological disorders.

Co-morbidity of personality disorder in schizophrenia among psychiatric outpatients in China: data from epidemiologic survey in a clinical population

BACKGROUND

The reported rates of personality disorder (PD) in subjects with schizophrenia (SZ) are quite varied across different countries, and less is known about the heterogeneity of PD among subjects with SZ. We examined the co-morbidity of PD among patients who are in the stable phase of SZ.

METHOD

850 subjects were randomly sampled from patients diagnosed with SZ in psychiatric and psycho-counseling clinics at Shanghai Mental Health Center. Co-morbidity of PDs was assessed through preliminary screening and patients were administered several modules of the SCID-II. Evidence of heterogeneity was evaluated by comparing patients diagnosed with SZ with those who presented with either affective disorder or neurosis (ADN).

RESULTS

204 outpatients (24.0 %) in the stable phase of SZ met criteria for at least one type of DSM-IV PD. There was a higher prevalence of Cluster-A (odd and eccentric PD) and C (anxious and panic PD) PDs in SZ (around 12.0 %). The most prevalent PD was the paranoid subtype (7.65 %). Subjects with SZ were significantly more likely to have schizotypal PD (4.4 % vs. 2.1 %, p = 0.003) and paranoid PD (7.6 % vs. 5.4 %, p = 0.034), but much less likely to have borderline, obsessive-compulsive, depressive, narcissistic and histrionic PD.

CONCLUSIONS

These findings suggest that DSM-IV PD is common in patients with SZ than in the general population. Patterns of co-morbidity with PDs in SZ are different from ADN.

Neurocognition, functional competence and self-reported functional impairment in psychometrically defined schizotypy

INTRODUCTION

Schizotypy is phenologically and genetically related to schizophrenia-spectrum illness. Previous studies find cognitive function to be mildly impaired, but specific impairments and their relationship to functioning are not well understood. In this study, we sought to examine how cognitive load affects performance in schizotypy and to examine whether impairments might manifest in functional capacity and quality of life.

METHODS

Undergraduate students were screened for abnormally high levels of schizotypy (N = 72) and compared to those without psychopathology (N = 80) on a standard battery of neuropsychological tests, cognitive tests with varying cognitive load, functional capacity measures and quality of life.

RESULTS

The high schizotypy group did not differ from controls on traditional measures of neuropsychological functioning, but an interaction of group by cognitive load was observed, where those with schizotypy manifested a greater decline in performance as information processing load was parametrically increased. Differences in functioning were observed and cognitive impairment was associated with impaired functioning.

CONCLUSIONS

Cognitive and functional impairment can be observed in those with high schizotypal traits who are non-treatment seeking. The sensitivity of cognitive tests to impairment in this population might be a function of their ability to parametrically increase cognitive load.

Schizotypal Traits are Associated with Poorer Executive Functioning in Healthy Adults

Previous research has shown mild forms of the neurocognitive impairments seen in schizophrenia among healthy individuals exhibiting high schizotypal traits. This study aimed to explore associations between schizotypy and cognitive performance in an adult community sample. Ninety-five females and 79 males completed the Oxford-Liverpool Inventory of Feelings and Experiences (O-LIFE), which measures four separable aspects of schizotypy: cognitive disorganization, unusual experiences, introvertive anhedonia, and impulsive non-conformity. Subsequently, participants were administered a neurocognitive battery incorporating measures of executive skills including inhibition, cognitive flexibility, reasoning, and problem solving along with measures of attention and processing speed and both verbal and spatial working memory. In line with predictions, the current study found that higher scores on the subscales of unusual experiences, cognitive disorganization, and impulsive non-conformity related to worse performance on a measure of inhibition. Additionally, as introvertive anhedonia increased, both attention and processing speed and reasoning and problem-solving performance became more impaired. In conclusion, this study extends schizotypy literature by examining the subscales of the O-LIFE, and enables inferences to be drawn in relation to cognitive impairment in schizophrenia.

MRI diffusion tractography study in individuals with schizotypal features: a pilot study

Diffusion tensor imaging (DTI) studies have identified changes in white matter tracts in schizophrenia patients and those at high risk of transition. Schizotypal samples represent a group on the schizophrenia continuum that share some aetiological risk factors but without the confounds of illness. The aim of the current study was to compare tract microstructural coherence as measured by fractional anisotropy (FA) between 12 psychometrically defined schizotypes and controls. We investigated bilaterally the uncinate and arcuate fasciculi (UF and AF) via a probabilistic tractography algorithm (PICo), with FA values compared between groups. Partial correlations were also examined between measures of subclinical hallucinatory/delusional experiences and FA values. Participants with schizotypal features were found to have increased FA values in the left hemisphere UF only. In the whole sample there was a positive correlation between FA values and measures of hallucinatory experience in the right AF. These findings suggest subtle changes in microstructural coherence are found in individuals with schizotypal features, but are not similar to changes predominantly observed in clinical samples. Correlations between mild hallucinatory experience and FA values could indicate increasing tract coherence could be associated with symptom formation.

Negative correlation between leftward bias in line bisection and schizotypal features in healthy subjects

Introduction: Recent studies have found a lack of normal pseudoneglect in schizophrenia patients and in their first degree relatives. Similarly, several contributions have reported that measures of schizotypy in the healthy population may be related to signs of right-sided lateralization, but most of these studies differ greatly in methodology (sample size, choice of schizotypy scales, and laterality tasks) and, consequently, the results cannot be compared and so definitive conclusion cannot be drawn. In this study, our purpose is to investigate whether some tasks of spatial attention may be related to different dimensions of schizotypy not only in a larger sample of healthy subjects (HS), but testing the same people with several supposedly related measures several times.

Materials and Methods: In the first part of the study (Part I), the performance on “paper and pencil” line bisection (LB) tasks in 205 HS was investigated. Each task was repeated three times. In the second part of the study (Part II), a subgroup of 80 subjects performed a computerized version of the LB test and of the mental number line bisection (MNL) test. In both parts of the study, every subject completed the 74-item version of the Schizotypal Personality Questionnaire (SPQ) and the Edinburgh Handedness Inventory (EHI).

Results: In both parts of the study, high scores on the subscale “magical thinking” of SPQ have resulted in being closely linked to a decreased pseudoneglect as assessed by the LB task. On the contrary, right handedness is related to an increased leftward bias at the same task. No association was found between MNL and the other variables.

Discussion: The main finding of this study is that a decreased spatial leftward bias at the LB task correlates with positive schizotypy in the healthy population. This finding supports the hypothesis that a deviation from leftward hemispatial visual preference may be related to the degree of psychosis-like schizotypal signs in non-clinical population and should be investigated as a possible marker of psychosis.

Schizotypy and personality profiles of Cluster A in a group of schizophrenic patients and their siblings

BACKGROUND

Schizotypy, or the set of personality traits related to schizophrenia, is considered an endophenotypic manifestation that is more represented in first-degree relatives of patients with schizophrenia than in the general population. The assessment of schizotypy is primarily based on self-reports, and for this reason it presents several limitations. In order to assess schizotypy, this study proposes a diagnostic instrument based on clinical reports.

METHODS

A sample of 66 subjects, composed of 25 outpatients with schizophrenia, 18 siblings of these patients and 23 healthy controls, was subjected to the personality assessment test SWAP-200 by trained clinical interviewers. To test the hypothesis of the difference between the profiles of the Personality Disorders within the schizophrenia spectrum, a Multivariate Analysis of Variance and subsequent planned comparisons were conducted.

RESULTS

Patients with schizophrenia scored higher than both their siblings and the controls on all SWAP-200 scales; their siblings, compared to the healthy controls, showed significant statistical differences, with higher mean scores for paranoid (F(1,63) = 7.02; p = 0.01), schizoid (F(1,63) = 6.56; p = 0.013) and schizotypal (F(1,63) = 6.47; p = 0.013) traits (PD T scores of Cluster A and Q-factor scores for the schizoid scale [F(1,63) = 6.47; p = 0.013]).

CONCLUSIONS

Consistent with previous data, first-degree relatives of patients with schizophrenia scored higher on schizophrenia-related personality traits than a general population comparison sample. SWAP-200, as an alternative diagnostic instrument to self-report measures, is able to reveal the higher prevalence of schizotypal traits in siblings of patients with schizophrenia, suggesting its possible use as a complementary instrument for the assessment of schizophrenia.

Schizotypal personality disorder

Early phenomenological descriptions of schizophrenia have acknowledged the existence of milder schizophrenia spectrum disorders characterized by the presence of attenuated symptoms typically present in chronic schizophrenia. The investigation of the schizophrenia spectrum disorders offers an opportunity to elucidate the pathophysiological mechanisms giving rise to schizophrenia. Differences and similarities between subjects with schizotypal personality disorder (SPD), the prototypical schizophrenia personality disorder, and chronic schizophrenia have been investigated with genetic, neurochemical, imaging, and pharmacological techniques. Patients with SPD and the more severely ill patients with chronic schizophrenia share cognitive, social, and attentional deficits hypothesized to result from common neurodevelopmentally based cortical temporal and prefrontal pathology. However, these deficits are milder in SPD patients due to their capacity to recruit other related brain regions to compensate for dysfunctional areas. Individuals with SPD are also less vulnerable to psychosis due to the presence of protective factors mitigating subcortical DA hyperactivity. Given the documented close relationship to other schizophrenic disorders, SPD will be included in the psychosis section of DSM-5 as a schizophrenia spectrum disorder as well as in the personality disorder section.

Heritability of functioning in families with schizophrenia in relation to neurocognition

The role of daily functioning is an integral part of the schizophrenia (SZ) phenotype and deficits in this trait appear to be present in both affected persons and some unaffected relatives; hence we have examined its heritability in our cohort of African American schizophrenia families. There is now ample evidence that deficits in cognitive function can impact family members who are not themselves diagnosed with SZ; there is some, but less evidence that role function behaves likewise. We evaluate whether role function tends to "run in families" who were ascertained because they contain an African American proband diagnosed with SZ.

METHODS

We analyzed heritability for selected traits related to daily function, employment, living situation, marital status, and Global Assessment Scale (GAS) score; modeling age, gender, along with neurocognition and diagnosis as covariates in a family based African-American sample (N=2488 individuals including 979 probands).

RESULTS

Measures of role function were heritable in models including neurocognitive domains and factor analytically derived neurocognitive summary scores and demographics as covariates; the most heritable estimate was obtained from the current GAS scores (h2=0.72). Neurocognition was not a significant contributor to heritability of role function.

CONCLUSIONS

Commonly assessed demographic and clinical indicators of functioning are heritable with a global rating of functioning being the most heritable. Measures of neurocognition had little impact on heritability of functioning overall. The family covariance for functioning, reflected in its heritability, supports the concept that interventions at the family level, such as evidenced-based family psychoeducation may be beneficial in schizophrenia.

Event-related potential correlates of suspicious thoughts in individuals with schizotypal personality features

Suspiciousness is a common feature of schizophrenia. However, suspicious thoughts are also commonly experienced by the general population. This study aimed to examine the underlying neural mechanism of suspicious thoughts in individuals with and without schizotypal personality disorder (SPD)-proneness, using an event-related potential (ERP) paradigm. Electroencephalography (EEG) was recorded when the "feeling of being seen through" was evoked in the participants. The findings showed a prominent positive deflection of the difference wave within the time window 250-400 ms after stimuli presentation in both SPD-prone and non-SPD-prone groups. Furthermore, the P3 amplitude was significantly reduced in the SPD-prone group compared to the non-SPD-prone group. The current density analysis also indicated hypoactivity in both frontal and temporal regions in the SPD-prone group, suggesting that the frontotemporal cortical network may play a role in the onset of suspicious thoughts. The P3 of difference wave was inversely correlated with the cognitive-perception factor and the suspiciousness/paranoid ideation trait, which provided preliminary electrophysiological evidence for the association of suspiciousness with SPD features.

Clair DM, Benson PJ. Atypical scanpaths in schizophrenia: evidence of a trait- or state-dependent phenomenon?

The development of trait markers of schizophrenia would represent an important advance in understanding the genetic architecture of the disease. To date, no candidate markers have satisfied all of the trait marker criteria, and many are not specific to the schizophrenia spectrum. Abnormalities in visual scanpaths are frequently reported in patients with schizophrenia and are emerging as a novel candidate for a schizophrenia biomarker. Here we review the suitability of scanpath measures as a target for trait marker research in schizophrenia. Papers reporting scanpath patterns in patients with schizophrenia were identified by PubMed and Google Scholar searches and by scanning reference lists in relevant articles. Search terms included "schizophrenia," "psychosis," "scanpath," "scan path," "fixation," "saccade" and "eye movement." Scanpath abnormalities afford impressive sensitivity and specificity and appear largely independent of psychotropic medications. Scanpaths may demonstrate some fluctuation with symptomatology and may be useful in illuminating illness state or subtypes. However, there is evidence that viewing behaviours remain atypical regardless of symptom remission and may be present in unaffected relatives of individuals with schizophrenia. This research is in its early stages, and further investigation regarding patterns of inheritance is required. Our findings support scanpath measures as a favourable topic for further investigation as a trait marker.

Exploratory study on the base-rate of paranoid ideation in a non-clinical Chinese sample

Recent findings from several large-scale community surveys suggest that delusions tend to occur in non-clinical samples as a continuous phenotype rather than as an all-or-none phenomenon. However, the majority of studies on the prevalence of delusions and paranoid ideation are limited to Western samples. The present study aims to examine the phenomenon and base-rate of paranoid ideation in a Chinese non-clinical sample. A total of 4951 undergraduates (65.9% male) completed a checklist for paranoid ideation and the Schizotypal Personality Questionnaire (SPQ). Participants were classified into individuals with and without schizotypal personality disorder (SPD) features based on the SPQ. For the frequency subscale, 2.1-18.2% of the participants without SPD features experienced certain types of paranoid ideation at least once a week during the survey. The prevalence rate even elevated to a higher proportion in conviction and distress dimensions. For the conviction subscale, 9.3-53.5% of the participants somewhat believed of the ideations. For the distress subscale, 14.7-31.3% of the participants felt somewhat distressing in the experienced paranoid ideation. Participants with SPD features reported significantly higher prevalence in most items across these three dimensions. Findings indicate a high base-rate of attenuated forms of psychotic-like symptoms in a non-clinical Chinese sample, and provide further evidence for the continuity of psychotic phenomenon in non-clinical samples.

Neurological soft signs in individuals with schizotypal personality features

OBJECTIVE

The current study attempted to examine the prevalence of neurological soft signs and their relationships with schizotypal traits in individuals with psychometrically defined schizotypal personality disorder (SPD) features.

METHOD

Sixty-four individuals with SPD-proneness and 51 without SPD-proneness were recruited for the present study. The soft signs subscales of the Cambridge Neurological Inventory were administered to all participants; the Schizotypal Personality Questionnaire (SPQ) was administered to SPD-proneness and non-SPD-proneness participants.

RESULTS

The SPD-proneness participants demonstrated significantly higher prevalence of soft signs than those without SPD-proneness. SPQ subscales were significantly associated with ratings of motor coordination, sensory integration and total soft signs.

CONCLUSION

These findings suggest that neurological soft signs are trait markers of schizophrenia.

MEG does not reveal impaired sensory gating in first-episode schizophrenia

OBJECTIVE

The inability to adequately suppress the second of two identical stimuli is called sensory gating deficit and can be studied by recording evoked potentials to auditory stimuli, e.g. the P50 and the N100. It has been considered the physiological correlate of schizophrenia patients' perception of being flooded by sensory impressions. According to the notion that the gating deficit constitutes a genetic trait, we expected to demonstrate the phenomenon in first-episode schizophrenia patients by using Magnetencephalography (MEG).

METHODS

Eighteen inpatients in remission of their first psychotic episode and 24 healthy, age- and sex-matched control subjects participated in the study. Diagnoses, psychopathology, and handedness were assessed with established instruments. Stimulation was performed with the double click paradigm (ISI 500 ms, ITI 9-10 s). MEG recordings of 15 patients and 18 controls entered further analyses with the software BESA for spatio-temporal source analyses and statistical analyses with MATLAB.

RESULTS

Neither P50 nor N100 responses differed statistically between the groups, which means that gating was not impaired in this sample of first-episode schizophrenia patients.

CONCLUSIONS

These results are not in line with the majority of studies on sensory gating in schizophrenia, however, studies on first-episode patients are scarce. The most likely reasons for not observing a gating deficit in our study are patients' first-episode status and atypical antipsychotic medication.

Relationship between prepulse inhibition of acoustic startle response and schizotypy in healthy Japanese subjects

Prepulse inhibition (PPI) of the acoustic startle reflex (ASR) is the most common psychophysiological index of sensorimotor gating. Several studies have investigated the relationship of PPI of ASR to schizotypy in Caucasians. However, little has been reported on this relationship in Asians. We investigated a possible relationship between PPI of ASR and schizotypy in 79 healthy Japanese subjects. Schizotypy was assessed by the Schizotypal personality Questionnaire (SPQ). PPI was evaluated at signal-to-noise ratios (SnRs: difference between background noise intensity and prepulse intensity) of +12, +16, and +20 dB. The total SPQ score, cognitive/perceptual score, and interpersonal score correlated negatively with PPI at SnR of +16 and +20 dB. We conclude that PPI is associated with the trait of schizotypy in healthy Asian subjects.

Neurological soft signs and schizotypal dimensions in unaffected siblings of patients with schizophrenia

The objectives were to determine the neurological soft signs (NSS) scores in unaffected siblings of patients with schizophrenia compared with healthy controls and to examine their relationships with schizotypal dimensions. Participants comprised 31 unaffected siblings of patients with schizophrenia and 60 healthy controls matched according to age, gender and school level who were assessed by the Schizotypal Personality Questionnaire (SPQ) and the Krebs et al. NSS Scale. Higher NSS total scores and sub-scores were found in the unaffected siblings compared with the controls. The SPQ total score was significantly higher in unaffected siblings compared with control subjects. The NSS total score was positively correlated with the SPQ total score and the SPQ disorganization sub-score in unaffected siblings of patients with schizophrenia. Additionally, in unaffected siblings, motor coordination and integration abnormalities were positively correlated with the SPQ total score and the cognitive-perceptual sub-score. Motor integration abnormalities were also correlated with the SPQ disorganization sub-score. These results reveal that NSS, especially motor signs, are associated with some schizotypal dimensions in siblings of patients with schizophrenia, suggesting the value of using both assessments to study high risk populations.

Attention network test (ANT) reveals gender-specific alterations of executive function in schizophrenia

The Attention Network Test (ANT) provides measures for three different components of visual attention: executive control (=conflict inhibition), orienting, and alerting. There is reasonable evidence that alterations of attention-mainly in the executive/conflict domain-are associated with susceptibility to psychiatric illness. Specific impairments may be a characteristic for a medical condition such as schizophrenia and thus shift our understanding from a neuropsychological endophenotype to a more precise genetic understanding of this disorder. Study subjects comprised 35 schizophrenic patients and 35 healthy controls (13 female and 22 male in both groups). The ANT was administered to all participants and rated individual responses for the three factors (alerting, orienting, and conflict) and their respective ratios relative to mean reaction times. With regard to gender differences, group comparisons were performed for schizophrenic patients vs. healthy controls. Significant differences between patients and controls could be detected for mean reaction time (639 vs. 538 ms) and for conflict ratio (0.158 vs. 0.191). The latter difference mainly resulted from gender-specific variances of the conflict network in opposite directions. The executive function as represented by the conflict network of visual attention of the ANT is affected in schizophrenia. We have detected hitherto unreported gender-specific differences between healthy controls and schizophrenic patients. Especially as regards the conflict network, the ANT offers a promising methodology to detect a neuropsychological endophenotype of schizophrenia.

The relationship between interview-based schizotypal personality dimension scores and the continuous performance test

The existing research that has examined cognitive performance in samples with subclinical schizotypal personality features has been largely limited to psychometric self-report questionnaires, which may be biased by distorted self-awareness of symptoms. The present study examined the relationship between performance on a degraded-AX continuous performance test (CPT) and continuous dimension scores created from a structured clinical interview for schizotypal personality disorder (SPD), which reflected both the breadth and severity of schizotypal personality symptoms, in 52 undergraduate students. Only one participant met full diagnostic criteria for SPD. The overall dimension score from the SPD clinical interview showed a positive correlation with both omission (r(s)=.47) and false alarm (r(s)=.41) errors on the CPT. Interpersonal symptoms were positively correlated with omission errors (r(s)=.47), while Disorganized symptoms were positively correlated with false alarm errors (r(s)=.40). Results suggest that higher SPD interview-based dimension scores are associated with lower levels of performance on the CPT, even when examining a relatively subclinical sample of young adults. In contrast, scores from the psychometric Abbreviated Schizotypal Personality Questionnaire in the same sample did not correlate with accuracy measures on the CPT, suggesting that the interview-based measure of schizotypal personality may have a stronger relationship with CPT accuracy. Findings also add to a growing literature suggesting that Interpersonal SPD symptoms are primarily related to omission errors, while Disorganized SPD symptoms are primarily related to false alarm errors.

Schizotypal dimensions: an intermediate phenotype associated with the COMT high activity allele

BACKGROUND

Although catechol-O-methyltransferase (COMT) has long been suggested to be implicated in the pathogenesis of schizophrenia, association studies have generated discrepant results concerning the involvement of the COMT gene in schizophrenia. As several studies have suggested that schizotypal traits might be genetically related to schizophrenia, increased statistical power to detect gene effects could be obtained by using dimensional personality traits in unaffected relatives.

METHODS

We tested the hypothesis that the functional Val158Met COMT polymorphism might contribute to the variance of self-reported schizotypal scores in a sample of 106 unaffected subjects, composed of controls (N = 57), first-degree relatives of schizophrenic (N = 27) and of bipolar (N = 22) probands. We also looked for specific associations between COMT polymorphisms and the three dimensions of schizotypy (positive, negative, disorganized) assessed by the Schizotypal Personality Questionnaire (SPQ).

RESULTS

We found that self-reported SPQ scores are related to COMT genotype (P = 0.01), with individuals homozygous for the high activity allele having the highest scores. This association is primarily due to specific associations with the positive (P = 0.001) and negative (P = 0.04) dimensions.

CONCLUSIONS

Our data support the hypothesis that the functional COMT polymorphism could be involved in different psychotic dimensions. This confirms that studying specific schizotypal dimensions can help to identify the genes involved in the pathogenesis of psychosis.

Comparison of three computer-administered cognitive tasks as putative endophenotypes of schizophrenia

It has been repeatedly demonstrated that individuals with schizotypal personality features (SPF) exhibit similar endophenotypic traits as persons with schizophrenia. Less research has compared the relative sensitivity of different endophenotypes in the same sample of individuals with SPF. Fourteen university students with SPF (mean age 20.5+/-1.6; 43% male) and 26 controls (mean age 20.3+/-1.1; 31% male) were defined by the Abbreviated Schizotypal Personality Questionnaire (SPQ-B). All participants reported no known biological relative with schizophrenia. Participants completed three computer-administered cognitive tasks: a 6-min degraded-stimuli A-X Continuous Performance Test (CPT), the Wisconsin Card Sort Test (WCST), and a Span of Apprehension (SOA) task (6- and 12-letter arrays). On the CPT, only omission errors resulted in a statistically significant group difference, U=115.5, p=.05, Cohen's d=0.54 (medium effect size), with the SPF group (mean errors: 3.43+/-3.28) making more omission errors than controls (mean errors: 1.88+/-2.66). Notably, 46% of the controls had no omission errors, compared to 14% of the SPF group. The only SPQ-B factor score to show a statistically significant linear relationship with CPT omission errors was the Cognitive-Perceptual factor (rs=.33, p=.04). Group differences on performance indices from the SOA and WCST did not approach statistical significance. Based on performance from the community-identified schizotypes, results suggest that performance on the CPT may represent a more robust endophenotype of schizophrenia, compared to the SOA and WCST.

Abnormalities of auditory event-related potentials in students with high scores on the Schizotypal Personality Questionnaire

Some auditory event-related potential (ERP) abnormalities characterize both patients with schizophrenia and subjects with schizotypal personality disorder. It was therefore hypothesized that subjects from the community with schizotypal traits might also present ERP abnormalities. In this study, we compared auditory ERP latencies and amplitudes in 13 subjects with high (H-SPQ) and 12 subjects with low (L-SPQ) scores on the Schizotypal Personality Questionnaire (SPQ), selected from 198 Tunisian students. Auditory ERPs were recorded at Fz, Cz, and Pz, with a standard oddball paradigm. Smaller P300 amplitudes and delayed P300 latencies were found in H-SPQ compared with L-SPQ participants. Confirming previous reports, our results suggest that reduced P300 amplitudes and delayed P300 latencies may be considered as vulnerability markers of the schizophrenia spectrum in nonclinical subjects from the community.

Generalized and specific cognitive performance in clinical high-risk cohorts: a review highlighting potential vulnerability markers for psychosis

Cognitive deficits are a core feature of established psychotic illnesses. However, the association between cognition and emerging psychosis is less understood. While there is some evidence that cognitive deficits are present prior to the onset of psychosis, findings are not consistent. In this article we provide an overview of the more general cognitive findings available from genetic high-risk studies, retrospective studies, and birth cohort studies. We then focus the review on neuropsychological performance in clinically "at-risk" groups. Overall, general cognitive ability as assessed by established batteries appears to remain relatively intact in these ultra-high risk cohorts and is a poor predictor close to illness onset relative to other vulnerability factors. Further decline may occur with illness progression, more consistent with state relative to trait factors. In addition, most established cognitive tasks involve several relatively discrete cognitive subprocesses, where findings from general batteries of subtests may mask specific deficits. In this context, our review suggests that relatively specific olfactory identification and spatial working memory deficits exist prior to illness onset and may be more potent trait markers for psychosis than cognitively dense tasks such as verbal memory. Suggestions for further research address the importance of standardization of inclusion criteria and the maintenance of basic neuropsychological assessment to allow better comparison of findings across centers. Further, in order to better understand the aetiopathology of cognitive dysfunction in psychosis, more experimental, hypothesis-driven measures of discrete cognitive processes are required. Delineation of the relationship between specific cognitive ability and symptoms from data-driven approaches may improve our understanding of the role of cognition during psychosis onset.

Genetically predisposed offspring with schizotypal features: an ultra high-risk group for schizophrenia?

Biomarkers proposed in the schizophrenia diathesis have included neurocognitive deficits in domains such as working memory that implicate prefrontal systems. However, the relationship between these biomarkers and psychopathological markers such as schizotypy has not been systematically assessed, particularly in adolescent offspring of schizophrenia patients. Convergence between these markers may identify individuals at especially high risk for schizophrenia. In the current study the authors assessed whether functional deficits in working memory assessed using the oculomotor delayed response task (ODR) and executive function assessed using the Wisconsin Card Sort task (WCST), and structural deficits in prefrontal cortex, in the adolescent offspring of patients were predictive of schizotypy. Schizotypal offspring made more perseverative errors on the WCST (p<.002) and showed age-related deficits on the ODR task (p<.02) compared to their non-schizotypal counterparts or healthy controls. Reduced gray matter concentration in prefrontal cortex (p<.001) was also associated with schizotypy. Schizotypy in offspring of schizophrenia patients appears to be highly associated with known biomarkers of the illness such as executive function impairment and reductions in cortical gray matter. Furthermore, schizotypy appears to interact with development leading to greater impairment in working memory in schizotypal offspring closer to the typical age of onset of schizophrenia than non-schizotypal offspring. Thus, clinical and neurocognitive biomarkers of the illness appear to be highly interrelated in this sample of at-risk offspring. We propose that schizotypy may define a hyper vulnerable sub-sample among individuals genetically predisposed to schizophrenia and that future studies that attempt to assess risk may benefit from such a convergent approach.

The emergence of a new paradigm of pharmacogenomics

A series of qualitatively new properties of the complex polygenic systems are transforming the dominant, genome-centric approach of pharmacogenomics towards a more integrative, holistic paradigm. The recent concepts of interposition of regulatory networks between genotype and phenotype, and the emergence of epigenotype as the locus of integration of genetic background with nutritional and lifestyle influences, render problematic any prediction of the consequences of individual gene alterations. In addition, the redefinition of the traditional boundaries of clinical phenotypes, with the promotion of the endophenotypes as methodological strategy, and the initiative of the phenome elucidation, reshape both the research, as well as the application, of pharmacogenomics. These concepts and developments can explain some of the complexity, and the multifactorial nature, of most drug responses and imply another understanding of education in the field, which aims at stimulating a critical reflection on these major shifts prior to a practical training on the immediate application of pharmacogenomics.

Lack of association between prepulse inhibition and antisaccadic deficits in chronic schizophrenia: implications for identification of schizophrenia endophenotypes

Individuals with schizophrenia, compared to healthy individuals, are known to exhibit deficient prepulse inhibition (PPI) of the startle response as well as reduced performance on the antisaccade task. There is evidence for genetic transmission of both PPI and antisaccadic abnormalities in schizophrenia. It has been suggested that PPI and antisaccade measures identify separate endophenotypes, on the basis of a lack of relationship between PPI and antisaccade deficits in patients with schizotypal personality disorder. However, given that patients with schizotypal personality disorder are unlikely to manifest all the abnormalities associated with schizophrenia, it is important to determine that there is no relationship present between these two abnormalities in people affected with schizophrenia. The main objective of this investigation therefore was to establish the lack of the association between PPI and antisaccade deficits in schizophrenia in two independent studies. Study 1 involved 39 patients with schizophrenia and 14 healthy controls and study 2 involved 35 patients with schizophrenia and 22 healthy controls. PPI (uninstructed paradigm) of the acoustically elicited startle (eye blink) was measured electromyographically. Antisaccadic eye movements (standard, non-overlap version) were measured using infrared oculography. Patients displayed reduced PPI and a lower percentage of correct antisaccades relative to healthy controls in both studies. As expected, no relationship occurred between PPI and the percentage of correct antisaccade responses in either group. It is concluded that PPI and antisaccade abnormalities in schizophrenia represent separate endophenotypes, reflecting the functions of different genetic aetiologies and different or only partially overlapping neural systems.

Effects of chronic olanzapine and haloperidol differ on the mouse N1 auditory evoked potential

Auditory evoked potentials have been used in a variety of animal models to assess information-processing impairments in schizophrenia. Previous mouse models have primarily employed a paired click paradigm to assess the transient measures of auditory gating. The current study uses stimulus trains at varied interstimulus intervals (ISI) between 0.25 and 8 s in mice to assess the effects of chronic olanzapine and haloperidol on auditory processing. Data indicate that olanzapine increases the amplitude of the N40, P80, and P20/N40 components of the auditory evoked potential, whereas haloperidol had no such effect. The ISI paradigm also allowed for an evaluation of several components of the mouse evoked potential to assess those that display response properties similar to the human P50 and N100. Data suggest that the mouse N40 displays an ISI response relationship that shares characteristics with the human N100, whereas the P20 appears more consistent with the human P50 across the ISI range evaluated in this task. This study suggests that olanzapine may help improve N100 impairments seen in schizophrenia, while haloperidol does not.

Vulnerability markers in the schizophrenia spectrum: implications for phenomenology, genetics, and the identification of the schizophrenia prodrome

A continuum of symptoms between "normality" and overt psychosis has been documented in relatives of schizophrenia patients, SPD, and individuals who may be in the early stages of a psychotic illness with "subsyndromal" symptoms. The empirically derived criteria for SPD have been refined to define a clinical phenotype that is linked to schizophrenia. The clinical SPD symptoms define a heterogeneous group of individuals who are often comorbid for Axis I and II disorders, may or may not have a family history of schizophrenia, and are at risk for developing schizophrenia themselves. SPD subjects have similar abnormalities to those observed in schizophrenia patients on various psychophysiologic paradigms designed to study central inhibition, including P50 event-related potential suppression, PPI of the startle response, and the antisaccade task. Because SPD subjects do not have many of the confounding variables observed in schizophrenia patients (i.e., medication effects), these paradigms might represent vulnerability markers that are possible endophenotypes for schizophrenia spectrum illness. Questions still remain as to whether SPD is genotypically linked to schizophrenia but has genes of lesser penetrance, fewer affected genes, lack of a second hit, or perhaps protective factors. It is also possible that SPD, like schizophrenia, is a common final pathway that can come about because of several etiologic factors that affect crucial neurodevelopmental periods. Future directions in SPD work might include the use of vulnerability markers to essentially subtype schizophrenia spectrum patients and create simpler endophenotypes to understand the phenomenologic and neurobiologic substrate. The use of vulnerability markers along with clinical symptoms may help to improve the predictive power for identifying individuals at risk for schizophrenia for early intervention. Finally, genetic studies have yet to be performed in SPD.

Schizophrenia and schizotypal personality: a tribute to Peter H. Venables

Peter Venables made multiple contributions to the field of schizophrenia and schizotypy, most notably in the areas of psychophysiology, neurocognition, and assessment. On the 50th anniversary of the start of his research career in 1951, a conference on schizophrenia and schizotypy was held in his honor in Tuscany, Italy. This special edition encapsulates many of the presentations given at that meeting, covering the areas of neurodevelopment, assessment, genetics, psychophysiology, neurocognition, brain imaging, psychopharmacology, intervention, and prevention. A key theme of this special edition concerns the integration of schizophrenia and schizotypy research in a manner that will allow for a more comprehensive understanding of both of these disorders.