Eye movement and neuropsychological studies in first-degree relatives of schizophrenic patients

Spatial and Temporal Abnormalities of Spontaneous Fixational Saccades and Their Correlates With Positive and Cognitive Symptoms in Schizophrenia

BACKGROUND AND HYPOTHESIS

Visual fixation is a dynamic process, with the spontaneous occurrence of microsaccades and macrosaccades. These fixational saccades are sensitive to the structural and functional alterations of the cortical-subcortical-cerebellar circuit. Given that dysfunctional cortical-subcortical-cerebellar circuit contributes to cognitive and behavioral impairments in schizophrenia, we hypothesized that patients with schizophrenia would exhibit abnormal fixational saccades and these abnormalities would be associated with the clinical manifestations.

STUDY DESIGN

Saccades were recorded from 140 drug-naïve patients with first-episode schizophrenia and 160 age-matched healthy controls during ten separate trials of 6-second steady fixations. Positive and negative symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). Cognition was assessed using the Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB).

STUDY RESULTS

Patients with schizophrenia exhibited fixational saccades more vertically than controls, which was reflected in more vertical saccades with angles around 90° and a greater vertical shift of horizontal saccades with angles around 0° in patients. The fixational saccades, especially horizontal saccades, showed longer durations, faster peak velocities, and larger amplitudes in patients. Furthermore, the greater vertical shift of horizontal saccades was associated with higher PANSS total and positive symptom scores in patients, and the longer duration of horizontal saccades was associated with lower MCCB neurocognitive composite, attention/vigilance, and speed of processing scores. Finally, based solely on these fixational eye movements, a K-nearest neighbors model classified patients with an accuracy of 85%. Conclusions: Our results reveal spatial and temporal abnormalities of fixational saccades and suggest fixational saccades as a promising biomarker for cognitive and positive symptoms and for diagnosis of schizophrenia.

The association between cytokines and psychomotor speed in a spectrum of psychotic disorders: A longitudinal study

Background

In schizophrenia, impaired psychomotor speed is a common symptom predicting worse functional outcome. Inflammation causes changes in white matter integrity, which may lead to reduced psychomotor speed. Therefore, we wanted to investigate if peripheral inflammation assessed with cytokines affected performance on psychomotor speed in patients with a spectrum of psychotic disorders.

Methods

The current study is a prospective cohort study, including participants from a pragmatic, randomised controlled trial comparing three atypical antipsychotics in patients with a spectrum of psychotic disorders. For the purposes of this sub-study, we analysed drug treatment groups collectively. Psychomotor speed was assessed at baseline, and at weeks 6, 12, 26 and 52 of follow-up, using the neuropsychological tests trail making test (TMT) A and B, and symbol coding. Serum concentration of the following cytokines were measured: interleukin (IL)-β, IL-2, IL-4, IL-6, IL-10, IL12 p70, IL-17a, interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Blood samples were collected at baseline and after 1, 3, 6, 12, 26, 39 and 52 weeks. We analysed the effect of cytokines levels on psychomotor speed over time in linear mixed effects models.

Results

In our linear mixed effects models controlling for possible confounders, IFN-γ had a significant negative effect on TMT-A and symbol coding performance. None of the other tests for psychomotor speed were significantly associated with cytokines. Overall psychomotor speed performance increased significantly across the study period while cytokine levels remained stable.

Conclusion

Our study indicates a negative association between IFN-γ and psychomotor speed, which might be of importance when understanding the mechanisms behind psychomotor deviations in psychotic disorders.

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The cytokine interferon (IFN) – γ is related to psychomotor speed in patients with psychotic disorders.

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For majority of cytokines, we found no significant association with psychomotor speed.

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Cytokines remained stable during the study period of 52 weeks.

Visual Attention Deficits in Schizophrenia Can Arise From Inhibitory Dysfunction in Thalamus or Cortex

Schizophrenia is associated with diverse cognitive deficits, including disorders of attention-related oculomotor behavior. At the structural level, schizophrenia is associated with abnormal inhibitory control in the circuit linking cortex and thalamus. We developed a spiking neural network model that demonstrates how dysfunctional inhibition can degrade attentive gaze control. Our model revealed that perturbations of two functionally distinct classes of cortical inhibitory neurons, or of the inhibitory thalamic reticular nucleus, disrupted processing vital for sustained attention to a stimulus, leading to distractibility. Because perturbation at each circuit node led to comparable but qualitatively distinct disruptions in attentive tracking or fixation, our findings support the search for new eye movement metrics that may index distinct underlying neural defects. Moreover, because the cortico-thalamic circuit is a common motif across sensory, association, and motor systems, the model and extensions can be broadly applied to study normal function and the neural bases of other cognitive deficits in schizophrenia.

Association of DISC1, BDNF, and COMT polymorphisms with exploratory eye movement of schizophrenia in a Chinese Han population

BACKGROUND

Previous studies suggested that exploratory eye movement (EEM) dysfunction appears to be a biological marker specific to schizophrenia, with an unknown molecular mechanism. Genetic studies indicate that disrupted-in-schizophrenia-1 (DISC1), brain-derived neurotrophic factor (BDNF), and catechol-O-methyl transferase (COMT) genes might be implicated in the etiology of schizophrenia, but not in all populations.

OBJECTIVES

The present study aimed to explore associations between these candidate genes and EEM endophenotypes for schizophrenia in a Chinese Han population.

METHODS

EEM recordings were examined in 139 patients with schizophrenia and 143 healthy control participants.

RESULTS

All five EEM parameters, responsive search score, cognitive search score, number of eye fixations, total eye scanning length, and mean eye scanning length, of schizophrenic patients differed significantly from those of healthy controls (P<0.001). The DISC1 SerCys, BDNF ValMet, and COMT ValMet were genotyped in a total sample of 818 schizophrenic patients and 827 healthy control participants, including the above EEM samples. We found that DISC1 Cys and BDNF Met were associated with an increased risk of developing schizophrenia (P<0.001). Furthermore, responsive search score scores of BDNF Met/Met carriers were significantly lower than those of Val allele carriers (P=0.022), which remained modest after Bonferroni correction.

CONCLUSION

The BDNF MetMet polymorphism might be associated with the EEM dysfunction of schizophrenia.

Oculomotricity and Neurological Soft Signs: Can we refine the endophenotype? A study in subjects belonging to the spectrum of schizophrenia

Alterations in eye tracking and motor impairments as well as Neurological Soft Signs (NSS) are frequently reported in patients with schizophrenia as well as in their relatives, and are proposed as endophenotype of the disease. This study investigated smooth pursuit eye movement and fixation task with distractors with a gap condition, two markers of inhibitory control mechanism, in 49 patients with schizophrenia, 24 ultra-high risk subjects, 41 full biological clinical siblings of patients and 48 controls. NSS were assessed as a marker of abnormal neurodevelopment. The results revealed more intrusive saccades respectively in smooth pursuit eye movement and in fixation task with distractors with a gap condition in patients, respect to controls and full siblings. Ultra high-risk participants with high NSS committed intrusive saccades compared to controls. Patients with schizophrenia with high NSS also displayed more of these abnormalities, compared to patients with schizophrenia with low NSS and controls. These findings highlight a global inhibitory control defect, and suggested that ultra-high risk subjects and patients with schizophrenia could share oculomotor abnormalities, especially when they express a high neurodevelopmental deviance. These oculomotor alterations might suggest that cerebral structures such as prefrontal and cerebellum could be involved in the expression of this vulnerability.

Executive function and genetic loading in nonpsychotic relatives of schizophrenia patients

Executive functions meet the "endophenotype candidate" criteria in neuropsychological measures for schizophrenic patients. To determine which area of executive functioning has the greatest value in differentiating the so called "candidate endophenotype" of schizophrenia through comparing the effect sizes of four commonly used executive function tests. A Wisconsin Card Sorting Test, a Stroop Test, a Trail Making Test and a Verbal Fluency Test were used to evaluate executive function in two study groups: healthy relatives of schizophrenia patients from simplex and multiplex families and a healthy control group. In all four tests, study groups performed poorly in contrast to the control group. In the B time, A error and B error results of the Trail Making Test, the multiplex group performed poorly compared to the simplex group; control group did better than both study groups. Our findings support that the presence of a schizophrenia patient in a family predicts worse performance on executive function tests in a group of healthy relatives of that individual. The results of our study suggest that the Trail Making Test in particular may signify a stronger endophenotypic trait.

"To see or not to see: that is the question." The "Protection-Against-Schizophrenia" (PaSZ) model: evidence from congenital blindness and visuo-cognitive aberrations

The causes of schizophrenia are still unknown. For the last 100 years, though, both “absent” and “perfect” vision have been associated with a lower risk for schizophrenia. Hence, vision itself and aberrations in visual functioning may be fundamental to the development and etiological explanations of the disorder. In this paper, we present the “Protection-Against-Schizophrenia” (PaSZ) model, which grades the risk for developing schizophrenia as a function of an individual's visual capacity. We review two vision perspectives: (1) “Absent” vision or how congenital blindness contributes to PaSZ and (2) “perfect” vision or how aberrations in visual functioning are associated with psychosis. First, we illustrate that, although congenitally blind and sighted individuals acquire similar world representations, blind individuals compensate for behavioral shortcomings through neurofunctional and multisensory reorganization. These reorganizations may indicate etiological explanations for their PaSZ. Second, we demonstrate that visuo-cognitive impairments are fundamental for the development of schizophrenia. Deteriorated visual information acquisition and processing contribute to higher-order cognitive dysfunctions and subsequently to schizophrenic symptoms. Finally, we provide different specific therapeutic recommendations for individuals who suffer from visual impairments (who never developed “normal” vision) and individuals who suffer from visual deterioration (who previously had “normal” visual skills). Rather than categorizing individuals as “normal” and “mentally disordered,” the PaSZ model uses a continuous scale to represent psychiatrically relevant human behavior. This not only provides a scientific basis for more fine-grained diagnostic assessments, earlier detection, and more appropriate therapeutic assignments, but it also outlines a trajectory for unraveling the causes of abnormal psychotic human self- and world-perception.

Reading in schizophrenic subjects and their nonsymptomatic first-degree relatives

Previous studies have demonstrated eye movement abnormalities during smooth pursuit and antisaccadic tasks in schizophrenia. However, eye movements have not been investigated during reading. The purpose of this study was to determine whether schizophrenic subjects and their nonsymptomatic first-degree relatives show eye movement abnormalities during reading. Reading rate, number of saccades per line, amplitudes of saccades, percentage regressions (reverse saccades), and fixation durations were measured using an eye tracker (EyeLink, SensoMotoric Instruments, Germany) in 38 schizophrenic volunteers, 14 nonaffected first-degree relatives, and 57 control volunteers matched for age and National Adult Reading Test scores. Parameters were examined when volunteers read full pages of text and text was limited to progressively smaller viewing areas around the point of fixation using a gaze-contingent window. Schizophrenic volunteers showed significantly slower reading rates (P = .004), increase in total number of saccades (P ≤ .001), and a decrease in saccadic amplitude (P = .025) while reading. Relatives showed a significant increase in total number of saccades (P = .013) and decrease in saccadic amplitude (P = .020). Limitation of parafoveal information by reducing the amount of visible characters did not change the reading rate of schizophrenics but controls showed a significant decrease in reading rate with reduced parafoveal information (P < .001). Eye movement abnormalities during reading of schizophrenic volunteers and their first-degree relatives suggest that visual integration of foveal and parafoveal information may be reduced in schizophrenia. Reading abnormalities in relatives suggest a genetic influence in reading ability in schizophrenia and rule out confounding effects of medication.

Simple viewing tests can detect eye movement abnormalities that distinguish schizophrenia cases from controls with exceptional accuracy

BACKGROUND

We have investigated which eye-movement tests alone and combined can best discriminate schizophrenia cases from control subjects and their predictive validity.

METHODS

A training set of 88 schizophrenia cases and 88 controls had a range of eye movements recorded; the predictive validity of the tests was then examined on eye-movement data from 34 9-month retest cases and controls, and from 36 novel schizophrenia cases and 52 control subjects. Eye movements were recorded during smooth pursuit, fixation stability, and free-viewing tasks. Group differences on performance measures were examined by univariate and multivariate analyses. Model fitting was used to compare regression, boosted tree, and probabilistic neural network approaches.

RESULTS

As a group, schizophrenia cases differed from control subjects on almost all eye-movement tests, including horizontal and Lissajous pursuit, visual scanpath, and fixation stability; fixation dispersal during free viewing was the best single discriminator. Effects were stable over time, and independent of sex, medication, or cigarette smoking. A boosted tree model achieved perfect separation of the 88 training cases from 88 control subjects; its predictive validity on retest assessments and novel cases and control subjects was 87.8%. However, when we examined the whole data set of 298 assessments, a cross-validated probabilistic neural network model was superior and could discriminate all cases from controls with near perfect accuracy at 98.3%.

CONCLUSIONS

Simple viewing patterns can detect eye-movement abnormalities that can discriminate schizophrenia cases from control subjects with exceptional accuracy.

Smooth pursuit and visual scanpaths: Independence of two candidate oculomotor risk markers for schizophrenia

OBJECTIVES

Smooth pursuit and visual scanpath deficits are candidate trait markers for schizophrenia. It is not clear whether eye tracking dysfunction (ETD) and atypical scanpath behaviour are the product of the same underlying neurobiological processes. We have examined co-occurrence of ETD and scanpath disturbance in individuals with schizophrenia and healthy volunteers.

METHODS

Eye movements of individuals with schizophrenia (N = 96) and non-clinical age-matched comparison participants (N = 100) were recorded using non-invasive infrared oculography during smooth pursuit in both predictable (horizontal sinusoid) and less predictable (Lissajous sinusoid) conditions and a free viewing scanpath task.

RESULTS

Individuals with schizophrenia demonstrated scanning deficits in both tasks. There was no association between performance measures of smooth pursuit and scene scanpaths in patient or control groups. Odds ratios comparing the likelihood of scanpath dysfunction when ETD was present, and the likelihood of finding scanpath dysfunction when ETD was absent were not significant in patients or controls in either pursuit variant, suggesting that ETD and scanpath dysfunction are independent anomalies in schizophrenia.

CONCLUSION

ETD and scanpath disturbance appear to reflect independent oculomotor or neurocognitive deficits in schizophrenia. Each task may confer unique information about the pathophysiology of psychosis.

Executive function impairment in first-degree relatives of persons with schizophrenia: A meta-analysis of controlled studies

A meta-analysis of past research evaluated the relationship between deficits in executive functioning among unaffected first-degree relatives of schizophrenia patients and healthy controls. The Wisconsin Cart Sorting Test (WCST), a reliable measurement of cognition and abstract thinking, was examined as the dependent variable. Unaffected first-degree relatives perform worse than controls on two important dimensions of the WCST. They achieve significantly less categories and significantly more perseverative errors.

Stroop and emotional Stroop interference in unaffected relatives of patients with schizophrenic and bipolar disorders: distinct markers of vulnerability?

Reduced inhibition has been demonstrated in both schizophrenic and bipolar patients through the findings of increased interference on the Stroop Colour-Word Task (SCWT) and increased emotional interference on specific versions of the Emotional Stroop Task (EST). Despite previous findings of enhanced interference in unaffected relatives of schizophrenic and bipolar patients, it remains unclear whether interference might be a candidate endophenotype to both disorders. Moreover, data regarding emotional interference in unaffected relatives are critically lacking. In the present study, we aimed to compare unaffected relatives of patients with schizophrenia (SZ-rel, N = 30) and bipolar disorder (BD-rel, N= 30) with normal controls (N = 60) when performing the SCWT and an EST designed with neutral, depressive, paranoid and manic words. SZ-rel exhibited greater interference effect on both the SCWT and the EST as compared to either BD-rel or normal controls. BD-rel, and by contrast to SZ-rel and controls, showed increased emotional interference effect on the EST that was specifically associated to the disease-related words. The findings support the hypothesis of different markers of vulnerability to schizophrenic and bipolar disorders; impairment in cognitive inhibition could characterize high-risk individuals for schizophrenia whereas an emotional bias towards mood-related information could be a trait marker of bipolar disease.

Leukemia inhibitory factor gene is associated with schizophrenia and working memory function

Leukemia inhibitory factor (LIF), a member of the interleukin-6 cytokine family, regulates the neuronal phenotype and coordinates astrocyte, oligodendrocyte, microglia, and inflammatory cell responses. The LIF gene is located on 22q12.1-q12.2, a hot spot for schizophrenia. Three polymorphisms of the LIF gene (rs929271, rs737812, and rs929273) were examined in a case-control association study of 390 patients with schizophrenia and 410 age- and sex-matched controls. Effects of a risk genotype of LIF on cognitive domains were evaluated by the Wechsler Adult Intelligence Scale-Revised, Wechsler Memory Scale-Revised, and Wisconsin Card Sorting Test (WCST) in 355 healthy volunteers. The LIF gene showed significant associations with schizophrenia at rs929271 and a haplotype consisting of rs929271-rs737812. After stratification by subtype of schizophrenia, the hebephrenic, but not paranoid, type was associated with the LIF gene at rs929271 (allele, P=0.014) and the haplotype (permutation P=0.013). Having the T-allele and T-carrier genotypes (TT and TG) of rs929271 were risks for hebephrenic schizophrenia, and the odds ratios were 1.38 (95% CI: 1.21-1.56) and 1.54 (95%CI: 1.19-1.98), respectively. Subjects with T-carrier genotypes made significantly more errors on the WCST compared with those without (P=0.04). The present study indicated that the LIF gene variant may produce susceptibility to hebephrenic schizophrenia and deterioration of working memory function.

Neuropsychological correlates of eye movement abnormalities in schizophrenic patients and their unaffected relatives

Impairments on neuropsychological and eye movement tasks have been demonstrated in schizophrenic patients and also reported in their unaffected relatives. However, it is not clear to what extent these phenotypes overlap. This study examined the relationship between specific eye movement and neuropsychological measures. The relationship between performance on eye movement and neuropsychological tasks was measured in 79 schizophrenic patients (63% from multiply affected families), 129 of their healthy first-degree relatives, and 72 normal controls. Antisaccade scores were correlated with most measures of neurocognitive functioning, and this correlation was strongest in schizophrenic patients in all cases. In the schizophrenic patients, but not their relatives or controls, the antisaccade distractibility error (ADE) score correlated significantly with current intelligence, verbal memory (immediate and delayed recall), and associative learning. In the case of crystallised IQ and delayed verbal memory, smaller correlations were present in unaffected relatives, although neither survived Bonferroni correction. Smooth pursuit performance was unrelated to any neuropsychological measure. Our study suggests that antisaccade errors are likely to represent part of a generalized neuropsychological deficit in schizophrenia.

Executive functions and cognitive deficits in schizophrenia: comparisons between probands, parents and controls in India

BACKGROUND

Cognitive impairment is said to be a core feature of schizophrenia. Executive function is an important cognitive domain.

AIM

This study was undertaken to assess cognitive impairment among Indian patients with schizophrenia (Sz) or schizoaffective disorder (SzA), compared with their parents and unaffected individuals (controls).

SETTINGS AND DESIGN

Executive functions as measured by Trail-making Test (TMT), of patients and their parents were compared with controls. The patients were recruited from the Outpatients' Department (OPD) of a government hospital.

MATERIALS AND METHODS

Patients diagnosed as Sz or SzA (n=172) and their parents (n=196: families n=132, 119 fathers and 77 mothers) participated. We also included 120 persons with no history of psychiatric illness. Cognitive function was assessed with the TMT. The Information Score of the Post Graduate Institute Battery of Brain Dysfunction test, developed in India for Indian subjects was used as a proxy for general fixed knowledge.

STATISTICAL ANALYSIS

Logistic and linear regression was used to compare cognitive deficits of cases, parents and controls.

RESULTS

Cases and their parents took significantly more time than controls on Part B of the TMT. There were no statistically significant differences between cases and parents on any of the TMT parameters. Using regression analysis, the most significant correlates of all TMT parameters among cases were with occurrence of auditory hallucinations and current age.

CONCLUSION

Cases, as well as their parents showed more cognitive impairment than controls on the TMT.

Endophenotypes in schizophrenia: a selective review

BACKGROUND

Given the wealth of data in the literature on schizophrenia endophenotypes, it is useful to have one source to reference their frequency data. We reviewed the literature on disease-liability associated variants in structural and functional magnetic resonance images (MRI), sensory processing measures, neuromotor abilities, neuropsychological measures, and physical characteristics in schizophrenia patients (SCZ), their first-degree relatives (REL), and healthy controls (HC). The purpose of this review was to provide a summary of the existing data on the most extensively published endophenotypes for schizophrenia.

METHODS

We searched PubMed and MedLine for all studies on schizophrenia endophenotypes comparing SCZ to HC and/or REL to HC groups. Percent abnormal values, generally defined as >2 SD from the mean (in the direction of abnormality) and/or associated effect sizes (Cohen's d) were calculated for each study.

RESULTS

Combined, the articles reported an average 39.4% (SD=20.7%; range=2.2-100%) of abnormal values in SCZ, 28.1% (SD=16.6%; range=1.6-67.0%) abnormal values in REL, and 10.2% (SD=6.7%; range=0.0-34.6%) in HC groups.

CONCLUSIONS

These findings are reviewed in the context of emerging hypotheses on schizophrenia endophenotypes, as well as a discussion of clustering trends among the various intermediate phenotypes. In addition, programs for future research are discussed, as instantiated in a few recent large-scale studies on multiple endophenotypes across patients, relatives, and healthy controls.

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.

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.

Executive function and genetic predisposition to schizophrenia--the Maudsley family study

Executive cognitive impairment has been found in families affected by schizophrenia and is a putative endophenotype. We wished to explore its genetic basis further by studying the association between impairment and genetic loading for schizophrenia. We studied 30 schizophrenia patients with a family history of schizophrenia, 53 of their nonpsychotic first-degree relatives (familial), 32 patients with schizophrenia but no known family history of psychosis, 52 of their first-degree relatives (nonfamilial), and 47 normal controls. They were tested using the National Adult Reading Test (NART), Trails A and B, Verbal fluency tasks, and a computerized version of the Wisconsin Card Sorting Test (WCST). Familial, but not nonfamilial, relatives were impaired on NART, letter fluency, Trails B, and WCST total errors. They were inferior to nonfamilial relatives on letter fluency and Trails A. Both sets of relatives were impaired on Trails B controlling for Trails A, and on WCST categories achieved. There were no significant differences between schizophrenia patients with and without a family history. Our results suggest that executive deficits qualitatively similar to those seen in those with schizophrenia reflect familial susceptibility, even taking early IQ and education into consideration, consistent with a genetic mechanism.

Polymorphisms of the Fyn kinase gene and a performance on the Wisconsin Card Sorting Test in schizophrenia

The glutamatergic system has been implicated in the pathogenesis and prefrontal cortex dysfunctions in schizophrenia. The Src-family tyrosine kinase Fyn plays a key role in the interaction between brain-derived neurotrophic factor and glutamatergic receptor N-methyl-D-aspartate, in prefrontal cortex. We estimated an association between three polymorphisms of Fyn gene and performance on the Wisconsin Card Sorting Test, measuring prefrontal cortex functions, in 188 schizophrenic patients. Patients with T/T genotype of IVS10+T/C polymorphism and T/T genotype of Ex12+894T/G polymorphism made significantly less perseverative errors in the Wisconsin Card Sorting Test compared with patients with remaining genotypes, and obtained numerically better results in other Wisconsin Card Sorting Test domains. No significant differences in Wisconsin Card Sorting Test performance were found as to -93 A/G polymorphism. The main finding of the study is showing a relationship between polymorphisms of the Fyn gene, related to the function of glutamatergic system, and a performance on neuropsychological test of prefrontal cortex activity in schizophrenic patients.

The endophenotype concept in psychiatric genetics

The idea that some phenotypes bear a closer relationship to the biological processes that give rise to psychiatric illness than diagnostic categories has attracted considerable interest. Much effort has been devoted to finding such endophenotypes, partly because it is believed that the genetic basis of endophenotypes will be easier to analyse than that of psychiatric disease. This belief depends in part on the assumption that the effect sizes of genetic loci contributing to endophenotypes are larger than those contributing to disease susceptibility, hence increasing the chance that genetic linkage and association tests will detect them. We examine this assumption by applying meta-analytical techniques to genetic association studies of endophenotypes. We find that the genetic effect sizes of the loci examined to date are no larger than those reported for other phenotypes. A review of the genetic architecture of traits in model organisms also provides no support for the view that the effect sizes of loci contributing to phenotypes closer to the biological basis of disease is any larger than those contributing to disease itself. While endophenotype measures may afford greater reliability, it should not be assumed that they will also demonstrate simpler genetic architecture.

Administration and interpretation of the Trail Making Test

Measurement of cognitive functions is an increasingly important goal for clinicians and researchers. Many neuropsychological test batteries are comprehensive and require specialized training to administer and interpret. The Trail Making Test is an accessible neuropsychological instrument that provides the examiner with information on a wide range of cognitive skills and can be completed in 5-10 min. Its background, psychometric properties, administration procedures and interpretive guidelines are provided in this protocol.

Impaired working speed and executive functions as frontal lobe dysfunctions in young first-degree relatives of schizophrenic patients

The aim of the investigation was to detect neuropsychological markers, such as sustained and selective attention and executive functions, which contribute to the vulnerability to schizophrenia especially in young persons. Performance was assessed in 32 siblings and children of schizophrenic patients and 32 matched controls using Wisconsin Card Sorting Test, Colour-Word-Interference-Test, Trail Making Test, and d2-Concentration-Test. The first-degree relatives showed certain impairments on all four tests, in particular, slower times on all time-limited tests. These results suggest the need for more time when completing neuropsychological tasks involving selected and focused attention, as well as cognitive flexibility, as a possible indicator of genetic vulnerability to schizophrenia.

Performance on the Wisconsin Card Sorting Test in schizophrenia and genes of dopaminergic inactivation (COMT, DAT, NET)

The aim of the study was to test an association between polymorphisms of genes connected with dopaminergic inactivation in prefrontal cortex [catechol-O-methyltransferase (COMT), dopamine transporter (DAT), norepinephrine transporter (NET)], and performance on the Wisconsin Card Sorting Test (WCST), in schizophrenic patients. The number of perseverative errors (WCST-P), non-perseverative errors (WCST-NP), completed corrected categories (WCST-CC), conceptual level responses (WCST-%CONC) and set to the first category (WCST-1st CAT) were measured. Genotyping was done for the Val108(158)Met polymorphism of the COMT gene (79 patients), the 3'UTR VNTR polymorphism of the DAT gene (124 patients) and the 1287 A/G polymorphism of the NET gene (63 patients). Male schizophrenic patients with Val/Val genotype of COMT obtained better results on WCST-P, while female patients had worse results on the WCST-NP compared with the remaining genotypes. There was a slight trend for patients with the A9/A9 genotype of DAT and with the A/A genotype of NET to perform better on some domains of the WCST, compared with other genotypes. A limitation to the interpretation of results could be small number of patients studied as well as variable psychopathological state and medication during cognitive testing.

Prefrontal cognition in schizophrenia and bipolar illness in relation to Val66Met polymorphism of the brain-derived neurotrophic factor gene

The measures of prefrontal cognition have been used as endophenotype in molecular-genetic studies. Brain-derived neurotrophic factor (BDNF) has been implicated in cognitive functions and in the pathogenesis of major psychoses. This study investigates the relationship between Val66Met polymorphisms of the BDNF gene and prefrontal cognitive function in 129 patients with schizophrenia and 111 patients with bipolar mood disorder. Cognitive tests included the Wisconsin Card Sorting Test (WCST), with such domains as number of perseverative errors, non-perseverative errors, completed corrected categories, conceptual level responses, and set to the first category, and the N-back test, where mean reaction time and percent of correct reactions were measured. Genotyping for Val66Met BDNF polymorphism was done by polymerase chain reaction method. In schizophrenia, no relationship between Val66Met polymorphism of the BDNF gene and the results of the WCST was observed. Patients with Val/Val genotype had a higher percentage of correct reactions in the N-back test than those with the remaining genotypes. Bipolar patients with Val/Val genotype obtained significantly better results on three of five domains of the WCST. No relationship between BDNF polymorphism and the results of the N-back test was found in this group. A limitation to the results could be variable psychopathological state and medication during cognitive testing and lack of Hardy-Weinberg equilibrium in schizophrenia group. Val66Met polymorphism of the BDNF gene may be associated with cognitive performance on the WCST in bipolar mood disorder but not in schizophrenia. An association of this polymorphism with performance on the N-back test in schizophrenia and not in bipolar illness may suggest that in schizophrenia, the BDNF system may be connected with early phases of information processing.

[Wiscosin card sorting task in patients with schizophrenia and thier siblings]

OBJECTIVE

This study's first objective was to confirm that patients with schizophrenia and their nonmentally ill siblings share the same impaired executive function when compared to healthy control subjects. The second objective was to study the relation between Wisconsin card sorting task (WCST) performance and the persistence and severity of clinical symptoms, as well as different clinical dimensions.

METHOD

Ninety subjects were involved in this study, divided in 3 groups of 30 each: one group of patients with schizophrenia, one group of their siblings, and a control group. Symptom severity was assessed with the Positive and Negative Syndrome Scale (PANSS), and social functioning was measured by the Global functioning scale (GFS). The WCST was administered to all 3 groups.

RESULTS

Patients with schizophrenia and their siblings had a significantly lower WCST performance than control subjects. Statistical analysis showed that the patient group had a significantly greater impaired WCST performance than the 2 other groups. Siblings also had a significantly lower performance than the control subjects. Furthermore, no significant relation was found between WCST performance and other variables, including age, gender, education, illness duration, treatment, and different PANSS and GFS scores.

CONCLUSION

Patients with schizophrenia and their nonmentally ill siblings share the same impaired executive function. These findings suggest that WCST performance can be considered a schizophrenia vulnerability marker in siblings of patients with schizophrenia.

The European First Episode Schizophrenia Trial (EUFEST): rationale and design of the trial

BACKGROUND

Most studies comparing second generation antipsychotics with classical neuroleptics have been conducted in more or less chronic schizophrenia patients. Such studies were usually conducted in highly selected samples, and were generally designed and financed by the manufacturer of the drug tested. These and other facts have stimulated discussions regarding the effectiveness of the new generation of antipsychotics.

AIMS

The aim of the European First Episode Schizophrenia Trial (EUFEST) is to compare treatment with amisulpride, quetiapine, olanzapine and ziprasidone to a low dose of haloperidol in an unselected sample of first episode schizophrenia patients with minimal prior exposure to antipsychotics.

METHODS

500 patients between the ages of 18-40 meeting DSM-IV criteria for schizophrenia, schizoaffective disorder or schizophreniform disorder are randomly allocated to one year of treatment with one of the drugs under study. The primary outcome measure is retention in treatment, defined as time to discontinuation of study drug. Loss of retention can be the result of insufficient clinical effect, or lack of tolerability or acceptance. Secondary measures include changes in different dimensions of psychopathology, side effects, compliance, social needs, quality of life, substance abuse and cognitive functions.

CONCLUSIONS

At present, more than 400 patients have been recruited and randomized in the following countries: Austria, Belgium, Bulgaria, Czech Republic, Germany, France, Israel, Italy, the Netherlands, Poland, Rumania, Spain, Sweden and Switzerland: The study should be finished by the end of 2006 and it is expected that results will yield relevant clinical information with regard to the effectiveness of the second generation antipsychotics. This effort represents the first independently designed trans-European schizophrenia treatment trial.

An association study of dopamine receptors polymorphisms and the Wisconsin Card Sorting Test in schizophrenia

Dopamine (DA), an important neurotransmitter in prefrontal cortex (PFC), is involved in the pathogenesis of schizophrenia. The aim of the study was to test an association between common polymorphism of genes for DA receptors DRD1, DRD2, DRD3, DRD4, and performance on the Wisconsin Card Sorting Test (WCST), measuring various functions of PFC, in 138 schizophrenic patients. Patients with G/G genotype of DRD1 tended to obtain worse results in all domains of WCST compared to patients with remaining genotypes, particularly for number of completed corrected categories, and trials to set the first category. A relationship was also found in female patients between DRD2 polymorphism and number of perseverative errors, while no association between WCST results and DRD3 or DRD4 polymorphism was observed in patients studied. The results may suggest an association between DRD1 gene polymorphism and performance on PFC test in schizophrenia. Also, the gender-dependent role of DRD2 in this process may be presumed.

Do schizophrenia patients make more perseverative than non-perseverative errors on the Wisconsin Card Sorting Test? A meta-analytic study

The Wisconsin Card Sorting Test (WCST) is widely used to explore executive functions in patients with schizophrenia. Among other findings, a higher number of perseverative errors has been suggested to implicate a deficit in task switching and inhibitory functions in schizophrenia. Many studies of patients with schizophrenia have focused on perseverative errors as the primary performance index in the WCST. However, do schizophrenia patients characteristically make more perseverative than non-perseverative errors compared with healthy controls? We reviewed the literature where schizophrenia patients were engaged in the WCST irrespective of the primary goal of the study. The results showed that while both schizophrenia patients and healthy participants made more perseverative than non-perseverative errors, the contrast between perseverative and non-perseverative errors is higher in schizophrenia patients only at a marginal level of significance. This result suggests that schizophrenia patients do make a comparable number of non-perseverative errors and cautions against simplistic interpretation of poor performance of schizophrenia patients in WCST as entirely resulting from impairment in set-shifting or inhibitory functions.

The fractal box dimension on human eyeball movement--objective, biological marker of schizophrenia?

The authors developed a method of measuring the fractal box dimension of the human eyeball movement. We found a fractal property in schizophrenic subjects (n = 20) and normal controls (n = 20). The value of the fractal box dimension for schizophrenic patients differs from the results obtained in the control group.

Cognitive deficits in relatives of patients with schizophrenia: a meta-analysis

BACKGROUND

Schizophrenia is characterized by a generalized cognitive impairment with pronounced deficits in the domains of verbal memory, executive functioning and attention.

AIM

To investigate whether cognitive deficits found in patients with schizophrenia are also found in non-affected relatives.

METHOD

A meta-analytic review of the published literature on cognitive performance between relatives of schizophrenic patients and healthy controls.

RESULTS

The meta-analyses yielded nine weighted effect sizes from 37 studies comprising 1639 relatives of schizophrenia patients and 1380 control subjects. The largest differences were found on verbal memory recall (d=0.54, 95% CI=0.43-0.66) and executive functioning (d=0.51, 0.36-0.67). Attentional functioning showed smaller effect sizes (d=0.28, 0.06-0.50). These effect sizes are in the moderate range.

CONCLUSION

Cognitive deficits found in patients with schizophrenia are also found in non-affected relatives. This finding is consistent with the idea that certain cognitive deficiencies in relatives are caused by familial predisposition to schizophrenia and that these deficiencies might be putative endophenotypes for schizophrenia. However, our results do not address genetic causes directly. Further work is needed to determine whether certain cognitive traits are familial and whether there is co-inheritance of these traits with schizophrenia within families.

Trait characteristic of impaired visuomotor integration during Trail-Making Test B performance in schizophrenia

Using concurrent recording of eye and hand movements during the performance of the Trail-Making Test B (TMT-B), Wölwer and Gaebel have recently reported impaired visuomotor integration in patients with acute schizophrenia, which mainly accounted for patients' poor test performance. In order to replicate these exploratory findings in an independent sample of patients and to further investigate their stability during different stages of the illness, the performance process during a computerized TMT-B was assessed in 22 remitted outpatients with schizophrenia, 12 unaffected first-degree relatives and 26 healthy controls. As an estimate of longitudinal stability, a partial sample of 12 patients and 19 controls was reassessed after a period of 3 months. Remitted schizophrenia patients showed exactly the same strategic problems during the performance process of TMT-B as previously found in acute patients. Compared with healthy controls, patients more often sequenced searching ('planning') and connecting targets instead of time-sparing parallel execution, and their planning periods contained more and longer planning fixations (i.e. fixations outside the cursor area), which was related to longer performance time. Unaffected relatives mostly scored between patients and healthy controls without statistically significant differences to either group. Thus, the abnormalities in the process of TMT-B performance proved to be reliable and stable trait characteristics in schizophrenia.

Eye movement disturbances in schizophrenia and a polymorphism of catechol-O-methyltransferase gene

Previous studies suggested an association between the catechol-O-methyltransferase (COMT) Val/Met polymorphism and the performance on neuropsychological tests, measuring prefrontal function in schizophrenia. The aim of this study was to examine the relationship between this polymorphism and performance on oculomotoric tests in schizophrenic patients. The intensity of eye movement disturbances on fixation and smooth pursuit tests and the Val/Met polymorphism of COMT gene were studied in 117 schizophrenic patients (74 male and 43 female). In male schizophrenic patients, the mean intensity of both kinds of eye movement disturbances was lower in subjects who had the Met/Met genotype, with significant difference compared to other genotypes. Also, a significantly higher frequency of the Met allele and the Met/Met genotype was found in male schizophrenic patients exhibiting a lower intensity of smooth pursuit disturbances, and a trend in this direction was observed for the intensity of fixation disturbances. No such relationship was found in female schizophrenic patients. The results obtained suggest that, in male schizophrenic patients the Met allele of the COMT Val/Met polymorphism may have an alleviating effect on eye movement disturbances. They also point to possible gender differences as to the role of COMT in brain function in schizophrenia.

Does risperidone act better in schizophrenic patients who have a family or obstetric history?

PURPOSE

The aim of the study was to assess the effect of treatment with risperidone on psychopathological symptoms and cognitive deficits in schizophrenic patients, in relation to family history, obstetric complications and duration of the illness.

METHODS

Fifty schizophrenic inpatients (29 males, 21 females), aged 16-50 (mean 28 years), with duration of the illness 1-15 (mean 4 years) who successfully completed a 3-month risperidone treatment were included into the study. Family history of psychiatric illness and the presence of obstetric complications were estimated by a semistructured questionnaire. Schizophrenic symptoms were assessed using the Positive and Negative Symptoms Scale (PANSS). Cognitive abilities were measured by neuropsychological "frontal lobe" tests: Trail Making Test (TMT), part B, Stroop Color Word Interference Test, part B, and Wisconsin Card Sorting Test (WCST). The clinical and neuropsychological evaluation was performed before and after 3 months of risperidone treatment, in doses 2-6 mg (mean 4.2 mg/day).

RESULTS

Before treatment, patients with family history had significantly higher intensity of negative symptoms, and obtained worse results on WCST perseverative errors (PE) and correct categories (CC). These measures were also impaired in subjects with obstetric complications. Additionally, in patients with obstetric complications, total and general PANSS psychopathology was higher and the results of Stroop B were worse. After a 3-month treatment with risperidone, no difference between respective groups was observed both in psychopathology and in neuropsychological tests. Patients with obstetric complications had higher degree of improvement on positive and negative symptoms and on TMT-B than the remaining ones. Patients with longer duration of the illness had less improvement on positive symptoms with risperidone treatment.

CONCLUSIONS

The results of this study show that treatment with risperidone results in better compensation of psychopathological (negative symptoms) and neuropsychological (working memory) deficits in patients who have a family history and/or obstetric complications. This may be due to a favourable effect of risperidone on the prefrontal cortex dysfunction mediating these deficits.

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.