The relation of integrated psychological therapy to resting state functional brain connectivity networks in patients with schizophrenia

Functional brain dysconnectivity measured with resting state functional magnetic resonance imaging (rsfMRI) has been linked to cognitive impairment in schizophrenia. This study investigated the effects on functional brain connectivity of Integrated Psychological Therapy (IPT), a cognitive behavioral oriented group intervention program, in 31 patients with schizophrenia. Patients received IPT or an equal intensity non-specific psychological treatment in a non-randomized design. Evidence of improvement in executive and social functions, psychopathology and overall level of functioning was observed after treatment completion at six months only in the IPT treatment group and was partially sustained at one-year follow up. Independent Component Analysis and Isometric Mapping (ISOMAP), a non-linear manifold learning algorithm, were used to construct functional connectivity networks from the rsfMRI data. Functional brain dysconnectivity was observed in patients compared to a group of 17 healthy controls, both globally and specifically including the default mode (DMN) and frontoparietal network (FPN). DMN and FPN connectivity were reversed towards healthy control patterns only in the IPT treatment group and these effects were sustained at follow up for DMN but not FPN. These data suggest the use of rsfMRI as a biomarker for accessing and monitoring the therapeutic effects of cognitive remediation therapy in schizophrenia.

Social and non-social gaze cueing in autism spectrum disorder, attention-deficit/hyperactivity disorder and a comorbid group

Recent trends in literature, along with the changes to the Diagnostic and Statistical Manual (DSM), make it imperative to study Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) together, in order to better understand potential aetiological commonalities between these highly comorbid disorders. The present study examines social cueing, a highly studied construct in ASD, and intra-subject variability (ISV), a potential endophenotype of ADHD, in four groups of typically developing (TD), ADHD, ASD- (ASD without ADHD), ASD+ (ASD with ADHD) participants (N = 85) aged 10-13 years. Results showed that social cueing is intact in the 'pure' ASD group when task expectations are clear. The ADHD group showed faster saccadic reaction times, no increased ISV and a pattern of viewing comparable to the TD group. However, the ASD + group showed a differences in processing style and ISV. A secondary analysis gives evidence of non-additive effects of the ASD and ADHD factors.

Visual search in ADHD, ASD and ASD + ADHD: overlapping or dissociating disorders?

Recent debates in the literature discuss commonalities between Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) at multiple levels of putative causal networks. This debate requires systematic comparisons between these disorders that have been studied in isolation in the past, employing potential markers of each disorder to be investigated in tandem. The present study, choose superior local processing, typical to ASD, and increased Intra-Subject Variability (ISV), typical to ADHD, for a head-to-head comparison of the two disorders, while also considering the comorbid cases. It directly examined groups of participants aged 10-13 years with ADHD, ASD with (ASD+) or without (ASD-) comorbid ADHD and a typically developing (TD) group (total N = 85). A visual search task consisting of an array of paired words was designed. The participants needed to find the specific pair of words, where the first word in the pair was the cue word. This visual search task was selected to compare these groups on overall search performance and trial-to-trial variability of search performance (i.e., ISV). Additionally, scanpath analysis was also carried out using Recurrence Quantification Analysis (RQA) and the Multi-Match Model. Results show that only the ASD- group exhibited superior search performance; whereas, only the groups with ADHD symptoms showed increased ISV. These findings point towards a double dissociation between ASD and ADHD, and argue against an overlap between ASD and ADHD.

Examining the Overlap Between ADHD and Autism Spectrum Disorder (ASD) Using Candidate Endophenotypes of ADHD

Objective: Recent discussions of aetiological overlap between ADHD and Autism Spectrum Disorder (ASD) require comparative studying of these disorders.

METHOD

We examined performance of ASD patients with (ASD+) and without (ASD-) comorbid ADHD, ADHD patients, and controls for selected putative endophenotypes of ADHD: Intrasubject Variability (ISV) of reaction times, working memory (WM), inhibition, and temporal processing.

RESULTS

We found that patients with ADHD or ASD+, but not ASD-, had elevated ISV across the entire task battery and temporal processing deficits, and that none of the groups were impaired in WM or inhibition. High levels of ISV and generally poor performance in ASD+ patients were only partially due to additive effects of the pure disorders.

CONCLUSION

Overall, we conclude that, within our limited but heterogeneous task battery, ISV and temporal processing deficits are most sensitive to ADHD symptomatology and that controlling for ADHD comorbidity is mandatory when assessing ISV in autism.

P300 response modulation reflects breaches of non-probabilistic expectations

In oddball paradigms, infrequent stimuli elicit larger P300 event related potentials (ERPs) than frequent ones. One hypothesis is that P300 modulations reflect the degree of “surprise” associated with unexpected stimuli. That is the P300 represents how unlikely the stimulus is and this signal is then used to update the observer’s expectations. It could be hypothesized that P300 is modulated by any factor affecting an observer’s expectations, not only target probability. Alternatively, the P300 may reflect an evaluative process engaged whenever a discrepancy between task context and sensory inputs arises, irrespective of the latter probability. In previous ERP studies, stimulus probability was often the only determinant of task set confounding the effects of stimulus probability and set stimulus discrepancy. In this study, we used a speeded luminance detection task. The target was preceded by a central cue that predicted its location. The probability that the target was valid, i.e. would appear at the cued location was manipulated by varying the reliability of the cue. Reaction times were modulated by probabilistic expectations based on cue reliability and target validity while P300 was affected by target validity only. We conclude that increased P300 amplitude reflects primarily breaches of non-probabilistic expectations, rather than target probability.

Studying global processing in autism and attention-deficit/hyperactivity disorder with gaze movements: The example of a copying task

Recent discussions in the literature, along with the revision of the Diagnostic and Statistical Manual (DSM) (American Psychiatric Association 2013), suggest aetiological commonalities between the highly comorbid Attention-Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD). Addressing this discussion requires studying these disorders together by comparing constructs typical to each of them. In the present study, we investigate global processing, known to be difficult for participants with ASD, and Intra-Subject Variability (ISV), known to be consistently increased in participants with ADHD, in groups, aged 10–13 years, with ADHD (n = 25), ASD without comorbid ADHD (ASD-) (n = 13) and ASD with ADHD (ASD+) (n = 18) in comparison with a typically developing group (n = 22). A Copying task, typically requiring global processing and in this case particularly designed using equally complex stimuli to also measure ISV across trials, was selected. Oculomotor measures in this task proved to be particularly sensitive to group differences. While increased ISV was not observed in the present task in participants with ADHD, both ASD groups looked longer on the figure to be drawn, indicating that global processing takes longer in ASD. However, the ASD+ group fixated on the figure only between drawing movements, whereas the ASD- group did this throughout the drawing process. The present study provides evidence towards ASD and ADHD being separate, not-overlapping, disorders. Since the pure ASD- group was affected more by central coherence problems than the ASD+ group, it may suggest that neuropsychological constructs interact differently in different clinical groups and sub-groups.

Hypo-activity of the dorsolateral prefrontal cortex relates to increased reaction time variability in patients with schizophrenia

Increased reaction time intra-subject variability (RT-ISV) in fast decision tasks has been confirmed in patients with schizophrenia and has been hypothesized to result from a deficit in the control of attention. Here, an attentional task and functional brain imaging were used to probe the neural correlates of increased RT-ISV in schizophrenia.

Thirty patients and 30 age and sex matched controls performed the Eriksen flanker spatial attention task with concurrent measurement of brain activity using functional magnetic resonance imaging (fMRI). The behavioral measures included accuracy, mean, standard deviation of RT (RTSD), coefficient of variation of RT (RTCV) and ex-Gaussian model of RT distribution parameters (mu, sigma and tau).

Larger mean RT and Ex-Gaussian mu was observed for patients compared to controls. The group difference was larger for incongruent (attentionally demanding) versus congruent trials confirming a deficit in the control of spatial attention for patients. Significant increase in RT-ISV measures (RTSD, sigma and tau) for patients compared to controls was observed and was not modulated by trial congruency. Attention modulation (congruency effect) resulted in activation of bilateral frontal and parietal areas that was not different between patients and controls. Right middle frontal, right superior temporal and bilateral cingulate areas were more active in controls compared to patients independent of congruency. Activation in ROIs extracted from attention (congruency) and group related areas correlated with RT-ISV measures (especially RTCV and tau). Hypo-activation of the right middle frontal area correlated with increased tau specifically in patients.

Hypo-activity of the right prefrontal cortex predicted increased RT-ISV in schizophrenia. This effect was unrelated to the effects of spatial attention and might be linked to a deficit in the inhibitory control of action for these patients.

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Schizophrenia patients show increased reaction time intra-subject variability (RT-ISV).

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fMRI of patients and aged matched controls while performing a spatial attention task.

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RT-ISV measures were increased in patients independent of spatial attention load.

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Activity of the right middle frontal cortex predicted RT-ISV increase in patients.

The impact of the COMT genotype and cognitive demands on facets of intra-subject variability

Intra-Subject Variability (ISV), a potential index of catecholaminergic regulation, is elevated in several disorders linked with altered dopamine function. ISV has typically been defined as reaction time standard deviation. However, the ex-Gaussian and spectral measures capture different aspects and may delineate different underlying sources of ISV; thus reflecting different facets of the construct. We examined the impact of factors associated with dopamine metabolism, namely, Catechol-O-Methyltransferase Val158Met (COMT) genotype and Working Memory (WM) and response-switching on ISV facets in young healthy adults. The Met allele was associated with overall increased variability. The rather exclusive sensitivity of ex-Gaussian tau to frequencies below 0.025 Hz and the quasi-periodic structure of particularly slow responses support the interpretation of tau as low frequency fluctuations of neuronal networks. Sigma, by contrast, may reflect neural noise. Regarding cognitive demands, a WM load-related increase in variability was present for all genotypes and all ISV facets. Contrastingly, ISV facets reacted differently to variations in response-switching as, across genotypes, sigma was elevated for rare target trials whereas tau was elevated for frequent standard trials, particularly for Met homozygotes. Our findings support the significant role of COMT in regulating behavioural ISV with its facetted structure and presumed underlying neural processes.

Electro-cortical correlates of multisensory integration using ecologically valid emotional stimuli: Differential effects for fear and disgust

Multisensory integration (MSI) is crucial for human communication and social interaction and has been investigated in healthy populations and neurodevelopmental disorders. However, the use of stimuli with high ecological validity is sparse, especially in event-related potential (ERP) studies. The present study examined the ERP correlates of MSI in healthy adults using short (500 ms) ecologically valid professional actor-produced emotions of fear or disgust as vocal exclamation or facial expression (unimodal conditions) or both (bimodal condition). Behaviourally, our results show a general visual dominance effect (similarly fast responses following bimodal and visual stimuli) and an MSI-related speedup of responses only for fear. Electrophysiologically, both P100 and N170 showed MSI-related amplitude increases only following fear, but not disgust stimuli. Our results show for the first time that the known differential neural processing of fear and disgust also holds for the integration of dynamic auditory and visual information.

Shared variance of oculomotor phenotypes in a large sample of healthy young men

This study used canonical correlation analysis to investigate patterns of shared variance between parameters measured in seven different occulomotor function tasks, namely the visually guided saccade task, the antisaccade task, the closed-loop smooth-pursuit task, the open-loop smooth-pursuit task, and three active visual fixation tasks. These tasks were performed by 2130 young army recruits. Only a small percentage (1-10%) of shared variance existed between sets of parameters for all oculomotor function tasks measured. The most correlated tasks were the visually guided saccade and the antisaccade. The first common factor correlated with speed of performance between these tasks (latency), while the second and third correlated with accuracy of performance. Better performance in active visual fixation tasks correlated with better performance accuracy (lower error rate) and increased speed (lower latency) in the antisaccade and saccade tasks as well as better performance in the closed-loop smooth-pursuit task (increase in gain and decrease in the rate of unwanted saccades during pursuit). Better performance in the closed-loop smooth-pursuit task (increased gain and decreased number of unwanted saccades) also correlated with increased accuracy and increased speed of performing saccades and antisaccades. Finally, the open-loop fixation task had no correlation with all other oculomotor tasks except for a very weak negative correlation with the closed-loop pursuit task where better performance (increased gain) in one correlated with worse performance (decreased gain) in the other. The results of this analysis showed that a small percentage of variance is shared among different oculomotor function tasks. The structure of this shared variance could be used to derive common oculomotor function indices to study their relation to genetic and other sources of inter-subject variation.

GWAS meta-analysis reveals novel loci and genetic correlates for general cognitive function: a report from the COGENT consortium

This corrects the article DOI: 10.1038/mp.2016.244.

GWAS meta-analysis reveals novel loci and genetic correlates for general cognitive function: a report from the COGENT consortium

The complex nature of human cognition has resulted in cognitive genomics lagging behind many other fields in terms of gene discovery using genome-wide association study (GWAS) methods. In an attempt to overcome these barriers, the current study utilized GWAS meta-analysis to examine the association of common genetic variation (~8M single-nucleotide polymorphisms (SNP) with minor allele frequency ⩾1%) to general cognitive function in a sample of 35 298 healthy individuals of European ancestry across 24 cohorts in the Cognitive Genomics Consortium (COGENT). In addition, we utilized individual SNP lookups and polygenic score analyses to identify genetic overlap with other relevant neurobehavioral phenotypes. Our primary GWAS meta-analysis identified two novel SNP loci (top SNPs: rs76114856 in the CENPO gene on chromosome 2 and rs6669072 near LOC105378853 on chromosome 1) associated with cognitive performance at the genome-wide significance level (P<5 × 10^-8). Gene-based analysis identified an additional three Bonferroni-corrected significant loci at chromosomes 17q21.31, 17p13.1 and 1p13.3. Altogether, common variation across the genome resulted in a conservatively estimated SNP heritability of 21.5% (s.e.=0.01%) for general cognitive function. Integration with prior GWAS of cognitive performance and educational attainment yielded several additional significant loci. Finally, we found robust polygenic correlations between cognitive performance and educational attainment, several psychiatric disorders, birth length/weight and smoking behavior, as well as a novel genetic association to the personality trait of openness. These data provide new insight into the genetics of neurocognitive function with relevance to understanding the pathophysiology of neuropsychiatric illness.

The relationship between premorbid adjustment and cognitive dysfunction in schizophrenia

Introduction

Premorbid adjustment (PA) is one of the main prognostic indicators of schizophrenia. Both social and cognitive deficits observed during the premorbid period hold a predictive value for the onset of schizophrenia.

Objectives

To investigate how cognitive functions are related to aspects of PA.

Aims

To examine the relationship of each PA domain (academic and social) at each of the three developmental stages (childhood, early adolescence and late adolescence), as well as their course with the cognitive functions in schizophrenia patients.

Methods

PA, intellectual quotient (IQ), verbal learning, memory, processing speed, executive functions and verbal fluency were assessed using PAS, WAIS, RAVLT, TMT, WCST and COWAT measures respectively in a sample of 85 clinically stabilized male schizophrenia inpatients.

Results

Negative correlations emerged between academic PA during adolescence and both verbal IQ and processing speed, while positive correlations were found with working memory. Negative correlations emerged between deterioration in academic PA during adolescence and both processing speed and immediate auditory verbal recall, while correlations with verbal learning were positive. There was no relationship between cognitive functions and either social PA or its deterioration.

Conclusion

Our findings revealed significant associations between both academic PA and its course with cognitive functions in schizophrenia patients. In summary, deficits in several fields of cognitive functions seem to follow a different path long before and after the onset of the disease, but further investigation is necessary.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Myocarditis after administration of clozapine

OBJECTIVE

Clozapine is an atypical antpsychotic medication with established efficacy in patients diagnosed of resistant schizophrenia. However, clozapine has multiple side effects. Cardiac complications such as myocarditis and cardiomyopathy have always been related with treatment with clozapine.

METHODS

A 42 year old Caucasian male, with history of schizophrenia developed a acute myocarditis after commencement of clozapine.

RESULTS

The patient recovered with intensive medical support. The symptoms occurred approximately 20 days after starting clozapine.

CONCLUSIONS

Myocarditis is an ingreasingly recognized complication associated with clozapine. Use of clozapine must be based on a balance of its risks and benefits on an individual basis which for the most part defines its use in treatment refractory schizophrenia. Appropriate monitoring of adverse events is an essential part of the clinical usage of clozapine and should be charted for at least two years.

Cognitive impairments and psychopathological parameters in patients of the schizophrenic spectrum

Cognitive impairment is a core feature of schizophrenia and it is considered by many researchers as one of the dimensional components of the disorder. Cognitive dysfunction occurs in 85% of schizophrenic patients and it is negatively associated with the outcome of the disorder, the psychosocial functioning of the patients, and non-compliance with treatment. Many different cognitive domains are impaired in schizophrenia, such as attention, memory, executive functions and speech. Nowadays, it is argued that apart from clinical heterogeneity of schizophrenia, there is probable heterogeneity in the accompanying neurocognitive dysfunction. Recent studies for cognitive dysfunction in schizophrenia employ computerized assessment batteries of cognitive tests, designed to assess specific cognitive impairments. Computerized cognitive testing permits for more detailed data collection (e.g. precise timing scores of responses), eliminates researcher's measurement errors and bias, assists the manipulation of data collected, and improves reliability of measurements through standardized data collection methods. The aims of the present study are: the comparison of cognitive performance of our sample of patients and that of healthy controls, on different specific cognitive tests, and the testing for possible association between patients' psychopathological symptoms and specific cognitive impairments, using the Cogtest computerized cognitive assessment battery. 71 male inpatients diagnosed with schizophrenia or other psychotic spectrum disorders (mean = 30.23 ± 7.71 years of age), admitted in a psychiatric unit of the First Department of Psychiatry, Athens University Medical School, Eginition Hospital (continuous admissions) were studied. Patients were excluded from the study if they suffered from severe neurological conditions, severe visual or hearing impairment, mental retardation, or if they abused alcohol or drugs. The patients' diagnoses were based on the semi-structured diagnostic interview "Diagnostic Interview for Psychosis" (DIP) and were clinically confirmed by two independent expert psychiatrists, according to the criteria of DSM-IVTM. Our healthy control group consisted of 20 healthy male participants (mean = 31.65 ± 5.90 years of age), who met the same inclusion criteria for the study as the patient group, as well as the same exclusion criteria from the study, having no history of psychiatric disorders. All statistical analyses were conducted using the statistical package SPSS.17. According to our results, healthy controls cognitively outperform our patient sample in all cognitive tests, with the differences between performances being statistically significant. Results concerning the association between psychotic symptoms and cognitive deficits of our patients indicated that hallucinations, highly organized delusions, persecutory delusions, agitation, catatonia and inappropriate affect did not associate with any subtype of cognitive deficit. Blunted affect associated significantly with response inhibition ("GoNoGo test", p = 0.007), and poor speech associated significantly with declarative memory of faces ("FMT test", p = 0.002). Moreover, psychomotor ability (non-dominant hand) associated significantly with generalized delusions ("TST test", p = 0.033), and with constricted affect ("TST test", p = 0.026). Furthermore, there was a tendency towards significance association between persecutory delusions and executive function ("CPT test", p = 0.053), inappropriate affect and declarative face memory ("FMT test", p = 0.056), and psychomotor ability and poor speech (p = 0.086).

Theory of Mind as a potential trait marker of schizophrenia: a family study

INTRODUCTION

Although there is some evidence that Theory of Mind (ToM) deficits may be trait markers of schizophrenia it is not clear yet if ToM deficits are primary deficits, that is, to be independent of deficits in general intellectual abilities and executive function. The aim was to examine if ToM deficits may be trait markers of the illness and the effect of cognitive inhibition, general intellectual abilities and depression on ToM abilities of patients with schizophrenia and their unaffected parents.

METHODS

We assessed ToM abilities (first-order and second-order ToM stories, The Revised Eyes Test), cognitive inhibition (Stroop Task), general intellectual ability (Standard Progressive Matrices Test Plus) in patients with schizophrenia (N=21) and their unaffected fathers (N=21) and mothers (N=21) in comparison with healthy control families (healthy control males, N=21, healthy control fathers, N=21, healthy control mothers, N=21)

RESULTS

Patients showed deficits in first-order ToM tasks but some of these deficits were mediated by general intellectual abilities. Impairments in cognitive inhibition mediated only patients' performance in The Revised Eyes Test. Patients showed deficits in second-order ToM stories independently of deficits in general intellectual abilities and cognitive inhibition. Unaffected parents did not show deficits in first-order ToM tasks, whereas they showed deficits in second-order ToM stories. However, the deficits that unaffected parents showed in second-order ToM stories were mediated by their deficits in general intellectual abilities, and there was an effect of remitted depression on the unaffected mothers' performance.

CONCLUSIONS

The results suggest that intact neurocognitive and general intellectual abilities are necessary in order patients and their unaffected parents to pass successfully ToM tasks. Patients and their unaffected parents show ToM deficits but these deficits are not similar. Patients show ToM deficits but these deficits seem to be a component of the pathophysiology of the illness (e.g., deficits in executive function, general intellectual abilities).

Schizophrenia-related RGS4 gene variations specifically disrupt prefrontal control of saccadic eye movements

BACKGROUND

The gene encoding the regulator of G-protein signaling subtype 4 (RGS4), located on chromosome 1q23-3, has been proposed as a possible susceptibility gene for schizophrenia and has been specifically linked to prefrontal cortical structural and functional integrity.

METHOD

The effects of four core single nucleotide polymorphisms (SNPs) within the RGS4 gene on oculomotor parameters in a battery of oculomotor tasks (saccade, antisaccade, smooth eye pursuit, fixation) were investigated in a sample of 2243 young male military conscripts.

RESULTS

The risk allele of RGS4SNP18 was found to be associated with two variables of antisaccade performance, increased error rate and variation in the correct antisaccade latency. By contrast, the same allele and also the risk allele of RGS4SNP4 led to an improvement in smooth eye pursuit performance (increased gain). Structural equation modeling confirmed that the combined gene variation of RGS4SNP4 and RGS4SNP18 was a significant predictor of antisaccade but not smooth eye pursuit performance.

CONCLUSIONS

These results provide evidence for a specific effect of schizophrenia-related RGS4 genotype variations to prefrontal dysfunction measured by oculomotor indices of performance in normal individuals, further validating the hypothesis that RGS4 is related to prefrontal dysfunction in schizophrenia.

Serotonin transporter gene variants and prediction of stress-induced risk for psychological distress

The response to psychosocial stress is influenced by both psychosocial factors and genetic vulnerability. The most investigated gene in gene × environment studies in abnormal response to environmental stressors is the one coding for the serotonin transporter (SLC6A4). Variability within this gene has been associated with functional brain differences, personality dimensions, reactivity to stress and risk for various psychopathological conditions. In the present study, we set out to investigate the association of common genetic variants within SLC6A4 with state psychopathology in a community sample homogeneously exposed to stress, thus inquiring about potential genetic differences in stress sensitivity. One thousand eight hundred seventy-five young conscripts were evaluated for psychopathological distress with the 90-item Symptoms Checklist Revised in their first 2 weeks of admission to obligatory military service. Of these, 1594 were genotyped for the biallelic ins/del polymorphism (5-HTTLPR S/L) within the promoter region of SLC6A4, as well as the variation within the 'long' 5-HTTLPR allele (rs25531A/G). Homozygous for the 5-HTTLPR S allele reported significantly higher scores for paranoid ideation as compared with L-allele carriers. Slight effects on other subscales were observed, but were not significant after correction for multiple testing. Despite limitations linked to the evaluation of psychopathology by a single general scale and multiple comparisons, the present study support a role of SLC6A4 in modulating abnormal responses to environmental stress. In particular, variation within this gene may confer risk for paranoid/defensive reactions under conditions of environmental stress associated with military induction.

Is the excess risk of psychosis-like experiences in urban areas attributable to altered cognitive development?

BACKGROUND

Rates of psychotic disorder and related attenuated psychotic experiences are higher in urban areas. We examined to what degree differences between urban and rural areas could be attributed to differences in cognitive development.

METHOD

Scores on the nine subscales of the schizotypal personality questionnaire (SPQ) as well as IQ and specific neuropsychological functions of memory and attention were assessed in a representative sample of 943 young army conscripts from the 49 counties of Greece.

RESULTS

Young men from urban areas had higher scores on the SPQ subscale Odd beliefs/magical thinking (OR = 1.99, 95% CI: 1.42, 2.78), but lower scores on Excessive social anxiety (OR = 0.63, 95 % CI: 0.49, 0.81) and No close friends (OR = 0.42, 95% CI: 0.29, 0.62). Adjustment for demographic factors, IQ and specific neuropsychological functions did not change the results. When the lower scores on Excessive social anxiety and No close friends were taken into account, the differences on the Odd beliefs/magical thinking subscale became even more pronounced (OR = 2.33, 95% CI: 1.56, 3.49).

CONCLUSIONS

Young men from urban areas are socially more competent, but display higher levels of positive psychotic experiences, which are not mediated by lower IQ or higher levels of neuropsychological impairment.

Active eye fixation performance in 940 young men: effects of IQ, schizotypy, anxiety and depression

A total of 940 young men performed a task in which they actively maintained fixation for 50 s in three conditions: a). on a visual target, b). on a visual target while distracting targets appeared briefly on the periphery and c). with no visual target present. The same individuals completed psychometric evaluation tests measuring IQ, schizotypy and current state-dependent psychopathology. The proportion of fixation time decreased and saccade frequency increased in condition b compared wih condition a, and sequentially in condition c compared with condition b. A trend towards a decrease in proportion of fixation time and increase in saccade frequency was found as the subjects maintained fixation during the task and this time-dependent deterioration of performance was again most pronounced in condition c, less so in condition b and absent in condition a. Psychometric test scores were significantly correlated with fixation performance in the population. Worse performance in all three fixation conditions was observed for individuals with lower IQ scores. A deterioration of fixation performance with time in condition b was correlated with disorganization characteristics of schizotypy, suggesting that these individuals had difficulty maintaining active fixation in the presence of increased inhibitory load. A connection of such a difficulty with the frontal lobes and their role in the control of voluntary inhibitory functions is discussed.

Effects of direction on saccadic performance in relation to lateral preferences

A sample of 676 healthy young males performed visually guided saccades and antisaccades and completed the Porac-Coren questionnaire measuring lateral preferences. There was no difference in mean latency between rightward versus leftward saccades or for saccades executed in the left versus right hemispace. There was also no right/left asymmetry for individuals with left or right dominance as assessed by the lateral preferences questionnaire. The same results were observed for the latency of antisaccades and for the error rate in the antisaccade task. Finally, we did not confirm any substantial subpopulation of individuals with idiosyncratic left/right latency asymmetries that persisted both in the saccade and antisaccade task. These results suggest that neither latency nor antisaccade error rate are good indicators of lateral preferences in these tasks. Other oculomotor tasks might be more sensitive to hemifield differences, or cerebral hemispheric asymmetry is not present at the level of cortical organization of saccades and antisaccades.

Higher scores of self reported schizotypy in healthy young males carrying the COMT high activity allele

The gene for COMT is located on chromosome 22q11, an area that has been implicated in the pathogenesis of schizophrenia through linkage studies and through the detection of deletions in schizophrenics and velocardiofacial syndrome patients that often present psychotic symptomatology. Additionally catechol-O-methyl transferase activity has been found increased in schizophrenia and a functional polymorphism in the COMT gene itself has been associated with the disease, as well as with aggression in patients. We tested the hypothesis that COMT genotype for the functional Val158Met might contribute to the variance of self reported schizotypy and aggression scores in the normal population. We genotyped 379 healthy 18- to 24-year-old male individuals who had completed the PAS, SPQ and AQ questionnaires. Our results showed that self-reported schizotypy scores in both questionnaires were significantly related to COMT genotype (P = 0.028 for the PAS and P = 0.015 for the SPQ) with individuals homozygous for the high activity allele showing the highest scores. No significant differences were detected for AQ scores. We conclude that the COMT genotype for the functional Val158Met polymorphism is correlated to self-reported schizotypy in healthy males. This finding is in the same direction as reported findings on schizophrenia and it adds to the list of evidence that COMT or a nearby gene in linkage disequilibrium is involved in the pathogenesis of the disease.

The antisaccade task in a sample of 2,006 young men. I. Normal population characteristics

A population of 2,075 young men aged 18-25 years selected from the conscripts of the Greek Air Force performed an antisaccade task as part of a prospective study for the identification of risk factors in the development of psychoses. The aim of this study, which is ongoing, is to follow this population and investigate the possible predictive value of oculomotor, cognitive, and psychometric factors for the development of psychosis and other psychiatric conditions. In this report we present data concerning the antisaccade task in this population. We measured performance indices, including the percentage of errors (PE), the latencies of different eye movement responses (latency for correct antisaccades, errors, corrections), and performance in perseveration-prone trials. These indices were also evaluated with respect to IQ (measured by the Raven progressive matrices test) and educational level. Mean PE was 23%, with 17% variance. This large variance is of particular importance whenever the detection of a putative deviant behavior is explored. As mean latency of the first eye movement decreased, the PE increased, as did the latency variance. While the negative correlation between percentage of error and mean latency is well established, the relationship of the latency variability of the first response to error production has not been studied before. Thus, optimal performance appears to require both an intermediate mean latency and a small variability. Furthermore, performance seems to be affected by IQ (the higher the IQ score, the lower the percentage of errors). This report offers an analysis of the interindividual variation in the performance of the antisaccade task and discusses some of the sources of this variation.

The antisaccade task in a sample of 2,006 young males. II. Effects of task parameters

Antisaccade performance was investigated in a sample of 2,006 young males as part of a large epidemiological study investigating psychosis proneness. This report summarizes the effects of task parameters on performance using a sample of 55,678 antisaccade trials collected from a subpopulation of 947 individuals. Neither the amplitude nor the latency of an error prosaccade in the antisaccade task was correlated with the latency of the ensuing corrective antisaccade that almost always followed an error. However, the latency of the corrective antisaccade decreased with increasing stimulus distance. Concerning the effects of specific task parameters, trials with stimuli closer to the central fixation point and trials preceded by shorter fixation intervals resulted in more errors and longer latencies for the antisaccades. Finally, there were learning and fatigue effects reflected mainly in the error rate, which was greater at the beginning and at the end of the 5-min task. We used a model to predict whether an error or a correct antisaccade would follow a particular trial. All task parameters were significant predictors of the trial outcome but their power was negligible. However, when modeled alone, response latency of the first movement predicted 40% of errors. In particular, the smaller this latency was, the higher the probability of an error. These findings are discussed in light of current hypotheses on antisaccade production mechanisms involving mainly the superior colliculus.

Frontal lobe dysfunction in amyotrophic lateral sclerosis

The aim of the present study was to investigate the involvement of frontal lobe dysfunction in amyotrophic lateral sclerosis (ALS) using ocular motor paradigms and neuropsychological testing. Fifty-one patients with ALS participated in the following ocular motor tasks: (1) a three-choice task and (2) a remembered saccade task. The patients underwent a clinical and neuropsychological evaluation. One-third of ALS patients presented with signs of frontal dysfunction, as determined by their high distractibility factors (DF) in the three-choice task and their performances in both the Wisconsin and Stroop tests. ALS patients exhibited longer latencies to eye movement than controls in the performance of the remembered saccade task, specifically in performance of both remembered and delayed saccades, but saccade accuracy was not impaired. Finally, performance indices of the ocular motor tasks, in particular the DF, was correlated only with the degree of dysarthria.

Frontal-parietal activation differences observed before the execution of remembered saccades: an event-related potentials study

Healthy subjects performed saccadic eye movements in one memory (MEM) and two delay tasks (delay, DEL and modified delay, M-DEL) while we recorded scalp event-related potentials (ERPs) from 25 electrode sites. In the MEM task the subjects were instructed to retain in memory the location of a visual target for a delay of 1-6 s and then perform a remembered saccade at the go signal. In the DEL task the target remained on until movement completion and in the M-DEL task the target, that was visible during the delay period, disappeared synchronously with the go signal. A reduction in response latency and an increase in the percentage of dysmetric movements were observed for the MEM task compared to the two delay tasks. An increased ERP activity at the central-frontal electrode sites compared to the parietal sites was significant only for the MEM task early on during the delay period (500-1000 ms). During the period preceding the onset of the saccade, a parietal increase of activity was observed for all tasks. Furthermore the activity was smaller for the frontal compared to the parietal areas only for the memory task thus indicating a near reversal of the previous pattern of activity observed during the early delay period. This specific activation pattern of frontal and parietal areas, observed for the MEM task only, requires further investigation focusing on the temporal pattern of activation of large brain areas involved in working memory processing.

An early transient 40 Hz activity discriminates a following pro-saccade from a no-move and anti-saccade choice

We studied the oscillatory activity of the scalp-recorded EEG in healthy humans performing a task that required a particular eye-movement response choice according to the shape of a visual target. We observed a significant stimulus-aligned activity at the 40 Hz frequency band 100 ms after the appearance of the target only when that target was the end point for the subsequent eye movement (pro-saccade). This activity was most prominent over the central-parietal area of the right hemisphere. When the target indicated a movement to the opposite direction (anti-saccade) or indicated that no movement was required (no-move), this 40 Hz activity was nearly absent. This difference in activity between the pro-saccade and the other two tasks was evident in the single subject ERPs for four of the six subjects studied. In contrast, the movement-aligned 40 Hz activity for the pro-saccade and anti-saccade was almost identical. We speculate that this early stimulus-aligned 40 Hz activity might reflect a fast transformation of a visual stimulus to a motor response (eye movement) that can be performed for the pro-saccade task where stimulus-response compatibility is strong compared to the anti-saccade and no-move tasks. The movement-aligned 40 Hz activity might be related to the motor response preparation per se. We conclude that this task specific transient oscillatory activity could be used as a probe in the study of the temporal dynamics of visuomotor transformations.

Systematic errors of planar arm movements provide evidence for space categorization effects and interaction of multiple frames of reference

Healthy humans performed arm movements in a horizontal plane, from an initial position toward remembered targets, while the movement and the targets were projected on a vertical computer monitor. We analyzed the mean error of movement endpoints and we observed two distinct systematic error patterns. The first pattern resulted in the clustering of movement endpoints toward the diagonals of the four quadrants of an imaginary circular area encompassing all target locations (oblique effect). The second pattern resulted in a tendency of movement endpoints to be closer to the body or equivalently lower than the actual target positions on the computer monitor (y-effect). Both these patterns of systematic error increased in magnitude when a time delay was imposed between target presentation and initiation of movement. In addition, the presence of a stable visual cue in the vicinity of some targets imposed a novel pattern of systematic errors, including minimal errors near the cue and a tendency for other movement endpoints within the cue quadrant to err away from the cue location. A pattern of systematic errors similar to the oblique effect has already been reported in the literature and is attributed to the subject's conceptual categorization of space. Given the properties of the errors in the present work, we discuss the possibility that such conceptual effects could be reflected in a broad variety of visuomotor tasks. Our results also provide insight into the problem of reference frames used in the execution of these aiming movements. Thus, the oblique effect could reflect a hand-centered reference frame while the y-effect could reflect a body or eye-centered reference frame. The presence of the stable visual cue may impose an additional cue-centered (allocentric) reference frame.

Speed-accuracy trade-off in the performance of pointing movements in different directions in two-dimensional space

Nine healthy subjects performed 2D pointing movements using a joystick that controlled a screen cursor. Continuous visual feedback was provided until movement completion. Three variables were systematically manipulated: (1) target distance, (2) target size and (3) target direction. A four-way factorial ANOVA was used to analyze the effects of these fixed factors and of the random factor of subject on several movement parameters. Movement time increased with increasing distance and decreasing target size and as predicted from Fitts' law. The target direction did not affect movement time. In contrast the direction, distance and size of the target significantly affected the movement time until the first zero crossing on the speed record reflecting the time to bring the arm into the vicinity of the target. Movements on the lateral axis of the horizontal plane (horizontal movements) resulted in a decrease in initial movement time compared to movements on the anterior axis of the horizontal plane (vertical movements). A significant effect of target distance and direction but not target size was observed for the magnitude of maximum acceleration, maximum speed and maximum deceleration. Horizontal movements had a larger maximum acceleration, speed and deceleration. Furthermore the maximum speed and deceleration occurred earlier in time for these horizontal movements. Finally the number of secondary peaks on the speed record increased with decreasing target size and was not affected by the target distance or target direction. In conclusion our results indicate that different movement parameters are affected by target distance, size and direction. The crucial distinction was between parameters affected by target size and direction. These parameters did not overlap. Target direction affects the first part of movement execution while target size affects the final part of movement execution. Thus a clear segmentation of movement execution in two phases is supported by these results. The implications of these results for theoretical models of speed-accuracy trade-off are discussed.

A systematic directional error in 2-D arm movements increases with increasing delay between visual target presentation and movement execution

Forty-seven normal subjects performed two-dimensional arm movements on a digitizer board using a mouse device. The movements were projected on a computer monitor. Subjects were instructed to move the mouse using the whole arm from a center position to a peripheral target so that the projected movement would pass over the target without stopping on the target. A large number of targets (360) were used to cover the entire directional continuum. The direction of the arm movement was the parameter of interest, which was measured at an initial position, at one third of the distance towards the target, and at the vicinity of the target. Four conditions of delay between target presentation and movement execution were used (0, 2, 4, 6 s). A systematic directional error was observed at the initial portion of the trajectory. This error resulted from a clustering of movement directions on an axis that was perpendicular to the axis of the resting forearm before movement onset. This pattern of errors can be explained by the initial inertial anisotropy of the arm. As the trajectory evolved, a different directional error emerged, resulting from a clustering of movement directions in two orthogonal axes. This pattern of directional error increased in amplitude as the delay increased, in contrast to the error at the initial portion of the trajectory which remained invariant with increasing delay. Finally, the information transmitted by the movement direction was shown to increase with the evolution of the trajectory. The increase in delay resulted in a decrease in directional-information transmission. It is proposed that the directional bias towards the end of the movement trajectory might reflect the action of "movement primitives", that is patterns of muscle activation resulting from spinal interneuronal activation. It is further proposed that the directional bias observed at the vicinity of the target might reflect a loss of cortical directional information with increasing delay between target presentation and movement onset.

The effects of slow waves in the screening EEGs of pilot cadets on P300 ERP and memory scanning performance

BACKGROUND

Electroencephalography (EEG) screening of pilot candidates has long been established but remains controversial. The EEG records of 0-15% of the test population demonstrate the presence of brief periods of slow waves (theta, 4-7.9 Hz and delta, 0-3.9 Hz). The significance of these EEG findings for pilot selection has not been defined.

HYPOTHESIS

We investigated whether the existence of slow waves in the EEG records of cadet pilots was related to differences in their cognitive performance. If so, the EEG could serve as a tool for cognitive assessment in candidate pilot screening. The relationship between spontaneous EEG slowing and cognitive performance has not been investigated although there is evidence of EEG slowing during the performance of short-term memory tasks.

METHODS

Some 116 screening EEG records were re-evaluated for the presence of slow wave activity. Cadets with positive records and a control group performed: a) a modified version of Sternberg's visual memory scanning task on a PC computer; and b) the auditory "OddBall" behavioral task for eliciting the P300 evoked response using the Nicolet Spirit Evoked Potential System.

RESULTS

Analysis of the behavioral and electrophysiological data was divided in EEG groups: a) Normal; b) Bilateral slowing only during hyperventilation; c) Bilateral slowing; d) Slowing with right dominance; and e) Slowing with left dominance, showed no significant difference among the groups for all parameters measured.

CONCLUSIONS

Brief periods of bilateral or focal EEG slow activity in the records of pilot cadets could not predict differences in cognitive function as this was assessed in these experiments. Specific neuropsychological screening procedures might be more valuable for this purpose than the standard EEG screening.

On the relations between single cell activity in the motor cortex and the direction and magnitude of three-dimensional static isometric force

We examined the relations between the steady-state frequency of discharge of cells in the arm area of the motor cortex of the monkey and the direction and magnitude of the three-dimensional static force exerted by the arm on an isometric manipulandum. Data were analyzed from two monkeys (n = 188 cells) using stepwise multiple linear regression. In 154 of 188 (81.9%) cells the regression model was statistically significant (P < 0.05). In 121 of 154 (78.6%) cells the direction but not the magnitude of force had a statistically significant effect on cell activity; in 11 of 154 (7.1%) cells only the magnitude effect was significant; and in 22 of 154 (14.3%) cells both the direction and magnitude effects were significant. The same analysis was used to assess the effect of the direction and magnitude of force on the electromyographic activity of 9 muscles of the arm and shoulder girdle. The regression model was statistically significant. For all the muscles studied in 4 of 9 (44.4%) muscles only the direction effect was significant whereas in the remaining 5 of 9 (55.6%) muscles both the direction and the magnitude were significant. No muscle studied showed a significant effect of force magnitude alone. These differences in the frequency of occurrence of directional and magnitude effects between cells and muscles were statistically significant (P < 0.005, chi 2 test). These findings underscore the fundamental importance of the direction of force in space for both motor cortical cells and proximal muscles and underline the differential relations of the cells and muscles to the direction and magnitude of force. These results indicate that the specification of the magnitude of three-dimensional force is embedded within the directional signal; this combined direction+magnitude effect was 3.9 times more prevalent in the muscles than in the cells studied. In contrast, the pure directional effect was 1.8 times more prevalent in the cells than in the muscles studied. This suggests that the direction of force can be controlled independently of its magnitude and that this direction signal is especially prominent in the motor cortex.

Motor cortical activity preceding a memorized movement trajectory with an orthogonal bend

Two monkeys were trained to make an arm movement with an orthogonal bend, first up and then to the left ([symbol: see text]), following a waiting period. They held a two-dimensional manipulandum over a spot of light at the center of a planar working surface. When this light went off, the animals were required to hold the manipulandum there for 600-700 ms and then move the handle up and to the left to receive a liquid reward. There were no external signals concerning the "go" time or the trajectory of the movement. It was hypothesized that during that period signs of directional processing relating to the upcoming movement would be identified in the motor cortex. Following 20 trials of the memorized movement trajectory, 40 trials of visually triggered movements in radially arranged directions were performed. The activity of 137 single cells in the motor cortex was recorded extracellularly during performance of the task. It was found that 62.8% of the cells changed activity during the memorized waiting period. During the waiting period, the population vector (Georgopoulos et al. 1983, 1984) began to grow approximately 130 ms after the center light was turned off; it pointed first in the direction of the second part of the memorized movement (<--) and then rotated clockwise towards the direction of the initial part of the movement (increases). These findings indicate processing of directional information during the waiting period preceding the memorized movement. This conclusion was supported by the results of experiments in ten human subjects, who performed the same memorized movement ([symbol: see text]). In 10% of the trials a visual stimulus was shown in radially arranged directions in which the subjects had to move; this stimulus was shown at 0, 200, and 400 ms from the time the center light was turned off. We found that as the interval increased the reaction time shortened for the visual stimulus that was in the same direction as the upward component of the memorized movement.

Motor cortical activity in a memorized delay task

Two rhesus monkeys were trained to move a handle on a two-dimensional (2D) working surface in directions specified by a light at the plane. They first captured with the handle a light on the center of the plane and then moved the handle in the direction indicated by a peripheral light (cue signal). The signal to move (go signal) was given by turning off the center light. The following tasks were used: (a) In the non-delay task the peripheral light was turned on at the same time as the center light went off. (b) In the memorized delay task the peripheral light stayed on for 300 ms and the center light was turned off 450-750 ms later. Finally, (c) in the non-memorized delay task the peripheral light stayed on continuously whereas the center light went off 750-1050 ms after the peripheral light came on. Recordings in the arm area of the motor cortex (N = 171 cells) showed changes in single cell activity in all tasks. In both delay tasks, the neuronal population vector calculated every 20 ms after the onset of the peripheral light pointed in the direction of the upcoming movement, which was instructed by the cue light. Moreover, the strength of the population signal showed an initial peak shortly after the cue onset in both the memorized and non-memorized delay tasks but it maintained a higher level during the memorized delay period, as compared to the non-memorized task.(ABSTRACT TRUNCATED AT 250 WORDS)

The motor cortex and the coding of force

The relation of cellular activity in the motor cortex to the direction of two-dimensional isometric force was investigated under dynamic conditions in monkeys. A task was designed so that three force variables were dissociated: the force exerted by the subject, the net force, and the change in force. Recordings of neuronal activity in the motor cortex revealed that the activity of single cells was directionally tuned and that this tuning was invariant across different directions of a bias force. Cell activity was not related to the direction of force exerted by the subject, which changed drastically as the bias force changed. In contrast, the direction of net force, the direction of force change, and the visually instructed direction all remained quite invariant and congruent and could be the directional variables, alone or in combination, to which cell activity might relate.