Oculomotor delayed response abnormalities in young offspring and siblings at risk for schizophrenia

Antisaccade and memory-guided saccade in individuals at ultra-high-risk for bipolar disorder

BACKGROUND

Ultra-high-risk for bipolar disorder (UHR-BD) is an important paradigm to investigate the potential early-stage biomarkers of bipolar disorder, including eye-tracking abnormalities and cognitive functions. Antisaccade (AS) described as looking in the opposite direction of the target, and memory-guided saccade (MGS), identified as maintaining fixation, and remembering the location of the target, were used in this study. The aim of this study was to evaluate the differences in saccadic eye movements between UHR-BD and healthy controls (HCs) via AS-MGS.

METHODS

The study included 28 UHR-BD and 29 HCs. Participants were selected using a structured clinical interview for prodromal symptoms of BD. AS-MGS were measured with parameters like uncorrected errors, anticipatory saccades, and latency. Eye movements were recorded with the EyeLink 1000-Plus eye-tracker.

RESULTS

In the AS, the number of correct saccades was significantly decreased in UHR-BD (p = 0.020). Anticipatory (p = 0.009) and express saccades (p = 0.040) were increased in UHR-BD. In the MGS paradigm, the correct saccades were reduced in UHR-BD (p = 0.031). In addition, anticipatory (p = 0.004) and express saccades (p = 0.012) were significantly increased in cue-screen in UHR-BD.

CONCLUSIONS

To our knowledge, this is the first study to evaluate cognitive functions with eye movements in individuals at UHR-BD. The current findings showed that eye movement functions, particularly in saccadic parameters related to inhibition and spatial perception, may be affected in the UHR-BD group. Therefore, assessment of oculomotor functions may provide observation of clinical and cognitive functions in the early-stage of bipolar disorder. However, further research is needed because the potential effects of medication may affect saccadic results.

Sustained attention induces altered effective connectivity of the ascending thalamo-cortical relay in obsessive-compulsive disorder

Abnormal function of the thalamo-cortical relay is considered a hallmark of obsessive-compulsive disorder (OCD) and aberrant network interactions may underpin many of the clinical and cognitive symptoms that characterize the disorder. Several statistical approaches have been applied to in vivo fMRI data to support the general loss of thalamo-cortical connectivity in OCD. However, (a) few studies have assessed the contextual constraints under which abnormal network interactions arise or (b) have used methods of effective connectivity to understand abnormal network interactions. Effective connectivity is a particularly valuable method as it describes the putative causal influences that brain regions exert over each other, as opposed to the largely statistical consistencies captured in functional connectivity techniques. Here, using dynamic causal modeling (DCM), we evaluated how attention demand induced inter-group differences (HC ≠ OCD) in effective connectivity within a motivated thalamo-cortical network. Of interest was whether these effects were observed on the ascending thalamo-cortical relay, essential for the sensory innervation of the cortex. fMRI time series data from sixty-two participants (OCD, 30; HC, 32) collected using an established sustained attention task were submitted to a space of 162 competing models. Across the space, models distinguished between competing hypotheses of thalamo-cortical interactions. Bayesian model selection (BMS) identified marginally differing likely generative model architectures in OCD and HC groups. Bayesian model averaging (BMA), was used to weight connectivity parameter estimates across all models, with each parameter weighted by each model's posterior probability, thus providing more stable estimates of effective connectivity. Inferential statistical analyses of estimated parameters revealed two principal results: (1) Significantly reduced intrinsic connectivity of the V1 → SPC pathway in OCD, suggested connective weakness in the early constituents of the dorsal visual pathway; (2) More pertinent with the discovery possibilities afforded by DCM, sustained attention in OCD patients induced significantly reduced contextual modulation of the ascending relay from the thalamus to the prefrontal cortex. These results form an important complement to our understanding of the contextual bases of thalamo-cortical network deficits in OCD, emphasizing vulnerability of the ascending relay.

Insights to the schizophrenia continuum: A systematic review of saccadic eye movements in schizotypy and biological relatives of schizophrenia patients

Myles, J.B., S. Rossell, A. Phillipou, Thomas, E and C. Gurvich. A systematic review of saccadic eye movements across the schizophrenia continuum: Characterisation, pathophysiology and genetic associations. NEUROSCI BIOBEHAV REV 21(1) XXX-XXX, 2015. One of the cognitive hallmarks of schizophrenia is impaired eye movements, particularly for the antisaccade task. Less saccade research has been conducted in relation to the broader schizophrenia continuum, that is, people with high schizotypy or first-degree relatives of people with schizophrenia. This systematic review sought to identify, collate and appraise prosaccade, antisaccade and memory-guided saccade studies involving behavioural, neuroimaging and genetic data published between 1980 and September 2016 in individuals with high schizotypy and first-degree relatives. A systematic literature search was conducted, using Ovid MEDLINE, PsycINFO, PubMed and SCOPUS databases. Of 913 references screened, 18 schizotypy, 29 family studies and two schizotypy and relatives articles studies were eligible for inclusion. Antisaccade error rate was the most consistent deficit found for high schizotypy. Relatives had intermediate antisaccade error rates between patients and healthy controls. Results from the limited genetic and neuroimaging studies echoed schizophrenia findings. Confounds were also identified. It was concluded that future research is required to refine the saccade endophenotype and to expand genetic and neuroimaging research.

Dysfunction and Dysconnection in Cortical-Striatal Networks during Sustained Attention: Genetic Risk for Schizophrenia or Bipolar Disorder and its Impact on Brain Network Function

Abnormalities in the brain's attention network may represent early identifiable neurobiological impairments in individuals at increased risk for schizophrenia or bipolar disorder. Here, we provide evidence of dysfunctional regional and network function in adolescents at higher genetic risk for schizophrenia or bipolar disorder [henceforth higher risk (HGR)]. During fMRI, participants engaged in a sustained attention task with variable demands. The task alternated between attention (120 s), visual control (passive viewing; 120 s), and rest (20 s) epochs. Low and high demand attention conditions were created using the rapid presentation of two- or three-digit numbers. Subjects were required to detect repeated presentation of numbers. We demonstrate that the recruitment of cortical and striatal regions are disordered in HGR: relative to typical controls (TC), HGR showed lower recruitment of the dorsal prefrontal cortex, but higher recruitment of the superior parietal cortex. This imbalance was more dramatic in the basal ganglia. There, a group by task demand interaction was observed, such that increased attention demand led to increased engagement in TC, but disengagement in HGR. These activation studies were complemented by network analyses using dynamic causal modeling. Competing model architectures were assessed across a network of cortical-striatal regions, distinguished at a second level using random-effects Bayesian model selection. In the winning architecture, HGR were characterized by significant reductions in coupling across both frontal-striatal and frontal-parietal pathways. The effective connectivity analyses indicate emergent network dysconnection, consistent with findings in patients with schizophrenia. Emergent patterns of regional dysfunction and dysconnection in cortical-striatal pathways may provide functional biological signatures in the adolescent risk-state for psychiatric illness.

Epigenetics, stress, and their potential impact on brain network function: a focus on the schizophrenia diatheses

The recent sociodevelopmental cognitive model of schizophrenia/psychosis is a highly influential and compelling compendium of research findings. Here, we present logical extensions to this model incorporating ideas drawn from epigenetic mediation of psychiatric disease, and the plausible effects of epigenetics on the emergence of brain network function and dysfunction in adolescence. We discuss how gene-environment interactions, effected by epigenetic mechanisms, might in particular mediate the stress response (itself heavily implicated in the emergence of schizophrenia). Next, we discuss the plausible relevance of this framework for adolescent genetic risk populations, a risk group characterized by vexing and difficult-to-explain heterogeneity. We then discuss how exploring relationships between epigenetics and brain network dysfunction (a strongly validated finding in risk populations) can enhance understanding of the relationship between stress, epigenetics, and functional neurobiology, and the relevance of this relationship for the eventual emergence of schizophrenia/psychosis. We suggest that these considerations can expand the impact of models such as the sociodevelopmental cognitive model, increasing their explanatory reach. Ultimately, integration of these lines of research may enhance efforts of early identification, intervention, and treatment in adolescents at-risk for schizophrenia.

Assessment of cognition in non-affected full biological siblings of patients with schizophrenia

BACKGROUND

Schizophrenia is a devastating psychotic illness which is like the most mental disorders, shows complex inheritance; the transmission of the disorder most likely involves several genes and environmental factors. It is difficult to judge whether a particular person without schizophrenia has predisposing factors for the said disease. A few studies have shown the relative sensitivity and reliability of cognitive and psychophysiological markers of brain function as the susceptibility factors for schizophrenia which may aid us to find people with an increased risk of complex disorders like schizophrenia. The present work is an exploration on cognitive impairments in unaffected siblings of patients suffering from schizophrenia with a framework to explore why a mental disorder occurs in some families but not in others.

MATERIALS AND METHODS

This is a single point non-invasive study of non-affected full biological siblings of patients with schizophrenia, involving administration of a battery of neuropsychological tests to assess the cognitive function in the sibling group and a control group of volunteers with no history of psychiatric illness. The control group was matched for age, gender, and education. The siblings were also divided on the basis of the type of schizophrenia their siblings (index probands) were suffering from and their results compared with each other.

RESULTS

The siblings performed significantly poorly as compared to the controls on Wisconsin card sorting test (WCST), continuous performance test (CPT), and spatial working memory test (SWMT). The comparison between the sibling subgroups based on the type of schizophrenia in the index probands did not reveal any significant difference.

CONCLUSION

These findings suggest that there is a global impairment in the cognition of the non-affected siblings of patients of schizophrenia. Cognitive impairment might be one of the factors which will help us to hit upon people who are predisposed to develop schizophrenia in the future.

Disordered corticolimbic interactions during affective processing in children and adolescents at risk for schizophrenia revealed by functional magnetic resonance imaging and dynamic causal modeling

CONTEXT

Disordered functional architecture of brain networks may contribute to the well-documented increased risk for psychiatric disorders in offspring of patients with schizophrenia.

OBJECTIVE

To investigate aberrant interactions between regions associated with affective processing in children and adolescent offspring of patients with schizophrenia (HR-SCZ group) and healthy control subjects using dynamic causal modeling of functional magnetic resonance imaging data.

DESIGN

Subjects participated in a continuous affective processing task during which positive, negative, and neutral valenced faces were presented. Interactions between regions in the brain's face- and emotion-processing network were modeled using dynamic causal modeling. Multiple competing models were evaluated by a combinatorial approach and distinguished at the second level using Bayesian model selection before parameter inference.

SETTING

Participants were recruited from the community.

PARTICIPANTS

Twenty-four controls with no family history of psychosis (to the second degree) and 19 children and adolescent offspring of a parent with schizophrenia (age range, 8 to 20 years).

RESULTS

Bayesian model selection revealed a winning model, the architecture of which revealed bidirectional frontolimbic connections that were modulated by valence. Analyses of parameter estimates revealed that HR-SCZ group members were characterized by (1) decreased driving inputs to the visual cortex; (2) decreased intrinsic coupling, most robustly between frontolimbic regions; and (3) increased modulatory inhibition by negative valence of frontolimbic connections (all P < .01, Bonferroni corrected).

CONCLUSIONS

These results are the first demonstration of network analyses techniques for functional magnetic resonance imaging data in children and adolescents at risk for schizophrenia. Dysfunctional interactions within the emotional processing network provide evidence of latent vulnerabilities that may confer risk for disordered adolescent development and eventually the emergence of the manifest disorder.

The neural correlates of performance in adolescents at risk for schizophrenia: inefficiently increased cortico-striatal responses measured with fMRI

BACKGROUND

fMRI studies indicate that schizophrenia patients and their adult relatives require greater prefrontal activation to maintain performance at levels equal to controls, but studies have not established if this pattern of inefficiency is observed in child and adolescent offspring of schizophrenia patients (SCZ-Off).

METHODS

Using a task with visual working memory demands, we investigated activation in cortico-striatal networks and dorsal prefrontal modulation of regions underlying visual working memory in a group of SCZ-Off (n = 19) and controls with no family history of psychosis (n = 25 subjects) using an event-related design. Trials were divided based on memory performance (correct vs. incorrect) to specifically identify the neural correlates of correct working memory performance.

RESULTS

Whereas groups did not differ in terms of behavioral accuracy, SCZ-Off demonstrated significantly increased fMRI-measured activation in dorsal prefrontal cortex and the caudate nucleus during correct, relative to incorrect memory performance. Whereas activation in SCZ-Off was high and independent of performance in each region, in controls the fMRI response was related to behavioral proficiency in the caudate. Further, exploratory analyses indicated that this inefficiency in the dorsal prefrontal cortex response increased with age in SCZ-Off (but in no other regions or group). Finally, these differences were not based in differences in dorsal prefrontal modulation of other regions during successful performance.

DISCUSSION

These results are consistent with observed patterns in adult patients and first-degree relatives. Inefficient fronto-striatal responses during working memory may characterize the schizophrenia diathesis and may reflect the effects of the illness and vulnerability for the illness.

Inefficiently increased anterior cingulate modulation of cortical systems during working memory in young offspring of schizophrenia patients

BACKGROUND

Children and adolescent offspring of schizophrenia patients are at increased risk for schizophrenia and are also characterized by impairments in brain structure and function. To date, few studies have investigated whether functional interactions between brain regions are intact or altered. Using an established verbal working memory paradigm with variable levels of memory load, we investigated the modulatory effect of activity in cognitive control regions of the brain (specifically the dorsal anterior cingulate cortex) on activity in core working memory regions, in particular the dorsal prefrontal cortex and the parietal lobe.

METHODS

Forty four subjects participated. An n-back task with two levels of working memory load (1- and 2-back) was employed during fMRI (4 T Bruker MedSpec system). Data were processed with SPM5 and the modulatory effects of the anterior cingulate were investigated using psycho-physiological interaction (PPI).

RESULTS

In spite of only subtle activation differences, and no significant differences in performance accuracy, a significant group x memory load interaction in the parietal lobe, indicated aberrantly increased modulatory inputs to this region under conditions of high working memory load in schizophrenia offspring.

DISCUSSION

Increased modulatory inputs from a central control region like the anterior cingulate presumably reflect relative inefficiency in intra-cortical interactions in the vulnerable brain. This inefficiency may reflect a developmentally mediated impairment in functional brain interactions in this important vulnerable population. It is highly plausible that the resultant effect of these altered interactions is an increased vulnerability to impaired brain development, and therefore to psychiatric disorders including schizophrenia.

Working memory and attention deficits in adolescent offspring of schizophrenia or bipolar patients: comparing vulnerability markers

BACKGROUND

Working memory deficits abound in schizophrenia and attention deficits have been documented in schizophrenia and bipolar disorder. Adolescent offspring of patients may inherit vulnerabilities in brain circuits that subserve these cognitive domains. Here we assess impairments in offspring of schizophrenia (SCZ-Offspring) or bipolar (BP-Offspring) patients compared to controls (HC) with no family history of mood or psychotic disorders to the second degree.

METHODS

Three groups (n=100 subjects; range: 10-20 yrs) of HC, SCZ-Offspring and BP-Offspring gave informed consent. Working memory was assessed using a delayed spatial memory paradigm with two levels of delay (2s & 12s); sustained attention processing was assessed using the Continuous Performance Task-Identical Pairs version.

RESULTS

SCZ-Offspring (but not BP-Offspring) showed impairments in working memory (relative to HC) at the longer memory delay indicating a unique deficit. Both groups showed reduced sensitivity during attention but only BP-Offspring significantly differed from controls.

CONCLUSIONS

These results suggest unique (working memory/dorsal frontal cortex) and potentially overlapping (attention/fronto-striatal cortex) vulnerability pathways in adolescent offspring of patients with schizophrenia and bipolar disorder. Working memory and attention assessments in these offspring may assist in the clinical characterization of the adolescents vulnerable to SCZ or BP.

Fronto-parietal hypo-activation during working memory independent of structural abnormalities: conjoint fMRI and sMRI analyses in adolescent offspring of schizophrenia patients

Adolescent offspring of schizophrenia patients (HR-S) are an important group in whom to study impaired brain function and structure, particularly of the frontal cortices. Studies of working memory have suggested behavioral deficits and fMRI-measured hypoactivity in fronto-parietal regions in these subjects. Independent structural MRI (sMRI) studies have suggested exaggerated frontal gray matter decline. Therefore the emergent view is that fronto-parietal deficits in function and structure characterize HR-S. However, it is unknown if fronto-parietal sub-regions in which fMRI-measured hypo-activity might be observed are precisely those regions of the cortex in which gray matter deficits are also observed. To investigate this question we conducted conjoint analyses of fronto-parietal function and structure in HR-S (n=19) and controls (n=24) with no family history of psychoses using fMRI data during a continuous working memory task (2 back), and sMRI collected in the same session. HR-S demonstrated significantly reduced BOLD activation in left dorso-lateral prefrontal cortex (BA 9/46) and bilateral parietal cortex (BA 7/40). Sub-regions of interest were created from the significant fronto-parietal functional clusters. Analyses of gray matter volume from volume-modulated gray matter segments in these clusters did not reveal significant gray matter differences between groups. The results suggest that functional impairments in adolescent HR-S can be independent of impairments in structure, suggesting that the relationship between impaired function and structure is complex. Further studies will be needed to more closely assess whether impairments in function and structure provide independent or interacting pathways of vulnerability in this population.

Hypo-activation in the executive core of the sustained attention network in adolescent offspring of schizophrenia patients mediated by premorbid functional deficits

Adolescent offspring of schizophrenia patients (SCZ-Off) are vulnerable to psychiatric disorders. Assessing relationships between clinical and biological measures (such as functional magnetic resonance imaging, fMRI) may elucidate pathways of vulnerability in this group. Here we assessed the relationship between clinically assessed premorbid function, and cortico-striatal activity during sustained attention in controls (HC: with no family history of psychosis) and SCZ-Off. Subjects (n=39) were assessed using the Structured Interview for Prodromal Syndromes and the Scale of Prodromal Symptoms. Based on the Global Assessment of Functioning (GAF) score, SCZ-Off were cleaved into "high" or "low" clinically functioning sub-groups (SCZ-Off(HF), SCZ-Off(LF) respectively). During fMRI, subjects participated in a modified continuous performance task (CPT-IP). fMRI was conducted on a Bruker MedSpec 4T system (345 EPI scans; TR=2s; 24 slices; 3.8×3.8×4mm). Results show SCZ-Off(LF) evinced less activation than both HC and SCZ-Off(HF) in the executive core of the brain's attentional system (anterior cingulate, dorsal prefrontal cortex and caudate), but not visuo-spatial regions such as primary visual or superior parietal cortex. Differences were independent of behavioral performance, and reduction in activity was related to GAF score in a dose-dependent manner. Assessing the relationship between clinical measures and brain activity in domains such as attention provides a window into mechanisms of vulnerability in the developing adolescent brain.

Reduced intra-amygdala activity to positively valenced faces in adolescent schizophrenia offspring

Studies suggest that the affective response is impaired in both schizophrenia and adolescent offspring of schizophrenia patients. Adolescent offspring of patients are developmentally vulnerable to impairments in several domains, including affective responding, yet the bases of these impairments and their relation to neuronal responses within the limbic system are poorly understood. The amygdala is the central region devoted to the processing of emotional valence and its sub-nuclei including the baso-lateral and centro-medial are organized in a relative hierarchy of affective processing. Outputs from the centro-medial nucleus converge on regions involved in the autonomous regulation of behavior, and outputs from the baso-lateral nucleus modulate the response of reward processing regions. Here using fMRI we assessed the intra-amygdala response to positive, negative, and neutral valenced faces in a group of controls (with no family history of psychosis) and offspring of schizophrenia parents (n=44 subjects in total). Subjects performed an affective continuous performance task during which they continually appraised whether the affect signaled by a face on a given trial was the same or different from the previous trial (regardless of facial identity). Relative to controls, offspring showed reduced activity in the left centro-medial nucleus to positively (but not negatively or neutral) valenced faces. These results were independent of behavioral/cognitive performance (equal across groups) suggesting that an impaired affective substrate in the intra-amygdala response may lie at the core of deficits of social behavior that have been documented in this population.

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

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

Longitudinal alterations of executive function in non-psychotic adolescents at familial risk for schizophrenia

Genetic diathesis to schizophrenia may involve alterations of adolescent neurodevelopment manifesting as cognitive deficits. Brain regions mediating executive function (fronto-striatal circuits) develop during adolescence while those supporting elementary aspects of attention (e.g. sustained focused attention) have a more protracted maturation beginning in childhood. We hence predicted that adolescents at risk for schizophrenia would show a failure of normal maturation of executive function. We prospectively assessed 18 offspring and 6 siblings of schizophrenia patients (HR) and 28 healthy controls at baseline, year-1 and year-2 follow-up using the Continuous Performance Test [visual-d'] and Wisconsin Card Sort Test (WCST). Perseverative errors on the WCST in HR remained stable but decreased in controls over the follow-up (study-group by assessment-time interaction, p=0.01, controlling for IQ). No significant study-group by assessment-time interactions were seen for sustained attentional performance. HR may not improve while healthy subjects progressively improve on executive function during adolescence and early adulthood. Our results suggest an altered maturational trajectory of executive function during adolescence in individuals at familial risk for schizophrenia.

Premorbid cognitive deficits in young relatives of schizophrenia patients

Neurocognitive deficits in schizophrenia (SZ) are thought to be stable trait markers that predate the illness and manifest in relatives of patients. Adolescence is the age of maximum vulnerability to the onset of SZ and may be an opportune "window" to observe neurocognitive impairments close to but prior to the onset of psychosis. We reviewed the extant studies assessing neurocognitive deficits in young relatives at high risk (HR) for SZ and their relation to brain structural alterations. We also provide some additional data pertaining to the relation of these deficits to psychopathology and brain structural alterations from the Pittsburgh Risk Evaluation Program (PREP). Cognitive deficits are noted in the HR population, which are more severe in first-degree relatives compared to second-degree relatives and primarily involve psychomotor speed, memory, attention, reasoning, and social-cognition. Reduced general intelligence is also noted, although its relationship to these specific domains is underexplored. Premorbid cognitive deficits may be related to brain structural and functional abnormalities, underlining the neurobiological basis of this illness. Cognitive impairments might predict later emergence of psychopathology in at-risk subjects and may be targets of early remediation and preventive strategies. Although evidence for neurocognitive deficits in young relatives abounds, further studies on their structural underpinnings and on their candidate status as endophenotypes are needed.

Encoding dysfunctions in a dynamic-static paradigm for visuospatial working memory in first-episode psychosis patients: a 2-year follow-up study

AIM

To investigate static and dynamic visuospatial working memory (VSWM) processes in first-episode psychosis (FEP) patients and explore the validity of such measures as specific trait markers of schizophrenia.

METHODS

Twenty FEP patients and 20 age-, sex-, laterality- and education-matched controls carried out a dynamic and static VSWM paradigm. At 2-year follow up 13 patients met Diagnostic and Statistical Manual (of Mental Health Disorders)--Fourth Edition (DSM-IV) criteria for schizophrenia, 1 for bipolar disorder, 1 for brief psychotic episode and 5 for schizotypal personality disorder.

RESULTS

Compared with controls, the 20 FEP patients showed severe impairment in the dynamic VSWM condition but much less impairment in the static condition. No specific bias in stimulus selection was detected in the two tasks. Two-year follow-up evaluations suggested poorer baseline scores on the dynamic task clearly differentiated the 13 FEP patients who developed schizophrenia from the seven who did not.

CONCLUSIONS

Results suggest deficits in VSWM in FEP patients. Specific exploratory analyses further suggest that deficit in monitoring-manipulation VSWM processes, especially involved in our dynamic VSWM task, can be a reliable marker of schizophrenia.

Memory-guided saccade abnormalities in schizophrenic patients and their healthy, full biological siblings

BACKGROUND

Ocular-motor inhibition errors and saccadic hypometria occur at elevated rates in biological relatives of schizophrenic patients. The memory-guided saccade (MS) paradigm requires a subject to inhibit reflexive saccades (RSs) and to programme a delayed saccade towards a remembered target.

METHOD

MS, RS, and central fixation (CF) tasks were administered to 16 patients who met the criteria for DSM-IV schizophrenia, 19 of their psychiatrically healthy siblings, and 18 controls.

RESULTS

Patients and siblings showed elevated MS error rates reflecting a failure to inhibit RSs to a visible target, as required by the task. In contrast to controls, prior errors did not improve MS accuracy in patients and siblings.

CONCLUSIONS

The specific characteristics of the elevated MS error rate help to clarify the nature of the disinhibition impairment found in schizophrenics and their healthy siblings. Failure to inhibit premature saccades and to improve the accuracy of subsequent volitional saccades implicates a deficit in spatial working-memory integration, mental representation and/or motor learning processes in schizophrenia.

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

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

Premorbid indicators and risk for schizophrenia: a selective review and update

Prospective studies of young relatives at risk for schizophrenia (high-risk studies, HR) can shed light on premorbid precursors of schizophrenia. Early HR studies pointed to a wide prevalence of schizophrenia spectrum psychopathology among young relatives at increased genetic risk. Recent studies suggest that young HR relatives have neurobehavioral deficits and structural, physiological, and neurochemical brain abnormalities that may date back to childhood or earlier. In this paper, we provide a selected overview of the lessons and limitations of early "first generation" studies and the beginning insights from recent "second generation" studies. We also provide an interim summary of data from the ongoing studies of young relatives at risk for schizophrenia in Pittsburgh. Collectively, such data may help us to predict the eventual emergence of schizophrenia, and schizophrenia spectrum or non-spectrum psychopathology.

Approaches for adolescents with an affected family member with schizophrenia

Prospective studies of adolescents at risk for schizophrenia (high-risk studies) can shed light on the possible premorbid precursors of schizophrenia. Recent studies have provided evidence of neurobehavioral, brain structural, physiologic, and neurochemical deficits in adolescent nonpsychotic high-risk relatives that may date back to childhood or earlier. These results are collectively providing a critical window into the inter-relationships between genetic predisposition, neurodevelopment, and premorbid indicators of risk in schizophrenia. Convergent approaches are inherently powerful in mutually informing each other in enriching the knowledge of the risk factors that predict the eventual onset of schizophrenia. Defining such reliable predictors of the onset of schizophrenia may provide us with the tools to better understand the etiology and pathophysiology of the illness, and may pave the way for innovative methods of treatment and possibly prevention. The authors review the relevant literature in this promising field of inquiry and summarize recent findings from high-risk studies.

Considering schizophrenia from a prevention perspective

Schizophrenia is a serious mental illness that causes major disability and psychosocial impairment. Recent advances in the neurosciences are prompting considerations of schizophrenia from a preventive perspective. An overview of the literature is provided on two important aspects of the development of a prevention orientation in schizophrenia research: elucidation of potential causal risk factors for schizophrenia and research on risk markers. Risk factors for schizophrenia include, but are not limited to, family history, older paternal age, velo-cardio-facial syndrome, maternal infections during pregnancy, pregnancy and delivery complications, and social adjustment difficulties in childhood and adolescence. Potential risk markers include structural brain pathology, minor physical anomalies and dermatoglyphic abnormalities, neurocognitive deficits, eye-tracking dysfunction, certain electrophysiologic findings, and olfactory identification deficits. Several early efforts at indicated preventive interventions targeting individuals at particularly high risk for developing the disorder are discussed. The preventive medicine and public health disciplines may have a role in future research and interventions that apply a preventive perspective to schizophrenia and other mental illnesses. Like any other chronic medical condition, schizophrenia can be considered from a preventive perspective.