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

The development in rating-based executive functions in children at familial high risk of schizophrenia or bipolar disorder from age 7 to age 11: the Danish high risk and resilience study

Executive functions (EF) deficits are well documented in children at familial high risk of schizophrenia (FHR-SZ), and to a lesser degree in children at familial high risk of bipolar disorder (FHR-BP). The aim of this study was to assess EF development in preadolescent children at FHR-SZ, FHR-BP and population-based controls (PBC) using a multi-informant rating scale. A total of 519 children (FHR-SZ, n = 201; FHR-BP, n = 119; PBC, n = 199) participated at age 7, at age 11 or at both time points. Caregivers and teachers completed the Behavior Rating Inventory of Executive Functions (BRIEF). The developmental pattern from age 7 to age 11, did not differ between groups. At age 11, caregivers and teachers rated children at FHR-SZ as having widespread EF deficits. A higher proportion of children at FHR-SZ had clinically significant scores on the General executive composite (GEC) and all BRIEF indices compared to PBC. According to the caregivers, children at FHR-BP had significantly more EF deficits than PBC on 9 out of 13 BRIEF scales, whereas according to teachers, they only had significantly more deficits on one subdomain (Initiate). Likewise, caregivers rated a significantly higher proportion of children at FHR-BP above the clinical cut-off on the GEC and Metacognition index, compared to PBC, whereas there were no significant differences according to teachers. This study highlights the relevance of including multi-informant rating scales in the assessment of EF in children at FHR-SZ and FHR-BP. The results imply a need to identify children at high risk who would benefit from targeted intervention.

Brain structural abnormalities of the associative striatum in adolescents and young adults at genetic high-risk of schizophrenia: Implications for illness endophenotypes

OBJECTIVE

Dysfunction in cortico-striatal circuitry represents a core component of the pathophysiology in schizophrenia (SZ) but its potential as a candidate endophenotype of the illness is often confounded by neuroleptic medication.

METHODS

Accordingly, 26 adolescent and young adult participants at genetic high-risk for schizophrenia, but who were asymptomatic and neuroleptic naïve, and 28 age-matched controls underwent 1.5T structural magnetic resonance imaging of the striatum, manually parcellated into limbic (LST), associative (AST), and sensorimotor (SMST) functional subregions.

RESULTS

In relation to their age peers, participants at genetic high-risk for schizophrenia showed overall lower striatal gray matter volume with their most pronounced loss, bilaterally in the AST, but not the LST or SMST. Neuropsychological testing revealed reduced executive functioning for genetically at-risk participants, although the groups did not differ significantly in overall intelligence or oral reading. For controls but not for at-genetic high-risk participants, stronger executive functioning correlated with increased bilateral AST volume.

CONCLUSIONS

Reduced bilateral AST volume in genetic high-risk adolescents and young adults, accompanied by heritable loss of higher cognitive brain-behavior relationships, might serve as a useful endophenotype of SZ.

Neurocognitive Development in Children at Familial High Risk of Schizophrenia or Bipolar Disorder

IMPORTANCE

Neurocognitive impairments exist in children at familial high risk (FHR) of schizophrenia and bipolar disorder. Studies on preadolescent developmental courses of neurocognition are important to describe shared and distinct neurodevelopmental pathways in these groups.

OBJECTIVE

To assess the development in specific neurocognitive functions from age 7 to 11 years in children at FHR of schizophrenia or bipolar disorder compared with children in a population-based control (PBC) group.

DESIGN, SETTING, AND PARTICIPANTS

The Danish High Risk and Resilience Study is a prospective, longitudinal, cohort study that collected data from January 1, 2013, to January 31, 2016 (phase 1), and from March 1, 2017, to June 30, 2020 (phase 2). Data were collected at 2 university hospitals in Denmark, and participants included 520 children at FHR of schizophrenia or bipolar disorder along with a PBC group matched with the group of children at FHR of schizophrenia by age, sex, and municipality.

EXPOSURES

Parental schizophrenia, bipolar disorder, or neither.

MAIN OUTCOMES AND MEASURES

Neurocognitive functioning was assessed with validated tests of intelligence, processing speed, attention, memory, verbal fluency, and executive functioning. Multilevel mixed-effects linear regression models with maximum likelihood estimation were used to estimate neurocognitive development from age 7 to 11 years.

RESULTS

At 4-year follow-up, a total of 451 children (mean [SD] age; 11.9 [0.2] years; 208 girls [46.1%]) underwent neurocognitive testing. There were a total of 170 children at FHR of schizophrenia (mean [SD] age, 12.0 [0.3]; 81 girls [47.7%]), 103 children at FHR of bipolar disorder (mean [SD] age, 11.9 [0.2] years; 45 girls [43.7%]), and 178 children in the PBC group (mean [SD] age, 11.9 [0.2] years; 82 girls [46.1%]). At either age 7 or 11 years or at both assessments, 520 children participated in the neurocognitive assessment and were therefore included in the analyses. When correcting for multiple comparisons, no statistically significant time × group interactions were observed across the 3 groups. Compared with the PBC group at 4-year follow-up, children at FHR of schizophrenia showed significant neurocognitive impairment in 7 of 24 neurocognitive measures (29.2%; Cohen d range, 0.29-0.37). Compared with children at FHR of bipolar disorder, children at FHR of schizophrenia had significant neurocognitive impairment in 5 of 24 measures (20.8%; Cohen d range, 0.29-0.38). Children at FHR of bipolar disorder and those in the PBC group did not differ significantly.

CONCLUSIONS AND RELEVANCE

In this cohort study, findings suggest that neurocognitive maturation was comparable across groups of children at FHR of schizophrenia or bipolar disorder compared with PBCs from age 7 to 11 years. Compared with the PBC group, children at FHR of schizophrenia demonstrated widespread, stable, neurocognitive impairments during this period, whereas children at FHR of bipolar disorder showed no neurocognitive impairments, which may indicate distinct neurodevelopmental pathways in children at FHR of schizophrenia and bipolar disorder.

Executive functions in 7-year-old children of parents with schizophrenia or bipolar disorder compared with controls: The Danish High Risk and Resilience Study-VIA 7, a population-based cohort study

Cognitive impairments are strongly associated with schizophrenia (SZ) and bipolar disorder (BP) with executive functions (EF) impairments as a likely key feature. Studies of everyday behavior rated EF in young children at familial high risk of SZ (FHR-SZ) are scarce and, to our knowledge, non-existent in young children at familial high risk of BP (FHR-BP). We aimed to compare everyday behavior-rated EF of FHR-SZ, FHR-BP, and control children. A nationwide population-based cohort of 522 7-year-old children with parents diagnosed with either SZ (N = 202) or BP (N = 120) and matched controls (N = 200) were recruited using the Danish national registries. The children's EF were assessed with the Behavior Rating Inventory of Executive Functions questionnaire rated by primary caregivers and teachers. According to primary caregiver assessments, FHR-SZ children displayed widespread EF impairments and had an odds ratio of 3.7 (2.0-6.9) of having clinically significant global EF impairments compared to controls. FHR-BP children were most severely impaired regarding EF related to emotional control and had an odds ratio of 2.5 (1.2-5.1) of clinically significant global EF impairments compared to controls. Teacher assessments were overall comparable to primary caregiver assessments but teachers rated more difficulties in the FHR-SZ group than primary caregivers. Already at age 7, children with a parental history of SZ or BP displayed significant impairments of EF in everyday-life situations. FHR-SZ children displayed widespread significant impairments of EF, whereas FHR-BP children were most severely impaired on emotional control. Clinicians should be aware of potential EF impairments in FHR children.

Neuropsychological development in the child and adolescent offspring of patients diagnosed with schizophrenia or bipolar disorder: A two-year follow-up comparative study

There has been growing scientific evidence in recent years that schizophrenia and bipolar disorder share clinical, cognitive, neuroimaging and genetic characteristics. This overlap might also be present in their offspring, who have an increased risk of developing both disorders. Comparing the characteristics of these samples may have important implications for understanding etiological processes. This study aimed to assess the development of cognitive functions over two years in a sample of child and adolescent offspring of patients diagnosed with schizophrenia (SZoff) or bipolar disorder (BDoff), comparing them with a community control group (CCoff).

METHODS

90 BDoff, 41 SZoff and 107 CCoff aged between 6 and 17 years were included at baseline. At the two-year follow-up, 84.9% of the sample was re-assessed (78 BDoff, 32 SZoff and 92 CCoff). All subjects were assessed with a comprehensive neuropsychological test battery at baseline and at the two-year follow-up to evaluate: intelligence quotient, working memory, processing speed, verbal memory and learning, visual memory, executive functions and sustained attention.

RESULTS

Processing speed, verbal memory and executive functions showed different developmental patterns among the SZoff, BDoff and CCoff groups. The SZoff group maintained baseline performances in the three variables over time, while the BDoff group presented improved processing speed and executive functioning and the CCoff group showed improvements in verbal memory and executive functions at follow-up.

CONCLUSIONS

These findings suggest that the development of some cognitive functions might differ between child and adolescent SZoff and BDoff, indicating different trajectories during neurodevelopment.

Clinical psychopathology in youth at familial high risk for psychosis

AIM

While the course of psychopathology has been explored from an index mental health diagnosis onwards, there are few detailed, prospective studies of the occurrence of clinical psychopathology in youth with familial risk for severe mental illnesses such as psychosis. We sought to describe the appearance of Axis I psychopathology in a unique sample of adolescents with a family history of schizophrenia (FHR).

METHODS

One hundred and sixty two first- and second-degree relatives (mean age 15.7 ± 3.6; range 8-25) of probands with schizophrenia or schizoaffective disorder were assessed at baseline and annual intervals for up to 3 years, focusing on Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) Axis I psychopathology.

RESULTS

Fourteen individuals (8.6%) developed a psychotic disorder. One hundred and five subjects (65%) met criteria for an Axis I disorder over the course of the study, the most common of which was a depressive episode (40 subjects; 25%). Of the 148 individuals who did not develop psychosis, 91 (61%) had one or more Axis I disorders compared with 10/14 converters who had a comorbid Axis I disorder (71%). Ordered by increasing age of onset, diagnoses included cognitive and externalizing disorders, anxiety disorders, affective disorders, substance use disorders and psychotic disorders.

CONCLUSIONS

In addition to an elevated risk of psychosis, young FHR relatives manifest a broad range of non-psychotic Axis I psychopathology in childhood and adolescence. This breadth of diagnoses has implications for the structure and function of mental health services for young people.

Variability of ecological executive function in children and adolescents genetically at high risk for schizophrenia: a latent class analysis

Executive impairments have been observed both in patients with schizophrenia and in their unaffected first-degree relatives. Very few studies have investigated neurocognitive subgroups in unaffected first-degree relatives and in healthy participants using data-driven methods. The study included a high-risk group consisting of 100 unaffected young offspring and siblings of patients with schizophrenia and 198 healthy controls, all aged between 9 and 23 years. Executive function, victimization, and emotional and behavioral problems of participants were assessed by a series of self-report scales. Neurocognitive subgroups were investigated using latent class analysis of executive function measures. Four neurocognitive clusters were identified: a good performance cluster, a good self-control cluster, a low self-control cluster, and a severe impairment cluster. Participants in severe impaired executive function cluster reported a significantly higher level of victimization and had more prominent emotional and behavioral problems than the good performance cluster. Neurocognitive differences between high-risk young people and healthy controls were driven by individuals who have severe and global, rather than selective, executive deficits. Our results may provide clues to an explanation of the mechanisms behind executive impairments in young individuals at genetic risk and help to identify new targets for early interventions.

Schizotypal traits and cognitive performance in siblings of patients with psychosis

INTRODUCTION

Schizotypy has been proposed to be the expression of genetic vulnerability to schizophrenia. The available literature shows cognitive similarities between schizotypy and schizophrenia, with mildly impaired performance being associated with schizotypy. This study aims to determine the relationship between schizotypy and cognitive performance in siblings of patients with psychosis.

METHODS

Schizotypal features and cognitive performance on a neuropsychological battery were compared between 48 siblings of patients with psychosis and 44 healthy controls. The relationships between schizotypy and cognitive performance were analysed by controlling the condition of being a sibling.

RESULTS

Siblings showed poorer performance on vigilance/sustained attention (M = 37.6; SD = 7.1) and selective attention/interference control/working memory (M = 23.28; SD = 2.7) tasks. The variance in vigilance/sustained attention performance was explained, at 30%, by the interpersonal factor of schizotypy on the suspiciousness dimension and the condition of being a sibling.

CONCLUSIONS

Interpersonal features of schizotypy in siblings of patients with psychosis are associated with deficits in vigilance/sustained attention performance.

Are there glutamate abnormalities in subjects at high risk mental state for psychosis? A review of the evidence

New approaches to underlying alterations in psychosis suggest increasing evidence of glutamatergic abnormalities in schizophrenia and an association between these abnormalities and certain core psychopathological alterations such as cognitive impairment and negative symptoms. Proton magnetic resonance spectroscopy ((1)H MRS) is an MR-based technique that enables investigators to study glutamate function by measuring in vivo glutamatergic indices in the brain. In this article we review the published studies of (1)H MRS in subjects with an at-risk mental state (ARMS) for psychosis. The primary aim was to investigate whether alterations in glutamate function are present before the illness develops in order to expand our understanding of glutamatergic abnormalities in prodromal phases. Three databases were consulted for this review. Titles and abstracts were examined to determine if they fulfilled the inclusion criteria. The reference lists of the included studies were also examined to identify additional trials. Eleven final studies were included in this review. Significant alterations in glutamate metabolites across different cerebral areas (frontal lobe, thalamus, and the associative striatum) in subjects with an ARMS for psychosis are reported in six of the trials. A longitudinal analysis in two of these trials confirmed an association between these abnormalities and worsening of symptoms and final transition to psychosis. Considering that five other studies found no significant differences across these same areas, we can conclude that more research is needed to confirm glutamatergic abnormalities in subjects with an ARMS for psychosis. However, future research must overcome the methodological limitations of existing studies to obtain reliable results.

Neurocognitive Functioning in Schizophrenia, their Unaffected Siblings and Healthy Controls: A Comparison

AIM

Neurocognitive functions are considered to be reliable endophenotypes for schizophrenia. This study aimed to study the neurocognitive functioning of unaffected siblings of patients with schizophrenia and compare the same with a group of patients with schizophrenia and a group of healthy controls.

MATERIALS AND METHODS

Three study groups, that is, unaffected siblings of patients with schizophrenia, patients of schizophrenia and healthy controls, each group comprising of 20 participants were evaluated on Wisconsin Card Sorting Test, Brief Visuospatial Memory Test-Revised, Hopkins Verbal Learning Test-Revised, Wechsler Adult Intelligence Scale and Digit Symbol Test.

RESULTS

Compared to healthy controls, unaffected siblings of patients with schizophrenia performed poorly on the tests of short-term verbal learning and memory, but no significant differences were seen between the two groups for executive functions, visual learning and psychomotor speed, concentration and graphomotor abilities. However, when compared with patients with schizophrenia, unaffected siblings performed poorly on the tests of executive functions, visual memory, verbal memory, psychomotor speed, concentration and graphomotor abilities.

CONCLUSION

Cognitive markers like verbal memory deficits can distinguish unaffected siblings of schizophrenia from healthy controls and serve as an endophenotype for schizophrenia.

Ecological assessment of executive functions in adolescents genetically at high risk for schizophrenia

OBJECTIVE

This study sought to examine specific executive deficits in the real-life environment among adolescents genetically at high risk for schizophrenia and understand the role of the genetic risk, victimization and family functioning, and their interaction on the deficits.

METHODS

The study included 96 non-affected adolescent offspring and siblings of patients with schizophrenia in the high-risk group (HR) and 193 healthy adolescents in the healthy control group (HC), all aged between 9 and 20 years. All participants completed assessments of executive functions (EFs), victimization, and family functioning.

RESULTS

The multivariate analysis revealed that the HR group reported more difficulties on the Shift, Plan/Organize, and Task Completion scale than the HC group. Significant main effects were also detected for victimization level on all domains of EFs and for adaptability level on Inhibit, Working Memory, Plan, and Task Completion scales. Besides, the group×victimization level interactions were significant for Working Memory and Task Completion scales. Hierarchical regression analysis revealed that the genetic risk and victimization were predictors of executive deficits.

CONCLUSIONS

The HR group showed impaired EFs in the everyday environment. And, the genetic risk for schizophrenia and victimization may be related to executive dysfunction. Our results may provide clues about explaining the mechanisms of executive impairments in the HR group and help to identify new targets for early interventions.

Brain metabolite alterations in young adults at familial high risk for schizophrenia using proton magnetic resonance spectroscopy

BACKGROUND

Proton magnetic resonance spectroscopy ((1)H MRS) enables in-vivo measurement of several relevant brain metabolites and has provided evidence of a range of neurochemical abnormalities in schizophrenia, especially in glutamate and N-acetyl-aspartate (NAA). While individuals at high familial risk for schizophrenia (HR) exhibit some neurobiological findings observed in the disorder, (1)H MRS findings and their clinical correlates are not well characterized in this population.

METHODS

We compared 23 adolescent and young adult offspring of schizophrenia patients with 24 age- and sex-matched healthy controls using (1)H MRS. We acquired multi-voxel, short TE (1)H MRS measurements at 1.5T and obtained metabolite concentrations of N-acetyl-aspartate (NAA), combined glutamate and glutamine (Glu+Gln) and choline-containing compounds (GPC+PC) for the left and right thalamus, anterior cingulate gyrus, and caudate. We also assessed the relationship between regional metabolite levels, clinical measures and brain volume in a subset of 16 high-risk and 15 control subjects.

RESULTS

Compared to healthy controls, high-risk subjects showed reductions in NAA levels in all three regions (thalamus, caudate, and anterior cingulate cortex), increases in Glu+Gln in the thalamus and caudate, and increases in GPC+PC in the anterior cingulate. In HR, thalamic Glu+Gln concentration was positively correlated and thalamic NAA inversely correlated with measures of schizotypy. Anterior cingulate GPC+PC and caudate Glu+Gln were significantly correlated with attenuated psychotic symptom severity. Anterior cingulate NAA was correlated with executive function.

CONCLUSIONS

Our data suggest the occurrence of metabolic alterations in young relatives of schizophrenia patients similar to those seen in patients with established illness. The observed correlations with cognitive deficits and psychosis-related psychopathology suggest that these metabolic measures may have value as biomarkers of risk for schizophrenia.

Rethinking schizophrenia in the context of normal neurodevelopment

The schizophrenia brain is differentiated from the normal brain by subtle changes, with significant overlap in measures between normal and disease states. For the past 25 years, schizophrenia has increasingly been considered a neurodevelopmental disorder. This frame of reference challenges biological researchers to consider how pathological changes identified in adult brain tissue can be accounted for by aberrant developmental processes occurring during fetal, childhood, or adolescent periods. To place schizophrenia neuropathology in a neurodevelopmental context requires solid, scrutinized evidence of changes occurring during normal development of the human brain, particularly in the cortex; however, too often data on normative developmental change are selectively referenced. This paper focuses on the development of the prefrontal cortex and charts major molecular, cellular, and behavioral events on a similar time line. We first consider the time at which human cognitive abilities such as selective attention, working memory, and inhibitory control mature, emphasizing that attainment of full adult potential is a process requiring decades. We review the timing of neurogenesis, neuronal migration, white matter changes (myelination), and synapse development. We consider how molecular changes in neurotransmitter signaling pathways are altered throughout life and how they may be concomitant with cellular and cognitive changes. We end with a consideration of how the response to drugs of abuse changes with age. We conclude that the concepts around the timing of cortical neuronal migration, interneuron maturation, and synaptic regression in humans may need revision and include greater emphasis on the protracted and dynamic changes occurring in adolescence. Updating our current understanding of post-natal neurodevelopment should aid researchers in interpreting gray matter changes and derailed neurodevelopmental processes that could underlie emergence of psychosis.

Neurocognitive profile and its association with psychopathology in first-degree relatives of patients with schizophrenia. a case-control study

BACKGROUND

People with schizophrenia show a broad range of neurocognitive deficits, which are considered as core features of the disorder and are thought to be partly heritable. Similar deficits, albeit at a lesser degree, have been also found in their healthy biological relatives. These deficits, if better characterized, might represent underlying vulnerable traits for psychosis.

METHODS

This case-control study compared neurocognitive functioning of adult first-degree relatives of patients with schizophrenia (SCZ-RELs) (n=55) with healthy control subjects (n=55) and explored its association with the negative symptoms. Subjects in both study and control group were assessed with an extensive neurocognitive test battery (Trail Making test, Phonemic Verbal fluency, Wisconsin Card Sorting Test, Bushke Fuld Test, Stroop Test, n-Back and Digit span) and a set of clinical measures (SANS, GAF and DAS).

RESULTS

SCZ-RELs were more significantly impaired on executive function tasks (i.e. Wisconsin Card Sorting Test and the Phonemic Verbal fluency) and displayed significantly more severe negative symptoms and poorer social functioning than control subjects. Significant correlations between neurocognitive measures and negative symptoms were found in the study group, whereas no significant correlations were detected among the controls.

DISCUSSION

Subtle executive impairments, associated with negative symptoms, are shown to be evident in healthy relatives of patients with schizophrenia. These deficits, which reflect subtle dysfunction in concept formation, flexibility and mental shifting, may be seen as potential phenotypic markers of vulnerability for schizophrenia. This raises the question of underlying prefrontal dysfunction as core feature of the disorder.

Early prodromal symptoms can predict future psychosis in familial high-risk youth

BACKGROUND

Efforts to predict psychosis in individuals at high risk for schizophrenia have focused on the identification of sub-threshold clinical criteria and neurobiological markers, including neuropsychological assessment, structural and functional brain imaging, and psychophysiological testing. We sought to evaluate the relative utility of "psychosis-proneness" measures for prospective prediction of psychotic disorders in a group of young relatives at familial risk for schizophrenia.

METHODS

We examined the receiver operating characteristics of sub-threshold symptoms in predicting conversion to psychosis in a group of 97 young first- and second- degree relatives of persons with schizophrenia over a 2-year period. Towards this end, we utilized the Structured Interview of prodromal symptoms to derive measures of two of the four Scale of Prodromal Symptoms subscales (positive and disorganized) and the Chapman Magical Ideation and Perceptual Aberration scales. These four measures were, together, taken to reflect a putative index of psychosis-proneness.

RESULTS

Eleven of the 97 subjects developed a psychotic disorder over 2 years of follow-up. Seventeen of the 97 subjects tested positive on this index of psychosis-proneness at baseline and of these 10 converted to psychosis. The sensitivity and specificity of the test were 91 percent and 92 percent respectively. The positive predictive value of the test was 59 percent and its negative predictive value was 99 percent. Addition of measures of cognitive or social function to the index decreased its predictive ability, reducing its specificity and/or sensitivity.

CONCLUSIONS

A relatively simple set of clinical measures can be utilized to prospectively identify familial high risk individuals who convert to psychosis with high specificity and sensitivity. Implications for the proposed addition of an "attenuated psychosis syndrome" in DSM-5 are discussed.

Hypomethylation of the serotonin receptor type-2A Gene (HTR2A) at T102C polymorphic site in DNA derived from the saliva of patients with schizophrenia and bipolar disorder

Several lines of evidence indicate that dysfunction of serotonin signaling and HTR2A receptor are involved in the pathogenesis of schizophrenia (SCZ) and bipolar disorder (BD). DNA methylation of HTR2A at T102C polymorphic site influences HTR2A expression and aberrant DNA methylation of HTR2A promoter was reported in postmortem brain of patients with SCZ and BD. Hypothesizing that the brain's epigenetic alteration of HTR2A may also exist in peripheral tissues that can be used as a diagnostic/therapeutic biomarker, we analyzed HTR2A promoter DNA methylation in DNA extracted from the saliva of patients with SCZ and BD, and their first degree relatives versus normal controls. Bisulfite sequencing was used to screen DNA methylation status of the HTR2A promoter CpGs and qMSP was used to quantify the degree of cytosine methylation at differentially methylated sites. Most of the cytosines of the HTR2A promoter were unmethylated. However, CpGs of the -1438A/G polymorphism site, -1420 and -1223 were >95% methylated. The CpG at T102C polymorphic site and neighboring CpGs were ∼70% methylated both in the patients and controls. qMSP analysis revealed that the cytosine of the T102C polymorphic site was significantly hypo-methylated in SCZ, BD, and their first degree relatives compared to the controls. Cytosine methylation of HTR2A at T102C polymorphic site in DNA derived from the saliva can potentially be used as a diagnostic, prognostic, and/or therapeutic biomarker in SCZ and BD. However, these preliminary observations need to be replicated in other populations with a larger sample size to be considered for clinical applications.

Calcyon upregulation in adolescence impairs response inhibition and working memory in adulthood

Calcyon regulates activity-dependent internalization of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) glutamate receptors and long-term depression of excitatory synapses. Elevated levels of calcyon are consistently observed in brains from schizophrenic patients, and the calcyon gene is associated with attention-deficit hyperactivity disorder. Executive function deficits are common to both disorders, and at least for schizophrenia, the etiology appears to involve both heritable and neurodevelopmental factors. Here, we show with calcyon-overexpressing Cal(OE) transgenic mice that lifelong calcyon upregulation impairs executive functions including response inhibition and working memory, without producing learning and memory deficits in general. As response inhibition and working memory, as well as the underlying neural circuitry, continue to mature into early adulthood, we functionally silenced the transgene during postnatal days 28-49, a period corresponding to adolescence. Remarkably, the response inhibition and working memory deficits including perseverative behavior were absent in adult Cal(OE) mice with the transgene silenced in adolescence. Suppressing the calcyon transgene in adulthood only partially rescued the deficits, suggesting calcyon upregulation in adolescence irreversibly alters development of neural circuits supporting mature response inhibition and working memory. Brain regional immunoblots revealed a prominent downregulation of AMPA GluR1 subunits in hippocampus and GluR2/3 subunits in hippocampus and prefrontal cortex of the Cal(OE) mice. Silencing the transgene in adolescence prevented the decrease in hippocampal GluR1, further implicating altered fronto-hippocampal connectivity in the executive function deficits observed in the Cal(OE) mice. Treatments that mitigate the effects of high levels of calcyon during adolescence could preempt adult deficits in executive functions in individuals at risk for serious mental illness.

Early and broadly defined psychosis risk mental states

Current definitions of the prodromal (or at-risk mental state) phase of schizophrenia include attenuated and/or transient psychotic symptoms as well as a combination of different risk indicators and a recent significant deterioration in global functioning. Data accumulated to date suggest rates of conversion to frank psychosis within two years in 25 to 40% of cases supporting the validity of these criteria. However, at this late phase of illness, functional deterioration is often already pronounced, highlighting the need for earlier identification. Moreover, negative symptoms and social impairments, cognitive deficits, other non-psychotic psychopathology and/or functional decline and non-specific biological indicators, often can be detected well before the at-risk mental state as currently defined; indicating that a broad characterization of an earlier stage may be possible. Identifying specific criteria to define this group of individuals, starting from the framework of familial high-risk, can help define a broader group of people, including earlier at-risk mental states, for future research. The hope is that this research will help facilitate intervention at earlier stages that may in turn minimize functional deterioration, and delay, attenuate or even prevent transition to psychosis. The disadvantages as well as the potential benefits of this approach are discussed.