Evaluation of spontaneous dense array gamma oscillatory activity and minor physical anomalies as a composite neurodevelopmental endophenotype in schizophrenia

Resting-state EEG and MEG gamma frequencies in schizophrenia: a systematic review and exploratory power-spectrum metanalysis

The hypoactivity of parvalbumin-containing interneurons (PV-interneurons) is a pathogenetic mechanism of schizophrenia according to the glutamatergic theory, and PV-interneurons are necessary for the generation of EEG/MEG gamma-frequencies (30-100 Hz). The present study aims to a literature synthesis on resting-state gamma-frequency changes in patients with schizophrenia vs healthy controls, and to examine the relationship between these changes and severity of symptoms. A protocol was enregistered in PROSPERO and a systematic search was conducted in PubMed, PsycINFO and Cochrane Database of Systematic Reviews, following PRISMA guidelines. An exploratory metanalysis was realized. Out of 1391 records, 43 were included for a qualitative synthesis (N = 2133 [11-185], females 37.4%, age 33.9 ± 9.2). Results on power spectra were heterogeneous: in 12 studies gamma power was increased, involving the whole brain (N = 3), multiple regions (N = 6) or only frontal (N = 1), central (n = 1) and temporal (N = 1) areas; in 3 studies gamma power was reduced, involving multiple areas (N = 2) or the right temporal region (N = 1); one study revealed mixed results and 13 studies showed no differences. The meta-analysis on 4 studies (N = 211) showed non-significant differences between patients and controls and a large heterogeneity. The functional connectivity picture consists of sparse patterns of decreases and/or increases, widespread to multiple regions. Relationships emerged between gamma power and connectivity and severity of psychotic and cognitive symptoms. Theta-gamma coupling was increased in patients, with limited evidence for other changes in phase-amplitude coupling. Resting-state gamma-frequencies alterations in schizophrenia were inconsistent across studies; the heterogeneity of patients and methods could partially explain this outcome.

Identification of youth at clinical high-risk for psychosis: A community-based study from India

AIM

A two-stage process, wherein self-report screening precedes the structured interview, is suggested for identifying individuals at clinical high-risk for psychosis (CHR-P) in community samples. Aim of this study was to screen a community youth sample from India for CHR-P using the two-stage method. Specific objectives were to assess concordant validity of the self-report measure and predictive validity of the two-stage method.

METHODS

Based on probability sampling, 2025 youth aged 15-24 years were recruited from one rural and one urban area of Telangana, a Telugu-speaking state in India. Telugu version of the PRIME Screen-Revised (PS-R) and structured interview for psychosis-risk syndromes (SIPS) were used. CHR-P positive and negative cohorts were followed-up for transition to psychosis at 3-monthly intervals.

RESULTS

One hundred ten individuals screened positive on PS-R. SIPS conducted on 67 out of 110 individuals confirmed 62 (92.54%) to be CHR-P positive. PS-R showed 98.41% sensitivity and 90.74% specificity. Among CHR-P positive, three participants transitioned to psychosis in 15 months. The hazard ratio for psychosis transition was 11.4.

CONCLUSIONS

Screening accuracy of PS-R in the community youth sample in Telangana is optimum. The hazard ratio for psychosis transition in the community identified CHR-P indicates good predictive validity for the two-stage method.

Minor physical anomalies in schizophrenia and first-degree relatives in comparison to healthy controls: A systematic review and meta-analysis

Minor physical anomalies (MPAs) are anatomical variations that are markers of aberrant early neurodevelopment. Schizophrenia is associated with increased MPA frequency, however, the frequency and distribution of MPAs exhibit substantial heterogeneity in schizophrenia and are not exclusive to this disorder. MPAs at different localizations might represent different developmental origins and might be related to latent genetic predisposition or vulnerability to develop full-blown psychosis. Therefore, we conducted a thorough review of minor physical anomalies (MPAs) in schizophrenia (Sch) and first-degree relatives (SchRel). Analyzing 52 studies published from January 1980 to October 2023, the meta-analysis compared MPA scores between 3780 schizophrenia patients and 3871 controls, as well as 1415 SchRel and 1569 controls. The total MPA score was significantly increased in schizophrenia compared to controls (g = 0.78 [0.63-0.93], p<0.001). In regional MPA meta-analyses, effect sizes ranged from 0.56 to 0.78. The difference between SchRel and controls was moderate (g = 0.44 [0.28-0.61], p<0.001). When individual MPA items were analyzed separately, fine electric hair, malformed ear, asymmetrical ear, curved 5th finger were anomalies that were shared between both schizophrenia and SchRel. Also, direct comparisons of the frequency of MPAs in schizophrenia and their relatives were conducted. Additionally, the early age of onset of schizophrenia was associated with mouth anomalies (Z=-2.13, p = 0.03), and ear anomalies were associated with a higher percentage of males in the schizophrenia group (Z = 2.64, p = 0.008). These findings support the notion that different MPAs might be associated with genetic susceptibility as well as vulnerability to developing full-blown psychosis. Studies investigating clinical and neurobiological correlates of MPAs in schizophrenia might be helpful in characterizing subtypes of psychoses that are associated with different developmental processes.

Cognitive impairment in 'non-user' first-degree relatives of persons with cannabis dependence syndrome: A pilot, endophenotype study

INTRODUCTION

Cannabis use disorders are global emerging problem nowadays, with high prevalence and morbidity. Cognitive impairments, and also corresponding genetic vulnerability, has been fairly replicated in individuals with cannabis dependence. However, there are few studies that assess cognitive functioning as an endophenotype or a trait marker for cannabis dependence. While the primary objective of this study was to assess the endophenotype pattern of cognitive dysfunction in cannabis dependence, assessing the association between the degree of cognitive functioning, and their socio-demographic and clinical variables in the cannabis dependence patients and their first-degree relatives was the secondary objective.

METHODOLOGY

We compared cognitive functioning across three groups- patients with cannabis dependence syndrome, their 'non-user' first-degree relatives and healthy controls, with 30 participants in each group. Five cognitive domains- attention and concentration, verbal fluency, memory, visuospatial ability and executive functions were assessed. We assessed for endophenotype pattern of statistical significance in pairwise analyses of Kruskal-Wallis test, which was corrected for multiple comparisons. Subsequently, correlation analysis to assess association of cognitive impairment with socio-demographic and clinical variables was conducted.

RESULTS

Although impairment in attention and executive functions also was seen in patients with cannabis dependence, endophenotype pattern of statistical significance in pairwise analyses, with impairment in first-degree relatives too, was seen in all sub-scores of verbal fluency and verbal memory. None of the correlations were significant.

CONCLUSION

'Non-user' first-degree relatives of patients with cannabis dependence too show significant cognitive impairment. Verbal fluency and verbal memory are possible endophenotypes or trait markers for cannabis dependence syndrome.

"Efficacy of intensive bilateral Temporo-Parietal Continuous theta-burst Stimulation for Auditory VErbal hallucinations (TPC-SAVE) in schizophrenia: A randomized sham-controlled trial"☆

Transcranial magnetic stimulation (TMS) is a non-invasive tool that moderates specific brain regions to ameliorate auditory verbal hallucinations (AVH) in schizophrenia. Citing the critical involvement of temporoparietal cortex (TPC) in AVH, our study aimed to evaluate the effect of continuous theta burst stimulation (cTBS) targeting bilateral TPC in schizophrenia subjects with AVH, on a randomized rater blinded placebo control trial. 59 patients were randomly allocated to active and sham groups. They received 20 cTBS sessions (2 per day: first right TPC, then left TPC) 5 days a week for 2 weeks. PANSS (Positive and Negative Syndrome Scale), AVHRS (Auditory vocal hallucination rating scale), PSYRAT-AH (Psychiatric symptoms rating scale- Auditory hallucinations scale), CDSS (Calgary depression scale for schizophrenia), SCoRS (Schizophrenia cognition rating scale) and CGI-S (Clinical global impression-severity) were rated at baseline, immediately post 20th session and 2 weeks post-TBS. 50 patients (25-active, 25-sham) completed the study. Conducting an intention to treat analysis, we found a significant group*time effect for PANSS, AVHRS, PSYRAT-AH, CDSS, SCoRS, CGI-S but when controlled for confounding variables and multiple comparisons, only PANSS-PS (F=26.617, p < 0.001), PANSS-TOTAL (F=23.671, p < 0.001), AVHRS (F=17.779, p < 0.001), PSYRAT-AH (F=11.385, p < 0.001) and CGI-S (F=28.462, p < 0.001) retained significance. We conclude that cTBS over TPC is safe and has efficacy in treating AVH in schizophrenia. Limited sample size and lack of integrity assessment for blinding in the study participants are major limitations of the study.

Minor Physical Anomalies in Bipolar Disorder-A Meta-Analysis

Introduction: Minor physical anomalies (MPAs) may reflect basic neurobiological features underlying bipolar disorders (BPD), as they are sensitive physical indicators of morphogenetic failure of the brain. Despite several researches about the presence of MPAs in BPD, the results are still controversial. Objectives: The aim of the present meta-analysis was to assess the standardized weighted mean effect sizes of MPAs in BPD and to examine if MPAs may be found predominantly in the head and/or facial regions in BPD patients compared to controls (HC). Methods: Four studies, involving 155 patients with BPD, and 187 HC, were involved in the analysis after searching the literature. For the investigation of MPAs in the peripheral (MPA-P) and in the head and facial regions (MPA-CF), two studies involving 121 BPD patients, and 133 HC passed the inclusion criteria. Results: The number of the MPAs in the BPD group was significantly higher compared to HC. Another important finding of the present study is that BPD patients' MPA-P scores do not significantly differ from those of the HC. In contrast, BPD patients' MPA-CF scores were found to be significantly higher compared to HC subjects. It is important to note that there was a low number of eligible publications included, which caused higher heterogeneity. Conclusions: Low quality of evidence suggests that MPAs are more common in patients with BPD than in HC and the higher rate of MPAs is found predominantly in the head and facial regions.

Evaluation of N-400 Evoked Response Potential in schizophrenia: An endophenotype or a disease marker?

N400 evoked response potentials (ERP) reliably map key semantic deficits in schizophrenia. Assessing them as endophenotypes might help in better understanding of schizophrenia risk and their use as biomarkers. We aimed to study N400 as an endophenotype marker by comparing schizophrenia (SCZ), unaffected first-degree relatives (FDR) and healthy controls (HC) and, by assessing its ability to discriminate these groups. Drug naïve or free SCZ probands (n=30), their unaffected FDRs (n=30) and HC (n=30), underwent a 40-channel ERP recording while performing a custom-made, Hindi- sentence context paradigm task, containing congruent and incongruent conditions. Fifteen centro-parietal (CP) leads, further classified into three regions-midline (CPM), right (CPR) and left (CPL) were selected as electrodes-of-interest for assessing N400. During the incongruent condition, compared to both FDRs and HC, SCZ showed significantly longer N400 latency, at CPM, CPR and CPL, and significantly lesser (more negative) amplitude, at CPM; no significant difference was noted between FDR and HC groups. On discriminant functional analysis, significant N400 predictors could accurately classify 73.3% SCZ from HC and 75% of SCZ from FDR. We conclude that N400 deficits, elicited by the incongruent condition of the sentence task, could be potential biomarkers to define disease state in schizophrenia; they may not be endophenotype markers.

Increased Prevalence of Minor Physical Anomalies Among the Healthy First-Degree Relatives of Bipolar I Patients - Results With the Méhes Scale

Minor physical anomalies are somatic markers of aberrant neurodevelopment, so the higher prevalence of these signs among the relatives of bipolar I patients can confirm minor physical anomalies as endophenotypes. The aim of the study was to evaluate the prevalence of minor physical anomalies in first-degree healthy relatives of patients with bipolar I disorder compared to normal control subjects. Using a list of 57 minor physical anomalies (the Méhes Scale), 20 first-degree unaffected relatives of patients with the diagnosis of bipolar I disorder and as a comparison 20 matched normal control subjects were examined. Minor physical anomalies were more common in the ear, head, mouth and trunk regions among the relatives of bipolar I patients compared to normal controls. By the differentiation of minor malformations and phenogenetic variants, we have found that both minor malformations and phenogenetic variants were more common among the relatives of bipolar I patients compared to the control group, while individual analyses showed, that one minor malformation (sole crease) and one phenogenetic variant (high arched palate) were more prevalent in the relative group. This is the first report in literature on the increased prevalence of minor physical anomalies among the first-degree unaffected relatives of bipolar I patients. The study support the concept, that minor physical anomalies can be endophenotypic markers of bipolar I affective disorder.

Social cognitive endophenotypes in schizophrenia: A study comparing first episode schizophrenia patients and, individuals at clinical- and familial- 'at-risk' for psychosis

Impairments in specific domains of social cognition have been suggested as possible endophenotypes for schizophrenia and clinical markers for accurate identification of 'at-risk' (AR) states. Aim of the present study was to find out whether performance on social cognition tasks will distinguish 'clinical at-risk (CAR)' and 'familial at-risk (FAR)' individuals from remitted first episode schizophrenia (FES) patients and healthy controls. Fifty in each of these four groups were included for analysis. Schizophrenia psychopathology in FES group was assessed using the Positive and Negative Syndrome Scale (PANSS). Theory of mind (ToM; first and second order (SOT and FOT), and faux pas composite (FPC)), attributional bias (AB) and social perception (SP) were assessed using the Social Cognition Rating Tool in Indian Setting (SOCRATIS). Facial emotion recognition task was used to assess emotional-expression recognition (ER). Significant differences in ToM, SP and ER between the four groups were found, even after controlling for performance on various neurocognitive tasks. ToM and SP were identified to follow an endophenotype pattern. While, both ToM and SP classified FES from healthy with large accuracy rates, SP, specifically, distinguished at-risk from disease groups. None of the social cognitive domains accurately classified familial at-risk from clinical at-risk groups. We conclude that social cognitive measures may be used as reliable endophenotype markers for schizophrenia and its sub-domains may be used for valid identification of AR individuals.

Alterations in resting-state gamma activity in patients with schizophrenia: a high-density EEG study

Alterations of EEG gamma activity in schizophrenia have been reported during sensory and cognitive tasks, but it remains unclear whether changes are present in resting state. Our aim was to examine whether changes occur in resting state, and to delineate those brain regions where gamma activity is altered. Furthermore, we wanted to identify the associations between changes in gamma activity and psychopathological characteristics. We studied gamma activity (30-48 Hz) in 60 patients with schizophrenia and 76 healthy controls. EEGs were acquired in resting state with closed eyes using a high-density, 256-channel EEG-system. The two groups were compared in absolute power measures in the gamma frequency range. Compared to controls, in patients with schizophrenia the absolute power was significantly elevated (false discovery rate corrected p < 0.05). The alterations clustered into fronto-central and posterior brain regions, and were positively associated with the severity of psychopathology, measured by the PANSS. Changes in gamma activity can lead to disturbed coordination of large-scale brain networks. Thus, the increased gamma activity in certain brain regions that we found may result in disturbances in temporal coordination of task-free/resting-state networks in schizophrenia. Positive association of increased gamma power with psychopathology suggests that altered gamma activity provides a contribution to symptom presentation.

Social anhedonia and gamma band abnormalities as a composite/multivariate endophenotype for schizophrenia: a dense array EEG study

AIM

Social anhedonia and gamma band oscillations are proposed as a promising endophenotype for schizophrenia (SZ). The aim was to assess whether social anhedonia and spontaneous gamma band oscillations could be used as multivariate/composite endophenotypic measures for SZ.

METHODS

Sixty consented subjects, of which 20 remitted SZ patients, 20 unaffected siblings of patients with schizophrenia (US) and 20 healthy controls (HC) were recruited for the study. The Revised Social Anhedonia Scale, Temporal Experience of Pleasure Scale and the Schizotypal Personality Questionnaire assessed social anhedonia, temporal experience of pleasure and schizotypal features. All participants underwent awake, resting state 192-channel dense array electroencephalographic recording. Gamma spectral power and coherence were calculated. We performed chi-square test, one-way analysis of variance, Pearsons correlation coefficient and step-by-step linear discriminant functional analysis.

RESULTS

Social anhedonia was significantly higher and anticipatory aspects of pleasure were significantly lower in both SZ and US compared with HC. US scored significantly higher than HC in the Schizotypal Personality Questionnaire. Spectral power of high gamma band (>70 Hz) was significantly lower over the right temporo-parietal and midline regions in both SZ and US than HC. We accurately classified (85%) three groups when social anhedonia, high gamma band spectral power of midline, right frontal and right fronto-temporal interhemispheric gamma coherence were considered as composite measures rather than each variable representing independently.

CONCLUSION

We propose region-specific high gamma spectral 'power and coherence' and social anhedonia as composite/multivariate measures could be a useful measure in distinguishing schizophrenia patients and unaffected siblings from healthy controls.

Effects of Ketamine on Resting-State EEG Activity and Their Relationship to Perceptual/Dissociative Symptoms in Healthy Humans

N-methyl-D-aspartate (NMDA) receptor antagonists administered to healthy humans results in schizophrenia-like symptoms, which preclinical research suggests are due to glutamatergically altered brain oscillations. Here, we examined resting-state electroencephalographic activity in 21 healthy volunteers assessed in a placebo-controlled, double-blind, randomized study involving administration of either a saline infusion or a sub-anesthetic dose of ketamine, an NMDA receptor antagonist. Frequency-specific current source density (CSD) was assessed at sensor-level and source-level using eLORETA within regions of interest of a triple network model of schizophrenia (this model posits a dysfunctional switching between large-scale Default Mode and Central Executive networks by the monitor-controlling Salience Network). These CSDs were measured in each session along with subjective symptoms as indexed with the Clinician Administered Dissociative States Scale. Ketamine-induced CSD reductions in slow (delta/theta and alpha) and increases in fast (gamma) frequencies at scalp electrode sites were paralleled by frequency-specific CSD changes in the Default Mode, Central Executive, and Salience networks. Subjective symptoms scores were increased with ketamine and ratings of depersonalization in particular were associated with alpha CSD reductions in general and in specific regions of interest in each of the three networks. These results tentatively support the hypothesis that pathological brain oscillations associated with hypofunctional NMDA receptor activity may contribute to the emergence of the perceptual/dissociate symptoms of schizophrenia.

Minor physical anomalies are more common among the first-degree unaffected relatives of schizophrenia patients - Results with the Méhes Scale

Minor physical anomalies are external markers of abnormal brain development,so the more common appearance of these signs among the relatives of schizophrenia patients can confirm minor physical anomalies as intermediate phenotypes. The aim of the present study was to investigate the rate and topological profile of minor physical anomalies in the first-degree unaffected relatives of patients with schizophrenia compared to matched normal control subjects. Using a list of 57 minor physical anomalies (the Méhes Scale), 20 relatives of patients with the diagnosis of schizophrenia and as a comparison 20 matched normal control subjects were examined. Minor physical anomalies were more common in the head and mouth regions among the relatives of schizophrenia patients compared to normal controls. By the differentiation of minor malformations and phenogenetic variants, we have found that only phenogenetic variants were more common in the relatives of schizophrenia patients compared to the control group, however individual analyses showed, that one minor malformation (flat forehead) was more prevalent in the relative group. The results can promote the concept, that minor physical anomalies can be endophenotypic markers of the illness.

Schneiderian first rank symptoms in schizophrenia: A developmental neuroscience evaluation

INTRODUCTION

Self disorders in schizophrenia have been suggested to have distinct neurobiological underpinnings. Using comprehensive neuro-scientific assessments including a neurophysiological, a neurochemical and a neuropsychological marker, this study assesses disordered-"self" in schizophrenia.

METHODS

Twenty schizophrenia patients with first rank symptoms (FRS;FRS+), 20 patients without FRS (FRS-) and 20 healthy controls (HC) were assessed for psychopathology, especially on specially designed FRS score sheets with a narrow and a broad definition. Resting state electroencephalography was acquired using 256-electrodes; gamma spectral-power was measured in 8 regions of interest. Serum BDNF and self-monitoring were also assessed. Comparative and correlation analysis were conducted in addition to a step-wise discriminant function analysis.

RESULTS

FRS+ group with greater positive symptom score and a lower negative symptom score, showed significantly increased gamma spectral power, especially on right hemispheric regions, along with lower BDNF levels and lower scores on self-monitoring compared to FRS- and HC. Serum BDNF levels and gamma spectral power in the region corresponding right inferior parietal lobule were identified as predictors that most accurately classified the defined groups.

CONCLUSIONS

Schizophrenia patients satisfying the criteria of presence of first rank symptoms represent a distinct neurodevelopmental subgroup with associated features of predominantly positive symptoms, significantly lower neurotrophin levels, aberrant resting state brain activity in the heteromodal association cortex and performing poorer on self-monitoring tasks.