Developmental trajectories of subcortical structures in relation to dimensional schizotypy expression along adolescence

Neuropsychology and Neurobiology of Negative Schizotypy: A Selective Review

Schizotypy refers to a latent personality organization that reflects liability to schizophrenia. Because schizotypy is a multidimensional construct, people with schizotypy vary in behavioral and neurobiological features. In this article, we selectively review the neuropsychological and neurobiological profiles of people with schizotypy, with a focus on negative schizotypy. Empirical evidence is presented for alterations of neuropsychological performance in negative schizotypy. We also cover the Research Domain Criteria domains of positive valence, social process, and sensorimotor systems. Moreover, we systematically summarize the neurobiological correlates of negative schizotypy at the structural, resting-state, and task-based neural levels, as well as the neurochemical level. The convergence and inconsistency of the evidence are critically reviewed. Regarding theoretical and clinical implications, we argue that negative schizotypy represents a useful organizational framework for studying neuropsychology and neurobiology across different psychiatric disorders.

Childhood trauma moderates schizotypy-related brain morphology: analyses of 1182 healthy individuals from the ENIGMA schizotypy working group

BACKGROUND

Schizotypy represents an index of psychosis-proneness in the general population, often associated with childhood trauma exposure. Both schizotypy and childhood trauma are linked to structural brain alterations, and it is possible that trauma exposure moderates the extent of brain morphological differences associated with schizotypy.

METHODS

We addressed this question using data from a total of 1182 healthy adults (age range: 18-65 years old, 647 females/535 males), pooled from nine sites worldwide, contributing to the Enhancing NeuroImaging Genetics through Meta-Analysis (ENIGMA) Schizotypy working group. All participants completed both the Schizotypal Personality Questionnaire Brief version (SPQ-B), and the Childhood Trauma Questionnaire (CTQ), and underwent a 3D T1-weighted brain MRI scan from which regional indices of subcortical gray matter volume and cortical thickness were determined.

RESULTS

A series of multiple linear regressions revealed that differences in cortical thickness in four regions-of-interest were significantly associated with interactions between schizotypy and trauma; subsequent moderation analyses indicated that increasing levels of schizotypy were associated with thicker left caudal anterior cingulate gyrus, right middle temporal gyrus and insula, and thinner left caudal middle frontal gyrus, in people exposed to higher (but not low or average) levels of childhood trauma. This was found in the context of morphological changes directly associated with increasing levels of schizotypy or increasing levels of childhood trauma exposure.

CONCLUSIONS

These results suggest that alterations in brain regions critical for higher cognitive and integrative processes that are associated with schizotypy may be enhanced in individuals exposed to high levels of trauma.

Longitudinal hippocampal subfield development associated with psychotic experiences in young people

Hippocampal volumetric reductions are observed across the psychosis spectrum, with interest in the localisation of these reductions within the hippocampal subfields increasing. Deficits of the CA1 subfield in particular have been implicated in the neuropathophysiology of psychotic disorders. Investigating the trajectory of these abnormalities in healthy adolescents reporting sub-threshold psychotic experiences (PE) can provide insight into the neural mechanisms underlying psychotic symptoms without the potentially confounding effects of a formal disorder, or antipsychotic medication. In this novel investigation, a sample of 211 young people aged 11-13 participated initially in the Adolescent Brain Development study. PE classification was determined by expert consensus at each timepoint. Participants underwent neuroimaging at 3 timepoints, over 6 years. 78 participants with at least one scan were included in the final sample; 33 who met criteria for a definite PE at least once across all the timepoints (PE group), and 45 controls. Data from bilateral subfields of interest (CA1, CA2/3, CA4/DG, presubiculum and subiculum) were extracted for Linear Mixed Effects analyses. Before correction, subfield volumes were found to increase in the control group and decrease in the PE group for the right CA2 and CA2/3 subfields, with moderate to large effect sizes (d = -0.61, and d = -0.79, respectively). Before correction, right subiculum and left presubiculum volumes were reduced in the PE group compared to controls, regardless of time, with moderate effect sizes (d = -0.52, and d = -0.59, respectively). However, none of these effects survived correction. Severity of symptoms were not associated with any of the noted subfields. These findings provide novel insight to the discussion of the role of hippocampal subfield abnormalities in the pathophysiology underlying psychotic experiences.

Schizotypy, childhood trauma and brain morphometry

BACKGROUND

Childhood trauma confers risk for psychosis and is associated with increased 'schizotypy' (a multi-dimensional construct reflecting risk for psychosis in the general population). Structural brain alterations are associated with both childhood trauma and schizotypy, but the potential role of trauma exposure in moderating associations between schizotypy and brain morphology has yet to be determined.

METHODS

Participants were 160 healthy individuals (mean age: 40.08 years, SD = 13.64, range 18-64; 52.5% female). Childhood trauma exposure was assessed using the Childhood Adversity Questionnaire, and schizotypy was assessed using the Schizotypal Personality Questionnaire. Univariate voxel-based morphometry and multivariate analyses of grey matter volume covariation (GMC; derived from independent component analysis) were performed to determine the main effects of schizotypy, trauma exposure and their interaction on these indices of grey matter volume. Moderation analyses were performed following significant interaction.

RESULTS

Levels of schizotypy, in particular the Cognitive-Perceptual and Interpersonal dimensions, were negatively associated with GMC in the striatum, the hippocampus/parahippocampal gyrus, thalamus and insulae. Trauma exposure was negatively associated with GMC of the middle frontal gyrus and parietal lobule, while negatively associated with GMC in the cerebellum. Levels of schizotypy (total scores, and the cognitive-perceptual dimension) were negatively associated with striatal GMC in individuals not exposed to trauma, but not in those exposed to trauma.

CONCLUSIONS

Schizotypy and childhood trauma were independently associated with changes of grey matter in brain regions critical for cognition and social cognition. In individuals not exposed to trauma, increased schizotypy was associated with decreased striatal and limbic grey matter.

Nonclinical psychotic-like experiences and schizotypy dimensions: Associations with hippocampal subfield and amygdala volumes

Schizotypy and psychotic‐like experiences (PLE) form part of the wider psychosis continuum and may have brain structural correlates in nonclinical cohorts. This study aimed to compare the effects of differential schizotypy dimensions, PLE, and their interaction on hippocampal subfields and amygdala volumes in the absence of clinical psychopathology. In a cohort of 367 psychiatrically healthy individuals, we assessed schizotypal traits using the Oxford‐Liverpool Inventory of Life Experiences (O‐LIFE) and PLE using the short form of the Prodromal Questionnaire (PQ‐16). Based on high‐resolution structural MRI scans, we used automated segmentation to estimate volumes of limbic structures. Sex and total intracranial volume (Step 1), PLE and schizotypy dimensions (Step 2), and their interaction terms (Step 3) were entered as regressors for bilateral amygdala and hippocampal subfield volumes in hierarchical multiple linear regression models. Positive schizotypy, but not PLE, was negatively associated with left amygdala and subiculum volumes. O‐LIFE Impulsive Nonconformity, as well as the two‐way interaction between positive schizotypy and PLE, were associated with larger left subiculum volumes. None of the estimators for right hemispheric hippocampal subfield volumes survived correction for multiple comparisons. Our findings support differential associations of hippocampus subfield volumes with trait dimensions rather than PLE, and support overlap and interactions between psychometric positive schizotypy and PLE. In a healthy cohort without current psychosis risk syndromes, the positive association between PLE and hippocampal subfield volume occurred at a high expression of positive schizotypy. Further studies combining stable, transient, and genetic parameters are required.

Anterior vs Posterior Hippocampal Subfields in an Extended Psychosis Phenotype of Multidimensional Schizotypy in a Nonclinical Sample

Numerous studies have implicated involvement of the hippocampus in the etiology and expression of schizophrenia-spectrum psychopathology, and reduced hippocampal volume is one of the most robust brain abnormalities reported in schizophrenia. Recent studies indicate that early stages of schizophrenia are specifically characterized by reductions in anterior hippocampal volume; however, studies have not examined hippocampal volume reductions in subclinical schizotypy. The present study was the first to examine the associations of positive, negative, and disorganized schizotypy dimensions with hippocampal subfield volumes in a large sample (n = 195) of nonclinically ascertained young adults, phenotyped using the Multidimensional Schizotypy Scale (MSS). Hippocampal subfields were analyzed from high-resolution 3 Tesla structural magnetic resonance imaging scans testing anatomical models, including anterior vs posterior regions and the cornu ammonis (CA), dentate gyrus (DG), and subiculum subfields separately for the left and right hemispheres. We demonstrate differential spatial effects across anterior vs posterior hippocampus segments across different dimensions of the schizotypy risk phenotype. The interaction of negative and disorganized schizotypy robustly predicted left hemisphere volumetric reductions for the anterior and total hippocampus, and anterior CA and DG, and the largest reductions were seen in participants high in negative and disorganized schizotypy. These findings extend previous early psychosis studies and together with behavioral studies of hippocampal-related memory impairments provide the basis for a dimensional neurobiological hippocampal model of schizophrenia risk. Subtle hippocampal subfield volume reductions may be prevalent prior to the onset of detectable prodromal clinical symptoms of psychosis and play a role in the etiology and development of such conditions.