Schizophrenia in the flesh: Revisiting schizophrenia as a disorder of the bodily self

Abnormal Oculomotor Corollary Discharge Signaling as a Trans-diagnostic Mechanism of Psychosis

BACKGROUND AND HYPOTHESIS

Corollary discharge (CD) signals are "copies" of motor signals sent to sensory areas to predict the corresponding input. They are a posited mechanism enabling one to distinguish actions generated by oneself vs external forces. Consequently, altered CD is a hypothesized mechanism for agency disturbances in psychosis. Previous studies have shown a decreased influence of CD signals on visual perception in individuals with schizophrenia-particularly in those with more severe positive symptoms. We therefore hypothesized that altered CD may be a trans-diagnostic mechanism of psychosis.

STUDY DESIGN

We examined oculomotor CD (using the blanking task) in 49 participants with schizophrenia or schizoaffective disorder (SZ), 36 bipolar participants with psychosis (BPP), and 40 healthy controls (HC). Participants made a saccade to a visual target. Upon saccade initiation, the target disappeared and reappeared at a horizontally displaced position. Participants indicated the direction of displacement. With intact CD, participants can make accurate perceptual judgements. Otherwise, participants may use saccade landing site as a proxy of pre-saccadic target to inform perception. Thus, multi-level modeling was used to examine the influence of target displacement and saccade landing site on displacement judgements.

STUDY RESULTS

SZ and BPP were equally less sensitive to target displacement than HC. Moreover, regardless of diagnosis, SZ and BPP with more severe positive symptoms were more likely to rely on saccade landing site.

CONCLUSIONS

These results suggest that altered CD may be a trans-diagnostic mechanism of psychosis.

Subcortical contributions to the sense of body ownership

The sense of body ownership (i.e. the feeling that our body or its parts belong to us) plays a key role in bodily self-consciousness and is believed to stem from multisensory integration. Experimental paradigms such as the rubber hand illusion have been developed to allow the controlled manipulation of body ownership in laboratory settings, providing effective tools for investigating malleability in the sense of body ownership and the boundaries that distinguish self from other. Neuroimaging studies of body ownership converge on the involvement of several cortical regions, including the premotor cortex and posterior parietal cortex. However, relatively less attention has been paid to subcortical structures that may also contribute to body ownership perception, such as the cerebellum and putamen. Here, on the basis of neuroimaging and neuropsychological observations, we provide an overview of relevant subcortical regions and consider their potential role in generating and maintaining a sense of ownership over the body. We also suggest novel avenues for future research targeting the role of subcortical regions in making sense of the body as our own.

The schizophrenia syndrome, circa 2024: What we know and how that informs its nature

With new data about different aspects of schizophrenia being continually generated, it becomes necessary to periodically revisit exactly what we know. Along with a need to review what we currently know about schizophrenia, there is an equal imperative to evaluate the construct itself. With these objectives, we undertook an iterative, multi-phase process involving fifty international experts in the field, with each step building on learnings from the prior one. This review assembles currently established findings about schizophrenia (construct, etiology, pathophysiology, clinical expression, treatment) and posits what they reveal about its nature. Schizophrenia is a heritable, complex, multi-dimensional syndrome with varying degrees of psychotic, negative, cognitive, mood, and motor manifestations. The illness exhibits a remitting and relapsing course, with varying degrees of recovery among affected individuals with most experiencing significant social and functional impairment. Genetic risk factors likely include thousands of common genetic variants that each have a small impact on an individual's risk and a plethora of rare gene variants that have a larger individual impact on risk. Their biological effects are concentrated in the brain and many of the same variants also increase the risk of other psychiatric disorders such as bipolar disorder, autism, and other neurodevelopmental conditions. Environmental risk factors include but are not limited to urban residence in childhood, migration, older paternal age at birth, cannabis use, childhood trauma, antenatal maternal infection, and perinatal hypoxia. Structural, functional, and neurochemical brain alterations implicate multiple regions and functional circuits. Dopamine D-2 receptor antagonists and partial agonists improve psychotic symptoms and reduce risk of relapse. Certain psychological and psychosocial interventions are beneficial. Early intervention can reduce treatment delay and improve outcomes. Schizophrenia is increasingly considered to be a heterogeneous syndrome and not a singular disease entity. There is no necessary or sufficient etiology, pathology, set of clinical features, or treatment that fully circumscribes this syndrome. A single, common pathophysiological pathway appears unlikely. The boundaries of schizophrenia remain fuzzy, suggesting the absence of a categorical fit and need to reconceptualize it as a broader, multi-dimensional and/or spectrum construct.

Proverb comprehension in schizophrenia: A comprehensive review and meta-analysis.2

BACKGROUND

Examination of proverb comprehension has a long tradition in clinical diagnostics of individuals with schizophrenia (iSCZ). Deficits in the comprehension are considered common. Interpretations of proverbs are traditionally measured by their degree of abstraction and concreteness ('literalness'), but iSCZ's responses may also be illogical or 'bizarre'. Experimental research on proverb comprehension starts in the 1940s. Since then, the specificity of proverb tests has often been questioned, but has never been the subject of a meta-analysis. The aim of this meta-analysis is to include all experimental research, including historical studies, that meets quality criteria and compares the responses to proverbs in iSCZ with those in healthy controls (HC) or clinical controls (CC).

METHODS

PubMed, Web of Science, and PsycInfo databases were searched. After coding 121 articles, 27 (median publication year 1982) were included and multi-level meta-analyses performed. Moderator analyses were performed on response format (multiple-choice vs. verbal responses), proverb test, scoring method, language, acute vs. chronic stage of iSCZ, time of publication, clinical vs. healthy control group, age, IQ/education, and gender. Publication bias was assessed using funnel plots, trim and fill method and Egger's test.

RESULTS

The search identified 27 eligible studies for inclusion. Studies were published between 1956 and 2020 and predominantly older than 30 years (median: 1982). The Gorham Proverbs Test was the most established test and predominantly conducted in English. CC mostly consisted of depressive disorders. Pooled estimates yielded statistically significant less abstract (g = -1.00; 95%CI, -1.34 to -1.67), more concrete (g = 0.69; 95%CI, 0.35-1.03), and more bizarre (g = 1.08; 95%CI, 0.74-1.41) responses in iSCZ compared to controls. The type of control group moderated all three effects, with greater differences of iSCZ compared to HC than to CC in abstraction and bizarreness, and no significant group difference between iSCZ and CC in concreteness. Meta-regressions indicated IQ/education and age as possible sources of variability in abstraction and bizarreness.

CONCLUSIONS

While lower abstraction and higher bizarreness seems a characteristic of iSCZ, the diagnostic specificity of a concrete response was astonishingly low. The lack of a unified definition for concretism and limited consideration of cultural diversity contributed to these complex findings. Future research should focus on exploring the qualitative aspects of proverb comprehension and the association between symptomatology types and misinterpretations to improve diagnostic accuracy.

Schizophrenia in the mind, the brain and the body

The author describes three lines of research programs that have guided her goal of elucidating the etiology of schizophrenia: working memory and representational guidance of behavior, disrupted social cognition and bodily-self disturbances.

Attachment Style and Self-Experience: The Association Between Attachment Style and Self-Reported Altered Self-Experience in Patients With Psychotic Disorders, Unaffected Siblings, and Healthy Controls

ABSTRACT

The present study aimed to examine the cross-sectional association between attachment style and self-reported disturbed self-awareness (disturbed sense of mineness of experiences) and depersonalization (disturbed sense of first-person perspective) in patients with psychotic disorders, unaffected siblings, and healthy controls. Data pertain to a subsample of the GROUP (Genetic Risk and Outcome of Psychosis) study. We found positive associations between anxious attachment and disturbed self-awareness and depersonalization across participants with different psychosis vulnerability. We also found a positive association between avoidant attachment and depersonalization, although on a trend level. Findings indicate that attachment style is associated with self-reported disturbed self-awareness and depersonalization over and above the influence of psychotic or depressive experiences in people across the vulnerability spectrum of psychosis. This supports the importance of attachment style, self-awareness, and depersonalization as potential targets in prevention and treatment interventions in patients with psychotic disorders or those with increased vulnerability.

Disembodiment and Language in Schizophrenia: An Integrated Psychopathological and Evolutionary Perspective

Different hypotheses have flourished to explain the evolutionary paradox of schizophrenia. In this contribution, we sought to illustrate how, in the schizophrenia spectrum, the concept of embodiment may underpin the phylogenetic and developmental pathways linking sensorimotor processes, the origin of human language, and the construction of a basic sense of the self. In particular, according to an embodied model of language, we suggest that the reuse of basic sensorimotor loops for language, while enabling the development of fully symbolic thought, has pushed the human brain close to the threshold of a severe disruption of self-embodiment processes, which are at the core of schizophrenia psychopathology. We adopted an inter-disciplinary approach (psychopathology, neuroscience, developmental biology) within an evolutionary framework, to gain an integrated, multi-perspectival model on the origin of schizophrenia vulnerability. A maladaptive over-expression of evolutionary-developmental trajectories toward language at the expense of embodiment processes would have led to the evolutionary "trade-off" of a hyper-symbolic activity to the detriment of a disembodied self. Therefore, schizophrenia psychopathology might be the cost of long-term co-evolutive interactions between brain and language.

Social anhedonia and other indicators of risk for schizophrenia: Theory and inquiry

In this commentary, the author traces theoretical contributions that fueled her interest in the role of social/interpersonal striving, relating, and enjoyment in terms of schizophrenia. Social anhedonia is discussed in the context of schizophrenia. The author reviews selective empirical evidence indicating that social anhedonia has a unique role in terms of risk for schizophrenia as well as schizophrenia outcome. Other risk indicators for adult schizophrenia-spectrum outcomes are briefly considered. The author discusses the measurement of social anhedonia across the lifespan and transdiagnostically. Finally, this commentary offers a critique of current strategies for risk calculation.

Posture, gait and self‐disorders: An empirical study in individuals with schizophrenia

AIM

In schizophrenia, subjectively perceived disruptions of the sense of the Self (also referred to as "self-disorders") seem to be intimately associated with a perturbation of the implicit awareness of one's own body. Indeed, an early impairment of the motor system, including posture and gait, is now considered a marker of schizophrenia neurodevelopmental substrate and appears more pronounced in early-onset schizophrenia. Therefore, the present study was aimed at: (1) investigating a possible relationship between self-disorders, symptom dimensions and postural and gait profile in schizophrenia; (2) identifying a specific motor profile in early-onset conditions.

METHODS

A total of 43 schizophrenia outpatients and 38 healthy controls underwent an exhaustive investigation of posture and gait pattern. The positive and negative syndrome scale (PANSS), the examination of anomalous self experience scale (EASE) and the abnormal involuntary movement scale (AIMS) were administered to the schizophrenia group. Subsequently, schizophrenia patients were divided into early and adult-onset subgroups and compared with respect to their motor profile.

RESULTS

We found an association between specific postural patterns (impaired sway area), a general disruption of the gait cycle and subjective bodily experiences (concerning the loss of bodily integrity, cohesion and demarcation). Only motor parameters (increased sway area and gait cadence reduction) differentiated between early and adult-onset patients.

CONCLUSION

The results of the present study hint at a link between motor impairment and self-disturbances in schizophrenia and candidate a specific motor profile as a possible marker of early-onset forms.

The positive dimension of schizotypy is associated with a reduced attenuation and precision of self-generated touch

The brain predicts the sensory consequences of our movements and uses these predictions to attenuate the perception of self-generated sensations. Accordingly, self-generated touch feels weaker than an externally generated touch of identical intensity. In schizophrenia, this somatosensory attenuation is substantially reduced, suggesting that patients with positive symptoms fail to accurately predict and process self-generated touch. If an impaired prediction underlies the positive symptoms of schizophrenia, then a similar impairment should exist in healthy nonclinical individuals with high positive schizotypal traits. One hundred healthy participants (53 female), assessed for schizotypal traits, underwent a well-established psychophysics force discrimination task to quantify how they perceived self-generated and externally generated touch. The perceived intensity of tactile stimuli delivered to their left index finger (magnitude) and the ability to discriminate the stimuli (precision) was measured. We observed that higher positive schizotypal traits were associated with reduced somatosensory attenuation and poorer somatosensory precision of self-generated touch, both when treating schizotypy as a continuous or categorical variable. These effects were specific to positive schizotypy and were not observed for the negative or disorganized dimensions of schizotypy. The results suggest that positive schizotypal traits are associated with a reduced ability to predict and process self-generated touch. Given that the positive dimension of schizotypy represents the analogue of positive psychotic symptoms of schizophrenia, deficits in processing self-generated tactile information could indicate increased liability to schizophrenia.