Effectiveness of Cerebellar Circuitry Modulation in Schizophrenia: A Systematic Review

Predictive coding in neuropsychiatric disorders: A systematic transdiagnostic review

The predictive coding framework postulates that the human brain continuously generates predictions about the environment, maximizing successes and minimizing failures based on prior experiences and beliefs. This PRISMA-compliant systematic review aims to comprehensively and transdiagnostically examine the differences in predictive coding between individuals with neuropsychiatric disorders and healthy controls. We included 72 articles including case-control studies investigating predictive coding as the primary outcome and reporting behavioral, neuroimaging, or electrophysiological findings. Thirty-three studies investigated predictive coding in the schizophrenia spectrum, 33 in neurodevelopmental disorders, 5 in mood disorders, 4 in neurocognitive disorders, 1 in post-traumatic stress disorder, and 1 in substance use disorders. Oddball and oddball-like paradigms were most frequently used to quantify predictive coding performance. Evidence showed heterogeneous impairments in the predictive coding abilities of the brain across neuropsychiatric disorders, particularly in schizophrenia and autism. Patients within the schizophrenia spectrum showed a consistent pattern of impaired non-social predictive coding. Conversely, predictive coding deficits were more selective for social cues in the autism spectrum. Predictive coding impairments were correlated with clinical symptom severity. These findings underscore the potential utility of predictive coding as a framework for understanding cognitive dysfunctions in the neuropsychiatric population, even though more evidence is needed on underexplored conditions, also considering potential confounders such as medication use and sex/gender. The potential role of predictive coding as a determinant of treatment response may also be considered to tailor personalized interventions.

Deviant sound frequency and time stimuli in auditory oddball tasks reveal persistent aberrant brain activity in patients with psychosis and symptomatic remission

The detection of rare or deviant stimuli shares common brain circuits involved in temporal processing and salience, critical for cognitive control. Disruption in these processes may contribute to the mechanisms of the disease and explain cognitive deficits observed in psychosis and related disorders. We designed a neuroimaging study, using oddball task-based functional sequences (fMRI) and diffusion tensor imaging (DTI), comparing healthy controls (HC, n = 14, 7 females) and patients with stable psychosis (PSY, n = 20, 10 females). The PSY individuals had schizophrenia or bipolar disorder diagnosis (ICD-10), meeting symptom remission criteria in the last 6 months. Two variants of the auditory oddball paradigm were employed, focusing on sound frequency (SF) and time discrimination (TD) tasks, adapted for fMRI. We used a general linear model to analyze fMRI data and a random effects model for group analysis, complemented by an exploratory statistical agnostic mapping analysis. DTI data were processed using FSL (FMRIB Software Library) and TBSS (Tract Based Spatial Statistics). Distinct activation patterns between groups were observed, with increased brain activity in PSY in TD and SF oddball tasks. In response to increased task difficulty, HC predominantly activated cerebellar regions, whereas PSY relied more on frontal regions. Reduced fractional anisotropy in PSY correlated with lower performance scores in the MATRICS (Measurement and Treatment Research to Improve Cognition in Schizophrenia) Consensus Cognitive Battery (MCCB). The study underscores aberrant brain activity and white matter deficits in stable psychosis patients, highlighting distinct responses to cognitive challenges compared to HC. These findings may support the hypothesis of cognitive dysmetria as a potential underlying mechanism in psychosis and highlight future therapeutic strategies, including non-invasive brain stimulation techniques.

Time perception in bipolar disorder: a systematic review

OBJECTIVE

Time distortions characterise severe mental disorders, exhibiting different clinical and neurobiological manifestations. This systematic review aims to explore the existing literature encompassing experimental studies on time perception in patients with bipolar disorder (BD), considering psychopathological and cognitive correlates.

METHODS

Studies using an experimental paradigm to objectively measure the capacity to judge time have been searched for. Selected studies have been described based on whether i) explicit or implicit time perception was investigated, ii) the temporal intervals involved were sub-second or supra-second, and iii) a perceptual or motor timing paradigm was used.

RESULTS

Only 11 met the criteria for inclusion in the review. The available literature shows that the performance of BD patients mostly aligns with controls within sub-second timeframes (six articles), while a different pattern emerges within supra-second intervals based on the clinical phase of the disease (seven articles). Specifically, for longer temporal spans, BD patients tend to overestimate the duration during manic states and underestimate it during depressive states. Notably, no studies have directly investigated the neurobiological mechanisms associated with time perception.

CONCLUSION

This review indicates that BD patients exhibit time perception similar to controls within sub-second intervals, but tend to overestimate time and underestimate it based on the clinical phase within supra-second intervals. Expanding the understanding of time perception in BD, particularly in relation to clinical phases and cognitive function, is of great importance. Such insights could deepen our understanding of the disorder, refine diagnostic processes, and guide the development of innovative therapeutic interventions.

The involvement of the cerebellar vermis across the psychotic-affective spectrum in enriched samples of recent-onset schizophrenia, bipolar disorder, and major depressive disorder

BACKGROUND

The cerebellar vermis is implicated in cognition and emotion, two key components of the psychotic-affective spectrum that includes schizophrenia (SCZ), bipolar disorder (BD), and major depressive disorder (MDD).

METHODS

Volumes [N = 391; 97 SCZ, 78 BD, 103 MDD, and 113 healthy controls (HC)] and seed-to-whole brain functional connectivity (FC) [N = 136; 33 SCZ, 23 BD, 51 MDD, and 29 HC] of total vermis and its subregions, V1 (anterior), V2 (posterior superior), and V3 (posterior inferior), were examined across SCZ, BD, MDD, and HC in samples enriched for first episode individuals. The relationship between vermis volumes and FC and cognitive measures were explored.

RESULTS

Significant diagnosis (p = 0.05) and diagnosis by subregion (p = 0.02) effects on vermis volumes were observed across the four groups, particularly in V2 (p = 0.01) with decreased V2 volumes in SCZ compared to BD (pFDR = 0.01). SCZ, BD, and MDD had significant effects on vermis FC, with SCZ having the greatest effects. SCZ had effects on FC of V1, V2, and V3 with broadly distributed cortical and subcortical regions, while BD and MDD effects were observed in FC of V2 and V3 with frontotemporal regions. Exploratory analyses found significant canonical correlation between V3 FC and WM and visual learning for SCZ and MDD. No significant associations were shown between vermis volumes and cognitive measures.

CONCLUSIONS

Structural and functional alterations of the vermis appear to vary across the psychotic-affective spectrum of SCZ, BD, and MDD. Posterior vermis may be a key neural intersection between affective and psychotic psychopathology.

Possible compensatory role of cerebellum in bipolar disorder. A cortical thickness study

Recent studies suggested that structural changes in the cerebellum are implicated in the pathophysiology of bipolar disorder (BD). Here, we aimed to characterize the structural alterations of cerebellar lobules in BD, evaluating their possible relation with those occurring in the rest of the brain. One-hundred-fifty-five type I BD patients were recruited and compared with one-hundred-nineteen controls subjects. Cerebral cortical thickness (CT) was evaluated vertex-wise, while cerebellar CT at the level of its twelve lobules. A widespread pattern of cortical thinning was found in several clusters of BD patients. In the cerebellum, we found an anterior thinning (lobule I_II, III, X) and a posterior thickening (crus I, crus II, lobule VI and lobule IX) of its lobules in BD. Exploring the relation between cerebral and cerebellar CT changes in BD patients, after correcting for age and disease duration, the CT of a large subset of cerebral regions, found thinned in BD, were also inversely correlated with the thickening of cerebellar lobule IX. We speculate that this lobule may undergo adaptive changes to compensate the widespread cortical thinning which characterizes BD syndrome. Such a compensatory adaptation of the cerebellum would be similar to that found in other neurological and psychiatric disorders.

Correlates of Impaired Timing Abilities in Schizophrenia: A Systematic Review

ABSTRACT

This review aimed at summarizing the literature evidence on clinical, cognitive, and neurobiological correlates of impaired timing abilities in schizophrenia (SCZ). Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic literature search was conducted in PubMed, EMBASE, and PsycInfo by looking at correlates between timing abilities and either symptom severity, cognition, and neurobiological data (imaging and electroencephalography) in individuals with SCZ, without restrictions on study design. A total of 45 articles were selected: associations were identified between impaired timing performance and positive, negative, and disorganization symptoms, as well as with executive functioning, working memory, and attention. Timing impairments were associated with altered motor coordination neural circuits. Despite high methodological and clinical heterogeneity, timing dysfunction may be associated with the symptom severity and cognitive impairments in SCZ. Further studies are needed to clarify the pathophysiology of this association and offer new therapeutic targets.

Theta-burst rTMS in schizophrenia to ameliorate negative and cognitive symptoms: study protocol for a double-blind, sham-controlled, randomized clinical trial

BACKGROUND

Treatment effects of conventional approaches with antipsychotics or psychosocial interventions are limited when it comes to reducing negative and cognitive symptoms in schizophrenia. While there is emerging clinical evidence that new, augmented protocols based on theta-burst stimulation can increase rTMS efficacy dramatically in depression, data on similar augmented therapies are limited in schizophrenia. The different patterns of network impairments in subjects may underlie that some but not all patients responded to given stimulation locations.

METHODS

Therefore, we propose an augmented theta-burst stimulation protocol in schizophrenia by stimulating both locations connected to negative symptoms: (1) the left dorsolateral prefrontal cortex (DLPFC), and (2) the vermis of the cerebellum. Ninety subjects with schizophrenia presenting negative symptoms and aging between 18 and 55 years will be randomized to active and sham stimulation in a 1:1 ratio. The TBS parameters we adopted follow the standard TBS protocols, with 3-pulse 50-Hz bursts given every 200 ms (at 5 Hz) and an intensity of 100% active motor threshold. We plan to deliver 1800 stimuli to the left DLPFC and 1800 stimuli to the vermis daily in two 9.5-min blocks for 4 weeks. The primary endpoint is the change in negative symptom severity measured by the Positive and Negative Syndrome Scale (PANSS). Secondary efficacy endpoints are changes in cognitive flexibility, executive functioning, short-term memory, social cognition, and facial emotion recognition. The difference between study groups will be analyzed by a linear mixed model analysis with the difference relative to baseline in efficacy variables as the dependent variable and treatment group, visit, and treatment-by-visit interaction as independent variables. The safety outcome is the number of serious adverse events.

DISCUSSION

This is a double-blind, sham-controlled, randomized medical device study to assess the efficacy and safety of an augmented theta-burst rTMS treatment in schizophrenia. We hypothesize that social cognition and negative symptoms of patients on active therapy will improve significantly compared to patients on sham treatment.

TRIAL REGISTRATION

The study protocol is registered at "ClinicalTrials.gov" with the following ID: NCT05100888. All items from the World Health Organization Trial Registration Data Set are registered. Initial release: 10/19/2021.

Time in schizophrenia: a link between psychopathology, psychophysics and technology

It has been widely demonstrated that time processing is altered in patients with schizophrenia. This perspective review delves into such temporal deficit and highlights its link to low-level sensory alterations, which are often overlooked in rehabilitation protocols for psychosis. However, if temporal impairment at the sensory level is inherent to the disease, new interventions should focus on this dimension. Beyond more traditional types of intervention, here we review the most recent digital technologies for rehabilitation and the most promising ones for sensory training. The overall aim is to synthesise existing literature on time in schizophrenia linking psychopathology, psychophysics, and technology to help future developments.

Mathematical Model Insights into EEG Origin under Transcranial Direct Current Stimulation (tDCS) in the Context of Psychosis

Schizophrenia is a psychotic disease that develops progressively over years with a transition from prodromal to psychotic state associated with a disruption in brain activity. Transcranial Direct Current Stimulation (tDCS), known to alleviate pharmaco-resistant symptoms in patients suffering from schizophrenia, promises to prevent such a psychotic transition. To understand better how tDCS affects brain activity, we propose a neural cortico-thalamo-cortical (CTC) circuit model involving the Ascending Reticular Arousal System (ARAS) that permits to describe major impact features of tDCS, such as excitability for short-duration stimulation and electroencephalography (EEG) power modulation for long-duration stimulation. To this end, the mathematical model relates stimulus duration and Long-Term Plasticity (LTP) effect, in addition to describing the temporal LTP decay after stimulus offset. This new relation promises to optimize future stimulation protocols. Moreover, we reproduce successfully EEG-power modulation under tDCS in a ketamine-induced psychosis model and confirm the N-methyl-d-aspartate (NMDA) receptor hypofunction hypothesis in the etiopathophysiology of schizophrenia. The model description points to an important role of the ARAS and the δ-rhythm synchronicity in CTC circuit in early-stage psychosis.

Cerebellar stimulation in schizophrenia: A systematic review of the evidence and an overview of the methods

BACKGROUND

Cerebellar structural and functional abnormalities underlie widespread deficits in clinical, cognitive, and motor functioning that are observed in schizophrenia. Consequently, the cerebellum is a promising target for novel schizophrenia treatments. Here we conducted an updated systematic review examining the literature on cerebellar stimulation efficacy and tolerability for mitigating symptoms of schizophrenia. We discuss the purported mechanisms of cerebellar stimulation, current methods for implementing stimulation, and future directions of cerebellar stimulation for intervention development with this population.

METHODS

Two independent authors identified 20 published studies (7 randomized controlled trials, 7 open-label studies, 1 pilot study, 4 case reports, 1 preclinical study) that describe the effects of cerebellar circuitry modulation in patients with schizophrenia or animal models of psychosis. Published studies up to October 11, 2022 were identified from a search within PubMed, Scopus, and PsycInfo.

RESULTS

Most studies stimulating the cerebellum used transcranial magnetic stimulation or transcranial direct-current stimulation, specifically targeting the cerebellar vermis/midline. Accounting for levels of methodological rigor across studies, these studies detected post-cerebellar modulation in schizophrenia as indicated by the alleviation of certain clinical symptoms (mainly negative and depressive symptoms), as well as increased frontal-cerebellar connectivity and augmentation of canonical neuro-oscillations known to be abnormal in schizophrenia. In contrast to a prior review, we did not find consistent evidence for cognitive improvements following cerebellar modulation stimulation. Modern cerebellar stimulation methods appear tolerable for individuals with schizophrenia, with only mild and temporary side effects.

CONCLUSION

Cerebellar stimulation is a promising intervention for individuals with schizophrenia that may be more relevant to some symptom domains than others. Initial results highlight the need for continued research using more methodologically rigorous designs, such as additional longitudinal and randomized controlled trials.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42022346667].

The Immediate Effects of Intermittent Theta Burst Stimulation of the Cerebellar Vermis on Cerebral Cortical Excitability During a Balance Task in Healthy Individuals: A Pilot Study

Objective: This pilot study aimed to investigate the immediate effects of single-session intermittent theta-burst stimulation (iTBS) on the cerebellar vermis during a balance task, which could unveil the changes of cerebral cortical excitability in healthy individuals.

Subjects: A total of seven right-handed healthy subjects (26.86 ± 5.30 years) were included in this study.

Interventions: Each subject received single-session iTBS on cerebellar vermis in a sitting position.

Main Measures: Before and after the intervention, all subjects were asked to repeat the balance task of standing on the left leg three times. Each task consisted of 15 s of standing and 20 s of resting. Real-time changes in cerebral cortex oxygen concentrations were monitored with functional near-infrared spectroscopy (fNIRS). During the task, changes in blood oxygen concentration were recorded and converted into the mean HbO₂ for statistical analysis.

Results: After stimulation, the mean HbO₂ in the left SMA (P = 0.029) and right SMA (P = 0.043) significantly increased compared with baseline. However, no significant changes of mean HbO₂ were found in the bilateral dorsolateral prefrontal lobe (P > 0.05).

Conclusion: Single-session iTBS on the cerebellar vermis in healthy adults can increase the excitability of the cerebral cortex in the bilateral supplementary motor areas during balance tasks.

Clinical Trial Registration: [www.ClinicalTrials.gov], identifier [ChiCTR2100048915].

The Involvement of the Posterior Cerebellum in Reconstructing and Predicting Social Action Sequences

Recent advances in social neuroscience have highlighted the critical role of the cerebellum and especially the posterior cerebellar Crus in social mentalizing (i.e., theory of mind). Research in the past 5 years has provided growing evidence supporting the view that the posterior cerebellum builds internal action models of our social interactions to predict how other people's actions will be executed, and what our most likely responses to these actions will be. This paper presents an overview of a series of fMRI experiments on novel tasks involving a combination of (a) the learning or generation of chronological sequences of social actions either in an explicit or implicit manner, which (b) require social mentalizing on another person's mental state such as goals, beliefs, and implied traits. Together, the results strongly confirm the central role of the posterior cerebellar Crus in identifying and automatizing action sequencing during social mentalizing, and in predicting future action sequences based on social mentalizing inferences about others. This research program has important implications: It provides for the first time (a) fruitful starting points for diagnosing and investigating social sequencing dysfunctions in a variety of mental disorders which have also been related to cerebellar dysfunctions, (b) provides the necessary tools for testing whether non-invasive neurostimulation targeting the posterior cerebellum has a causal effect on social functioning, and (c) whether these stimulation techniques and training programs guided by novel cerebellar social sequencing insights, can be exploited to increase posterior cerebellar plasticity in order to alleviate social impairments in mental disorders.

Efficacy of Intensive Cerebellar Intermittent Theta Burst Stimulation (iCiTBS) in Treatment-Resistant Schizophrenia: a Randomized Placebo-Controlled Study

Trans-cranial magnetic stimulation (TMS) can noninvasively modulate specific brain regions to dissipate symptoms in treatment-resistant schizophrenia (TRS). Citing impaired resting state connectivity between cerebellum and prefrontal cortex in schizophrenia, we aimed to study the effect of intermittent theta burst stimulation (iTBS) targeting midline cerebellum in TRS subjects on a randomized rater blinded placebo control study design. In this study, 36 patients were randomly allocated (using block randomization method) to active and sham iTBS groups. They were scheduled to receive ten iTBS sessions, two per day (total of 1200 pulses) for 5 days in a week. The Positive and Negative Syndrome Scale (PANSS), Brief Psychiatric Rating Scale (BPRS), Schizophrenia Cognition Rating Scale (SCoRS), Simpson-Angus Extrapyramidal Side Effects Scale (SAS), and Clinical Global Impression (CGI) were assessed at baseline, after last session, and at 2 weeks post-rTMS. Thirty patients (16 and 14 in active and sham groups) completed the study. Intention to treat analysis (ITT) using mixed (growth curve) model analysis was conducted. No significant group (active vs sham) × time (pretreatment–end of 10th session–end of 2 weeks post iTBS) interaction was found for any of the variable. No major side effects were reported. Our study fails to show a significant effect of intensive cerebellar iTBS (iCiTBS) on schizophrenia psychopathology, cognitive functions, and global improvement, compared with sham stimulation, in treatment resistant cases. However, we conclude that it is safe and well tolerated. Trials using better localization technique with large sample, longer duration, and better dosing protocols are needed.