White matter pathway organization of the reward system is related to positive and negative symptoms in schizophrenia

Learning without contingencies: A loss of synergy between memory and reward circuits in schizophrenia

Motivational deficits in schizophrenia may interact with foundational cognitive processes including learning and memory to induce impaired cognitive proficiency. If such a loss of synergy exists, it is likely to be underpinned by a loss of synchrony between the brains learning and reward sub-networks. Moreover, this loss should be observed even during tasks devoid of explicit reward contingencies given that such tasks are better models of real world performance than those with artificial contingencies. Here we applied undirected functional connectivity (uFC) analyses to fMRI data acquired while participants engaged in an associative learning task without contingencies or feedback. uFC was estimated and inter-group differences (between schizophrenia patients and controls, n = 54 total, n = 28 patients) were assessed within and between reward (VTA and NAcc) and learning/memory (Basal Ganglia, DPFC, Hippocampus, Parahippocampus, Occipital Lobe) sub-networks. The task paradigm itself alternated between Encoding, Consolidation, and Retrieval conditions, and uFC differences were quantified for each of the conditions. Significantly reduced uFC dominated the connectivity profiles of patients across all conditions. More pertinent to our motivations, these reductions were observed within and across classes of sub-networks (reward-related and learning/memory related). We suggest that disrupted functional connectivity between reward and learning sub-networks may drive many of the performance deficits that characterize schizophrenia. Thus, cognitive deficits in schizophrenia may in fact be underpinned by a loss of synergy between reward-sensitivity and cognitive processes.

Abnormal functional connectivity of the striatum in first-episode drug-naive early-onset Schizophrenia

Abnormal brain network connectivity is strongly implicated in the pathogenesis of schizophrenia. The striatum, consisting of the caudate and putamen, is the major treatment target for antipsychotics, the primary treatments for schizophrenia; however, there are few studies on the functional connectivity (FC) of striatum in drug-naive early-onset schizophrenia (EOS) patients. We examined the FC values of the caudate nucleus and putamen with whole brain by resting-state functional magnetic resonance imaging (RS-fMRI) and the associations with indices of clinical severity. Patients demonstrated abnormal FC between subregions of the putamen and both the visual network (left middle occipital gyrus) and default mode network (bilateral anterior cingulate, left superior frontal, and right middle frontal gyri). Furthermore, FC between dorsorostral putamen and left superior frontal gyrus correlated with both positive symptom subscore and total score on the Positive and Negative Syndrome Scale (PANSS). These findings demonstrate abnormal FC between the striatum and other brain areas even in the early stages of schizophrenia, supporting neurodevelopmental disruption in disease etiology and expression.

Transdiagnostic role of glutamate and white matter damage in neuropsychiatric disorders: A Systematic Review

Neuropsychiatric disorders including generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ) have been considered distinct categories of diseases despite their overlapping characteristics and symptomatology. We aimed to provide an in-depth review elucidating the role of glutamate/Glx and white matter (WM) abnormalities in these disorders from a transdiagnostic perspective. The PubMed online database was searched for studies published between 2010 and 2021. After careful screening, 401 studies were included. The findings point to decreased levels of glutamate in the Anterior Cingulate Cortex in both SZ and BD, whereas Glx is elevated in the Hippocampus in SZ and MDD. With regard to WM abnormalities, the Corpus Callosum and superior Longitudinal Fascicle were the most consistently identified brain regions showing decreased fractional anisotropy (FA) across all the reviewed disorders, except GAD. Additionally, the Uncinate Fasciculus displayed decreased FA in all disorders, except OCD. Decreased FA was also found in the inferior Longitudinal Fasciculus, inferior Fronto-Occipital Fasciculus, Thalamic Radiation, and Corona Radiata in SZ, BD, and MDD. Decreased FA in the Fornix and Corticospinal Tract were found in BD and SZ patients. The Cingulum and Anterior Limb of Internal Capsule exhibited decreased FA in MDD and SZ patients. The results suggest a gradual increase in severity from GAD to SZ defined by the number of brain regions with WM abnormality which may be partially caused by abnormal glutamate levels. WM damage could thus be considered a potential marker of some of the main neuropsychiatric disorders.

Relationships between Diffusion Tensor Imaging and Resting State Functional Connectivity in Patients with Schizophrenia and Healthy Controls: A Preliminary Study

Schizophrenia is widely seen as a disorder of dysconnectivity. Neuroimaging studies have examined both structural and functional connectivity in the disorder, but these modalities have rarely been integrated directly. We scanned 29 patients with schizophrenia and 25 healthy control subjects, and we acquired resting state fMRI and diffusion tensor imaging. We used the Functional and Tractographic Connectivity Analysis Toolbox (FATCAT) to estimate functional and structural connectivity of the default mode network. Correlations between modalities were investigated, and multimodal connectivity scores (MCS) were created using principal component analysis. Of the 28 possible region pairs, 9 showed consistent (>80%) tracts across participants. Correlations between modalities were found among those with schizophrenia for the prefrontal cortex, posterior cingulate, and lateral temporal lobes, with frontal and parietal regions, consistent with frontotemporoparietal network involvement in the disorder. In patients, MCS correlated with several aspects of the Positive and Negative Syndrome Scale, with higher multimodal connectivity associated with outward-directed (externalizing) behavior and lower multimodal connectivity related to psychosis per se. In this preliminary sample, we found FATCAT to be a useful toolbox to directly integrate and examine connectivity between imaging modalities. A consideration of conjoint structural and functional connectivity can provide important information about the network mechanisms of schizophrenia.

Magnetic resonance imaging of the dopamine system in schizophrenia - A scoping review

For decades, aberrant dopamine transmission has been proposed to play a central role in schizophrenia pathophysiology. These theories are supported by human in vivo molecular imaging studies of dopamine transmission, particularly positron emission tomography. However, there are several downsides to such approaches, for example limited spatial resolution or restriction of the measurement to synaptic processes of dopaminergic neurons. To overcome these limitations and to measure complementary aspects of dopamine transmission, magnetic resonance imaging (MRI)-based approaches investigating the macrostructure, metabolism, and connectivity of dopaminergic nuclei, i.e., substantia nigra pars compacta and ventral tegmental area, can be employed. In this scoping review, we focus on four dopamine MRI methods that have been employed in patients with schizophrenia so far: neuromelanin MRI, which is thought to measure long-term dopamine function in dopaminergic nuclei; morphometric MRI, which is assumed to measure the volume of dopaminergic nuclei; diffusion MRI, which is assumed to measure fiber-based structural connectivity of dopaminergic nuclei; and resting-state blood-oxygenation-level-dependent functional MRI, which is thought to measure functional connectivity of dopaminergic nuclei based on correlated blood oxygenation fluctuations. For each method, we describe the underlying signal, outcome measures, and downsides. We present the current state of research in schizophrenia and compare it to other disorders with either similar (psychotic) symptoms, i.e., bipolar disorder and major depressive disorder, or dopaminergic abnormalities, i.e., substance use disorder and Parkinson's disease. Finally, we discuss overarching issues and outline future research questions.

Limbic links to paranoia: increased resting-state functional connectivity between amygdala, hippocampus and orbitofrontal cortex in schizophrenia patients with paranoia

Paranoia is a frequent and highly distressing experience in psychosis. Models of paranoia suggest limbic circuit pathology. Here, we tested whether resting-state functional connectivity (rs-fc) in the limbic circuit was altered in schizophrenia patients with current paranoia. We collected MRI scans in 165 subjects including 89 patients with schizophrenia spectrum disorders (schizophrenia, schizoaffective disorder, brief psychotic disorder, schizophreniform disorder) and 76 healthy controls. Paranoia was assessed using a Positive And Negative Syndrome Scale composite score. We tested rs-fc between bilateral nucleus accumbens, hippocampus, amygdala and orbitofrontal cortex between groups and as a function of paranoia severity. Patients with paranoia had increased connectivity between hippocampus and amygdala compared to patients without paranoia. Likewise, paranoia severity was linked to increased connectivity between hippocampus and amygdala. Furthermore, paranoia was associated with increased connectivity between orbitofrontal and medial prefrontal cortex. In addition, patients with paranoia had increased functional connectivity within the frontal hubs of the default mode network compared to healthy controls. These results demonstrate that current paranoia is linked to aberrant connectivity within the core limbic circuit and prefrontal cortex reflecting amplified threat processing and impaired emotion regulation. Future studies will need to explore the association between limbic hyperactivity, paranoid ideation and perceived stress.

Investigating the Relationship between White Matter Connectivity and Motivational Circuits in Subjects with Deficit Schizophrenia: A Diffusion Tensor Imaging (DTI) Study

Deficit schizophrenia is a subtype of schizophrenia presenting primary and enduring negative symptoms (NS). Although one of the most updated hypotheses indicates a relationship between NS and impaired motivation, only a few studies have investigated abnormalities of motivational circuits in subjects with deficit schizophrenia (DS). Our aim was to investigate structural connectivity within motivational circuits in DS. We analyzed diffusion tensor imaging (DTI) data from 46 subjects with schizophrenia (SCZ) and 35 healthy controls (HCs). SCZ were classified as DS (n = 9) and non-deficit (NDS) (n = 37) using the Schedule for Deficit Syndrome. The connectivity index (CI) and the Fractional Anisotropy (FA) of the connections between selected brain areas involved in motivational circuits were examined. DS, as compared with NDS and HCs, showed increased CI between the right amygdala and dorsal anterior insular cortex and increased FA of the pathway connecting the left nucleus accumbens with the posterior insular cortex. Our results support previous evidence of distinct neurobiological alterations underlying different clinical subtypes of schizophrenia. DS, as compared with NDS and HCs, may present an altered pruning process (consistent with the hyperconnectivity) in cerebral regions involved in updating the stimulus value to guide goal-directed behavior.

Adjuvant High-Definition Transcranial Direct Current Stimulation for Negative Symptoms in Schizophrenia: A Pilot Study

OBJECTIVE

In schizophrenia, negative symptoms account for a substantial amount of the comorbidity resulting in poor performance in social interaction, interpersonal relationships, economic functioning, and recreational activities. Research has implicated hypofrontality in the pathogenesis of negative symptoms of schizophrenia. Conventional transcranial direct current stimulation (tDCS) to the dorsolateral prefrontal cortex has attracted significant interest as an add-on treatment for negative symptoms in schizophrenia. High-definition tDCS (HD-tDCS), an optimized form of tDCS, has the potential for more focalized neuromodulation. Hence, we aimed to evaluate the efficacy of HD-tDCS over the left dorsolateral prefrontal cortex in the improvement of negative symptoms in schizophrenia.

METHODS

Fourteen patients with schizophrenia with predominantly negative symptoms were enrolled for this pilot, randomized, sham-controlled, double-blind trial. Each participant received 10 sessions of HD-tDCS at 2 mA for 20 minutes twice daily over 5 days. Negative symptoms were assessed with the Scale for Assessment of Negative Symptoms and Positive and Negative Syndrome Scale for Schizophrenia. The Calgary Depression Scale for Schizophrenia was used to rule out depressive symptoms. Assessments were carried out at baseline and at 2 weeks.

RESULTS

The improvement in negative symptoms in the active group was statistically significant at P value of 0.05 as compared with the sham group.

CONCLUSION

These results suggest that HD-tDCS may lead to improvement in negative symptoms of schizophrenia. Its use as an adjunct to pharmacological treatment of negative symptoms may be worth considering.

Effective connectivity predicts cognitive empathy in cocaine addiction: a spectral dynamic causal modeling study

Social cognition plays a crucial role in the development and treatment of cocaine dependence. However, studies investigating social cognition, such as empathy and its underlying neural basis, are lacking. To explore the neural interactions among reward and memory circuits, we applied effective connectivity analysis on resting-state fMRI data collected from cocaine-dependent subjects. The relationship between effective connectivity within these two important circuits and empathy ability - evaluated with the Interpersonal Reactivity Index (IRI) - was assessed by machine learning algorithm using multivariate regression analysis. In accordance with the neurocircuitry disruptions of cocaine addiction, the results showed that cocaine-dependent subjects relative to healthy controls had altered resting state effective connectivity between parts of the memory and reward systems. Furthermore, effective connectivity between the memory and reward system could predict the fantasy empathy (FE) subscale scores in cocaine dependence. Overall, our findings provide further evidence for the neural substrates of social cognition in cocaine-dependent patients. These new insights could be useful for the development of new treatment programs for this substance dependency disorder.

Executive Dysfunctions in Schizophrenia: A Critical Review of Traditional, Ecological, and Virtual Reality Assessments

In recent years, interest has grown in measuring executive function in schizophrenia with ecological and virtual reality (VR) tools. However, there is a lack of critical analysis comparing those tools with traditional ones. This paper aims to characterize executive dysfunction in schizophrenia by comparing ecological and virtual reality assessments with traditional tools, and to describe the neurobiological and psychopathological correlates. The analysis revealed that ecological and VR tests have higher levels of verisimilitude and similar levels of veridicality compared to traditional tools. Both negative symptoms and disorganization correlate significantly with executive dysfunction as measured by traditional tools, but their relationships with measures based on ecological and VR methods are still unclear. Although there is much research on brain correlates of executive impairments in schizophrenia with traditional tools, it is uncertain if these results will be confirmed with the use of ecological and VR tools. In the diagnosis of executive dysfunction, it is important to use a variety of neuropsychological methods—especially those with confirmed ecological validity—to properly recognize the underlying characteristics of the observed deficits and to implement effective forms of therapy.

Altered Functional Connectivity of the Nucleus Accumbens Network Between Deficit and Non-deficit Schizophrenia

Deficit schizophrenia (DS), which is marked by stable negative symptoms, is regarded as a homogeneous subgroup of schizophrenia. While DS patients have structurally altered nucleus accumbens (NAcc) compared to non-deficit schizophrenia (NDS) patients and healthy individuals, the investigation of NAcc functional connectivity (FC) with negative symptoms and neurocognition could provide insights into the pathophysiology of schizophrenia. 58 DS, 93 NDS, and 113 healthy controls (HCs) underwent resting-state functional magnetic resonance (rsfMRI). The right and left NAcc were respectively used as seed points to construct the functional NAcc network in whole-brain FC analysis. ANCOVA compared the differences in NAcc network FC and partial correlation analysis explored the relationships between altered FC of NAcc, negative symptoms and neurocognition. Compared to HCs, both DS and NDS patients showed decreased FC between the left NAcc (LNAcc) and bilateral middle cingulate gyrus, and between the right NAcc (RNAcc) and right middle frontal gyrus (RMFG), as well as increased FC between bilateral NAcc and bilateral lingual gyrus. Moreover, the FC between the LNAcc and bilateral calcarine gyrus (CAL) was lower in the DS group compared to NDS patients. Correlation analysis indicated that FC value of LNAcc-CAL was negatively correlated to negative symptoms. Furthermore, aberrant FC values within the NAcc network were correlated with severity of clinical symptoms and neurocognitive impairments in DS and NDS patients. This study demonstrated abnormal patterns of FC in the NAcc network between DS and NDS. The presence of altered LNAcc-CAL FC might be involved in the pathogenesis of negative symptoms in schizophrenia.

Association between functional and structural connectivity of the corticostriatal network in people with schizophrenia and unaffected first-degree relatives

BACKGROUND

Dysfunction of the corticostriatal network has been implicated in the pathophysiology of schizophrenia, but findings are inconsistent within and across imaging modalities. We used multimodal neuroimaging to analyze functional and structural connectivity in the corticostriatal network in people with schizophrenia and unaffected first-degree relatives.

METHODS

We collected resting-state functional magnetic resonance imaging and diffusion tensor imaging scans from people with schizophrenia (n = 47), relatives (n = 30) and controls (n = 49). We compared seed-based functional and structural connectivity across groups within striatal subdivisions defined a priori.

RESULTS

Compared with controls, people with schizophrenia had altered connectivity between the subdivisions and brain regions in the frontal and temporal cortices and thalamus; relatives showed different connectivity between the subdivisions and the right anterior cingulate cortex (ACC) and the left precuneus. Post-hoc t tests revealed that people with schizophrenia had decreased functional connectivity in the ventral loop (ventral striatum-right ACC) and dorsal loop (executive striatum-right ACC and sensorimotor striatum-right ACC), accompanied by decreased structural connectivity; relatives had reduced functional connectivity in the ventral loop and the dorsal loop (right executive striatum-right ACC) and no significant difference in structural connectivity compared with the other groups. Functional connectivity among people with schizophrenia in the bilateral ventral striatum-right ACC was correlated with positive symptom severity.

LIMITATIONS

The number of relatives included was moderate. Striatal subdivisions were defined based on a relatively low threshold, and structural connectivity was measured based on fractional anisotropy alone.

CONCLUSION

Our findings provide insight into the role of hypoconnectivity of the ventral corticostriatal system in people with schizophrenia.

Differences in Functional Connectivity Networks Related to the Midbrain Dopaminergic System-Related Area in Various Psychiatric Disorders

OBJECTIVE

Disruptions in the dopamine system have been observed in psychiatric disorders. Since dopamine is mainly produced in the ventral tegmental area (VTA), elucidating the differences in the VTA neural network across psychiatric disorders would facilitate a greater understanding of the pathophysiological mechanisms underlying these disorders. However, no study has compared VTA-seed-based functional connectivity across psychiatric disorders. Therefore, we conducted a resting-state functional magnetic resonance imaging (rs-fMRI) study to perform a seed-based fMRI analysis, using the VTA as a seed.

METHODS

We included participants with major depressive disorder (MDD; n = 45), schizophrenia (n = 32), and bipolar disorder (BPD; n = 30), along with healthy control participants (n = 46) who were matched for age, gender, and handedness.

RESULTS

The results showed that patients with MDD and BPD had altered VTA-related connectivity in the superior frontal gyrus, frontal pole regions, hippocampus, cerebellum, and posterior cingulate cortex. Some of these differences in connectivity were also found between affective disorders and schizophrenia; however, there were no differences between the schizophrenia and control groups. Connectivity between the VTA and the hippocampus was correlated with positive symptoms in the schizophrenia group. The connectivity was not associated with medication dose, and the results remained significant after controlling for dose.

CONCLUSIONS

The results suggest that altered brain functional connectivity related to VTA networks could be associated with the distinctive pathophysiologies of psychiatric disorders, especially affective disorders.

Deep Learning-Based Human Activity Recognition for Continuous Activity and Gesture Monitoring for Schizophrenia Patients With Negative Symptoms

BACKGROUND

We aimed to develop a Human Activity Recognition (HAR) model using a wrist-worn device to assess patient activity in relation to negative symptoms of schizophrenia.

METHODS

Data were analyzed in a randomized, three-way cross-over, proof-of-mechanism study (ClinicalTrials.gov: NCT02824055) comparing two doses of RG7203 with placebo, given as adjunct to stable antipsychotic treatment in patients with chronic schizophrenia and moderate levels of negative symptoms. Baseline negative symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS) and Brief Negative Symptom Scale (BNSS). Patients were given a GeneActiv™ wrist-worn actigraphy device to wear over a 15-week period. For this analysis, actigraphy data and behavioral and clinical assessments obtained during placebo treatment were used. Motivated behavior was evaluated with a computerized effort-choice task. A trained HAR model was used to classify activity and an activity-time ratio was derived. Gesture events and features were inferred from the HAR-detected activities and the acceleration signal.

RESULTS

Thirty-three patients were enrolled: mean (±SD) age 36.6 ± 7 years; mean (±SD) baseline PANSS negative symptom factor score 23.0 ± 3.5; and mean (±SD) baseline BNSS total score 36.0 ± 11.5. Activity data were collected for 31 patients with a median monitoring time of 1,859 h per patient, equating to ~11 weeks or 74% monitoring ratio. The trained HAR model demonstrated >95% accuracy in separating ambulatory and stationary activities. A positive correlation was seen between the activity-time ratio and the percent of high-effort choices (Spearman r = 0.58; P = 0.002) in the effort-choice task. Median daily gesture counts correlated negatively with the BNSS total score (Spearman r = -0.44; P = 0.03), specifically with the diminished expression sub-score (Spearman r = -0.42; P = 0.03). Gesture features also correlated negatively with the BNSS total score and diminished expression sub-scores. Activity measures showed similar correlations with PANSS negative symptom factor but did not reach significance.

CONCLUSION

Our findings support the use of wrist-worn devices to derive activity and gesture-based digital outcome measures for patients with schizophrenia with negative symptoms in a clinical trial setting.

Sleep spindle activity in childhood onset schizophrenia: Diminished and associated with clinical symptoms

Neuroimaging studies of childhood onset schizophrenia (COS), a rare yet severe form of schizophrenia with an onset before the age of 13 years, have shown continuity with adult onset schizophrenia. Previous research in adult patients has shown reduced sleep spindle activity, transient oscillations in the sleep electroencephalogram (EEG) generated through thalamocortical loops. The current study examines sleep spindle activity in patients with COS. Seventeen children and adolescents with COS (16 years ±6.6) underwent overnight sleep EEG recordings. Sleep spindle activity was compared between patients with COS and age and gender matched controls and correlated with clinical symptom severity. We found pronounced deficits in sleep spindle amplitude, duration, density and frequency in patients with COS (effect size = 0.61 to 1.96; dependent on metric and EEG derivation). Non-rapid eye movement (NREM) sleep EEG power and coherence in the sigma band (11-16 Hz) corresponding to spindle activity were also markedly diminished in patients with COS as compared to controls. Furthermore, the degree of deficit in power and coherence of spindles was strongly associated with clinician rated hallucinations and positive symptoms over widespread cortical regions. Our finding of diminished spindle activity and its association with hallucinations likely reflect dysfunction of the thalamocortical circuits in children and adolescents with COS. Given the relative ease of sleep EEG recordings in vulnerable populations, this study highlights the potential of such recordings to characterize brain function in schizophrenia.

Frontal white matter abnormalities reveal the pathological basis underlying negative symptoms in antipsychotic-naïve, first-episode patients with adolescent-onset schizophrenia: Evidence from multimodal brain imaging

A major challenge in schizophrenia is to uncover the pathophysiological basis of its negative symptoms. Recent neuroimaging studies revealed that disrupted structural properties of frontal white matter (FWM) are associated with the negative symptoms of schizophrenia. However, there is little direct functional evidence of FWM for negative symptoms in schizophrenia. To address this issue, we combined resting-state connectome-wide functional connectivity (FC) and diffusion tensor imaging tractography to investigate the alteration of FWM underlying the negative symptoms in 39 drug-naive patients with adolescent-onset schizophrenia (AOS) and 31 age- and sex- matched healthy controls (HCs). Results revealed that the intrinsic FC and structural properties (fraction anisotropy and fibers) of the left FWM correspond to individual negative symptoms in AOS. Moreover, the serotonin network (raphe nuclei, anterior and posterior cingulate cortices, and prefrontal and inferior parietal cortices) and FWM-cingulum network were found to contributed to the negative symptom severity in AOS. Furthermore, the patients showed abnormal functional and structural connectivities between the interhemispheric FWM compared with HCs. Importantly, the decreased fiber counts between the interhemispheric FWM were inversely correlated with the negative symptoms in AOS. Our findings demonstrated the association between FWM and negative symptoms, and offered initial evidence by using WM connectome to uncover WM functional information in schizophrenia.

The Amygdala in Schizophrenia and Bipolar Disorder: A Synthesis of Structural MRI, Diffusion Tensor Imaging, and Resting-State Functional Connectivity Findings

Frequently implicated in psychotic spectrum disorders, the amygdala serves as an important hub for elucidating the convergent and divergent neural substrates in schizophrenia and bipolar disorder, the two most studied groups of psychotic spectrum conditions. A systematic search of electronic databases through December 2017 was conducted to identify neuroimaging studies of the amygdala in schizophrenia and bipolar disorder, focusing on structural MRI, diffusion tensor imaging (DTI), and resting-state functional connectivity studies, with an emphasis on cross-diagnostic studies. Ninety-four independent studies were selected for the present review (49 structural MRI, 27 DTI, and 18 resting-state functional MRI studies). Also selected, and analyzed in a separate meta-analysis, were 33 volumetric studies with the amygdala as the region-of-interest. Reduced left, right, and total amygdala volumes were found in schizophrenia, relative to both healthy controls and bipolar subjects, even when restricted to cohorts in the early stages of illness. No volume abnormalities were observed in bipolar subjects relative to healthy controls. Shape morphometry studies showed either amygdala deformity or no differences in schizophrenia, and no abnormalities in bipolar disorder. In contrast to the volumetric findings, DTI studies of the uncinate fasciculus tract (connecting the amygdala with the medial- and orbitofrontal cortices) largely showed reduced fractional anisotropy (a marker of white matter microstructure abnormality) in both schizophrenia and bipolar patients, with no cross-diagnostic differences. While decreased amygdalar-orbitofrontal functional connectivity was generally observed in schizophrenia, varying patterns of amygdalar-orbitofrontal connectivity in bipolar disorder were found. Future studies can consider adopting longitudinal approaches with multimodal imaging and more extensive clinical subtyping to probe amygdalar subregional changes and their relationship to the sequelae of psychotic disorders.

Effectiveness of Cerebellar Circuitry Modulation in Schizophrenia: A Systematic Review

Structural and functional abnormalities of the cerebellum have been observed in schizophrenia since the first neuroimaging studies. More recently, the functions of the cerebellum have been extended beyond sensorimotor control to include participation in higher-level cognition and affective regulation. Consistently, the "cognitive dysmetria" theory posits that dysfunctions of cortical-subcortical-cerebellar circuitry may be crucial for the pathogenesis of different clinical features of schizophrenia. This conceptual framework offers a set of testable hypotheses, now that various tools to exert direct modulation of cerebellar activity are available. We conducted a systematic review of studies examining the effects of cerebellar modulation in schizophrenia. Two independent authors conducted a search within PubMed for articles published up to April 2019 and identified 10 studies (three randomized controlled trials, two open-label studies, two case reports, one preclinical study) describing the effects of cerebellar circuitry modulation in patients with schizophrenia or animal models. The majority of interventions were uncontrolled and used stimulation of the cerebellar vermis, using transcranial magnetic stimulation or transcranial direct-current stimulation. Most studies detected improvements after cerebellar modulation. Clinical changes mostly pertained the domains of negative symptoms, depressive symptoms and cognitive functions. In conclusion, few studies examined the effects of cerebellar modulation in schizophrenia but yielded promising results. This approach may hold therapeutic potential, pending further methodologically robust replication.

Increased structural connectivity of the medial forebrain bundle in schizophrenia spectrum disorders is associated with delusions of paranoid threat and grandiosity

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Increased FA of bilateral slMFB can be found in delusional SSD-patients.

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Findings are supported by a psychopathological model of paranoia and grandiosity.

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Findings are in line with a model of underlying network physiology (slMFB).

In many cases delusions in schizophrenia spectrum disorders (SSD) are driven by strong emotions such as feelings of paranoia or grandiosity. We refer to these extreme emotional experiences as psychotic affectivity. We hypothesized that increased structural connectivity of the supero-lateral medial forebrain bundle (slMFB), a major tract of the reward system, is associated with delusional psychotic affectivity. Forty-six patients with SSD and 44 healthy controls (HC) underwent diffusion weighted magnetic resonance imaging (DW-MRI)-scans. The slMFB and a comparison tract (corticospinal tract) were reconstructed using diffusion tensor imaging (DTI)-based tractography. Fractional anisotropy (FA) was sampled across the tracts. We used a mixed-model analyses of variance controlling for age and gender to compare FA of bilateral slMFB between SSD-patients and HC. Correlations of FA of bilateral slMFB and the PANSS-positive item delusions were calculated. In addition, FA was compared between three clinically homogeneous SSD-subgroups in terms of psychotic affectivity (severe, mild and no PA, sPA, mPA, nPA) and HC. FA of the slMFB did not differ between all SSD-patients and HC. In SSD-patients there was a positive correlation between delusions and FA in bilateral slMFB. Likewise, SSD-subgroups of psychotic affectivity and HC differed significantly in FA of the slMFB. Results were driven by higher FA in the right slMFB in sPA as compared to nPA and to HC. There was no significant effect for the comparison tract. In conclusion, increased structural connectivity of the slMFB may underlie delusional experiences of paranoia and grandiosity in SSD.

Cognitive correlates of abnormal myelination in psychosis

Psychotic illness has consistently been associated with deficits in cognitive function and reduced white matter integrity in the brain. However, the link between white matter disruptions and deficits in cognitive domains remains poorly understood. We assessed cognitive performance and white matter myelin water fraction (MWF) using multicomponent driven equilibrium single pulse observation of T1 and T2 (mcDESPOT) in recent-onset psychosis patients and age-matched healthy controls (HC). Psychosis patients showed deficits in working memory, phonological and semantic fluency, general intelligence quotient and reduced MWF in the left temporal white matter compared to HC. MWF in the left inferior fronto-occipital fasciculus and inferior longitudinal fasciculus was positively associated with intelligence quotient and verbal fluency in patients, and fully mediated group differences in performance in both phonological and semantic verbal fluency. There was no association between working memory and MWF in the left temporal white matter. Negative symptoms demonstrated a negative association with MWF within the left inferior and superior longitudinal fasciculi. These findings indicate that psychosis-related deficits in distinct cognitive domains, such as verbal fluency and working memory, are not underpinned by a single common dysfunction in white matter connectivity.

Abnormalities of fronto-subcortical pathways in schizophrenia and the differential impacts of antipsychotic treatment: a DTI-based tractography study

The fronto-striato-thalamic circuitry is a key network in patients with schizophrenia (SZPs). We use diffusion tensor imaging (DTI) to investigate the integrity of white matter (WM) pathways involved in this network in SZPs relative to healthy controls (HCs). We also evaluate the differential impact of chronic exposure to clozapine as well as other atypical and typical antipsychotics. 63 HCs and 41 SZPs were included. Of the SZPs, 16 were treated with clozapine (SZPsC), 17 with atypical antipsychotics (SZPsA), and 8 with typical antipsychotics (SZPsT). Three tracts were reconstructed in the left hemisphere using tractography: one fronto-subcortical tract, one prefronto-subcortical tract, and one prefronto-frontal tract. Diffusion parameters were individually extracted in each tract. SZPs exhibited lower integrity in both the fronto-subcortical and prefronto-subcortical tracts relative to HCs, and SZPsT showed altered integrity compared to SZPsC. There were no WM integrity differences in the prefronto-frontal tract between SZP groups or between SZPs and HCs. SZPs exhibit structural connectivity abnormalities in the prefronto-fronto-subcortical network that are specifically and differentially impacted by the type of antipsychotic treatment. Additional studies are needed to separate the contributions of clozapine-mediated neuroprotection, neurotoxicity related to typical antipsychotics, and the illness itself to observed differences.

Confused Connections? Targeting White Matter to Address Treatment Resistant Schizophrenia

Despite development of comprehensive approaches to treat schizophrenia and other psychotic disorders and improve outcomes, there remains a proportion (approximately one-third) of patients who are treatment resistant and will not have remission of psychotic symptoms despite adequate trials of pharmacotherapy. This level of treatment response is stable across all stages of the spectrum of psychotic disorders, including early phase psychosis and chronic schizophrenia. Our current pharmacotherapies are beneficial in decreasing positive symptomology in most cases, however, with little to no impact on negative or cognitive symptoms. Not all individuals with treatment resistant psychosis unfortunately, even benefit from the potential pharmacological reductions in positive symptoms. The existing pharmacotherapy for psychosis is targeted at neurotransmitter receptors. The current first and second generation antipsychotic medications all act on dopamine type 2 receptors with the second generation drugs also interacting significantly with serotonin type 1 and 2 receptors, and with varying pharmacodynamic profiles overall. This focus on developing dopaminergic/serotonergic antipsychotics, while beneficial, has not reduced the proportion of patients experiencing treatment resistance to date. Another pharmacological approach is imperative to address treatment resistance both for response overall and for negative symptoms in particular. There is research suggesting that changes in white matter integrity occur in schizophrenia and these may be more associated with cognition and even negative symptomology. Here we review the evidence that white matter abnormalities in the brain may be contributing to the symptomology of psychotic disorders. Additionally, we propose that white matter may be a viable pharmacological target for pharmacoresistant schizophrenia and discuss current treatments in development for schizophrenia that target white matter.

Systems Neuroscience of Psychosis: Mapping Schizophrenia Symptoms onto Brain Systems

Schizophrenia research has been in a deadlock for many decades. Despite important advances in clinical treatment, there are still major concerns regarding long-term psychosocial reintegration and disease management, biological heterogeneity, unsatisfactory predictors of individual course and treatment strategies, and a confusing variety of controversial theories about its etiology and pathophysiological mechanisms. In the present perspective on schizophrenia research, we first discuss a methodological pitfall in contemporary schizophrenia research inherent in the attempt to link mental phenomena with the brain: we claim that the time-honored phenomenological method of defining mental symptoms should not be contaminated with the naturalistic approach of modern neuroscience. We then describe our Systems Neuroscience of Psychosis (SyNoPsis) project, which aims to overcome this intrinsic problem of psychiatric research. Considering schizophrenia primarily as a disorder of interindividual communication, we developed a neurobiologically informed semiotics of psychotic disorders, as well as an operational clinical rating scale. The novel psychopathology allows disentangling the clinical manifestations of schizophrenia into behavioral domains matching the functions of three well-described higher-order corticobasal brain systems involved in interindividual human communication, namely, the limbic, associative, and motor loops, including their corticocortical sensorimotor connections. The results of several empirical studies support the hypothesis that the proposed three-dimensional symptom structure, segregated into the affective, the language, and the motor domain, can be specifically mapped onto structural and functional abnormalities of the respective brain systems. New pathophysiological hypotheses derived from this brain system-oriented approach have helped to develop and improve novel treatment strategies with noninvasive brain stimulation and practicable clinical parameters. In clinical practice, the novel psychopathology allows confining the communication deficits of the individual patient, shifting attention from the symptoms to the intact resources. We have studied this approach and observed important advantages for therapeutic alliances, personalized treatment, and de-escalation strategies. Future studies will further conjoin clinical definitions of psychotic symptoms with brain structures and functions, and disentangle structural and functional deficit patterns within these systems to identify neurobiologically distinct subsyndromes. Neurobiologically homogeneous patient groups may provide new momentum for treatment research. Finally, lessons learned from schizophrenia research may contribute to developing a comprehensive perspective on human experience and behavior that integrates methodologically distinct, but internally consistent, insights from humanities and neuroscience.

Limbic Interference During Social Action Planning in Schizophrenia

Schizophrenia is characterized by social interaction deficits contributing to poor functional outcome. Hand gesture use is particularly impaired, linked to frontal lobe dysfunction and frontal grey matter deficits. The functional neural correlates of impaired gesturing are currently unclear. We therefore investigated aberrant brain activity during impaired gesturing in schizophrenia. We included 22 patients with schizophrenia and 25 healthy control participants matched for age, gender, and education level. We obtained functional magnetic resonance imaging data using an event-related paradigm to assess brain activation during gesture planning and execution. Group differences in whole brain effects were calculated using factorial designs. Gesture ratings were performed by a single rater, blind to diagnoses and clinical presentation. During gesture planning and execution both groups activated brain areas of the praxis network. However, patients had reduced dorsolateral prefrontal cortex (DLPFC) and increased inferior parietal lobe (IPL) activity. Performance accuracy was associated with IPL activity in patients. Furthermore, patients activated temporal poles, amygdala and hippocampus during gesture planning, which was associated with delusion severity. Finally, patients demonstrated increased dorsomedial prefrontal cortex activity during planning of novel gestures. We demonstrate less prefrontal, but more IPL and limbic activity during gesturing in schizophrenia. IPL activity was associated with performance accuracy, whereas limbic activity was linked to delusion severity. These findings may reflect impaired social action planning and a limbic interference with gestures in schizophrenia contributing to poor gesture performance and consequently poor social functioning in schizophrenia.

Relationship Between Persistent Negative Symptoms and Findings of Neurocognition and Neuroimaging in Schizophrenia

Negative symptoms are defined as loss or reduction of otherwise present behaviors or functions in illness situation, and they have constituted an important aspect of schizophrenia. Although negative symptoms have usually been considered as a single entity, neurobiological investigations yielded discrepant results. To overcome challenges that derive from this discrepancy, researchers have proposed several approaches to structure negative symptoms into more homogenous constructs. Concept of persistent negative symptoms (PNS) is one of the proposed approaches, and includes both primary and secondary negative symptoms that persist after adequate treatment. PNS is relatively easy to assess, and by definition, more inclusive; yet it represents an unmet therapeutic need. Therefore, it is a target of several neurobiological and pharmacological studies. There are several structural and functional brain alterations associated with negative symptoms. On the other hand, neurocognitive investigations in patients with schizophrenia have revealed deficits in several domains that showed correlations with negative symptoms. There are several shared features between negative symptoms and neurocognitive deficits in schizophrenia such as prevalence rates, course through the illness, prognostic importance, and impact on social functioning. However, exact mechanisms behind the neurobiology of PNS and how it interacts with neurocognition remain to be explained. Earlier reviews on neuroimaging and neurocognitive correlates of PNS have been focused on studies with broadly defined negative symptoms that were selected by methodological closeness to PNS. In this review, we focus on neural correlates and neurocognitive associations of PNS, and we discuss PNS findings available to date.

Avolition-Apathy and White Matter Connectivity in Schizophrenia: Reduced Fractional Anisotropy Between Amygdala and Insular Cortex

The avolition/apathy domain of negative symptoms includes motivation- and pleasure-related impairments. In people with schizophrenia, structural and functional abnormalities were reported in key regions within the motivational reward system, including ventral-tegmental area (VTA), striatum (especially at the level of the nucleus accumbens, NAcc), orbitofrontal cortex (OFC), as well as amygdala (Amy) and insular cortex (IC). However, the association of the reported abnormalities with avoliton-apathy is still controversial. In the present study, we investigated white matter connectivity patterns within these regions, using a probabilistic analysis of diffusion tensor imaging (DTI) data, in male subjects with schizophrenia. Thirty-five male subjects with schizophrenia (SCZ) and 17 male healthy controls (HC) matched for age, underwent DTI. SCZ were evaluated using the Schedule for Deficit Syndrome (SDS), the Positive and Negative Syndrome Scale (PANSS), and the MATRICS Consensus Cognitive Battery (MCCB). Probabilistic tractography was applied to investigate pathways connecting the Amy and the NAcc with the OFC and IC. Reduced fractional anisotropy (FA) was observed in left Amy-ventral anterior IC connections, in SCZ compared with controls. This abnormality was negatively correlated with avolition/apathy but not with expressive deficit scores. SCZ showed also a reduced connectivity index between right NAcc and medial OFC, as compared with controls. Finally, the left NAcc-dorsal anterior IC connectivity index was negatively correlated with working memory scores. Our results indicate that only the avolition/apathy domain of negative symptoms is related to abnormal connectivity in the motivation-related circuits. The findings also demonstrate that distinct alterations underlie cognitive impairment and avolition/apathy.

Specific cerebral perfusion patterns in three schizophrenia symptom dimensions

Dimensional concepts such as the Research Domain Criteria initiative have been proposed to disentangle the heterogeneity of schizophrenia. One model introduced three neurobiologically informed behavioral dimensions: language, affectivity and motor behavior. To study the brain-behavior associations of these three dimensions, we investigated whether current behavioral alterations were linked to resting state perfusion in distinct brain circuits in schizophrenia. In total, 47 patients with schizophrenia spectrum disorders and 44 healthy controls were included. Psychopathology was assessed with the Positive And Negative Syndrome Scale and the Bern Psychopathology scale (BPS). The BPS provides severity ratings of three behavioral dimensions (language, affectivity and motor). Patients were classified according to the severity of alterations (severe, mild, no) in each dimension. Whole brain resting state cerebral blood flow (CBF) was compared between patient subgroups and controls. Two symptom dimensions were associated with distinct CBF changes. Behavioral alterations in the language dimension were linked to increased CBF in Heschl's gyrus. Altered affectivity was related to increased CBF in amygdala. The ratings of motor behavior instead were not specifically associated with CBF. Investigating behavioral alterations in three schizophrenia symptom dimensions identified distinct regional CBF changes in the language and limbic brain circuits. The results demonstrate a hitherto unknown segregation of pathophysiological pathways underlying a limited number of specific symptom dimensions in schizophrenia.

Altered structural network architecture is predictive of the presence of psychotic symptoms in patients with 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11DS) represents a homogeneous model of schizophrenia particularly suitable for the search of neural biomarkers of psychosis. Impairments in structural connectivity related to the presence of psychotic symptoms have been reported in patients with 22q11DS. However, the relationships between connectivity changes in patients with different symptomatic profiles are still largely unknown and warrant further investigations.

In this study, we used structural connectivity to discriminate patients with 22q11DS with (N = 31) and without (N = 31) attenuated positive psychotic symptoms. Different structural connectivity measures were used, including the number of streamlines connecting pairs of brain regions, graph theoretical measures, and diffusion measures. We used univariate group comparisons as well as predictive multivariate approaches.

The univariate comparison of connectivity measures between patients with or without attenuated positive psychotic symptoms did not give significant results. However, the multivariate prediction revealed that altered structural network architecture discriminates patient subtypes (accuracy = 67.7%). Among the regions contributing to the classification we found the anterior cingulate cortex, which is known to be associated to the presence of psychotic symptoms in patients with 22q11DS. Furthermore, a significant discrimination (accuracy = 64%) was obtained with fractional anisotropy and radial diffusivity in the left inferior longitudinal fasciculus and the right cingulate gyrus.

Our results point to alterations in structural network architecture and white matter microstructure in patients with 22q11DS with attenuated positive symptoms, mainly involving connections of the limbic system. These alterations may therefore represent a potential biomarker for an increased risk of psychosis that should be further tested in longitudinal studies.

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Altered network architecture discriminates psychotic patients with 22q11DS;

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Altered diffusivity measures are evident in psychotic patients with 22q11DS;

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White matter alterations associated to psychosis are located in limbic regions.

Implication of reward alterations in the expression of negative symptoms in 22q11.2 deletion syndrome: a behavioural and DTI study

BACKGROUND

Alterations of the reward system have been proposed as one of the core mechanisms underlying the expression of negative symptoms in schizophrenia. Specifically, deficits in specific reward components and white matter (WM) integrity of the reward system have been highlighted. The putative link between negative symptoms and the hedonic experience, or structural connectivity of the reward system has never been examined in the 22q11.2 deletion syndrome (22q11DS), a condition with increased risk for psychosis.

METHOD

Anticipatory and consummatory dimensions of pleasure were assessed in participants with 22q11DS (N = 54) and healthy controls (N = 55). In patients with 22q11DS, the association between pleasure scores and positive or negative symptoms was investigated. Furthermore, WM integrity of the accumbofrontal tract was quantified using diffusion tensor imaging (DTI). Associations between DTI measures, pleasure dimensions and negative symptoms were examined.

RESULTS

Patients with 22q11DS showed reduced anticipatory and consummatory pleasure compared to controls. Furthermore, anticipatory pleasure scores were negatively correlated to negative and positive symptoms in 22q11DS. WM microstructural changes of the accumbofrontal tract in terms of increased fractional anisotropy and reduced radial anisotropy were also identified in patients. However, no significant correlation between the DTI measures and pleasure dimensions or psychotic symptoms was observed.

CONCLUSIONS

This study revealed that participants with 22q11DS differed in their experience of pleasure compared to controls. The anticipatory pleasure component appears to be related to negative and positive symptom severity in patients. Alterations of WM integrity of the accumbofrontal tract seem to be related to myelination abnormalities in 22q11DS patients.

Toward a neurobiologically informed psychiatry

Schizophrenia is a severe and, at the same time fascinating disorder. It is traditionally defined as a «dissociation» of higher brain functions, which implies a modular organization of the brain up to its highest levels of organization. This short review shows how the study of the disorder is still flawed by fundamentally different definitions of the disorder, and that a consistent naturalistic approach may help to revise the vocabulary of psychiatric disorders, opening the way towards a neurobiologically informed psychiatry. Empirical studies and clinical importance supporting this novel approach are summarized.

Comparison of psychopathological dimensions between major depressive disorder and schizophrenia spectrum disorders focusing on language, affectivity and motor behavior

This study tested whether patients with major depressive disorder (MDD) and schizophrenia spectrum disorders would differ in three dimensions of psychopathology (language, affectivity and motor behavior) as assessed by the Bern Psychopathology Scale (BPS) in a cohort of 58 patients with MDD and 146 patients with schizophrenia spectrum disorders. The overall estimation of severity of each of the three dimensions was rated on a seven-point Likert scale from severely inhibited to severely disinhibited. Here, more than half of the patients endorsed ratings that showed normal or mildly (dis-)inhibited behavior. At group level more pronounced negative ratings of affect were seen in MDD. Group comparisons of the severity ratings on language or motor behavior yielded no differences between schizophrenia spectrum disorders and MDD. At the individuals' levels, extreme ratings in the language and motor dimensions were more frequent in schizophrenia spectrum disorders and in the affectivity dimension more frequent in MDD. Shared psychopathological features could be seen across diagnoses, supporting a dimensional approach to psychopathology in endogenous psychoses. However, the groups differ in the severity of affect ratings as well as in the distribution of language, affectivity and motor ratings with more variance among the group of schizophrenia spectrum disorders.

Changes in White Matter Organization in Adolescent Offspring of Schizophrenia Patients

Schizophrenia is associated with frontostriatal network impairments underlying clinical and cognitive symptoms. We previously found disruptions in anatomical pathways, including the tract connecting the left nucleus accumbens and left dorsolateral prefrontal cortex (DLPFC). Similar deficits are observed in unaffected siblings of schizophrenia patients, indicating that these deficits are linked to a genetic vulnerability for the disorder. Frontostriatal tract disruptions may arise during adolescence, preceding the clinical manifestation of the disorder. However, to date, no studies have been performed to investigate frontostriatal tract connections in adolescents who are at increased familial risk for schizophrenia. In this study, we investigate the impact of familial risk on frontostriatal tract connections using diffusion tensor imaging in 27 adolescent offspring of schizophrenia patients and 32 matched control adolescents, aged 10-18 years. Mean fractional anisotropy (FA) was calculated for the tracts connecting the striatum (caudate nucleus, putamen, nucleus accumbens) and frontal cortex regions (DLPFC, medial orbital frontal cortex, inferior frontal gyrus). As expected, based on siblings data, we found an impact of familial risk on frontostriatal development: schizophrenia offspring showed increased FA in the tracts connecting nucleus accumbens and DLPFC as compared with control adolescents. Moreover, while FA increased across age in control adolescents, it did not in schizophrenia offspring. We did not find differences in FA in other frontostriatal tracts. These results indicate altered development of white matter in subjects who are at familial risk for schizophrenia and may precede frontostriatal white matter alterations in adult schizophrenia patients and siblings.

Interaction of language, auditory and memory brain networks in auditory verbal hallucinations

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The language, auditory and memory/limbic networks are of particular relevance for auditory verbal hallucinations.

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An increased interaction among the auditory-language and striatal brain regions occurs while patients hallucinate.

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Fronto-temporal connections are often altered in AVH individuals, but there is no consensus regarding increase or decrease.

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Connections of the interhemispheric auditory pathway are stronger for first episode patients, but they are weaker in chronic patients.

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The majority of studies support hybrid AVH hypotheses in which all three networks and the striatal network are involved.

Auditory verbal hallucinations (AVH) occur in psychotic disorders, but also as a symptom of other conditions and even in healthy people. Several current theories on the origin of AVH converge, with neuroimaging studies suggesting that the language, auditory and memory/limbic networks are of particular relevance. However, reconciliation of these theories with experimental evidence is missing. We review 50 studies investigating functional (EEG and fMRI) and anatomic (diffusion tensor imaging) connectivity in these networks, and explore the evidence supporting abnormal connectivity in these networks associated with AVH. We distinguish between functional connectivity during an actual hallucination experience (symptom capture) and functional connectivity during either the resting state or a task comparing individuals who hallucinate with those who do not (symptom association studies). Symptom capture studies clearly reveal a pattern of increased coupling among the auditory, language and striatal regions. Anatomical and symptom association functional studies suggest that the interhemispheric connectivity between posterior auditory regions may depend on the phase of illness, with increases in non-psychotic individuals and first episode patients and decreases in chronic patients. Leading hypotheses involving concepts as unstable memories, source monitoring, top-down attention, and hybrid models of hallucinations are supported in part by the published connectivity data, although several caveats and inconsistencies remain. Specifically, possible changes in fronto-temporal connectivity are still under debate. Precise hypotheses concerning the directionality of connections deduced from current theoretical approaches should be tested using experimental approaches that allow for discrimination of competing hypotheses.

Distinct resting-state perfusion patterns underlie psychomotor retardation in unipolar vs. bipolar depression

OBJECTIVE

Psychomotor abnormalities characterize both unipolar (UP) depression and bipolar (BP) depression. We aimed to assess their neurobiological correlates in terms of motor activity (AL) and resting-state cerebral blood flow (rCBF) and investigate their association in BP, UP, and healthy controls (HC).

METHOD

We enrolled 42 depressed patients (22 BP, 20 UP) and 19 HC matched for age, gender, education, income. AL and rCBF were objectively assessed with the use of wrist actigraphy and arterial spin labeling. Group differences and the association of AL and rCBF were computed.

RESULTS

Activity level was significantly reduced in patients, but no difference was found between BP and UP. Increased perfusion was found in BP compared with UP and HC, in multiple brain areas. We found positive correlations of rCBF and AL in BP and UP, in different parts of the insula and frontal regions. Only BP showed a cluster in the left precentral gyrus. In HC, only inverse correlations of AL and rCBF were found.

CONCLUSION

The differences in rCBF and in the localization of the clusters of positive AL/rCBF correlations between BP and UP suggest that different neural impairments may underlie motor symptoms in the two disorders, but finally converge in phenotypically similar manifestations.

Disrupted salience network functional connectivity and white-matter microstructure in persons at risk for psychosis: findings from the LYRIKS study

BACKGROUND

Salience network (SN) dysconnectivity has been hypothesized to contribute to schizophrenia. Nevertheless, little is known about the functional and structural dysconnectivity of SN in subjects at risk for psychosis. We hypothesized that SN functional and structural connectivity would be disrupted in subjects with At-Risk Mental State (ARMS) and would be associated with symptom severity and disease progression.

METHOD

We examined 87 ARMS and 37 healthy participants using both resting-state functional magnetic resonance imaging and diffusion tensor imaging. Group differences in SN functional and structural connectivity were examined using a seed-based approach and tract-based spatial statistics. Subject-level functional connectivity measures and diffusion indices of disrupted regions were correlated with CAARMS scores and compared between ARMS with and without transition to psychosis.

RESULTS

ARMS subjects exhibited reduced functional connectivity between the left ventral anterior insula and other SN regions. Reduced fractional anisotropy (FA) and axial diffusivity were also found along white-matter tracts in close proximity to regions of disrupted functional connectivity, including frontal-striatal-thalamic circuits and the cingulum. FA measures extracted from these disrupted white-matter regions correlated with individual symptom severity in the ARMS group. Furthermore, functional connectivity between the bilateral insula and FA at the forceps minor were further reduced in subjects who transitioned to psychosis after 2 years.

CONCLUSIONS

Our findings support the insular dysconnectivity of the proximal SN hypothesis in the early stages of psychosis. Further developed, the combined structural and functional SN assays may inform the prognosis of persons at-risk for psychosis.

Neural substrates underlying delusions in schizophrenia

Delusions are cardinal positive symptoms in schizophrenia; however, the neural substrates of delusions remain unknown. In the present study, we investigated the neural correlates of delusions in schizophrenia using multi-modal magnetic resonance imaging (MRI) techniques. Diffusion, structural and perfusion MRIs were performed in 19 schizophrenia patients with severe delusions, 30 patients without delusions and 30 healthy controls. Fractional anisotropy (FA), gray matter volume (GMV) and cerebral blood flow (CBF) were voxel-wisely compared among the three groups. Although patients without delusions exhibited decreased FA in white matter regions and decreased GMV in gray matter regions relative to controls, patients with severe delusions demonstrated comparable FA in all of these white matter regions and similar GMV in most of these gray matter regions. Both patient subgroups had less GMV in the amygdala and anterior cingulate cortex than controls. Although two patient subgroups showed consistent CBF changes relative to controls, only CBF in the anterior cingulate cortex was lower in patients with severe delusions than in patients without delusions. These findings suggest that schizophrenia patients with severe delusions have relatively normal structural integrity. Importantly, the excessively reduced perfusion in the anterior cingulate cortex may be associated with the development of delusions in schizophrenia.

Abnormal white matter microstructure and increased extracellular free-water in the cingulum bundle associated with delusions in chronic schizophrenia

Background

There is growing evidence to suggest that delusions associated with schizophrenia arise from altered structural brain connectivity. The present study investigated whether structural changes in three major fasciculi that interconnect the limbic system – the cingulum bundle, uncinate fasciculus and fornix – are associated with delusions in chronic schizophrenia patients.

Methods

Free-water corrected Diffusion Tensor Imaging was used to investigate the association between delusions and both microstructural changes within these three fasciculi and extracellular changes in the surrounding free-water. Clinical data and diffusion MRI scans were obtained from 28 healthy controls and 86 schizophrenia patients, of whom 34 had present state delusions, 35 had a lifetime history but currently remitted delusions, and 17 had never experienced delusions.

Results

While present state and remitted delusions were found to be associated with reduced free-water corrected fractional anisotropy (FA_T) and increased free-water corrected radial diffusivity (RD_T) in the cingulum bundle bilaterally, extracellular free-water (FW) in the left cingulum bundle was found to be specifically associated with present state delusions in chronic schizophrenia. No changes were observed in the remaining tracts.

Conclusions

These findings suggest that state and trait delusions in chronic schizophrenia are associated with microstructural processes, such as myelin abnormalities (as indicated by decreased FA_T and increased RD_T) in the cingulum bundle and that state delusions are additionally associated with extracellular processes such as neuroinflammation or atrophy (as indicated by increased FW) in the left cingulum bundle.

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Free-water imaging was used to differentiate microstructural and extracellular processes.

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Patients with delusions showed increased RD_T and FW in the cingulum bundle.

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Myelin abnormalities and neuroinflammation may be involved in the manifestation of delusions.

Cerebral white matter structure is associated with DSM-5 schizophrenia symptom dimensions

Diffusion tensor imaging (DTI) studies have provided evidence of widespread white matter (WM) abnormalities in schizophrenia. Although these abnormalities appear clinically significant, the relationship to specific clinical symptoms is limited and heterogeneous. This study examined the association between WM microstructure and the severity of the five main DSM-5 schizophrenia symptom dimensions. DTI was measured in forty patients with schizophrenia spectrum disorders. Using Tract-Based Spatial Statistics controlling for age, gender and antipsychotic dosage, our analyses revealed significant negative relationships between WM microstructure and two DSM-5 symptom dimensions: Whereas abnormal psychomotor behavior was particularly related to WM of motor tracts, negative symptoms were associated with WM microstructure of the prefrontal and right temporal lobes. However, we found no associations between WM microstructure and delusions, hallucinations or disorganized speech. These data highlight the relevance of characteristic WM disconnectivity patterns as markers for negative symptoms and abnormal psychomotor behavior in schizophrenia and provide evidence for relevant associations between brain structure and aberrant behavior.

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DTI study of brain-behavior associations of the new DSM-5 schizophrenia dimensions.

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The severity of the DSM-5 abnormal psychomotor behavior dimension is related to white matter microstructure in motor tracts.

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Associations of the DSM-5 negative symptom dimension with white matter microstructure are found in prefrontal and temporal clusters.

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Characteristic patterns of white matter microstructure argue for relevant associations between brain structure and aberrant behavior in schizophrenia.

[Negative symptoms and cerebral imaging]

A number of neuroanatomical and neurofonctional abnormalities have been evidenced by cerebral imaging studies in patients suffering from schizophrenia. Nevertheless, those specifically associated with the negative symptoms of this disease are still insufficiently known. This work is a review of selected studies that have assessed the brain correlates of negative symptoms in schizophrenia. Approaches using structural imaging have highlighted reduction of gray matter density or cortical thickness associated with negative symptoms, which is rather sparsely distributed within the frontal and temporal regions, localized nevertheless more particularly in the frontal medial and orbitofrontal areas, as well as the amygdalo-hippocampic complex. These deficits are concurrent with a loss of integrity of the principal paths of white matter tracts between frontal and limbic regions. On the other hand, neurofonctional abnormalities associated with negative symptoms involve especially the frontal areas and limbic striatum. A disturbed functioning within the fronto-striatal loops, related to a striatal dopaminergic deficit, may represent a potential explanatory hypothesis of the negative symptoms of schizophrenia, as suggested by studies using Positron Emission Tomography on this topic or neuroimaging studies on the effects of antipsychotics. A better identification of the cerebral abnormalities associated with the negative dimension of schizophrenia, with regard to the lateralization of these abnormalities or to their changes during the course of the disease, could offer new therapeutic modalities for the treatment of this dimension which, until now, remains few responsive to conventional pharmacological treatments.

Keep at bay!--Abnormal personal space regulation as marker of paranoia in schizophrenia

BACKGROUND

During threat, interpersonal distance is deliberately increased. Personal space regulation is related to amygdala function and altered in schizophrenia, but it remains unknown whether it is particularly associated with paranoid threat.

METHODS

We compared performance in two tests on personal space between 64 patients with schizophrenia spectrum disorders and 24 matched controls. Patients were stratified in those with paranoid threat, neutral affect or paranoid experience of power. In the stop-distance paradigm, participants indicated the minimum tolerable interpersonal distance. In the fixed-distance paradigm, they indicated the level of comfort at fixed interpersonal distances.

RESULTS

Paranoid threat increased interpersonal distance two-fold in the stop-distance paradigm, and reduced comfort ratings in the fixed-distance paradigm. In contrast, patients experiencing paranoid power had high comfort ratings at any distance. Patients with neutral affect did not differ from controls in the stop-distance paradigm. Differences between groups remained when controlling for gender and positive symptom severity. Among schizophrenia patients, the stop-distance paradigm detected paranoid threat with 93% sensitivity and 83% specificity.

CONCLUSIONS

Personal space regulation is not generally altered in schizophrenia. However, state paranoid experience has distinct contributions to personal space regulation. Subjects experiencing current paranoid threat share increased safety-seeking behavior.

DUF1220 copy number is associated with schizophrenia risk and severity: implications for understanding autism and schizophrenia as related diseases

The copy number of DUF1220, a protein domain implicated in human brain evolution, has been linearly associated with autism severity. Given the possibility that autism and schizophrenia are related disorders, the present study examined DUF1220 copy number variation in schizophrenia severity. There are notable similarities between autism symptoms and schizophrenia negative symptoms, and divergence between autism symptoms and schizophrenia positive symptoms. We therefore also examined DUF1220 copy number in schizophrenia subgroups defined by negative and positive symptom features, versus autistic individuals and controls. In the schizophrenic population (N=609), decreased DUF1220 copy number was linearly associated with increasing positive symptom severity (CON1 P=0.013, HLS1 P=0.0227), an association greatest in adult-onset schizophrenia (CON1 P=0.00155, HLS1 P=0.00361). In schizophrenic males, DUF1220 CON1 subtype copy number increase was associated with increased negative symptom severity (P=0.0327), a finding similar to that seen in autistic populations. Subgroup analyses demonstrated that schizophrenic individuals with predominantly positive symptoms exhibited reduced CON1 copy number compared with both controls (P=0.0237) and schizophrenic individuals with predominantly negative symptoms (P=0.0068). These findings support the view that (1) autism and schizophrenia exhibit both opposing and partially overlapping phenotypes and may represent a disease continuum, (2) variation in DUF1220 copy number contributes to schizophrenia disease risk and to the severity of both disorders, and (3) schizophrenia and autism may be, in part, a harmful by-product of the rapid and extreme evolutionary increase in DUF1220 copy number in the human species.

Retinal nerve fiber layer and macular thickness in patients with schizophrenia: Influence of recent illness episodes

Optical coherence tomography (OCT) has been recently used to investigate neuropsychiatric disorders. We aimed to study retinal OCT measures of patients with schizophrenia with respect to healthy controls, and to evaluate possible differences between recent illness episode (RIE) and non-recent illness episode (NRIE) patients. Thirty schizophrenia patients were classified as RIE (n=10) or NRIE (n=20), and compared with 30 matched controls. Statistical analyses included linear mixed-effects models to study the association between OCT measures and group membership. Multivariate models were used to control for potential confounders. In the adjusted linear mixed-effects regression model, patients had a significantly thinner retinal nerve fiber layer (RNFL) in overall measurements, and in the nasal, superior and inferior quadrants. Macular inner ring thickness and macular volume were also significantly smaller in patients than controls. Compared with controls, in the adjusted model only NRIE (but not RIE) patients had significantly reduced RNFL overall measures, superior RNFL, nasal RNFL, macular volume, and macular inner ring thickness. No significant correlation was found between illness duration and retinal measurements after controlling for age. In conclusion, retinal parameters observed using OCT in schizophrenia patients could be related to clinical status and merit attention as potential state biomarkers of the disorder.

Reduced fronto-striatal white matter integrity in schizophrenia patients and unaffected siblings: a DTI study

Background:

Schizophrenia is characterized by impairments in the fronto–striatal network. Underlying these impairments may be disruptions in anatomical pathways connecting frontal and striatal regions. However, the specifics of these disruptions remain unclear and whether these impairments are related to the genetic vulnerability of schizophrenia is not known.

Methods:

Here, we investigated fronto–striatal tract connections in 24 schizophrenia patients, 30 unaffected siblings, and 58 healthy controls using diffusion tensor imaging. Mean fractional anisotropy (FA) was calculated for tracts connecting the striatum with frontal cortex regions including the dorsolateral prefrontal cortex (DLPFC), medial orbital frontal cortex, and inferior frontal gyrus. Specifically, the striatum was divided into three subregions (caudate nucleus, putamen, and nucleus accumbens) and mean FA was computed for tracts originating from these striatal subregions.

Results:

We found no differences between patients, siblings, and controls in mean FA when taking the whole striatum as a seed region. However, subregion analyses showed reduced FA in the tract connecting the left nucleus accumbens and left DLPFC in both patients (P=0.0003) and siblings (P=0.0008) compared with controls.

Conclusions:

The result of reduced FA in the tract connecting the left nucleus accumbens and left DLPFC indicates a possible reduction of white matter integrity, commonly associated with schizophrenia. As both patients and unaffected siblings show reduced FA, this may represent a vulnerability factor for schizophrenia.

Limbic white matter microstructure plasticity reflects recovery from depression

BACKGROUND

White matter microstructure alterations of limbic and reward pathways have been reported repeatedly for depressive episodes in major depressive disorder (MDD) and bipolar disorder (BD). However, findings during remission are equivocal. It was the aim of this study to investigate if white matter microstructure changes during the time course of clinical remission.

METHODS

Fifteen depressed patients (11 MDD, 4 BD) underwent diffusion-weighted MRI both during depression, and during remission following successful antidepressive treatment (average time interval between scans = 6 months). Fractional anisotropy (FA) was sampled along reconstructions of the supero-lateral medial forebrain bundle (slMFB), the cingulum bundle (CB), the uncinate fasciculus (UF), the parahippocampal cingulum (PHC) and the fornix. Repeated measures ANCOVAs controlling for the effect of age were calculated for each tract.

RESULTS

There was a significant main effect of time (inter-scan interval) for mean-FA for the right CB and for the left PHC. For both pathways there was a significant time × age interaction. In the right CB, FA increased in younger patients, while FA decreased in older patients. In the left PHC, a reverse pattern was seen. FA changes in the right CB correlated positively with symptom reductions. Mean-FA of UF, slMFB and fornix did not change between the two time points.

LIMITATIONS

All patients were medicated, sample size, and lack of control group.

CONCLUSIONS

Right CB and left PHC undergo age-dependent plastic changes during the course of remission and may serve as a state marker in depression. UF, slMFB and FO microstructure remains stable.