Abnormalities of fine motor control in schizophrenia

Glymphatic System Dysfunction Underlying Schizophrenia Is Associated With Cognitive Impairment

BACKGROUND AND HYPOTHESIS

Despite the well-documented structural and functional brain changes in schizophrenia, the potential role of glymphatic dysfunction remains largely unexplored. This study investigates the glymphatic system's function in schizophrenia, utilizing diffusion tensor imaging (DTI) to analyze water diffusion along the perivascular space (ALPS), and examines its correlation with clinical symptoms.

STUDY DESIGN

A cohort consisting of 43 people with schizophrenia and 108 healthy controls was examined. We quantified water diffusion metrics along the x-, y-, and z-axis in both projection and association fibers to derive the DTI-ALPS index, a proxy for glymphatic activity. The differences in the ALPS index between groups were analyzed using a 2-way ANCOVA controlling for age and sex, while partial correlations assessed the association between the ALPS index and clinical variables.

STUDY RESULTS

People with schizophrenia showed a significantly reduced DTI-ALPS index across the whole brain and within both hemispheres (F = 9.001, P = .011; F = 10.024, P = .011; F = 5.927, P = .044; false discovery rate corrected), indicating potential glymphatic dysfunction in schizophrenia. The group by cognitive performance interaction effects on the ALPS index were not observed. Moreover, a lower ALPS index was associated with poorer cognitive performance on specific neuropsychological tests in people with schizophrenia.

CONCLUSION

Our study highlights a lower ALPS index in schizophrenia, correlated with more pronounced cognitive impairments. This suggests that glymphatic dysfunction may contribute to the pathophysiology of schizophrenia, offering new insights into its underlying mechanisms.

Color painting predicts clinical symptoms in chronic schizophrenia patients via deep learning

BACKGROUND

Individuals with psychiatric disorders perceive the world differently. Previous studies indicated impaired color vision and weakened color discrimination ability in psychotic patients. Examining the paintings from psychotic patients can measure the visual-motor function. However, few studies examined the potential changes in the color painting behavior in these individuals. The current study aims to discriminate schizophrenia patients from healthy controls (HCs) and predict PANSS scores of schizophrenia patients according to their paintings.

METHODS

In the present study, we retrospectively analyzed the paintings colored by 281 chronic schizophrenia patients and 35 HCs. The images were scanned and processed using series of computational analyses.

RESULTS

The results showed that schizophrenia patients tend to use less color and exhibit different strokes compared to HCs. Using a deep learning residual neural network (ResNet), we were able to discriminate patients from HCs with over 90% accuracy. Further, we developed a novel convolutional neural network to predict PANSS positive, negative, general psychopathology, and total scores. The Root Mean Square Error (RMSE) of the prediction was low, which indicates higher accuracy of prediction.

CONCLUSION

In conclusion, the deep learning paradigm showed the large potential to discriminate schizophrenia patients from HCs based on color paintings. Besides, this color painting-based paradigm can effectively predict clinical symptom severity for chronic schizophrenia patients. The color paintings by schizophrenia patients show potential as a tool for clinical diagnosis and prognosis. These findings show potential as a tool for clinical diagnosis and prognosis among schizophrenia patients.

Abnormal visuomotor processing in schizophrenia

Subtle disturbances of visual and motor function are known features of schizophrenia and can greatly impact quality of life; however, few studies investigate these abnormalities using simple visuomotor stimuli. In healthy people, electrophysiological data show that beta band oscillations in sensorimotor cortex decrease during movement execution (event-related beta desynchronisation (ERBD)), then increase above baseline for a short time after the movement (post-movement beta rebound (PMBR)); whilst in visual cortex, gamma oscillations are increased throughout stimulus presentation. In this study, we used a self-paced visuomotor paradigm and magnetoencephalography (MEG) to contrast these responses in patients with schizophrenia and control volunteers. We found significant reductions in the peak-to-peak change in amplitude from ERBD to PMBR in schizophrenia compared with controls. This effect was strongest in patients who made fewer movements, whereas beta was not modulated by movement in controls. There was no significant difference in the amplitude of visual gamma between patients and controls. These data demonstrate that clear abnormalities in basic sensorimotor processing in schizophrenia can be observed using a very simple MEG paradigm.

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Visual and motor deficits in schizophrenia are rarely investigated.

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We use MEG to non-invasively assess the neural basis of these deficits.

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Patients showed abnormalities in neuronal oscillations in motor cortex.

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Beta band power, reflecting cortical inhibition, was reduced after movements.

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Increased movement frequency may be a behavioural compensation for this reduction.

The impact of the genome-wide supported variant in the cyclin M2 gene on gray matter morphology in schizophrenia

BACKGROUND

Genome-wide significant associations of schizophrenia with eight SNPs in the CNNM2, MIR137, PCGEM1, TRIM26, CSMD1, MMP16, NT5C2 and CCDC68 genes have been identified in a recent mega-analysis of genome-wide association studies. To date, the role of these SNPs on gray matter (GM) volumes remains unclear.

METHODS

After performing quality control for minor-allele frequency > 5% using a JPT HapMap sample and our sample, a genotyping call rate > 95% and Hardy-Weinberg equilibrium testing (p > 0.01), five of eight SNPs were eligible for analysis. We used a comprehensive voxel-based morphometry (VBM) technique to investigate the effects of these five SNPs on GM volumes between major-allele homozygotes and minor-allele carriers in Japanese patients with schizophrenia (n = 173) and healthy subjects (n = 449).

RESULTS

The rs7914558 risk variant at CNNM2 was associated with voxel-based GM volumes in the bilateral inferior frontal gyri (right T = 4.96, p = 0.0088, left T = 4.66, p = 0.031). These peak voxels, which were affected by the variant, existed in the orbital region of the inferior frontal gyri. Individuals with the risk G/G genotype of rs7914558 had smaller GM volumes in the bilateral inferior frontal gyri than carriers of the non-risk A-allele. Although several effects of the genotype and the genotype-diagnosis interaction of other SNPs on GM volumes were observed in the exploratory VBM analyses, these effects did not remain after the FWE-correction for multiple tests (p > 0.05).

CONCLUSIONS

Our findings suggest that the genetic variant in the CNNM2 gene could be implicated in the pathogenesis of schizophrenia through the GM volumetric vulnerability of the orbital regions in the inferior frontal gyri.

[One decade of functional imaging in schizophrenia research. From visualisation of basic information processing steps to molecular-genetic oriented imaging]

Modern neuroimaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) have contributed tremendously to our current understanding of psychiatric disorders in the context of functional, biochemical and microstructural alterations of the brain. Since the mid-nineties, functional MRI has provided major insights into the neurobiological correlates of signs and symptoms in schizophrenia. The current paper reviews important fMRI studies of the past decade in the domains of motor, visual, auditory, attentional and working memory function. Special emphasis is given to new methodological approaches, such as the visualisation of medication effects and the functional characterisation of risk genes.

First- and second-generation antipsychotic medication and cognitive processing in schizophrenia

Schizophrenia has been consistently characterized by deficits in the cognitive domains of executive function, working memory, attention, and episodic memory. Although some cognitive abnormalities, such as motor slowing, may be associated with antipsychotic medication administration, generally the cognitive deficits shown by patients with schizophrenia can be attributed at least in part to the disease process. Modulation of the dopamine neurotransmitter system, notably through D2 receptor blockade, has been associated with psychotic symptom reduction and cognitive performance improvements in patients with schizophrenia. Although first-generation antipsychotic medication treatment initially was thought not to result in cognitive improvement, recent studies comparing second-generation antipsychotics to low doses of first-generation antipsychotic medication showed cognitive benefits for first-generation drugs, although perhaps not as great as that found after treatment with second-generation medication. Cognitive improvement associated with administration of antipsychotic medication may be a manifestation of improvement in general cortical information processing. Recent work has shown that specific genetic polymorphisms may interact with antipsychotic medication treatment to influence the degree to which cognitive abilities display improvement after treatment. In particular, the catechol-O-methyltransferase val108/158met polymorphism has been shown to predict working memory improvement after administration of antipsychotic medication to patients with schizophrenia.

Functional magnetic resonance imaging in schizophrenia: cortical response to motor stimulation

Previous functional magnetic resonance imaging (fMRI) studies suggest that motor system abnormalities are present in schizophrenia. However, these studies have often produced conflicting or ambiguous findings. The purpose of this study was to ascertain whether activation differences could be identified in stable schizophrenic patients on the basis of BOLD measures in two motor regions, the primary motor cortex, Brodmann area 4 (BA4) and the premotor and supplementary motor area, Brodmann area 6 (BA6). Twenty-one schizophrenic patients and 21 healthy control subjects were studied with BOLD fMRI methods during a sequential finger tapping task. Statistical parametric maps were generated for each subject, and anatomic regions were automatically defined using an anatomic atlas. Compared with controls, the schizophrenic patients showed a significant reduction in contralateral activation for both BA4 and BA6 (P<0.001), and in ipsilateral activation in BA4 (P=0.007) and BA6 (P=0.002). In healthy controls, the coactivation in the ipsilateral cortex is reduced in comparison with the contralateral cortex for right and left handed tasks. In BA4, this reduction is significant for right (P=0.007) and left (P=0.003) finger tapping. Similar results were obtained for BA6. Further analyses are necessary to evaluate the activation in other motor system regions.

Bimanual coordination in chronic schizophrenia

Anomalies of movement are observed both clinically and experimentally in schizophrenia. While the basal ganglia have been implicated in its pathogenesis, the nature of such involvement is equivocal. The basal ganglia may be involved in bimanual coordination through their input to the supplementary motor area (SMA). While a neglected area of study in schizophrenia, a bimanual movement task may provide a means of assessing the functional integrity of the motor circuit. Twelve patients with chronic schizophrenia and 12 matched control participants performed a bimanual movement task on a set of vertically mounted cranks at different speeds (1 and 2 Hz) and phase relationships. Participants performed in-phase movements (hands separated by 0 degrees ) and out-of-phase movements (hands separated by 180 degrees ) at both speeds with an external cue on or off. All participants performed the in-phase movements well, irrespective of speed or cueing conditions. Patients with schizophrenia were unable to perform the out-of-phase movements, particularly at the faster speed, reverting instead to the in-phase movement. There was no effect of external cueing on any of the movement conditions. These results suggest a specific problem of bimanual coordination indicative of SMA dysfunction per se and/or faulty callosal integration. A disturbance in the ability to switch attention during the out-of-phase task may also be involved.

Psychomotor slowing and planning deficits in schizophrenia

The relative contribution of cognitive and motor processing to psychomotor slowing in schizophrenia was investigated using three tasks: a simple line-copying task and a more complex figure-copying task, both following a reaction paradigm, and a standard psychomotor test, the Digit Symbol Test (DST). Various movement variables of the task performances were derived from recordings made with the aid of a digitizing tablet. The patients with schizophrenia appeared to be about one-third slower in their total performance time on all three tasks when compared with healthy controls, which suggests a general psychomotor slowing in this group. When itemized over the various movement variables, this slowing was found in both initiation time and movement time in the copying tasks and in the DST in the time to match the symbol and the digit, but not in writing the digit. Furthermore, in the figure-copying task it was found that increased figure complexity or decreased familiarity prolonged the initiation time. These latency increases were not significantly larger for the schizophrenia group as a whole, but only for a subgroup of patients with higher scores on negative symptoms. Regarding reinspection time, the effects of familiarity were larger in the schizophrenia group as a whole. These group findings suggest that patients tend to plan their actions less in advance, which, in the case of the more complex or unfamiliar task conditions, is a less sophisticated planning strategy. Given the longer latencies in patients with more severe negative symptoms, it seems that these patients have problems with turning a plan into action. The present study provides evidence of psychomotor slowing and planning deficits in schizophrenia.

A disturbance in the control of muscle force in neuroleptic-naive schizophrenic patients

The voluntary motor disturbances found among many schizophrenic patients consist of motor incoordination, disturbed pursuit tracking, difficulty following movement sequences, desynchronized tapping, and a myriad of neurologic soft signs. The problem with many of these observations is that it is extremely difficult to distinguish movement disorders related to neuroleptic treatment from those that may have occurred spontaneously. The aim of the present study was to examine potential disturbances in the voluntary control of steady-state force in neuroleptic-naive schizophrenic patients and normal comparison subjects. Twenty-one patients and 21 age- and gender-matched comparison subjects were studied. Spectral analyses of hand force instability revealed a significant difference between patients and comparison subjects. In 52 of the patients, the disturbance in the control of force exceeded the 95th percentile of the comparison mean. Degree of force instability was correlated with positive but not negative symptoms of schizophrenia. These findings suggest that schizophrenic patients may exhibit a disturbance in the control of muscle force that cannot be attributed to the neuroleptic effects of antipsychotic medication. The pattern of disruption, characterized by abnormal spectral energy within the 1.5 to 3.0 Hz range, suggests a motor disturbance that resembles tardive dyskinesia. Implicit within these findings of neuroleptic naive patients is the possibility that disturbances in the control of isometric force may represent spontaneous dyskinesia.

Negative symptoms and reaction time in schizophrenia

This study explored the association of negative symptoms and reaction time. Negative symptoms were specifically associated with reaction time slowing and variability in schizophrenics, but not in affective disorders. The finding of specificity did not extend to other measures of the deficit syndrome nor to motor performance. An abbreviated version of the negative symptom scale was especially effective in separating groups.