Relationship between brain structure and function in disorders of the schizophrenic spectrum: single positron emission computerized tomography, computerized tomography and psychopathology of first episodes

Terminology and assessment tools of psychosis: A systematic narrative review

AIM

Phenomena within the psychosis continuum that varies in frequency/duration/intensity have been increasingly identified. Different terms describe these phenomena, however there is no standardization within the terminology. This review evaluated the definitions and assessment tools of seven terms - (i) 'psychotic experiences'; (ii) 'psychotic-like experiences'; (iii) 'psychotic-like symptoms'; (iv) 'attenuated psychotic symptoms'; (v) 'prodromal psychotic symptoms'; (vi) 'psychotic symptomatology'; and (vii) 'psychotic symptoms'.

METHODS

EMBASE, MEDLINE, and CINAHL were searched during February-March 2019. Inclusion criteria included 1989-2019, full text, human, and English. Papers with no explicit definition or assessment tool, duplicates, conference abstracts, systematic reviews, meta-analyses, or no access were excluded.

RESULTS

A total of 2238 papers were identified and of these, 627 were included. Definitions and assessment tools varied, but some trends were found. Psychotic experiences and psychotic-like experiences were transient and mild, found in the general population and those at-risk. Psychotic-like symptoms were subthreshold and among at-risk populations and non-psychotic mental disorders. Attenuated psychotic symptoms were subthreshold but associated with distress, risk, and help-seeking. Prodromal psychotic symptoms referred to the prodrome of psychotic disorders. Psychotic symptomatology included delusions and hallucinations within psychotic disorders. Psychotic symptoms was the broadest term, encompassing a range of populations but most commonly involving hallucinations, delusions, thought disorder, and disorganization.

DISCUSSION

A model for conceptualizing the required terms is proposed and future directions needed to advance this field of research are discussed.

A systematic review of task-based functional neuroimaging studies investigating language, semantic and executive processes in thought disorder

The aim of the current systematic review was to synthesise the research that has investigated thought disorder (TD) using task-based functional neuroimaging techniques to target executive, language, or semantic functions. Thirty-five pertinent studies were identified from January 1990 to August 2016. Functional correlates of TD included the superior and middle temporal, fusiform, and inferior frontal gyri bilaterally, as well as the left and right cingulate cortex, the right caudate nucleus, and the cerebellum. TD-related increases and decreases in activation were both evident in most of these regions. However, the specificity of these correlates from general clinical and cognitive influences is unknown. The cortical regions implicated overlap with those thought to contribute to language and semantic systems. Cortico-striatal circuitry may also play a role in some aspects of TD through aberrant salience representation and inappropriate attentional prioritisation. To advance the field further, greater integration across structural, functional, and behavioural measures is required, in addition to non-unitary considerations of TD.

Housing condition-related changes involved in reversal learning and its c-Fos associated activity in the prefrontal cortex

Our study examined how different housing conditions modulated the acquisition of a spatial reference memory task and also, a reversal task in the 4-radial arm water maze (4-RAWM). The animals were randomly assigned to standard or enriched cages, and, as a type of complementary stimulation along with the environmental enrichment (EE), a group of rats also ran 15 min/day in a Rotarod. Elevated-zero maze results allowed us to discard that our exercise training increased anxiety-related behaviors. 4-RAWM results revealed that the non-enriched group had a worse performance during the acquisition and also, during the first trial of each session with respect to the enriched groups. Regarding the reversal task, this group made more perseverative errors in the previous platform position. Interestingly, we hardly found differences between the two enriched groups (with and without exercise). We also analyzed how the reversal learning, depending on the previous housing condition, modulated the expression of c-Fos-positive nuclei in different subdivisions of the medial prefrontal cortex (cingulate (Cg), prelimbic (PL) and infralimbic (IL) cortices) and in the orbitofrontal (OF) cortex. The enriched groups had higher c-Fos expression in the Cg and OF cortices and lower in the IL cortex respect to the non-enriched animals. In the PL cortex, we did not find significant differences between the groups that performed the reversal task. Therefore, our short EE protocol improved the performance in a spatial memory and a reversal task, whereas the exercise training, combined with the EE, did not produce a greater benefit. This better performance seemed to be related with the specific pattern of c-Fos expression in brain regions involved in cognitive flexibility.

Interneurons are necessary for coordinated activity during reversal learning in orbitofrontal cortex

BACKGROUND

Cerebral cortical gamma-aminobutyric acidergic interneuron dysfunction is hypothesized to lead to cognitive deficits comorbid with human neuropsychiatric disorders, including schizophrenia, autism, and epilepsy. We have previously shown that mice that harbor mutations in the Plaur gene, which is associated with schizophrenia, have deficits in frontal cortical parvalbumin-expressing interneurons. Plaur mice have impaired reversal learning, similar to deficits observed in patients with schizophrenia.

METHODS

We examined the role of parvalbumin interneurons in orbitofrontal cortex during reversal learning by recording single unit activity from 180 control and 224 Plaur mouse neurons during a serial reversal task. Neural activity was analyzed during correct and incorrect decision choices and reward receipt.

RESULTS

Neurons in control mice exhibited strong phasic responses both during discrimination and reversal learning to decisions and rewards, and the strength of the response was correlated with behavioral performance. Although baseline firing was significantly enhanced in Plaur mice, neural selectivity for correct or erroneous decisions was diminished and not correlated with behavior, and reward encoding was downscaled. In addition, Plaur mice showed a significant reduction in the number of neurons that encoded expected outcomes across task phases during the decision period.

CONCLUSIONS

These data indicate that parvalbumin interneurons are necessary for the representation of outcomes in orbitofrontal cortex. Deficits in inhibition blunt selective neural firing during key decisions, contributing to behavioral inflexibility. These data provide a potential explanation for disorders of cognitive control that accompany the loss of these gamma-aminobutyric acidergic interneurons in human neuropsychiatric disorders, such as autism, epilepsy, and schizophrenia.

Structural brain anomalies and chronic pain: a quantitative meta-analysis of gray matter volume

The diversity of chronic pain syndromes and the methods employed to study them make integrating experimental findings challenging. This study performed coordinate-based meta-analyses using voxel-based morphometry imaging results to examine gray matter volume (GMV) differences between chronic pain patients and healthy controls. There were 12 clusters where GMV was decreased in patients compared with controls, including many regions thought to be part of the "pain matrix" of regions involved in pain perception, but also including many other regions that are not commonly regarded as pain-processing areas. The right hippocampus and parahippocampal gyrus were the only regions noted to have increased GMV in patients. Functional characterizations were implemented using the BrainMap database to determine which behavioral domains were significantly represented in these regions. The most common behavioral domains associated with these regions were cognitive, affective, and perceptual domains. Because many of these regions are not classically connected with pain and because there was such significance in functionality outside of perception, it is proposed that many of these regions are related to the constellation of comorbidities of chronic pain, such as fatigue and cognitive and emotional impairments. Further research into the mechanisms of GMV changes could provide a perspective on these findings.

PERSPECTIVE

Quantitative meta-analyses revealed structural differences between brains of individuals with chronic pain and healthy controls. These differences may be related to comorbidities of chronic pain.

Gray matter volume deficits and correlation with insight and negative symptoms in first-psychotic-episode subjects

OBJECTIVE

To determine brain areas reduced in first episode of psychotic subjects and its association with lack of insight and negative symptoms.

METHOD

Twenty-one drug naive first-episode subjects and 20 controls underwent a structural MRI scan and were clinically assessed. Optimized voxel-based-morphometry analysis (VBM) was implemented to find between-group differences and correlations between GM volume and: (i) lack of insight and (ii) negative symptoms.

RESULTS

Patients showed GM reduction in prefrontal and left temporal areas. A significant correlation was found between insight and GM volume in the cerebellum (corrected P = 0.01), inferior temporal gyrus (corrected P = 0.022), medial superior frontal gyrus (corrected P < 0.001), and inferior frontal gyrus (corrected P = 0.012), as the insight decreased, the volume decreased. Negative symptoms correlated with decreased GM volume at cerebellum (corrected P = 0.037) and frontal inferior regions (corrected P < 0.001), the more negative symptoms, the less volume.

CONCLUSION

Our findings support an association between prefrontal, temporal, and cerebellar deficits and lack of insight in schizophrenia and confirm previous findings of GM deficits in patients since the first episode of psychosis.

Mourning and melancholia revisited: correspondences between principles of Freudian metapsychology and empirical findings in neuropsychiatry

Freud began his career as a neurologist studying the anatomy and physiology of the nervous system, but it was his later work in psychology that would secure his place in history. This paper draws attention to consistencies between physiological processes identified by modern clinical research and psychological processes described by Freud, with a special emphasis on his famous paper on depression entitled 'Mourning and melancholia'. Inspired by neuroimaging findings in depression and deep brain stimulation for treatment resistant depression, some preliminary physiological correlates are proposed for a number of key psychoanalytic processes. Specifically, activation of the subgenual cingulate is discussed in relation to repression and the default mode network is discussed in relation to the ego. If these correlates are found to be reliable, this may have implications for the manner in which psychoanalysis is viewed by the wider psychological and psychiatric communities.

SPECT study of Chinese schizophrenic patients suggests that cerebral hypoperfusion and laterality exist in different ethnic groups

Hypofrontality is a common finding in schizophrenia in many countries. To date, there have been few studies on Chinese patients with schizophrenia. We thus wondered whether hypofrontality exists in Chinese patients with schizophrenia. We investigated 45 patients with schizophrenia and 21 healthy controls using brain perfusion single photon emission computed tomography (SPECT). Subjects were also administered the Brief Psychiatric Rating Scale (BPRS), Scale for the Assessment of Positive Symptoms (SAPS), Scale for the Assessment of Negative Symptoms (SANS), Halstead-Reitan Neuropsychological Battery (HRNB) and the Wechsler Memory Scale-Revised (WMS-R). Images were analyzed using a semi-quantitative reading and a quantified region of interest analysis. We found that schizophrenic patients showed hypoperfusion in the frontal and temporal lobes and hyperperfusion in the basal ganglia. Schizophrenic patients with both negative and positive symptoms showed asymmetric perfusion in the temporal lobe. Schizophrenic patients with prominent negative symptoms also showed asymmetric perfusion in the prefrontal lobes. Negative symptoms showed a significantly negative correlation with regional cerebral blood flow (rCBF) in the left frontal lobe. Improved memory quotient (MQ) was significantly correlated with increased rCBF in the left temporal lobe. These findings from Chinese patients confirm a similar regional neuroanatomic dysfunction as in Western patients with the disease.

M50 sensory gating predicts negative symptoms in schizophrenia

Impaired auditory sensory gating is considered characteristic of schizophrenia and a marker of the information processing deficit inherent to that disorder. Predominance of negative symptoms also reflects the degree of deficit in schizophrenia and is associated with poorer pre-morbid functioning, lower IQ, and poorer outcomes. However, a consistent relationship between auditory sensory gating and negative symptoms in schizophrenia has yet to be demonstrated. The absence of such a finding is surprising, since both impaired auditory gating and negative symptoms have been linked with impaired fronto-temporal cortical function. The present study measured auditory gating using the P50 event related potential (ERP) in a paired-click paradigm and capitalized on the relative localization advantage of magnetoencephalography (MEG) to assess auditory sensory gating in terms of the event related field (ERF) M50 source dipoles on bilateral superior temporal gyrus (STG). The primary hypothesis was that there would be a positive correlation between lateralized M50 auditory sensory gating measures and negative symptoms in patients with schizophrenia. A standard paired-click paradigm was used during simultaneous EEG and MEG data collection to determine S2/S1 sensory gating ratios in a group of 20 patients for both neuroimaging techniques. Participants were administered the Schedule for the Assessment of Negative Symptoms (SANS), the Positive and Negative Symptom Scale (PANSS), and the Calgary Depression Scale for Schizophrenia. Consistent with previous reports, there was no relationship between ERP P50 sensory gating and negative symptoms. However, right (not left) hemisphere ERF M50 sensory gating ratio was significantly and positively correlated with negative symptoms. This finding is compatible with information processing theories of negative symptoms and with more recent findings of fronto-temporal abnormality in patients with predominantly negative symptoms.

Do schizophrenia patients make more perseverative than non-perseverative errors on the Wisconsin Card Sorting Test? A meta-analytic study

The Wisconsin Card Sorting Test (WCST) is widely used to explore executive functions in patients with schizophrenia. Among other findings, a higher number of perseverative errors has been suggested to implicate a deficit in task switching and inhibitory functions in schizophrenia. Many studies of patients with schizophrenia have focused on perseverative errors as the primary performance index in the WCST. However, do schizophrenia patients characteristically make more perseverative than non-perseverative errors compared with healthy controls? We reviewed the literature where schizophrenia patients were engaged in the WCST irrespective of the primary goal of the study. The results showed that while both schizophrenia patients and healthy participants made more perseverative than non-perseverative errors, the contrast between perseverative and non-perseverative errors is higher in schizophrenia patients only at a marginal level of significance. This result suggests that schizophrenia patients do make a comparable number of non-perseverative errors and cautions against simplistic interpretation of poor performance of schizophrenia patients in WCST as entirely resulting from impairment in set-shifting or inhibitory functions.

Effects on the brain of a psychological treatment: cognitive remediation therapy: functional magnetic resonance imaging in schizophrenia

BACKGROUND

The results of one randomised control trial testing a psychological rehabilitation programme aimed at information processing strategies showed improvements in cognition post-treatment.

AIMS

To determine whether there are concomitant brain activation changes as a result of engaging in cognitive remediation therapy (CRT).

METHOD

Three groups (patients receiving control therapy or CRT and a healthy control group) were investigated in a repeated measures design using the two-back test. Functional magnetic resonance imaging (fMRI) data and a broad assessment of executive functioning were completed at baseline and post-treatment. Brain activation changes were identified after accounting for possible task-correlated motion artefact.

RESULTS

fMRI analyses indicate that the control group showed decreased activation but the two patient groups showed an increase in activation over time. The patient group that received successful CRT had significantly increased brain activation in regions associated with working memory, particularly the frontocortical areas.

CONCLUSIONS

This is the first time that brain activation changes in a seriously disabled group of patients with schizophrenia can be associated clearly with psychological rather than pharmacological therapy.

Working memory deficits in schizophrenia are not necessarily specific or associated with MRI-based estimates of area 46 volumes

Despite substantial evidence that the prefrontal cortex does not function normally in patients diagnosed with schizophrenia, evidence for prefrontal structural abnormalities, as measured by magnetic resonance imaging (MRI), has been inconsistent. Additionally, evidence for relationships between prefrontal structural and functional measures has been limited. The inconsistencies in the MRI literature are, at least in part, due to a lack of standard and specific measurement protocols that allow delineation of functionally distinct cortical regions. In this study, reliable methods for measuring an estimate of area 46 (estimate referred to as area 46(e)), as defined by 'Cereb. Cortex 5 (1995) 323', were developed and used to examine relationships between area 46(e) volumes, working memory, and symptom severity in 23 male patients and 23 healthy male comparison subjects. Patients performed more poorly than healthy reference subjects on all cognitive measures including measures of spatial and non-spatial working memory, but showed no significant corresponding deficits in area 46(e) volumes or whole brain volumes. Moreover, there were no significant relationships between symptom severity and area 46(e) volumes. These findings suggest that the prefrontal functional abnormalities observed in schizophrenia may occur in the absence of prefrontal volume deficits, and may instead involve more widespread brain systems or prefrontal connections with other brain regions.

Positive and negative symptoms and regional cerebral perfusion in antipsychotic-naive schizophrenic patients: a high-resolution SPECT study

In 17 antipsychotic-naive schizophrenic patients, the scores of positive and negative symptoms of schizophrenia were correlated with relative regional cerebral perfusion measured by 99m-Tc-ECD (ethyl cysteinate dimer) single photon emission computed tomography (SPECT). Scans were performed in subjects at rest. The negative symptom dimension was significantly correlated with a decreased level of perfusion in the left thalamic region. Other non-significant trends were also observed; the positive symptom dimension was related to decreased perfusion in the left temporal region and to increased perfusion in the right frontal region, while the negative symptom dimension was related to increased perfusion in the left frontal region. These findings suggest that the positive and negative symptoms of schizophrenia are related to dysfunctions in different regions of the brain and different lateralized patterns of dysfunction.

Chemical and physiologic brain imaging in schizophrenia

Technologic advances in functional brain imaging have provided exciting and informative insights into the functional neuroanatomy and neurochemistry of schizophrenia. Using MR spectroscopy, it has been possible to examine in vivo brain metabolism and to relate observed changes to physiological processes occurring at a cellular level. Positron emission tomography and single photon emission computed tomography have revealed disturbances of cerebral blood flow and glucose metabolism in patients with schizophrenia. More recently, these tools have also proved most useful in studying the relative receptor occupancy of typical and atypical antipsychotic medications.

Schizophrenia, psychosis, and the basal ganglia

Schizophrenia is one of the most common and perhaps the most disabling of mental disorders, for which effective forms of treatment have not yet been established definitively. The findings reviewed in this article strongly suggest that basal ganglia abnormalities are involved in the pathophysiology of psychotic syndromes in general, and schizophrenia in particular.

Hypofrontality in schizophrenia: influence of normalization methods

1. Studies with Single Photon Emission Computed Tomography (SPECT) in schizophrenia research have utilized different approaches to normalization of data, such as cerebellar ratio and whole brain ratio methods, leading to conflicting findings. 2. The authors compared these two methods to test the hypofrontality hypothesis of schizophrenia. 3. Eighteen chronic and medicated DSM-IV schizophrenic patients and 10 healthy controls underwent two SPECT examinations using 99mTc HMPAO as a tracer at baseline and during frontal activation while applying the Wisconsin Card Sorting Test. 4. The hypofrontality hypothesis was supported with both indexes of relative perfusion, although the whole brain ratio method appeared to be more reliable and specific than the cerebellar ratio method. 5. Further studies are required to confirm these preliminary results on the specificity and sensitivity of both methods.

Cerebral perfusion correlates of negative symptomatology and parkinsonism in a sample of treatment-refractory schizophrenics: an exploratory 99mTc-HMPAO SPET study

There is a well recognized clinical overlap between primary and secondary neuroleptic negative symptoms in schizophrenia, but their cerebral substrates are probably different. The study of these substrates could contribute to a better understanding and management of these syndromes. In the present work, the cerebral perfusion correlates, as an indirect measure of the underlying neuronal function, of negative symptoms and parkinsonism were studied with single-photon emission tomography in a group of treatment-refractory paranoid schizophrenic patients. Perfusion ratios with respect to the homolateral cerebellum were compared with a normal database. Correlation coefficients were calculated between perfusion ratios, negative symptoms and parkinsonism scores on exploratory grounds. As a group, the patients showed a bilateral, but predominantly left-sided, hypofrontality and hypotemporality, as well as an increased perfusion in right basal ganglia. Negative symptoms scores negatively correlated with prefrontal perfusion, while parkinsonism positively correlated with the activity of primary motor and sensory cortex. These findings support the existence of different cerebral substrates for primary and secondary negative symptoms in schizophrenia.

Dopaminergic sensitization: implications for the pathogenesis of schizophrenia

1. Which transmitters are primarily or secondarily involved in the pathogenesis of schizophrenia has been extensively studied during the last years. This review concentrates on the two systems, that most constantly have been found dysfunctioning in patients; that are the dopaminergic and glutamatergic systems. 2. Numerous neuropathological defects have been found in schizophrenia, but it is as yet unknown which changes are causative and which reflect maladaptive reactions. 3. All findings, however, involve the cortico-striato-thalamo-cortical circuits, which are central for attention and information processing. 4. The article focuses on the consequence of transmitter dysfunction for perception and for the ability of the individual to adapt to a constantly changing environment. Both clinical and experimental studies point to a primary/early cortical defect involving the glutamatergic system, and to a later developed intermittent hyperactivity of the dopaminergic system superimposed on a basal hypodopaminergic state. 5. The authors have previously demonstrated, how it is possible to potentiate mesolimbic dopaminergic activity by intermittent electrical stimulations of the cells in the ventral tegmental area, and that influence on the central mesolimbic dopamine cells is essential for the strengthened neuroplastic response. A changed neuroplastic response to environmental stimulation due to dopaminergic sensitization can explain how an episodic, subcortical hyperactivity can act on a basic glutamatergic and dopaminergic hypofunction to produce psychotic symptoms. Based on our own and others clinical and experimental findings, the "filter" hypothesis for schizophrenia and the state-dependence of schizophrenic symptoms, the authors present a hypothesis for spontaneous mesolimbic dopaminergic sensitization and progressive evolution of psychosis.

Meta-analysis of brain and cranial size in schizophrenia

Several meta-analyses are presented that address the issue of brain and/or cranial size reductions in schizophrenia. Separate meta-analyses were conducted for brain size (n = 27 studies), intracranial size (n = 18) or extracranial size (n = 8). For each meta-analysis, the weighted composite effect size (d) was tested for statistical significance (the direction of the effect size was negative if patients with schizophrenia had smaller structure size than controls). The influence of several potential modifiers of effect size (age, methods, region, gender) was individually evaluated. The composite effect sizes for studies of brain, intracranial and extracranial measures were d = -0.26, (p < 0.0001), d = -0.18, (p = 0.0012), and d = +0.14, (p = 0.16), respectively. Thus, the review found evidence for a small, but statistically significant reduction in brain and intracranial size in schizophrenia, but no evidence for a reduction in extracranial size. Studies based on axial image slices had significantly larger effects (d = -0.60) than the studies based on sagittal images (d = -0.09) (chi(2) = 14.0, p = 0.0002). In summary, the findings clearly support a small yet highly significant reduction of brain and intracranial size in schizophrenia.

Phosphorus magnetic resonance spectroscopy in schizophrenia: correlation between membrane phospholipid metabolism in the temporal lobe and positive symptoms

1. To determine any correlations between phosphorus metabolites in the temporal lobes and clinical symptoms in schizophrenic patients, the authors performed 31phosphorus magnetic resonance spectroscopy in 31 medicated patients and age- and sex- matched normal subjects. 2. Schizophrenic patients demonstrated an increased level of phosphodiesters (PDE) in the temporal lobes bilaterally and a decreased level of beta-adenosine triphosphate (beta-ATP) in the left temporal lobe. 3. A significant positive correlation was observed between the level of PDE in the left temporal lobe and the score of positive symptoms on the Brief Psychiatric Rating Scale. 4. These results suggest that altered membrane phospholipid metabolism in the left temporal lobe is associated with neuroleptic-resistant positive symptoms in schizophrenic patients.