Brain dysfunction during motor activation and corpus callosum alterations in schizophrenia measured by cerebral blood flow and magnetic resonance imaging

A role for endothelial NMDA receptors in the pathophysiology of schizophrenia

Numerous genetic and postmortem studies link N-methyl-d-aspartate receptor (NMDAR) dysfunction with schizophrenia, forming the basis of the popular glutamate hypothesis. Neuronal NMDAR abnormalities are consistently reported from both basic and clinical experiments, however, non-neuronal cells also contain NMDARs, and are rarely, if ever, considered in the discussion of glutamate action in schizophrenia. We offer an examination of recent discoveries elucidating the actions and consequences of NMDAR activation in the neuroendothelium. While there has been mixed literature regarding blood flow alterations in the schizophrenia brain, in this review, we posit that some common findings may be explained by neuroendothelial NMDAR dysfunction. In particular, we emphasize that endothelial NMDARs are key mediators of neurovascular coupling, where increased neuronal activity leads to increased blood flow. Based on the broad conclusions that hypoperfusion is a neuroanatomical finding in schizophrenia, we discuss potential mechanisms by which endothelial NMDARs contribute to this disorder. We propose that endothelial NMDAR dysfunction can be a primary cause of neurovascular abnormalities in schizophrenia. Importantly, functional MRI studies using BOLD signal as a proxy for neuron activity should be considered in a new light if neurovascular coupling is impaired in schizophrenia. This review is the first to propose that NMDARs in non-excitable cells play a role in schizophrenia.

Altered interhemispheric signal propagation in schizophrenia and depression

OBJECTIVE

Altered interhemispheric connectivity is implicated in the pathophysiology of schizophrenia (SCZ) and major depressive disorder (MDD) and may account for deficits in lateralized cognitive processes. We measured transcranial magnetic stimulation evoked interhemispheric signal propagation (ISP), a non-invasive measure of transcallosal connectivity, and hypothesized that the SCZ and MDD groups will have increased ISP compared to healthy controls.

METHODS

We evaluated ISP over the dorsolateral prefrontal cortex in 34 patients with SCZ and 34 patients with MDD compared to 32 age and sex-matched healthy controls.

RESULTS

ISP was significantly increased in patients with SCZ and patients with MDD compared to healthy controls but did not differ between patient groups. There were no effects of antidepressant, antipsychotic, and benzodiazepine medications on ISP and our results remained unchanged after re-analysis with a region of interest method.

CONCLUSION

Altered ISP was found in both SCZ and MDD patient groups. This indicates that disruptions of interhemispheric signaling processes can be indexed with ISP across psychiatric populations.

SIGNIFICANCE

These findings enhance our knowledge of the physiological mechanisms of interhemispheric imbalances in SCZ and MDD, which may serve as potential treatment targets in future patients.

Structure and function of the corpus callosum in schizophrenia: What's the connection?

Tests of both structure and function of the corpus callosum have revealed abnormalities in schizophrenic patients. One such functional test employed lateralised Stroop stimuli presented tachistoscopically, to measure the transfer of interference and facilitation between the cerebral hemispheres. An attempt was made to relate indices of callosal transfer to clinical and demographic variables, including family history, as well as to indices of brain morphology. The latter included ventricle: brain ratio (VBR) measured by computed tomography (CT) scanning on 31 DSMIII schizophrenics, and the cross-sectional area of the corpus callosum from magnetic resonance imaging (MRI), obtained from 20 of these patients. VBR did not relate to functional measures; however, anterior callosal area correlated with indices of callosal connectivity. Patients with auditory hallucinations had smaller anterior callosal areas and tended to show less connectivity. The results show links between functional and structural measures of the corpus callosum, but their precise nature remains unclear.

Functional magnetic resonance imaging of motor cortex activation in schizophrenia

Previous fMRI studies of sensorimotor activation in schizophrenia have found in some cases hypoactivity, no difference, or hyperactivity when comparing patients with controls; similar disagreement exists in studies of motor laterality. In this multi-site fMRI study of a sensorimotor task in individuals with chronic schizophrenia and matched healthy controls, subjects responded with a right-handed finger press to an irregularly flashing visual checker board. The analysis includes eighty-five subjects with schizophrenia diagnosed according to the DSM-IV criteria and eighty-six healthy volunteer subjects. Voxel-wise statistical parametric maps were generated for each subject and analyzed for group differences; the percent Blood Oxygenation Level Dependent (BOLD) signal changes were also calculated over predefined anatomical regions of the primary sensory, motor, and visual cortex. Both healthy controls and subjects with schizophrenia showed strongly lateralized activation in the precentral gyrus, inferior frontal gyrus, and inferior parietal lobule, and strong activations in the visual cortex. There were no significant differences between subjects with schizophrenia and controls in this multi-site fMRI study. Furthermore, there was no significant difference in laterality found between healthy controls and schizophrenic subjects. This study can serve as a baseline measurement of schizophrenic dysfunction in other cognitive processes.

A systematic review and meta-analysis of the effects of antipsychotic medications on regional cerebral blood flow (rCBF) in schizophrenia: association with response to treatment

Evaluating the short- and long-term effects of antipsychotics on brain physiology is a key factor in advancing our understanding of neurophysiological changes in psychosis and improving prediction of treatment response. Understanding the nature of such changes is crucial to the interpretation of neuroimaging findings in patients with schizophrenia and psychoses in general. This review has systematically appraised existing evidence on resting cerebral blood flow (rCBF) in schizophrenia, before and after antipsychotic treatment, relating the findings to symptom severity. The review shows that antipsychotics exert regional effects on rCBF, particularly in frontal and basal ganglia regions, and that different antipsychotic generations have differential effects on rCBF. These findings are supported by an exploratory meta-analysis of a subset of studies. The review also highlights the relative lack of studies that use a priori definitions of treatment response, which is an important step in identifying testable hypotheses and ensuring clinical relevance of remission criteria. Finally, the review highlights important considerations for future psychopharmacological studies investigating the potential for rCBF to predict symptomatic improvement, which could inform the management of treatment in schizophrenia.

Abnormal functional motor lateralization in healthy siblings of patients with schizophrenia

Earlier neuroimaging studies of motor function in schizophrenia have demonstrated reduced functional lateralization in the motor network during motor tasks. Here, we used event-related functional magnetic resonance imaging during a visually guided motor task in 18 clinically unaffected siblings of patients with schizophrenia and 24 matched controls to investigate if abnormal functional lateralization is related to genetic risk for this brain disorder. Whereas activity associated with motor task performance was mainly contralateral with only a marginal ipsilateral component in healthy participants, unaffected siblings had strong bilateral activity with significantly greater response in ipsilateral and contralateral premotor areas as well as in contralateral subcortical motor regions relative to controls. Reduced lateralization in siblings was also identified with a measure of laterality quotient. These findings suggest that abnormal functional lateralization of motor circuitry is related to genetic risk of schizophrenia.

Attenuation of beta and gamma oscillations in schizophrenia spectrum patients following hand posture perturbation

Several electroencephalographic (EEG) studies in schizophrenia report that the patients have reduced evoked gamma activity following visual and auditory stimulation. Somatosensory gamma activity has not previously been examined. It has been suggested that a dysfunction basic to schizophrenia spectrum traits would involve proprioceptive information processing and this has recently been supported by the finding of diminished latency of early proprioceptive evoked potentials in a sample of chronic schizophrenia patients. The proprioceptive stimulus used previously, and presently, consisted of an abrupt increase of weight on a hand-held load. Eighteen first-time admitted schizophrenia spectrum patients and 18 healthy matched comparison subjects were included. Proprioceptive evoked potentials were recorded as 64-channels EEG for 120 trials in two runs differing in sequence. Contra-lateral evoked beta (latency 90 ms, frequency 21 Hz) and gamma (latency 70 ms, frequency 32 Hz) oscillations were attenuated in the patient group. The healthy comparison subjects had increased gamma amplitude in the left hemisphere in the regular sequence, a phenomenon not seen in the patients. The deviant findings were unexpectedly more circumscribed in the schizophrenia than in the schizotypal personality disorder (SPD) patients. Future studies should include several concurrent psychophysiological measures.

Corpus callosum abnormalities and potential age effect in men with schizophrenia: an MRI comparative study

The goal of this investigation was to evaluate corpus callosum (CC) morphometry in schizophrenia. In consideration of possible confounders such as age, gender and handedness, our study sample was restricted to right-handed male subjects, aged 18-55 years. In addition, we controlled for age at onset, illness duration and exposure to antipsychotic medication. Midsagittal CC linear and area Magnetic Resonance Imaging (MRI) measurements were performed on 50 subjects with schizophrenia and 50 healthy controls. After controlling for midsagittal cortical brain area and age, Analysis of Covariance (ANCOVA) revealed an overall effect of diagnosis on CC splenium width and CC anterior midbody area and a diagnosis by age interaction. Independent Student t tests revealed a smaller CC splenium width in the 36- to 45-year-old age group among the patients with schizophrenia and a smaller CC anterior midbody area in the 18- to 25-year-old age group among the patients with schizophrenia compared with controls. Age, age at onset, illness duration and psychopathology ratings did not show any significant correlations with the whole CC MRI measurements. A negative correlation was found between CC rostrum area and the estimated lifetime neuroleptic consumption. The results are discussed in terms of the possibility that CC structural changes may underlie the functional impairments, frequently reported in schizophrenia, of the associated cortical regions.

Neurological soft signs in schizophrenia: investigating motor overflow

Investigation of neurological soft signs (NSSs) in schizophrenia may allow for a greater understanding of its underlying pathology. Motor overflow, involuntary movement occurring during voluntary movement, is a NSS thought to occur to a greater degree in schizophrenia. The aim of the current study was to replicate the only objective investigation which found enhanced motor overflow in schizophrenia and to further characterise its properties in a more systematic manner than previous research. The current study involved examining motor overflow production in 30 participants (15 with schizophrenia, 15 controls). Participants exerted 25 and 75% of their maximal force output, while overflow was monitored in the passive hand using linear variable differential transformer (LVDT) units. Patients with schizophrenia not only exhibited a significantly greater degree of motor overflow, compared to controls, they also exhibited a differential pattern of overflow production. Direct investigation of the cortical processes leading to motor overflow may provide a more complete understanding of the pathological relevance of motor overflow, and by extension NSSs, in schizophrenia.

Neurological soft signs and their relationships to neurocognitive functions: a re-visit with the structural equation modeling design

Background

Neurological soft signs and neurocognitive impairments have long been considered important features of schizophrenia. Previous correlational studies have suggested that there is a significant relationship between neurological soft signs and neurocognitive functions. The purpose of the current study was to examine the underlying relationships between these two distinct constructs with structural equation modeling (SEM).

Methods

118 patients with schizophrenia and 160 healthy controls were recruited for the current study. The abridged version of the Cambridge Neurological Inventory (CNI) and a set of neurocognitive function tests were administered to all participants. SEM was then conducted independently in these two samples to examine the relationships between neurological soft signs and neurocognitive functions.

Results

Both the measurement and structural models showed that the models fit well to the data in both patients and healthy controls. The structural equations also showed that there were modest to moderate associations among neurological soft signs, executive attention, verbal memory, and visual memory, while the healthy controls showed more limited associations.

Conclusions

The current findings indicate that motor coordination, sensory integration, and disinhibition contribute to the latent construct of neurological soft signs, whereas the subset of neurocognitive function tests contribute to the latent constructs of executive attention, verbal memory, and visual memory in the present sample. Greater evidence of neurological soft signs is associated with more severe impairment of executive attention and memory functions. Clinical and theoretical implications of the model findings are discussed.

A longitudinal study of the corpus callosum in chronic schizophrenia

BACKGROUND

Decreased callosal size and anisotropy have been described in schizophrenia patients but their longitudinal progression remains poorly understood.

METHODS

We performed diffusion-tensor and structural magnetic resonance imaging at baseline and at follow-up four years later in 49 chronic schizophrenia patients and 16 healthy comparison subjects. Schizophrenia patients were subdivided into good-outcome (n=23) and poor-outcome (n=26) groups. Baseline-to-follow-up changes in size, shape, position and fractional anisotropy of the corpus callosum, divided into five sagittal sections and five rostro-caudal segments, were assessed.

RESULTS

At baseline scan and in comparison to healthy subjects, schizophrenia patients displayed 1) smaller callosal size, 2) lower average anisotropy in all sagittal sections except the midline, and 3) more dorsal average coordinate position. During the four years after the baseline scan, patients with schizophrenia exhibited a more pronounced decline in absolute size of the corpus callosum than healthy comparison subjects. As compared with the good-outcome group, the corpus callosum in poor-outcome patients at baseline was of smaller size and lower average anisotropy, more elongated and posteriorly positioned. During the follow-up interval, poor-outcome patients displayed a more pronounced decline in size but less pronounced decline in anisotropy of the corpus callosum than patients with good outcomes.

CONCLUSIONS

Differences in callosal size between schizophrenia patients and healthy subjects seen at baseline continue to widen in the chronic phase of the illness, especially in patients with poor functional outcome. Baseline differences in callosal anisotropy among patients with different outcomes, however, diminish over time.

Spontaneous movement disorders in antipsychotic-naive patients with first-episode psychoses: a systematic review

BACKGROUND

Spontaneous movement disorders (SMDs), such as spontaneous dyskinesia and parkinsonism, have been described in patients with schizophrenia who have never been treated with antipsychotic medication. Their presence has been documented extensively in chronic schizophrenia but not at the time of illness onset.

METHOD

We performed a systematic review of studies investigating spontaneous abnormal movements elicited on clinical examination in antipsychotic-naive patients with first-episode psychosis.

RESULTS

We identified a total of 13 studies. Findings suggest a spontaneous dyskinesia median rate of 9% and a spontaneous parkinsonism median rate of 17%. Information on akathisia and dystonia was limited. The presence of SMDs may be associated with negative symptoms and cognitive dysfunction.

CONCLUSIONS

These findings support the notion that spontaneous abnormal movements are part of a neurodysfunction intrinsic to the pathogenesis of schizophrenia. Future studies should further investigate the role of basal ganglia and extrapyramidal pathways in the pathophysiology of psychosis, with particular attention to treatment implications.

Fronto-temporal dysfunction in schizophrenia: A selective review

Schizophrenia is conceptualized as a disorder of aberrant neurodevelopment, with evident stigmata such as minor physical anomalies (MPA), neurological soft signs (NSS), and abnormalities of brain structure and function, proposed as disease endophenotypes. We have examined the neurobiology of schizophrenia using neurodevelopmental markers, structural MRI (sMRI), EEG spectral power, and coherence as well as neuropsychological testing in neuroleptic-naïve, recent-onset schizophrenia (NRS) subjects. It has been our focus to link the positive and negative symptom dimensions of schizophrenia with their underlying neural correlates specifically reflecting fronto-temporal circuitry dysfunction. We found that MPAs and NSSs constituted independent neurodevelopmental markers of schizophrenia and would afford greater predictive validity when used as a composite endophenotype. In an exploratory factor analytic study of the dimensionality of psychopathology, we noted that the symptoms segregated into three dimensions, viz., positive, negative, and disorganization, even in NRS subjects. Executive function tests as well as EEG spectral power and coherence studies revealed that the symptom dimensions of schizophrenia could be linked to specific neural correlates. In an attempt to study the relationship between the symptom dimensions and brain structure and function using MRI, we have proposed neuroanatomical definitions with cytoarchitectonic meaning for parcellation of the prefrontal sub-divisions. Using sMRI, we have found specific corpus callosal abnormalities that possibly link the temporo-parietal association cortices with the positive symptom dimension. Recently, we also found evidence for neurodevelopmental deviance in schizophrenia possibly involving the frontal pole (FP)-driven cortical network, in a sMRI study linking FP volume and total brain volume with age in NRS subjects and age-, gender- and education-matched healthy subjects. Overall, our findings highlight the potential significance of linking the homogeneous symptom dimensions of schizophrenia with dysfunctional connectivity in the fronto-temporal region.

M, Jain S. Corpus callosal area differences and gender dimorphism in neuroleptic-naïve, recent-onset schizophrenia and healthy control subjects

The study of corpus callosal morphometry is important to unravel the underlying connectivity disturbance in schizophrenia. We studied the corpus callosal area in schizophrenia subjects compared to healthy subjects, while controlling for several confounders that could affect morphometric measures of the corpus callosum (CC). Areas of the whole CC and its sub-regions obtained by two geometric partitioning schemes were studied in 23 right-handed neuroleptic-naïve, recent-onset, schizophrenia patients and compared with 23 right-handed age-, sex- and education-matched healthy subjects. The patients did not differ from controls in whole CC area. On tripartite division of the CC, the area of the anterior sub-region was significantly higher in patients compared to controls. On radial division into 5 sub-regions, the anterior truncus area was significantly higher in patients compared to controls. There was a significant effect of gender (F>M) on the area measures; however there was no significant diagnosis()gender effect. Age, age of onset, duration of illness and psychopathology ratings did not show any significant correlations with whole CC area and area of CC sub-regions. The finding of increased area of the anterior truncus that possibly comprises white fibres connecting the temporal association cortices could be indicative of an "abnormal functional hyperconnection" involving these regions in positive symptom schizophrenia. Additionally, the finding of females having larger areas of the whole CC and of the anterior and middle sub-regions could reflect a "normal hyperconnection" underlying increased ambilaterality in females.

Morphology of the corpus callosum at different stages of schizophrenia: cross-sectional study in first-episode and chronic illness

BACKGROUND

The shape of the corpus callosum may differ in schizophrenia, although no study has compared first-episode with established illness.

AIMS

To investigate the size and shape of the corpus callosum in a large sample of people with first-episode and established schizophrenia.

METHOD

Callosal size and shape were determined using high-resolution magnetic resonance imaging on 76 patients with first-episode schizophrenia-spectrum disorders, 86 patients with established schizophrenia and 55 healthy participants.

RESULTS

There were no significant differences in total area across groups. Reductions in callosal width were seen in the region of the anterior genu in first-episode disorder (P<0.005). Similar reductions were seen in the chronic schizophrenia group in the anterior genu, but also in the posterior genu and isthmus (P=0.0005).

CONCLUSIONS

Reductions in anterior callosal regions connecting frontal cortex are present at the onset of schizophrenia, and in established illness are accompanied by changes in other regions of the callosum connecting cingulate, temporal and parietal cortices.

Meta-analysis of magnetic resonance imaging studies of the corpus callosum in schizophrenia

OBJECTIVES

The corpus callosum plays a pivotal role in inter-hemispheric transfer and integration of information. Magnetic resonance studies have reported callosal abnormalities in schizophrenia but findings have been inconsistent. Uncertainty has persisted despite a meta-analytic evaluation of this structure several years ago. We set out to perform a further meta-analysis with the addition of the numerous reports published on the subject to test the hypothesis that the corpus callosum is abnormal in schizophrenia.

METHOD

A systematic search was carried out to identify suitable magnetic resonance studies which reported callosal areas in schizophrenia compared to controls. Results from the retrieved studies were compared in a meta-analysis whilst the influence of biological and clinical variables on effect size was ascertained with meta-regression analysis.

RESULTS

Twenty-eight studies were identified. Corpus callosum area was reduced in schizophrenia in comparison to healthy volunteers. This effect was larger in first episode patients. Similarly, heterogeneity detected among the studies was associated with course of illness indicating that chronic subjects with schizophrenia showed larger callosal areas. There was no evidence of publication bias.

CONCLUSIONS

This study confirms the presence of reduced callosal areas in schizophrenia. The effect is of a larger magnitude at first presentation and less so in subjects with a chronic course generally medicated with antipsychotics.

Association between absence of the adhesio interthalamica and amygdala volume in schizophrenia

Abnormal neurodevelopment in midline structures such as the adhesio interthalamica (AI) has been reported in schizophrenia, but not consistently replicated. We investigated the prevalence and anterior-posterior length of the AI in 62 schizophrenia patients (32 males, 30 females) and 63 healthy controls (35 males, 28 females) using magnetic resonance imaging. We also explored the relation between the AI and volumetric measurements for the third ventricle, medial temporal structures (amygdala, hippocampus, and parahippocampal gyrus), superior temporal sub-regions, and frontal lobe regions (prefrontal area and anterior cingulate gyrus). The AI was absent in 24.2% (15/62) of the schizophrenia patients and in 9.5% (6/63) of the controls, showing a significant group difference. For the length of the AI, schizophrenia patients had a shorter AI than controls, and males had a shorter AI than females. The subjects without an AI had a significantly larger third ventricle and smaller parahippocampal gyrus than the subjects with an AI for both groups. We found a significant diagnosis-by-AI interaction for the amygdala. The schizophrenia patients without an AI had a smaller bilateral amygdala than those with an AI, whereas the AI was not associated with the volume of the amygdala in the control subjects. These findings suggest that the absence of AI in schizophrenia could be a marker of developmental abnormalities in the neural network including the thalamus and connected amygdaloid regions, which may play an important role in the pathogenesis of schizophrenia.

Internal capsule, corpus callosum and long associative fibers in good and poor outcome schizophrenia: a diffusion tensor imaging survey

BACKGROUND

Prior voxelwise studies of white matter anisotropy found widespread reductions involving all major fiber tracts of the schizophrenic brain. We set out to confirm these exploratory findings and evaluate their relation to illness severity using a hypothesis-driven region-of-interest approach.

METHODS

104 schizophrenia patients (51 with good outcomes, 53 with poor outcomes) and 41 matched comparison subjects participated in the study. Regions of interest were selected on the basis of published voxelwise findings and placed within major fiber tracts using Talairach's stereotaxic coordinates.

RESULTS

Fractional anisotropy reductions in schizophrenia patients were confirmed in the left cingulum, anterior thalamic radiation, fronto-occipital and inferior longitudinal fasciculi, as well as bilaterally in the corpus callosum, anterior and posterior limbs of internal capsule, superior longitudinal fasciculus, optic radiation, and frontotemporal extrafascicular white matter. Anisotropy reductions were more extensive in patients with poor outcomes ("Kraepelinian"), particularly in the posterior corpus callosum, fronto-occipital fasciculus, left optic radiation and frontotemporal white matter. Lower anisotropy in the right hemisphere tracts was associated with more prominent positive symptomatology, whereas negative symptoms were inversely associated with anisotropy values in both hemispheres.

CONCLUSIONS

These results support a global neural disconnectivity in schizophrenia patients, which is more severe in those with poor clinical outcomes.

Functional connectivity between hemispheres and schizophrenic symptoms: a longitudinal study of interhemispheric EEG coherence in patients with acute exacerbations of schizophrenia

To clarify whether interhemispheric electroencephalogram (EEG) coherence reflecting functional connectivity between the two cerebral hemispheres can change in a symptom-dependent manner in schizophrenia, we measured resting EEG and symptom severity twice at an average interval of 32.7 days during the course of treatment in 15 patients hospitalized for acute exacerbations of schizophrenia. Symptom severity was estimated quantitatively by means of the Brief Psychiatric Rating Scale (BPRS). Correlation analysis showed that increases in the beta-band coherence for frontal electrode pairs during the treatment were associated with improvement in the total score and the score on the positive subscale of BPRS. This result suggests that functional disconnection between the left and right frontal lobes may be related to the generation of psychotic symptoms and can normalize following antipsychotic treatment.

Diffusion tensor imaging in schizophrenia

BACKGROUND

Diffusion tensor imaging (DTI) is a relatively new neuroimaging technique that can be used to examine the microstructure of white matter in vivo. A systematic review of DTI studies in schizophrenia was undertaken to test the hypothesis that DTI can detect white matter differences between schizophrenia patients and normal control subjects.

METHODS

EMBASE, PubMed, Medline, and PsychInfo were searched online and key journals were searched manually for studies comparing anisotropy (a measure of white matter integrity) between patients and control subjects. Nineteen articles were systematically reviewed.

RESULTS

Though 16 studies found differences, methodological and data differences prevented a meta-analysis. Fourteen studies found reduced anisotropy in patients; two studies found only a loss of normal asymmetry. The region of investigation varied across studies, however, and when the same region (for example, the cingulum) was examined in different studies, as many failed to find a difference as found one. These inconsistencies may be the result of small sample sizes and differences in methodology.

CONCLUSIONS

Diffusion tensor imaging has yet to provide consistent findings of white matter abnormalities in schizophrenia. Its potential as a means of examining anatomical connectivity may be realized with the study of larger, more homogenous groups of subjects and with ongoing improvements in image analysis.

Smaller corpus callosum subregions containing motor fibers in schizophrenia

Neuropsychological and neurophysiological studies provide evidence for abnormal interhemispheric communication in schizophrenia. These abnormalities may have a substrate in structural irregularities of the corpus callosum. This study investigated schizophrenia patients (n=27) and healthy comparison subjects (n=31). Global and regional measurements of the corpus callosum were acquired from one midsagittal SPGR slice. Eight subregions were approximately matched to fiber pathways from cortical regions. Overall effects of diagnosis [Wilks' Lambda F(8,46)=2.45, p=0.03] and diagnosis by age interaction [Wilks' Lambda F(8,46)=2.58, p=0.02] were found in a MANCOVA of the eight functionally specific subregions. Specifically, chronic schizophrenia was associated with a smaller rostral body [lower by 6.9%, F(1,53)=9.70, p=0.003] and anterior midbody [lower by 9.7%, F(1,53)=4.89, p=0.03] subregions. The rostral body and anterior midbody subregions of the corpus callosum primarily have premotor, supplementary motor, and motor cortical fibers transversing through them. Functional abnormalities of the associated cortical regions are reported in schizophrenia. These novel findings suggest that structural abnormalities of the corpus callosum exist in schizophrenia, with perhaps the motor-specific subregions affected more than others. Structural differences in the corpus callosum may be a substrate for interhemispheric functional dysconnectivity in schizophrenia.

Positronenemissionstomographie in den Neurowissenschaften

The role of molecular neuroimaging techniques is increasing in the understanding of pathophysiological mechanism of diseases. To date, positron emission tomography is the most powerful tool for the non-invasive study of biochemical and molecular processes in humans and animals in vivo. With the development in radiochemistry and tracer technology, a variety of endogenously expressed and exogenously introduced genes can be analyzed by PET. This opens up the exciting and rapidly field of molecular imaging, aiming at the non-invasive localisation of a biological process of interest in normal and diseased cells in animal models and humans in vivo. Besides its usefulness for basic research positron emission tomography has been proven to be superior to conventional diagnostic methods in several clinical indications. This is illustrated by detection of biological or anatomic changes that cannot be demonstrated by computed tomography or magnetic resonance imaging, as well as even before symptoms are expressed. The present review summarizes the clinical use of positron emission tomography in neuroscience that has helped elucidate the pathophysiology of a number of diseases and has suggested strategies in the treatment of these patients. Special reference is given to the neurovascular, neurodegenerative and neurooncological disease.

Hypofrontality in schizophrenia: a meta-analysis of functional imaging studies

OBJECTIVE

Hypofrontality is not a well-replicated finding in schizophrenia either at rest or under conditions of task activation.

METHOD

Studies comparing whole brain and frontal blood flow/metabolism in schizophrenic patients and normal controls were pooled. Voxel-based studies were also combined to examine the pattern of prefrontal activation in schizophrenia.

RESULTS

Whole brain flow/metabolism was reduced in schizophrenia to only a small extent. Resting and activation frontal flow/metabolism were both reduced with a medium effect size. Duration of illness significantly moderated resting hypofrontality, but the moderating effects of neuroleptic treatment were consistent with an influence on global flow/metabolism only. Pooling of voxel-based studies did not suggest an abnormal pattern of activation in schizophrenia.

CONCLUSION

Meta-analysis supports resting hypofrontality in schizophrenia. Task-activated hypofrontality is also supported, but there is little from voxel-based studies to suggest that this is associated with an altered pattern of regional functional architecture.

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.

Abnormal brain response of chronic schizophrenia patients despite normal performance during a visual vigilance task

Deficits of attention are common among individuals with schizophrenia (SZ) and are related both to genetic liability to the disorder and to functional outcome among patients. To explore the brain systems underlying these attentional abnormalities, we compared the response of nine patients with chronic SZ or schizoaffective disorder to that of 10 matched healthy individuals performing a simple visual vigilance task during functional magnetic resonance imaging. The two groups performed equivalently on the task. When the blood oxygen level dependent (BOLD) signal during identification of a target letter among similar-looking letters was compared to the response during fixation trials, both groups showed multiple clusters of significant brain response in widespread cortical regions. Compared with healthy participants, SZ patients showed a diminished response in the inferior frontal cortex and an abnormally enhanced response in right postcentral gyrus, right medial temporal lobe and left cerebellum. The results suggest that abnormalities of functional brain response to attentional tasks can be observed among patients with SZ even when behavioral performance is unimpaired, and provide further evidence that brain systems related to attention are likely to be involved in the pathophysiology of the disorder.

Schizophrenia, neurodevelopment and corpus callosum

The Zeitgeist favors an interpretation of schizophrenia as a condition of abnormal connectivity of cortical neurons, particularly in the prefrontal and temporal cortex. The available evidence points to reduced connectivity, a possible consequence of excessive synaptic pruning in development. A decreased thalamic input to the cerebral cortex appears likely, and developmental studies predict that this decrease should entail a secondary loss of both long- and short-range cortico-cortical connections, including connections between the hemispheres. Indeed, morphological, electrophysiological and neuropsychological studies over the last two decades suggest that the callosal connections are altered in schizophrenics. However, the alterations are subtle and sometimes inconsistent across studies, and need to be investigated further with new methodologies.

Synchronous gamma activity: a review and contribution to an integrative neuroscience model of schizophrenia

Synchronous high frequency (Gamma band) activity has been proposed as a candidate mechanism for the integration or 'binding' of distributed brain activities. Since the first descriptions of schizophrenia, attempts to characterize this disorder have focused on disturbances in such integrative processing. Here, we review both micro- and macroscopic neuroscience research into Gamma synchrony, and its application to understanding schizophrenia. The review encompasses evidence from both animal and human studies for the functional significance of Gamma activity, the association between Gamma dysfunction and information processing disturbances, and the relevance of specific Gamma dysfunctions to the integration and extension of previous disconnection models of schizophrenia. Attention is given to the relationship between Gamma activity and the heterogeneous symptoms of schizophrenia. Existing studies show that measures of Gamma activity have the potential to explain far more of the variance in schizophrenia performance than previous neurophysiological measures. It is concluded that measures of Gamma synchrony offer a valuable window into the core integrative disturbance in schizophrenia cognition.

A study of transcallosal inhibition in schizophrenia using transcranial magnetic stimulation

A considerable body of imaging research has demonstrated morphological changes in the corpus callosum (CC) of patients with schizophrenia. Transcranial magnetic stimulation (TMS) allows the possibility for the in vivo investigation of a variety of aspects of brain function including the spread of information across the CC. We aimed to investigate whether patients with schizophrenia demonstrate abnormalities of transcallosal inhibition (TCI), a TMS parameter measured with both single and paired pulse experiments. 25 patients with DSM-IV schizophrenia and 20 normal volunteers participated in the study. Electromyographic (EMG) recordings from the bilateral abductor pollicis brevis (APB) muscle were made during focal TMS stimulation to the motor cortex. Experimental paradigms were utilised to measure both the timing and degree of the effect of TCI. The patient group demonstrated a reduction in the degree of TCI at rest and during a sustained muscle contraction. TCI commenced at the same time in the patient and the control group but was of prolonged duration in the patient group although the length of TCI correlated with medication dose. Patients with schizophrenia demonstrate a reduction in the degree of TCI that appeared independent of medication dose. The latency of TCI is not altered in the patient group suggesting that cortical inhibitory mechanisms, rather than corpus callosal ones, are likely to be the cause of these TCI alterations.

Cortical connectivity in high frequency beta-rhythm in schizophrenics with positive and negative symptoms

During the last decade the role of high frequency EEG activity in the 'binding phenomenon' was discovered. It was supposed that this phenomenon provided the integration between different brain structures underlying higher nervous functions and possibly even consciousness [Proc. Natl. Acad. Sci. 90 (1993) 2078; Annu. Rev. Neurosci. 18 (1995) 555; J. Neurosci. V 16 (1996) 4240; Am. Physiol. Soc. (1998) 1567; Induced Rhythms in the Brain (1992) 425; NeuroReport 8 (1997) 531; Proc. Natl. Acad. Sci. USA 94 (1997) 12198]. Schizophrenia is considered as a disorder of the integration between different brain regions [Review of Psychiatry 18 (1999a) 29; Conceptual Advances in Russian Neuroscience: Complex Brain Functions (1999) 151; Brain Res. Rev. 31 (2000) 301], and in the present work we have studied cortical connectivity, focusing on those connections which are maintained by high frequency EEG-rhythm (20-40 Hz). The results showed a high degree of biopotential synchronisation between definite cortical areas during cognitive processes in normal subjects and have evidenced significant functional connectivity disturbances in schizophrenia in this EEG frequency domain.

Corpus callosum area and functioning in schizophrenic patients with auditory--verbal hallucinations

Auditory--verbal hallucinations (AVH) are a characteristic feature of schizophrenia. Patients with AVHs have been found to differ from non-hallucinating patients in volumes of certain asymmetrical brain structures on MRI, and on certain neuropsychological measures. There is also evidence of corpus callosum (CC) abnormalities in schizophrenia, and it has been proposed that abnormalities of inter-hemispheric transmission may underlie hallucinations and other symptoms. The aim of this study was to examine whether patients with AVHs have smaller corpora callosa than those without AVH, and whether CC size is related to performance on neuropsychological tests of functional cerebral asymmetry. Seventy-one DSM-IV male schizophrenics were recruited on the basis of their hallucination history plus 33 matched normal controls. Twenty-nine patients had no history of AVH, and 42 had a strong history of AVH. The mid-sagittal surface area and longitudinal length of the CC were measured from T(1)-weighted spin echo images. Callosal area was divided into four sections. There were no significant differences in any of the measurements between the two patient groups, or between patients with schizophrenia and controls. There was no association between CC measures and handedness, or performance on dichotic listening or finger tapping tasks. The results of this study do not lend support for there being a major morphological abnormality of the corpus callosum in schizophrenic patients, or for a specific relationship to AVH. However, a significant association between CC area and overall grey and white matter volumes was noted in the hallucinating patients and, to a lesser extent, in the non-hallucinators, which may point to differing influences on brain development or degeneration in such patients compared with normal controls.

Corpus callosum and P300 in schizophrenia

Functional abnormalities in the interhemispheric transfer via the corpus callosum in schizophrenia may result in filtering problems and information processing problems, which may in turn be related to the synchronization of cortical event-related activity. To explore whether a relationship exists between corpus callosum (CC) size, measured with in-vivo magnetic resonance imaging, and late auditory event-related P300 potentials, 50 patients with schizophrenia as well as 50 healthy controls were examined. The absolute CC size and subregional areas, as well as the CC areas adjusted for total brain volume, were not significantly different between patients with schizophrenia and controls. While no significant group differences were observed for P3a-, P3b-, PSW-amplitudes and P3b-latencies, P3a- and PSW-latencies were significantly prolonged for patients with schizophrenia. Absolute CC total size was significantly correlated with P3b-amplitudes in healthy controls (r=0.29; P=0.044). In patients with schizophrenia, significant correlations were observed between the subregion of the posterior body of the CC and positive slow wave (PSW; r=0.47; P=0.001). P3a-, P3b- and PSW-latencies were not significantly correlated to CC size in either patients with schizophrenia or healthy controls. The results are discussed in terms of the possibility that abnormalities in interhemispheric transfer may underlie the mechanisms of schizophrenia.

A review of MRI findings in schizophrenia

After more than 100 years of research, the neuropathology of schizophrenia remains unknown and this is despite the fact that both Kraepelin (1919/1971: Kraepelin, E., 1919/1971. Dementia praecox. Churchill Livingston Inc., New York) and Bleuler (1911/1950: Bleuler, E., 1911/1950. Dementia praecox or the group of schizophrenias. International Universities Press, New York), who first described 'dementia praecox' and the 'schizophrenias', were convinced that schizophrenia would ultimately be linked to an organic brain disorder. Alzheimer (1897: Alzheimer, A., 1897. Beitrage zur pathologischen anatomie der hirnrinde und zur anatomischen grundlage einiger psychosen. Monatsschrift fur Psychiarie und Neurologie. 2, 82-120) was the first to investigate the neuropathology of schizophrenia, though he went on to study more tractable brain diseases. The results of subsequent neuropathological studies were disappointing because of conflicting findings. Research interest thus waned and did not flourish again until 1976, following the pivotal computer assisted tomography (CT) finding of lateral ventricular enlargement in schizophrenia by Johnstone and colleagues. Since that time significant progress has been made in brain imaging, particularly with the advent of magnetic resonance imaging (MRI), beginning with the first MRI study of schizophrenia by Smith and coworkers in 1984 (Smith, R.C., Calderon, M., Ravichandran, G.K., et al. (1984). Nuclear magnetic resonance in schizophrenia: A preliminary study. Psychiatry Res. 12, 137-147). MR in vivo imaging of the brain now confirms brain abnormalities in schizophrenia. The 193 peer reviewed MRI studies reported in the current review span the period from 1988 to August, 2000. This 12 year period has witnessed a burgeoning of MRI studies and has led to more definitive findings of brain abnormalities in schizophrenia than any other time period in the history of schizophrenia research. Such progress in defining the neuropathology of schizophrenia is largely due to advances in in vivo MRI techniques. These advances have now led to the identification of a number of brain abnormalities in schizophrenia. Some of these abnormalities confirm earlier post-mortem findings, and most are small and subtle, rather than large, thus necessitating more advanced and accurate measurement tools. These findings include ventricular enlargement (80% of studies reviewed) and third ventricle enlargement (73% of studies reviewed). There is also preferential involvement of medial temporal lobe structures (74% of studies reviewed), which include the amygdala, hippocampus, and parahippocampal gyrus, and neocortical temporal lobe regions (superior temporal gyrus) (100% of studies reviewed). When gray and white matter of superior temporal gyrus was combined, 67% of studies reported abnormalities. There was also moderate evidence for frontal lobe abnormalities (59% of studies reviewed), particularly prefrontal gray matter and orbitofrontal regions. Similarly, there was moderate evidence for parietal lobe abnormalities (60% of studies reviewed), particularly of the inferior parietal lobule which includes both supramarginal and angular gyri. Additionally, there was strong to moderate evidence for subcortical abnormalities (i.e. cavum septi pellucidi-92% of studies reviewed, basal ganglia-68% of studies reviewed, corpus callosum-63% of studies reviewed, and thalamus-42% of studies reviewed), but more equivocal evidence for cerebellar abnormalities (31% of studies reviewed). The timing of such abnormalities has not yet been determined, although many are evident when a patient first becomes symptomatic. There is, however, also evidence that a subset of brain abnormalities may change over the course of the illness. The most parsimonious explanation is that some brain abnormalities are neurodevelopmental in origin but unfold later in development, thus setting the stage for the development of the symptoms of schizophrenia. Or there may be additional factors, such as stress or neurotoxicity, that occur during adolescence or early adulthood and are necessary for the development of schizophrenia, and may be associated with neurodegenerative changes. Importantly, as several different brain regions are involved in the neuropathology of schizophrenia, new models need to be developed and tested that explain neural circuitry abnormalities effecting brain regions not necessarily structurally proximal to each other but nonetheless functionally interrelated. (ABSTRACT TRUNCATED)

Differential neuropsychological patterns of frontal- and temporal-lobe dysfunction in patients with schizophrenia

The frontal and temporal lobes have been implicated as pathogenic sites for schizophrenia, although there is a marked heterogeneity of brain function and structure between individual patients. It is currently unclear whether some patients with schizophrenia exhibit primarily frontal lobe dysfunction, while others exhibit primarily temporal-lobe dysfunction. The current investigation examined this issue in a preliminary way by using neurocognitive tests to discriminate test performances of patients with schizophrenia from patients without schizophrenia who had definitive neurological evidence of either frontal- or temporal-lobe dysfunction. Of the patients with schizophrenia, 20.7% were classified as having a frontal lobe dysfunction profile, while 19.3% had a temporal lobe dysfunction profile. Results further clarify neurobiological heterogeneity in schizophrenia by demonstrating that a substantial number of patients with schizophrenia exhibit either primarily frontal- or temporal-lobe dysfunction. Results may partially explain the inadequacy of neurobiological models for schizophrenia that do not consider these differential patterns of dysfunction.

Cortical response to motor stimulation in neuroleptic-naive first episode schizophrenics

The purpose of the present study was to evaluate the cortical response to motor stimulation in neuroleptic-naive first episode schizophrenics in comparison to matched controls using a high speed functional magnetic resonance imaging technique (fMRI). Twelve patients satisfying ICD 10 criteria (F20.0) for schizophrenia (paranoid subtype) as well as sex- and age-matched healthy volunteers participated in this study. All subjects underwent fMRI examination on a conventional 1.5 T MR unit equipped with an echo-planar imaging booster. The blood oxygen level dependent (BOLD) response of the sensorimotor cortex and the higher order SMA region was evaluated during performance of a left hand sequential finger opposition task. Special care was taken to minimize performance and motion artifacts. Patients and controls showed no notable difference with respect to laterality, changes of signal intensity or spatial extent of activation within the primary and higher order motor regions. Using high speed fMRI no fundamental motor cortical dysfunction was evident in a group of paranoid neuroleptic-naive first episode schizophrenic patients. In contrast to data previously reported for chronic disorganized medicated patients, these results suggest that motor dysfunction is not part of the phenomenology of acute paranoid first episode patients.

Transcallosal inhibition and motor conduction studies in patients with schizophrenia using transcranial magnetic stimulation

BACKGROUND

Transcranial magnetic stimulation of the motor cortex may not only elicit excitatory responses in hand muscles contralateral to the stimulated hemisphere, but may also suppress tonic voluntary electromyogram activity in muscles ipsilateral to the stimulation. This inhibition is mediated between the motor cortices via the corpus callosum.

AIMS

To investigate motor excitability and interhemispheric (transcallosal) connections in patients with schizophrenia.

METHOD

Transcallosal inhibition and motor conduction parameters were investigated in ten patients with schizophrenia and in ten age- and gender-matched healthy subjects.

RESULTS

Transcallosal conduction time (TCT) and duration of the inhibition were significantly longer in patients with schizophrenia (mean (s.d.)): TCT, 12.4 (2.9) ms in normal subjects and 15.3 (2.6) ms in patients (P = 0.03); mean duration, 34.1 (4.9) ms in normal subjects and 51.9 (16.8) ms in patients (P = 0.01).

CONCLUSIONS

Magnetic motor conduction parameters are unaltered in schizophrenia, but transcallosal inhibition is significantly delayed and prolonged. This may indicate abnormal function of the corpus callosum in these patients.

Clinical and neuropathological abnormalities in baboons treated with HPTP, the tetrahydropyridine analog of haloperidol

Tardive dyskinesia (TD) is relatively common among psychiatric patients on maintenance therapy with typical neuroleptics and persists in more than 20% even after withdrawal of the medication. Such persistence suggests an underlying pathology due to neurotoxicity. We present evidence for such a neurotoxic mechanism in a baboon model of TD. Four baboons were treated chronically with the dehydration product of haloperidol, 4-(4-chlorophenyl)-1-[4-(4-fluorophenyl)-4-oxobutyl]-1,2,3,6- tetrahydropyridine (HPTP), which is metabolized, similarly to haloperidol, to two neurotoxic pyridinium species. The animals developed orofacial dyskinesia which persisted after HPTP was ceased. Serial sections of the entire brain from the four treated animals and four vehicle-treated controls revealed volume loss in the basal forebrain and hypothalamus. Histological evaluation demonstrated a reduction in the density of magnocellular neurons in the anterior region of the nucleus basalis of Meynert (NbM). We speculate that the loss of these NbM neurons may be associated with the persistent orofacial dyskinesia observed in the HPTP-treated animals. These findings may contribute to a better understanding of neuroleptic-induced TD.

MRI anatomy of schizophrenia

Structural magnetic resonance imaging (MRI) data have provided much evidence in support of our current view that schizophrenia is a brain disorder with altered brain structure, and consequently involving more than a simple disturbance in neurotransmission. This review surveys 118 peer-reviewed studies with control group from 1987 to May 1998. Most studies (81%) do not find abnormalities of whole brain/intracranial contents, while lateral ventricle enlargement is reported in 77%, and third ventricle enlargement in 67%. The temporal lobe was the brain parenchymal region with the most consistently documented abnormalities. Volume decreases were found in 62% of 37 studies of whole temporal lobe, and in 81% of 16 studies of the superior temporal gyrus (and in 100% with gray matter separately evaluated). Fully 77% of the 30 studies of the medial temporal lobe reported volume reduction in one or more of its constituent structures (hippocampus, amygdala, parahippocampal gyrus). Despite evidence for frontal lobe functional abnormalities, structural MRI investigations less consistently found abnormalities, with 55% describing volume reduction. It may be that frontal lobe volume changes are small, and near the threshold for MRI detection. The parietal and occipital lobes were much less studied; about half of the studies showed positive findings. Most studies of cortical gray matter (86%) found volume reductions were not diffuse, but more pronounced in certain areas. About two thirds of the studies of subcortical structures of thalamus, corpus callosum and basal ganglia (which tend to increase volume with typical neuroleptics), show positive findings, as do almost all (91%) studies of cavum septi pellucidi (CSP). Most data were consistent with a developmental model, but growing evidence was compatible also with progressive, neurodegenerative features, suggesting a "two-hit" model of schizophrenia, for which a cellular hypothesis is discussed. The relationship of clinical symptoms to MRI findings is reviewed, as is the growing evidence suggesting structural abnormalities differ in affective (bipolar) psychosis and schizophrenia.

Interhemispheric EEG coherence in never-medicated patients with paranoid schizophrenia: analysis at rest and during photic stimulation

We assessed functional relationships between hemispheres by calculating interhemispheric EEG coherence at rest and during photic stimulation in 18 never-medicated patients with paranoid schizophrenia and 30 control subjects. Although no significant group differences were found in the resting EEG, the schizophrenic patients had significantly higher coherence on EEGs recorded during photic stimulation, compared to the control subjects. In this study, we also examined the changes in interhemispheric coherence from rest to the stimulus condition (i.e., stimulation-related coherence reactivity); the patients were found to show significantly greater coherence reactivity to photic stimulation. These findings provide further evidence that schizophrenic patients have a higher degree of interhemispheric functional connectivity and thus have less lateralized cerebral organization than normal subjects. Our results also suggest that schizophrenic patients have excessive functional reorganization between hemispheres in association with photic stimulation.

Corpus callosum shape and size in male patients with schizophrenia

BACKGROUND

Corpus callosum (CC) morphology has recently been investigated in schizophrenia using refined imaging and analytic techniques; however, methodological problems and small sample sizes have led to inconsistent findings.

METHODS

This study used a large sample of male schizophrenics (n = 79) and male controls (n = 65) to investigate size and shape of the CC on midsagittal magnetic resonance images. Size was determined by tracing the area of the CC, and shape was determined using a landmark-based analysis. In addition, the relationship between CC morphology and phenomenologic variables such as age of onset, length of illness, exposure to medications, and symptom severity was explored.

RESULTS

After controlling for age, height, and parental socioeconomic status, there was a main effect of diagnosis on CC size (F = 5.05, df = 1,139, p < .03), with patients' CCs being significantly smaller. No difference was found between patients and controls in CC shape (F = 1.07, df = 18,125, p > .38) or orientation (F = 0.79, df = 18,125, p > .70), using a landmark-based technique. Finally, there was a significant inverse correlation between size of CC and severity of negative symptoms.

CONCLUSIONS

These findings support previous studies that have found a decrease in size of the CC in patients with schizophrenia. Moreover, the decrement in volume is generalized, not regional, and is related to the severity of negative symptoms.

Corpus callosum size and inter-hemispheric function in schizophrenia

We studied the relationship between corpus callosum area and both inter-hemispheric facilitation and interference in schizophrenics and controls. Mid-sagittal sections through the corpus callosum were measured using structural magnetic resonance imaging on 42 patients and 43 normal controls, along with symptom profiles. In a sub-sample, a modified version of the Stroop Test was also performed (27 patients and 29 controls) to assess inter-hemispheric facilitation and interference of colour naming. In the larger sample (total subjects, n = 85), there were no significant differences between patients and controls in CC area but a trend towards smaller values in patients in all but the posterior segment. In the sub-sample, bilateral facilitation was greater, and interference, less in schizophrenics compared with controls. There was a positive correlation between facilitation and posterior CC area, parallelled by a negative correlation between interference and posterior CC area, in both patients and controls, which only reached statistical significance when both groups were combined. These findings suggest that the link, between CC size and neuropsychological processes involving inter-hemispheric transfer of information, is common to both schizophrenics and normal controls. There were significant negative correlations between anterior CC area and psychomotor poverty (avolition, anhedonia and affective flattening), and a suggestion that the negative correlation between age and CC size in controls was not present in patients.

Quantitative magnetic resonance imaging of the corpus callosum in childhood onset schizophrenia

Corpus callosum size has been found to be abnormal in adult schizophrenia, and other studies have implicated abnormal interhemispheric communication in this disorder. To assess continuity with brain abnormalities in the later onset disorder and to further localize brain maldevelopment, this structure was examined in a unique sample of childhood onset schizophrenics. Anatomic brain magnetic resonance imaging scans were acquired for 25 patients (mean age 13.9 +/- 2.1) who had onset of schizophrenia by age 12 (mean age at onset 9.9 +/- 1.9) and 55 normal children. The midsagittal area of the corpus callosum was divided into seven sections. With no adjustment for brain volume, no diagnostic differences were observed. After adjustment for the smaller cerebral volume of the schizophrenics, larger total, anterior and posterior corpus callosum areas emerged for the schizophrenics. These findings provide further evidence for continuity between childhood onset and later onset schizophrenia and support other studies showing white matter sparing in the context of decreased cortical volume.

Memory deficits in subsyndromes of chronic schizophrenia

Recent psychopathological studies consistently identified a delusional, a negative, and a disorganized subsyndrome in chronic schizophrenia. The aim of the present study was to investigate these subsyndromes with respect to declarative, procedural and working memory deficits. While the delusional subsyndrome was associated with an impaired delayed recognition, the negative subsyndrome showed a marked deficit in delayed recall. In addition, the delusional and the negative subsyndrome shared procedural memory changes. The disorganized subsyndrome was associated with neurological soft signs and a poor working memory performance. These results do not seem to be effected by severity of illness, degree of chronicity, nor attentional deficits. Our findings support the differentiation of three subsyndromes in chronic schizophrenia and suggest that memory impairment in schizophrenia may reflect the involvement of different memory systems rather than an unspecific, global deficit.

Wisconsin card sorting activated regional cerebral blood flow in first break and chronic schizophrenic patients and normal controls

Dynamic 133Xe single photon emission computed tomography (SPECT) was used to measure regional cerebral blood flow (rCBF) during the Wisconsin Card Sorting test (WCS) and the Number Matching task (NM) in six never-medicated first break schizophrenic and schizophreniform patients, seven chronic schizophrenic patients, and seven normal controls. Because of a difference in mean age between first break patients and normals, we adjusted rCBF data for age effects using ANCOVA. For age-adjusted absolute superior and middle frontal rCBF bilaterally, we found significantly less activation from NM to WCS in first break patients compared to normals. Similarly, for age-adjusted absolute and relative left middle frontal rCBF, we found significantly less activation in chronics compared to normals. Changes in age-adjusted global cerebral blood flow (gCBF) were not statistically significant among the three groups, but were in the same direction as activated absolute frontal rCBF. Because of the small number of subjects in each group, the results of this study should be regarded as preliminary and interpreted cautiously.

Cerebral metabolic activity correlates of subsyndromes in chronic schizophrenia

Seventy-nine patients with schizophrenia and 47 healthy controls received positron-emission tomography (PET) with 18F-2-deoxyglucose uptake while executing the Continuous Performance Test (CPT). Patients had been off all psychoactive medication for at least four weeks. Patients' symptoms were assessed with the Brief Psychiatric Rating Scale and factor scale scores were obtained. These scores were used in cluster analysis to identify patients with predominantly delusional, negative, disorganized, and remitted symptoms. To address the interconnective nature of cerebral functioning, regions of interest were defined on the basis of the results of a factor analysis of metabolic rate in selected brain regions. This procedure identified six cortical and eight subcortical region of interest factors. Metabolic rate factor scale scores were compared between the patients' clusters and the healthy controls. The delusional cluster showed a significantly reduced hippocampal activity, while the negative symptoms cluster presented with a prominent hypofrontality and significantly increased left temporal cortex values. Concurrently, both clusters were associated with a decreased activity on the factor 'anterior cingulum and medial frontal gyrus'. The disorganized cluster was characterized by a significant overactivity in the parietal cortex and motor strip and a decreased activity in the corpus callosum. The subsyndromes of chronic schizophrenia are therefore characterized by deviant patterns of cerebral activity rather than deficits in a single location.

Sensorimotor cortex and supplementary motor area changes in schizophrenia. A study with functional magnetic resonance imaging

BACKGROUND

Neurological soft signs (NSS) such as a disturbed finger-to-thumb opposition are frequently found in schizophrenia. To identify the underlying cerebral changes we investigated sensorimotor cortex and supplementary motor area (SMA) activation during finger-to-thumb opposition using functional magnetic resonance imaging (fMRI).

METHOD

Ten DSM-III-R schizophrenics and seven healthy controls were included. All subjects were right-handed. fMRI was carried out in a resting condition followed by an activation state (finger-to-thumb opposition) and the activities in the sensorimotor cortices and SMA recorded.

RESULTS

All subjects showed a significant activation of the SMA and both ipsilateral and contralateral sensorimotor cortices. In the controls, ipsilateral finger-to-thumb opposition was associated with a greater left than right hemispheric sensorimotor cortex coactivation. When compared with the healthy controls, the schizophrenic patients showed a decreased activation of both sensorimotor cortices and SMA, as well as a reversed lateralisation effect.

CONCLUSION

Sensorimotor cortex and SMA dysfunction are associated with motor disturbances in schizophrenia.

Cognitive deficits and the neurobiology of schizophrenia

Recent research in schizophrenia has demonstrated widespread abnormalities in patients' brain structure, cognitive function, and physiology. These abnormalities are most probably developmental in origin and involve a network of connected frontal-temporal-limbic structures.

Meta-analysis of corpus callosum size in schizophrenia

Studies with MRI have shown differences in corpus callosum size between schizophrenic patients and controls. Most have found that the corpus callosum is smaller in schizophrenic patients, but in only a minority was this finding statistically significant, perhaps due to small sample sizes. Therefore a meta-analysis of 11 published studies of corpus callosum morphology in schizophrenia was conducted to ascertain whether there was a significant difference in corpus callosum size between schizophrenic patients and normal controls. These studies combined comprised 313 patients and 281 controls. Measures of corpus callosum midsagittal area, length, and corpus callosum area:brain area ratio were used in the meta-analysis. There was overall a statistically significant reduction in corpus callosum area in schizophrenic patients compared with controls (P < 0.02). Differences between patients and controls in measures of corpus callosum: brain area and corpus callosum length were not statistically significant. Age and corpus callosum area were related in both patients and controls. The influences on the corpus callosum of overall alterations of brain size, sex, handedness, and psychiatric illness in general remains to be determined.