Increased density of glutamate-immunoreactive vertical processes in superficial laminae in cingulate cortex of schizophrenic brain

Anterior cingulate glutamate levels associate with functional activation and connectivity during sensory integration in schizophrenia: a multimodal 1H-MRS and fMRI study

BACKGROUND

Glutamatergic dysfunction has been implicated in sensory integration deficits in schizophrenia, yet how glutamatergic function contributes to behavioural impairments and neural activities of sensory integration remains unknown.

METHODS

Fifty schizophrenia patients and 43 healthy controls completed behavioural assessments for sensory integration and underwent magnetic resonance spectroscopy (MRS) for measuring the anterior cingulate cortex (ACC) glutamate levels. The correlation between glutamate levels and behavioural sensory integration deficits was examined in each group. A subsample of 20 pairs of patients and controls further completed an audiovisual sensory integration functional magnetic resonance imaging (fMRI) task. Blood Oxygenation Level Dependent (BOLD) activation and task-dependent functional connectivity (FC) were assessed based on fMRI data. Full factorial analyses were performed to examine the Group-by-Glutamate Level interaction effects on fMRI measurements (group differences in correlation between glutamate levels and fMRI measurements) and the correlation between glutamate levels and fMRI measurements within each group.

RESULTS

We found that schizophrenia patients exhibited impaired sensory integration which was positively correlated with ACC glutamate levels. Multimodal analyses showed significantly Group-by-Glutamate Level interaction effects on BOLD activation as well as task-dependent FC in a 'cortico-subcortical-cortical' network (including medial frontal gyrus, precuneus, ACC, middle cingulate gyrus, thalamus and caudate) with positive correlations in patients and negative in controls.

CONCLUSIONS

Our findings indicate that ACC glutamate influences neural activities in a large-scale network during sensory integration, but the effects have opposite directionality between schizophrenia patients and healthy people. This implicates the crucial role of glutamatergic system in sensory integration processing in schizophrenia.

Dorsolateral Prefrontal Cortex Glutamate/Gamma-Aminobutyric Acid (GABA) Alterations in Clinical High Risk and First-Episode Schizophrenia: A Preliminary 7-T Magnetic Resonance Spectroscopy Imaging Study

Converging lines of evidence suggest that an imbalance between excitation and inhibition is present in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia (SCZ). Gamma-aminobutyric-acid (GABA) and, to a lesser extent, glutamate (Glu) abnormalities were reported in the DLPFC of SCZ patients, especially on the right hemisphere, by post-mortem studies. However, in vivo evidence of GABA, Glu, and Glu/GABA DLPFC abnormalities, particularly on the right side and the early stages of illness, is limited. In this preliminary study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to investigate bilateral Glu/Creatine (Cre), GABA/Cre, and Glu/GABA in the DLPFC of sixteen first episode schizophrenia (FES), seventeen clinical high risk (CHR), and twenty-six healthy comparison (HC) subjects. FES and CHR had abnormal GABA/Cre and Glu/GABA in the right DLPFC (rDLPFC) compared with HC participants, while no differences were observed in the left DLPFC (lDLPFC) among the three groups. Furthermore, HC had higher Glu/GABA in rDLPFC compared to lDLPFC (R > L), whereas the opposite relationship (R < L) was observed in the DLPFC Glu/GABA of FES patients. Altogether, these findings indicate that GABA/Cre and Glu/GABA DLPFC alterations are present before illness manifestation and worsen in FES patients, thus representing a putative early pathophysiological biomarker for SCZ and related psychotic disorders.

Frontal GABA in schizophrenia: A meta-analysis of 1H-MRS studies

OBJECTIVES

The primary objective was to conduct a meta-analysis of studies comparing the GABA levels of schizophrenia patients (SZP) and healthy controls (HC) using proton magnetic resonance spectroscopy (¹H-MRS) in the frontal cortex (FC) and its sub-regions.

METHODS

We included studies published in English language that used ¹H-MRS from MRI scanners having at-least 3 Tesla (3 T) magnetic field strength to measure GABA levels in SZP (n = 699) and HC (n = 718) in FC and its sub-regions. The outcome measures were the means and standard deviations of GABA levels and outcome measure was calculated using a random-effect model.

RESULTS

In FC, medial prefrontal cortex (MPFC) and dorsolateral prefrontal cortex (DLPFC), there were no significant group differences. On excluding the outlier studies, the GABA levels were lower in patients with schizophrenia compared to healthy controls in FC (Hedges' g = -0.2; p = 0.02). In ACC, significant group difference was noted in GABA levels (Hedges' g = -0.25; p = 0.03) with patients values being lower that is more pronounced in the first episode schizophrenia patients (Hedges' g: -0.41; p = 0.003).

CONCLUSIONS

The available ¹H-MRS studies suggest hypo-GABA ergia specifically in ACC and hint towards possible hypo GABA-ergic state in the FC. However, limitations of the analysis should be considered while interpreting the results.

Effects of Adolescent THC Exposure on the Prefrontal GABAergic System: Implications for Schizophrenia-Related Psychopathology

Marijuana is the most commonly used drug of abuse among adolescents. Considerable clinical evidence supports the hypothesis that adolescent neurodevelopmental exposure to high levels of the principal psychoactive component in marijuana, -delta-9-tetrahydrocanabinol (THC), is associated with a high risk of developing psychiatric diseases, such as schizophrenia later in life. This marijuana-associated risk is believed to be related to increasing levels of THC found within commonly used marijuana strains. Adolescence is a highly vulnerable period for the development of the brain, where the inhibitory GABAergic system plays a pivotal role in the maturation of regulatory control mechanisms in the central nervous system (CNS). Specifically, adolescent neurodevelopment represents a critical period wherein regulatory connectivity between higher-order cortical regions and sub-cortical emotional processing circuits such as the mesolimbic dopamine (DA) system is established. Emerging preclinical evidence demonstrates that adolescent exposure to THC selectively targets schizophrenia-related molecular and neuropharmacological signaling pathways in both cortical and sub-cortical regions, including the prefrontal cortex (PFC) and mesolimbic DA pathway, comprising the ventral tegmental area (VTA) and nucleus accumbens (NAc). Prefrontal cortical GABAergic hypofunction is a key feature of schizophrenia-like neuropsychopathology. This GABAergic hypofunction may lead to the loss of control of the PFC to regulate proper sub-cortical DA neurotransmission, thereby leading to schizophrenia-like symptoms. This review summarizes preclinical evidence demonstrating that reduced prefrontal cortical GABAergic neurotransmission has a critical role in the sub-cortical DAergic dysregulation and schizophrenia-like behaviors observed following adolescent THC exposure.

Distribution and levels of 5-HT1B receptors in anterior cingulate cortex of patients with bipolar disorder, major depressive disorder and schizophrenia - An autoradiography study

The serotonin 1B receptor has recently received more interest as a possible new target for pharmacological treatment of psychiatric disorders. However, the exact mechanisms of action remain unclear. This study aimed to examine the binding distribution and levels of the serotonin 1B receptor in-depth in the anterior cingulate cortex (ACC) and provide more insight in its functional role in bipolar disorder (BD), major depressive disorder (MDD) and schizophrenia (SZ). Serotonin 1B receptor binding distribution was visualized with high resolution autoradiography (ARG), using the radioligand [³H]AZ10419369, in postmortem ACC tissue from patients diagnosed with BD (n=14), MDD (n=12), SZ (n=13) and healthy subjects (n=13). Moreover, a quantification of receptor binding was made with ARG, in relation to patient group, age and gender. In all subject groups a significantly higher specific binding of serotonin 1B receptor was measured in the outer ACC layers compared to the inner ACC layers. Correlation analysis with ARG binding patterns of several radioligands resulted in a significant correlation with glutamatergic N-methyl-D-aspartate receptor binding in the outer layers. No significant difference was found between subject groups in binding levels and distribution. In female subjects a significantly lower receptor binding was found than in male subjects, which was most profound in patients diagnosed with MDD. The binding distribution of the serotonin 1B receptor found in this study supports a role in glutamate transmission in the ACC and was not shown to be significantly altered in BD, MDD or SZ. A gender difference in serotonin 1B receptor binding was found.

Theranostic Biomarkers for Schizophrenia

Schizophrenia is a highly heritable, chronic, severe, disabling neurodevelopmental brain disorder with a heterogeneous genetic and neurobiological background, which is still poorly understood. To allow better diagnostic procedures and therapeutic strategies in schizophrenia patients, use of easy accessible biomarkers is suggested. The most frequently used biomarkers in schizophrenia are those associated with the neuroimmune and neuroendocrine system, metabolism, different neurotransmitter systems and neurotrophic factors. However, there are still no validated and reliable biomarkers in clinical use for schizophrenia. This review will address potential biomarkers in schizophrenia. It will discuss biomarkers in schizophrenia and propose the use of specific blood-based panels that will include a set of markers associated with immune processes, metabolic disorders, and neuroendocrine/neurotrophin/neurotransmitter alterations. The combination of different markers, or complex multi-marker panels, might help in the discrimination of patients with different underlying pathologies and in the better classification of the more homogenous groups. Therefore, the development of the diagnostic, prognostic and theranostic biomarkers is an urgent and an unmet need in psychiatry, with the aim of improving diagnosis, therapy monitoring, prediction of treatment outcome and focus on the personal medicine approach in order to improve the quality of life in patients with schizophrenia and decrease health costs worldwide.

Effects of Immune Activation during Early or Late Gestation on N-Methyl-d-Aspartate Receptor Measures in Adult Rat Offspring

BACKGROUND

Glutamatergic receptor [N-methyl-d-aspartate receptor (NMDAR)] alterations within cortex, hippocampus, and striatum are linked to schizophrenia pathology. Maternal immune activation (MIA) is an environmental risk factor for the development of schizophrenia in offspring. In rodents, gestational timing of MIA may result in distinct behavioral outcomes in adulthood, but how timing of MIA may impact the nature and extent of NMDAR-related changes in brain is not known. We hypothesize that NMDAR-related molecular changes in rat cortex, striatum, and hippocampus are induced by MIA and are dependent on the timing of gestational inflammation and sex of the offspring.

METHODS

Wistar dams were treated the with viral mimic, polyriboinosinic:polyribocytidylic acid (polyI:C), or vehicle on either gestational day 10 or 19. Fresh-frozen coronal brain sections were collected from offspring between postnatal day 63-91. Autoradiographic binding was used to infer levels of the NMDAR channel, and NR2A and NR2B subunits in cortex [cingulate (Cg), motor, auditory], hippocampus (dentate gyrus, cornu ammonis area 3, cornu ammonis area 1), and striatum [dorsal striatum, nucleus accumbens core, and nucleus accumbens shell (AS)]. NR1 and NR2A mRNA levels were measured by in situ hybridization in cortex, hippocampus, and striatum in male offspring only.

RESULTS

In the total sample, NMDAR channel binding was elevated in the Cg of polyI:C offspring. NR2A binding was elevated, while NR2B binding was unchanged, in all brain regions of polyI:C offspring overall. Male, but not female, polyI:C offspring exhibited increased NMDAR channel and NR2A binding in the striatum overall, and increased NR2A binding in the cortex overall. Male polyI:C offspring exhibited increased NR1 mRNA in the AS, and increased NR2A mRNA in cortex and subregions of the hippocampus.

CONCLUSION

MIA may alter glutamatergic signaling in cortical and hippocampal regions via alterations in NMDAR indices; however, this was independent of gestational timing. Male MIA offspring have exaggerated changes in NMDAR compared to females in both the cortex and striatum. The MIA-induced increase in NR2A may decrease brain plasticity and contribute to the exacerbated behavioral changes reported in males and indicate that the brains of male offspring are more susceptible to long-lasting changes in glutamate neurotransmission induced by developmental inflammation.

GABAergic Mechanisms in Schizophrenia: Linking Postmortem and In Vivo Studies

Schizophrenia is a psychiatric disorder characterized by hallucinations, delusions, disorganized thinking, and impairments in cognitive functioning. Evidence from postmortem studies suggests that alterations in cortical γ-aminobutyric acid (GABAergic) neurons contribute to the clinical features of schizophrenia. In vivo measurement of brain GABA levels using magnetic resonance spectroscopy (MRS) offers the possibility to provide more insight into the relationship between problems in GABAergic neurotransmission and clinical symptoms of schizophrenia patients. This study reviews and links alterations in the GABA system in postmortem studies, animal models, and human studies in schizophrenia. Converging evidence implicates alterations in both presynaptic and postsynaptic components of GABAergic neurotransmission in schizophrenia, and GABA may thus play an important role in the pathophysiology of schizophrenia. MRS studies can provide direct insight into the GABAergic mechanisms underlying the development of schizophrenia as well as changes during its course.

Is There a Neuroanatomic Basis for Schizophrenia? An Old Question Revisited

In the past century, the finding of ventricular enlargement in structural brain imaging studies of schizophrenia has stimulated interest in the question of whether this disorder may involve an underlying neurodegenerative process. Recent microscopic investigations have revealed a subtle loss of neurons but no gliosis in several corticolimbic regions of schizophrenic brain, a pattern that is not consistent with a typical adult pattern of neuronal degeneration. The fact that a variety of histopathological changes have been found in cortical layer II of schizophrenic subjects has suggested that an early disturbance of neuronal migration may play an etiological role in this disorder. Overall, many investigators now consider schizophrenia to be a neurodevel opmental disorder in which a latent defect present from birth requires normal maturational changes in the brain to trigger the characteristic onset of illness during adolescence and early adulthood. The Neuroscientist 1:104-115, 1995

Decreased synaptic and mitochondrial density in the postmortem anterior cingulate cortex in schizophrenia

Schizophrenia (SZ) is a mental illness characterized by psychosis, negative symptoms, and cognitive deficits. The anterior cingulate cortex (ACC), a structurally and functionally diverse region, is one of several brain regions that is abnormal in SZ. The present study compared synaptic organization and mitochondrial number and morphology in postmortem ACC in SZ versus normal control (NC). Total synaptic density in the combined ACC was decreased in SZ, to 72% of normal controls (NCs), due to selective decreases in axospinous synapses, both asymmetric (excitatory) and symmetric (inhibitory). These changes were present in layers 3 and 5/6. The density of mitochondria in all axon terminals combined in SZ was decreased to 64% of NC. In layer 3, mitochondrial density was decreased only in terminals forming asymmetric synapses with spines, while in layers 5/6 mitochondrial density was decreased in terminals forming symmetric synapses with spines and dendrites. The proportion of terminals making symmetric synapses that contained mitochondria was significantly lower in SZ than in NCs, especially for symmetric axospinous synapses. The number of mitochondria per neuronal somata was decreased in the ACC in SZ compared to NCs; this finding was present in layers 5-6. The size of mitochondria in neuronal somata and throughout the neuropil was similar in SZ and NCs. Our results, though preliminary, are well supported by the literature, and support an anatomical substrate for some of the altered executive functions found in SZ.

Transcriptional regulation of GAD1 GABA synthesis gene in the prefrontal cortex of subjects with schizophrenia

Expression of GAD1 GABA synthesis enzyme is highly regulated by neuronal activity and reaches mature levels in the prefrontal cortex not before adolescence. A significant portion of cases diagnosed with schizophrenia show deficits in GAD1 RNA and protein levels in multiple areas of adult cerebral cortex, possibly reflecting molecular or cellular defects in subtypes of GABAergic interneurons essential for network synchronization and cognition. Here, we review 20years of progress towards a better understanding of disease-related regulation of GAD1 gene expression. For example, deficits in cortical GAD1 RNA in some cases of schizophrenia are associated with changes in the epigenetic architecture of the promoter, affecting DNA methylation patterns and nucleosomal histone modifications. These localized chromatin defects at the 5' end of GAD1 are superimposed by disordered locus-specific chromosomal conformations, including weakening of long-range promoter-enhancer loopings and physical disconnection of GAD1 core promoter sequences from cis-regulatory elements positioned 50 kilobases further upstream. Studies on the 3-dimensional architecture of the GAD1 locus in neurons, including developmentally regulated higher order chromatin compromised by the disease process, together with exploration of locus-specific epigenetic interventions in animal models, could pave the way for future treatments of psychosis and schizophrenia.

Molecular docking based screening of GABA (A) receptor inhibitors from plant derivatives

The present antipsychotic drugs have known to show serious concerns like extra pyramidal side effects therefore, pursuit for novel antipsychotic GABAnergic drugs has lately focused on the folkloric medicine from plant derivatives as better treatment option of schizophrenia. The present study centers to identify potential inhibitors of plant origin for GABA receptor through in silico approaches. Three compound datasets were undertaken in the study. The first set consisted of seven compounds which included Magnolol, Honokiol and other plant derivatives. The second set consisted of 16 derivatives of N-diarylalkenyl-piperidinecarboxylic acid synthesized by Zheng et al., 2006. The third dataset had thirty two compounds which were Magnolol and Honokiol analogues synthesized by Fuchs et al., 2014. All the compounds were docked at the allosteric site of the GABA (A) receptor. The compounds were further tested for ADMET and biological activity. We observed Honokiol and its derivatives demonstrated superior druglike properties than any compound undertaken in the study. Further, compound 61 [2-(4-methoxyphenyl)-4-propylphenol] of dataset three - a synthetic derivative of honokiol had better profile than its parent compound. In a possible attempt to identify compound with even better efficacious compound than 61, virtual screening was performed, 135 compounds akin to compound 61 were retrieved. Interestingly none of the 135 compounds showed better druggable properties than compound 61. Our in silico pharmacological profiling of compounds is in coherence and is complemented by the findings of Fuchs et al, which also revealed compound 61 to be the good potentiator of GABA receptor.

ABBREVIATIONS

GABA (A) R - Gamma Amino Butyric Acid Receptor, subtype A, GPCR - G Protein Coupled Receptor, OPLS - Optimized Potentials for Liquid Simulations, PDB - Protein Data Bank, PLP - Piece wise Linear Potential, T.E.S.T - Toxicity Estimation Software Tool, TCM - Traditional Chinese Medicine.

Imaging-based neurochemistry in schizophrenia: a systematic review and implications for dysfunctional long-term potentiation

Cognitive deficits are commonly observed in patients with schizophrenia. Converging lines of evidence suggest that these deficits are associated with impaired long-term potentiation (LTP). In our systematic review, this hypothesis is evaluated using neuroimaging literature focused on proton magnetic resonance spectroscopy, positron emission tomography, and single-photon emission computed tomography. The review provides evidence for abnormal dopaminergic, GABAergic, and glutamatergic neurotransmission in antipsychotic-naive/free patients with schizophrenia compared with healthy controls. The review concludes with a model illustrating how these abnormalities could lead to impaired LTP in patients with schizophrenia and consequently cognitive deficits.

Toward the identification of peripheral epigenetic biomarkers of schizophrenia

Schizophrenia (SZ) is a heritable, nonmendelian, neurodevelopmental disorder in which epigenetic dysregulation of the brain genome plays a fundamental role in mediating the clinical manifestations and course of the disease. The authors recently reported that two enzymes that belong to the dynamic DNA methylation/demethylation network-DNMT (DNA methyltransferase) and TET (ten-eleven translocase; 5-hydroxycytosine translocator)-are abnormally increased in corticolimbic structures of SZ postmortem brain, suggesting a causal relationship between clinical manifestations of SZ and changes in DNA methylation and in the expression of SZ candidate genes (e.g., brain-derived neurotrophic factor [BDNF], glucocorticoid receptor [GCR], glutamic acid decarboxylase 67 [GAD67], reelin). Because the clinical manifestations of SZ typically begin with a prodrome followed by a first episode in adolescence with subsequent deterioration, it is obvious that the natural history of this disease cannot be studied only in postmortem brain. Hence, the focus is currently shifting towards the feasibility of studying epigenetic molecular signatures of SZ in blood cells. Initial studies show a significant enrichment of epigenetic changes in lymphocytes in gene networks directly relevant to psychiatric disorders. Furthermore, the expression of DNA-methylating/demethylating enzymes and SZ candidate genes such as BDNF and GCR are altered in the same direction in both brain and blood lymphocytes. The coincidence of these changes in lymphocytes and brain supports the hypothesis that common environmental or genetic risk factors are operative in altering the epigenetic components involved in orchestrating transcription of specific genes in brain and peripheral tissues. The identification of DNA methylation signatures for SZ in peripheral blood cells of subjects with genetic and clinical high risk would clearly have potential for the diagnosis of SZ early in its course and would be invaluable for initiating early intervention and individualized treatment plans.

Impact of glutamate levels on neuronal response and cognitive abilities in schizophrenia

Schizophrenia is characterized by impaired cognitive functioning, and brain regions involved in cognitive control processes show marked glutamatergic abnormalities. However, it is presently unclear whether aberrant neuronal response is directly related to the observed deficits at the metabolite level in schizophrenia. Here, 17 medicated schizophrenia patients and 17 matched healthy participants underwent functional magnetic resonance imaging (fMRI) when performing an auditory cognitive control task, as well as proton magnetic resonance spectroscopy (¹H-MRS) in order to assess resting-state glutamate in the anterior cingulate cortex. The combined fMRI–¹H-MRS analysis revealed that glutamate differentially predicted cortical blood-oxygen level-dependent (BOLD) response in patients and controls. While we found a positive correlation between glutamate and BOLD response bilaterally in the inferior parietal lobes in the patients, the corresponding correlation was negative in the healthy control participants. Further, glutamate levels predicted task performance in patients, such that lower glutamate levels were related to impaired cognitive control functioning. This was not seen for the healthy controls. These findings suggest that schizophrenia patients have a glutamate-related dysregulation of the brain network supporting cognitive control functioning. This could be targeted in future research on glutamatergic treatment of cognitive symptoms in schizophrenia.

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Neuronal processing of cognitive control is different in schizophrenia patients (SZ).

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Cingulum glutamate levels predict the degree of parietal neuronal response.

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Lower glutamate predicts poorer cognitive control abilities in SZ.

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SZ have a glutamate-related neuronal dysregulation of cognitive control processing.

Glutamatergic gene expression is specifically reduced in thalamocortical projecting relay neurons in schizophrenia

BACKGROUND

Impairment of glutamate neurons that relay sensory and cognitive information from the medial dorsal thalamus to the dorsolateral prefrontal cortex and other cortical regions may contribute to the pathophysiology of schizophrenia. In this study, we have assessed the cell-specific expression of glutamatergic transcripts in the medial dorsal thalamus.

METHODS

We used laser capture microdissection to harvest two populations of medial dorsal thalamic cells, one enriched with glutamatergic relay neurons and the other with gamma-aminobutyric acidergic neurons and astroglia, from postmortem brains of subjects with schizophrenia (n = 14) and a comparison group (n = 20). Quantitative polymerase chain reaction of extracted RNA was used to assay gene expression in the different cell populations.

RESULTS

The transcripts encoding the ionotropic glutamate receptor subunits NR2D, GluR3, GluR6, GluR7, and the intracellular proteins GRIP1 and SynGAP1 were significantly decreased in relay neurons but not in the mixed glial and interneuron population in schizophrenia.

CONCLUSIONS

Our data suggest that reduced ionotropic glutamatergic expression occurs selectively in neurons, which give rise to the cortical projections of the medial dorsal thalamus in schizophrenia, rather than in thalamic cells that function locally. Our findings indicate that glutamatergic innervation is dysfunctional in the circuitry between the medial dorsal thalamus and cortex.

Tonic and phasic release of glutamate and acetylcholine neurotransmission in sub-regions of the rat prefrontal cortex using enzyme-based microelectrode arrays

The medial prefrontal cortex (mPFC) is an area of the brain critical for higher cognitive processes and implicated in disorders of the CNS such as drug addiction, depression and schizophrenia. Glutamate and acetylcholine are neurotransmitters that are essential for cortical functioning, yet little is known about the dynamic function of these neurotransmitters in subregions of the mPFC. In these studies we used a novel microelectrode array technology to measure resting levels (tonic release) of glutamate and acetylcholine as well as KCl-evoked release (stimulated phasic release) in the mPFC of the anesthetized rat to further our understanding of both tonic and phasic neurotransmission in the cingulate cortex, prelimbic cortex, and infralimbic cortex of the mPFC. Studies revealed homogeneity of tonic and phasic signaling among brain subregions for each neurotransmitter. However, resting levels of glutamate were significantly higher as compared to acetylcholine levels in all subregions. Additionally, KCl-evoked acetylcholine release in the cingulate cortex (7.1 μM) was significantly greater than KCl-evoked glutamate release in any of the three subregions (Cg1, 2.9 μM; PrL, 2.0 μM; IL, 1.8 μM). Interestingly, the time for signal decay following KCl-evoked acetylcholine release was significantly longer by an average of 240% as compared to KCL-evoked glutamate release for all three brain subregions. Finally, we observed a negative relationship between acetylcholine resting levels and KCl-evoked release in the Cg1. These data suggest a homogenous distribution of both glutamatergic and acetylcholinergic innervation in the mPFC, with alterations in tonic and phasic release regulation accounting for differences between these neurotransmitters.

Assessments of function and biochemistry of the anterior cingulate cortex in schizophrenia

BACKGROUND

Neuroimaging and electrophysiologic studies have consistently provided evidence of impairment in anterior cingulate cortex/medial frontal cortex function in people with schizophrenia. In this study, we sought to clarify the nature of this abnormality by combining proton magnetic resonance spectroscopy (1H-MRS) with functional magnetic resonance imaging (fMRI) at 3T.

METHODS

We used single-voxel MRS acquired in the dorsal anterior cingulate cortex and fMRI during performance of a Stroop color-naming task to investigate the neurochemistry and functional response of the anterior cingulate cortex/medial frontal cortex in 26 stable, medicated subjects with schizophrenia and 23 matched healthy control subjects.

RESULTS

In schizophrenia subjects, we found decreased blood oxygen level-dependent signal in the medial frontal wall, with significant clusters restricted to more dorsal regions compared with healthy subjects. In addition, we observed a trend-level decrease in N-acetylaspartate/creatine (NAA/Cr) levels and a significant positive correlation between NAA/Cr level and the blood oxygen level-dependent signal in schizophrenia subjects that did not exist in healthy subjects. Furthermore, in this group of medicated subjects, we did not find evidence of decreased glutamate + glutamine(Glx)/Cr levels, but there was a significant negative correlation between Glx/Cr levels and negative symptoms.

CONCLUSIONS

Our results suggest that abnormal NAA levels, which may reflect a neuronal dysfunction related to schizophrenia, affect neuronal physiology, as evidenced by reduced blood oxygen level-dependent response.

Cortical neuritic plaques and hippocampal neurofibrillary tangles are related to dementia severity in elderly schizophrenia patients

Cognitive decline has been described in elderly patients with schizophrenia, but the underlying pathology remains unknown. Some studies report increases in plaques and neurofibrillary tangles, but there is no evidence for an increased risk for Alzheimer's disease (AD) in elderly schizophrenics. Models of a decreased cerebral reserve suggest that increases in AD-related neuropathology below the threshold for a neuropathological diagnosis could be related to dementia severity in elderly schizophrenia patients. We tested this hypothesis in 110 autopsy specimens of schizophrenia patients, without a neuropathological diagnosis of AD or other neurodegenerative disorders. Furthermore, we assessed the effects of apolipoprotein E (ApoE) status, a known genetic risk factor for AD. Measures of density of neuritic plaques were obtained in five cortical regions, and the degree of hippocampal neurofibrillary tangles was rated. Dementia severity was measured prior to postmortem using the Clinical Dementia Rating (CDR) scale. multivariate analyses of variance were conducted with the factors dementia severity, by ApoE4 carrier status. Hippocampal neurofibrillary tangles correlated with increased dementia severity (p<.05). Neuritic plaque density increased with greater dementia severity (p<.005), and ApoE4 carrier status (p<.005), and these differences were magnified by the ApoE4 carrier status (p<.01). Even below the threshold for a neuropathological diagnosis of AD, neuritic plaques and hippocampal neurofibrillary tangles are associated with dementia severity in schizophrenia patients, even more so in the presence of genetic risk factors, suggesting that a decreased cerebral reserve in elderly schizophrenics may increase susceptibility for dementia.

Amygdalocortical circuitry in schizophrenia: from circuits to molecules

Schizophrenia is a disorder in which disturbances in the integration of emotion with cognition plays a central role and probably involves several different regions, including the dorsolateral prefrontal cortex, the rostral anterior cingulate cortex, the hippocampal formation, and basolateral amygdala (BLA). Recent brain imaging studies have reported changes in volume, whereas postmortem studies point to dysfunction of the GABA and glutamate systems in these regions. Microarray-based profiles indicate that complex changes in the expression of genes associated with synaptic transmission and ion channels are involved in GABA cell dysfunction in schizophrenics. Molecular abnormalities vary considerably on the basis of sector and layer, suggesting that the unique connectivity of intrinsic and extrinsic afferents may critical in regulating the activity of genes in specific subpopulations of GABA cells. Projections of the BLA may be of particular importance to the induction of abnormal circuitry in schizophrenia, as their ingrowth during late adolescence and early adulthood may help to 'trigger' the onset of illness in susceptible individuals. A preponderance of cellular and molecular abnormalities has been found in the stratum oriens (SO) of sectors CA3/2 in which BLA afferents provide a robust innervation. These observations have lead to the development of a rodent model for the study of abnormal circuitry in this disorder. For example, single-cell recordings in hippocampal slices exposed to increased activation from the BLA have shown decreases in GABA currents in pyramidal neurons in SO of CA3/2, but not CA1, and support the validity of this model. Overall, the postmortem studies of neural circuitry abnormalities in schizophrenia are beginning to implicate specific cellular, molecular, and electrophysiological mechanism in specific subtypes of cortical neurons defined by their afferent and efferent connectivity within key corticolimbic regions.

Executive function, neural circuitry, and genetic mechanisms in schizophrenia

After decades of research aimed at elucidating the pathophysiology and etiology of schizophrenia, it has become increasingly apparent that it is an illness knowing few boundaries. Psychopathological manifestations extend across several domains, impacting multiple facets of real-world functioning for the affected individual. Even within one such domain, arguably the most enduring, difficult to treat, and devastating to long-term functioning-executive impairment-there are not only a host of disrupted component processes, but also a complex underlying dysfunctional neural architecture. Further, just as implicated brain structures (eg, dorsolateral prefrontal cortex) through postmortem and neuroimaging techniques continue to show alterations in multiple, interacting signaling pathways, so too does evolving understanding of genetic risk factors suggest multiple molecular entry points to illness liability. With this expansive network of interactions in mind, the present chapter takes a systems-level approach to executive dysfunction in schizophrenia, by identifying key regions both within and outside of the frontal lobes that show changes in schizophrenia and are important in cognitive control neural circuitry, summarizing current knowledge of their relevant functional interactions, and reviewing emerging links between schizophrenia risk genetics and characteristic executive circuit aberrancies observed with neuroimaging methods.

Zinc: the brain's dark horse

Zinc is a life-sustaining trace element, serving structural, catalytic, and regulatory roles in cellular biology. It is required for normal mammalian brain development and physiology, such that deficiency or excess of zinc has been shown to contribute to alterations in behavior, abnormal central nervous system development, and neurological disease. In this light, it is not surprising that zinc ions have now been shown to play a role in the neuromodulation of synaptic transmission as well as in cortical plasticity. Zinc is stored in specific synaptic vesicles by a class of glutamatergic or "gluzinergic" neurons and is released in an activity-dependent manner. Because gluzinergic neurons are found almost exclusively in the cerebral cortex and limbic structures, zinc may be critical for normal cognitive and emotional functioning. Conversely, direct evidence shows that zinc might be a relatively potent neurotoxin. Neuronal injury secondary to in vivo zinc mobilization and release occurs in several neurological disorders such as Alzheimer's disease and amyotrophic lateral sclerosis, in addition to epilepsy and ischemia. Thus, zinc homeostasis is integral to normal central nervous system functioning, and in fact its role may be underappreciated. This article provides an overview of zinc neurobiology and reviews the experimental evidence that implicates zinc signals in the pathophysiology of neuropsychiatric diseases. A greater understanding of zinc's role in the central nervous system may therefore allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

Anatomical abnormalities of the anterior cingulate cortex in schizophrenia: bridging the gap between neuroimaging and neuropathology

The anterior cingulate cortex (ACC) is a functionally heterogeneous region involved in diverse cognitive and emotional processes that support goal-directed behaviour. Structural magnetic resonance imaging (MRI) and neuropathological findings over the past two decades have converged to suggest abnormalities in the region may represent a neurobiological basis for many of the clinical manifestations of schizophrenia. However, while each approach offers complimentary information that can provide clues regarding underlying patholophysiological processes, the findings from these 2 fields are seldom integrated. In this article, we review structural neuroimaging and neuropathological studies of the ACC, focusing on the unique information they provide. The available imaging data suggest grey matter reductions in the ACC precede psychosis onset in some categories of high-risk individuals, show sub-regional specificity, and may progress with illness duration. The available post-mortem findings indicate these imaging-related changes are accompanied by reductions in neuronal, synaptic, and dendritic density, as well as increased afferent input, suggesting the grey matter differences observed with MRI arise from alterations in both neuronal and non-neuronal tissue compartments. We discuss the potential mechanisms that might facilitate integration of these findings and consider strategies for future research.

Reconciling neuroimaging and neuropathological findings in schizophrenia and bipolar disorder

PURPOSE OF REVIEW

Although structural magnetic resonance imaging (sMRI) and neuropathological investigations offer complementary information that can be used to formulate and test hypotheses about pathophysiological mechanisms in psychiatric disorders, the findings from these two fields are seldom integrated in a systematic manner. In this study, we overview recent sMRI findings in schizophrenia and bipolar disorder and consider how they relate to neuropathological data.

RECENT FINDINGS

sMRI research indicates that schizophrenia is associated with volumetric reductions in a network of frontal, temporal, limbic, striatal, and thalamic regions. Some of these abnormalities are apparent prior to psychosis onset and may progress with ongoing illness. sMRI findings in bipolar disorder have been more variable, with both volumetric increases and decreases being reported across several brain regions at different illness stages. Neuropathological studies of both patient groups suggest the cellular changes associated with these volumetric differences affect diverse tissue compartments in a regionally heterogeneous way.

SUMMARY

These findings suggest that any putative pathophysiological mechanism in schizophrenia or bipolar disorder should account for the dynamic, complex, and regionally heterogeneous brain abnormalities seen in these patients. We contend that greater integration of the findings from these two fields will facilitate more targeted and hypothesis-driven research in the future.

The change in plasma GABA, glutamine and glutamate levels in fluoxetine- or S-citalopram-treated female patients with major depression

OBJECTIVE

The aim of this study was to investigate the relationship between plasma glutamate, glutamine and gamma-aminobutyric acid (GABA) levels in female patients with major depression treated with S-citalopram or fluoxetine.

METHODS

The patients were assigned into S-citalopram (10 mg/day) or fluoxetine (20 mg/day) groups (n = 15 per group). The Hamilton and Beck Depression Inventory Scales were performed on all study participants, and blood samples were collected. The same procedures were repeated 10 days following the onset of therapy. Fifteen female healthy volunteers were also included in the study for the evaluation of normal plasma levels.

RESULTS

The plasma GABA levels of the healthy volunteers were higher whereas those for glutamate and glutamine were lower than the day zero samples of the patients. An increase in plasma GABA levels and a decrease in glutamate and glutamine levels were observed on the 10th day of treatment. No difference was detected between the drug treatments.

CONCLUSION

Our findings may suggest that GABA, glutamate and glutamine play a role in depression and that plasma GABA may be used as a biomarker for treatment control.

Developmental changes in stress adaptation in relation to psychopathology

As modern neuroscience seeks to understand the neural bases for mental illness, it is becoming increasingly important to define how and when complex neural circuits may be altered in individuals who carry the genetic vulnerability for psychopathology. One factor that could potentially play a contributory role in mental illness is the stress response. A variety of studies suggest that stress can alter the activity of several key cortical neurotransmitters, including glutamate, γ-aminobutyric acid, dopamine, and serotonin. Specifically, exposure to neurotoxic levels of adrenal steroid hormone, particularly if this occurs early in life, could potentially induce permanent changes of these transmitter systems in corticolimbic regions, such as the hippocampal formation and cingulate gyrus, that have a high density of glucocorticoid receptors. Overall, exposure to severe stress during the perinatal period could potentially induce alterations in the circuitry of the anterior cingulate cortex and hippocampal formation and interfere with the normal mechanisms underlying attention and learning.

Surface-based morphometry of the anterior cingulate cortex in first episode schizophrenia

The anterior cingulate cortex (ACC) appears to be critically involved in the pathophysiology of schizophrenia, but past attempts at characterizing pathological changes in the region using magnetic resonance imaging have been restricted by a limited appreciation of its functional and anatomical diversity and a reliance on relatively coarse metrics (e.g., volume) to index anatomical change. In this study, we applied a novel, surface-based protocol to T1-weighted scans acquired from 40 first episode schizophrenia patients and 40 healthy controls individually matched for age, sex, and morphology of the paracingulate sulcus, a major anatomical variation that has been shown to affect morphometric estimates in the region. The surface-based approach enabled calculation of regional grey matter volume, surface area and curvature, cortical thickness, and depth of the cingulate sulcus, with sub-millimeter precision. Relative to controls, schizophrenia patients displayed a bilateral reduction in thickness of paralimbic regions of the ACC, along with a concomitant increase in surface area of both the limbic and paralimbic ACC. No differences were identified for regional grey matter volume, surface curvature, or CS depth. These findings illustrate the advantages of moving beyond traditional volume-based approaches when investigating cortical morphometry, and indicate that the early stages of schizophrenia are associated with a specific pattern of ACC abnormalities that cannot be attributed to variations in sulcal and gyral morphology.

Searching for unique endophenotypes for schizophrenia and bipolar disorder within neural circuits and their molecular regulatory mechanisms

The endophenotype is a construct that has utility for the study of postmortem brains from patients with psychotic disorders. By identifying networks of genes that show changes in expression within specific neuronal populations implicated in the pathophysiology of schizophrenia and bipolar disorder, it may be possible to move toward understanding these disorders at the cellular and molecular levels. The ultimate goal is to characterize their respective underlying genotypes.

Zincergic innervation of medial prefrontal cortex by basolateral projection neurons

The basolateral amygdaloid complex is a site of origin for zinc-containing pathways in the brain; it is also known for its massive innervation of the medial prefrontal cortex. The presence, and potential neuromodulatory role, of zinc within this fundamental corticolimbic circuit has not been described. For this study, basolateral neurons innervating the medial prefrontal cortex were retrogradely labeled with FluoroGold, and zinc-containing neurons were identified using autometallography to visualize zinc selenium precipitates. Upon quantification of single-labeled and double-labeled cells, 35% of basolateral neurons projecting to medial prefrontal cortex were found to also contain zinc. We conclude that zinc may act as a neuromodulator for a substantial proportion of basolateral-medial prefrontal cortical innervation, therefore implicating zinc in corticolimbic function as well as pathology.

Coalescence of psychiatry, neurology, and neuropsychology: from theory to practice

In a climate of renewed interest in the synergy between neurology and psychiatry, practitioners are increasingly recognizing the importance of exchange and collaboration between these two disciplines. However, there are few working models of interdisciplinary teams that freely share expertise in real time, while providing clinical and academic training to future physicians who specialize in the central nervous system. Over the past 11 years, the McLean Hospital Neuropsychiatry and Behavioral Neurology service has provided proof-of-principle for such collaboration, demonstrating that a team comprising psychiatrists, neurologists, and neuropsychologists can function effectively as a unit while maintaining the autonomy of these three disciplines and also synthesizing their combined knowledge. In addition to delivering enhanced patient care and promoting medical research, this clinical service has provided enriched cross-specialty training for fellows, residents, and medical students. The practical functioning of the team is described, and case vignettes are presented to illustrate the team's collaborative synergism in practice.

A proteome analysis of the anterior cingulate cortex gray matter in schizophrenia

The Anterior Cingulate Cortex (ACC, Brodmans Area 24) is implicated in the pathogenesis of schizophrenia due to its normal functions and connectivity together with reports of structural, morphological and neurotransmitter aberrations within this brain area in the disease state. Two-dimensional gel electrophoresis (2DE) was employed to scan and compare the ACC gray matter proteomes between schizophrenia (n = 10) and control (n = 10) post-mortem human tissue. This proteomic approach has detected 42 protein spots with altered levels in the schizophrenia cohort, which to our knowledge is the first proteomic analysis of the ACC in schizophrenia. Thirty nine of these proteins were subsequently identified using mass spectrometry and functionally classified into metabolism and oxidative stress, cytoskeletal, synaptic, signalling, trafficking and glial-specific groups. Some of the identified proteins have previously been implicated in the disease pathogenesis and some offer new insights into schizophrenia. Investigating these proteins, the genes encoding these proteins, their functions and interactions may shed light on the molecular mechanisms underlying the heterogeneous symptoms characteristic of schizophrenia.

Increased density of GABAA receptors in the superior temporal gyrus in schizophrenia

The superior temporal gyrus (STG) is strongly implicated in the pathophysiology of schizophrenia, particularly with regards to auditory hallucinations. In a previous study we reported a decrease in the density of M1 and M2/M4 muscarinic receptors in the STG in schizophrenia. In this study, we investigated the density of GABA(A) receptors in the left STG of schizophrenia patients compared to control subjects. We used quantitative autoradiography to investigate the binding of the agonist [(3)H] muscimol to GABA(A )receptors in the STG. A significantly higher density of [(3)H] muscimol binding was observed in the upper three quarters of the STG grey matter (corresponding to layers I-IV) than in the lower one-quarter (layers V-VI) in both groups. A significant increase (about 30%, P<0.05) in binding of [(3)H] muscimol was clearly observed in schizophrenia patients compared to control subjects. There were no significant correlations between [(3)H] muscimol binding density and age, post-mortem interval, brain pH or final recorded antipsychotic drug use. These results suggest an increase of GABA(A) receptor densities in the STG of schizophrenia patients.

Hypothesis: minimal changes in neural transmission in schizophrenia: decreased glutamatergic and GABAergic functions in the prefrontal cortex

As the pathophysiology, decreased glutamatergic neurotransmission in the postmortem prefrontal cortex of schizophrenics has been suggested to underlie the condition. But consistent reproducible results have not been seen with the molecular biological studies focused on examining glutamatergic parameters in schizophrenic brains. We noticed the lack of reproducibility of these studies and hypothesized that this was caused by "minimal (functional) changes" of schizophrenic pathophysiology that cannot be detected as a robust result by investigating only one marker (i.e., receptor). The authors then investigated glutamate levels, as well as mRNA expression of glutamate receptors and transporters simultaneously for the same schizophrenic and control brain samples, in order to detect the "minimal changes" of glutamatergic neurotransmission in schizophrenic synaptic clefts. The results showed a tendency of increased mGluRs and decreased EAAT2 mRNA in all Brodmann areas examined, but no significant difference was observed between schizophrenics and controls. To make these small changes of glutamatergic neurotransmission on the synaptic clefts more apparent, the "receptors/transporters ratio" (mGluRs/EAAT2 ratio) was calculated for each case and the results showed that the mGluRs/EAAT2 ratio was significantly increased in schizophrenics compared to controls. Glutamate levels, measured by HPLC, showed a decrease in the schizophrenics, but failed to reach statistical significance. The same phenomenon was recognized in our GABAergic study of schizophrenic brain. To interpret these results as a monism, the increase in mGluRs and the decrease of EAAT2 mRNA compensate for the decrease in glutamate transmission in the schizophrenic synaptic clefts. But these changes are small and failed to be statistically significant. The "receptors/transporters ratio" for each case magnified these changes, such that they became statistically significant.

Diminished serotonergic innervation of adult medial prefrontal cortex after 6-OHDA lesions in the newborn rat

The development of the serotonergic (5HT) and dopaminergic (DA) systems may contribute to the onset of psychotic disorders during late adolescence and early adulthood. Previous studies in our laboratory have suggested that these systems may compete for functional territory on neurons during development, as lesions of the serotonergic system at postnatal day 5 (P5) result in an increase in the density of dopaminergic fibers in rat medial prefrontal cortex (mPFC). In the present study, the dopaminergic system of P5 rats was lesioned with intracisternal injections of 6-hydroxydopamine (6-OHDA). Quantification of serotonin-immunoreactivity (5HT-IR) in mPFC at adulthood (P70) revealed a significant decrease in fiber density within layers II and III of the Cg3 subdivision of mPFC in lesioned rats compared to sham controls. We propose that the decrease in serotonergic fibers in mPFC in response to a neonatal depletion of dopamine may be due to the loss of a trophic effect of this system on 5HT neurons and/or fibers during development. Taken together with previous findings, our data suggest that there may be an "inverse trophic" relationship between the cortical DA and 5HT systems whereby dopamine facilitates the ingrowth of 5HT fibers, while serotonin suppresses the ingrowth of DA fibers. We present a model based on neurotrophic interactions at the cortical and brainstem levels that could potentially explain these unexpected results.

Expression of human neuronal protein 22, a novel cytoskeleton-associated protein, was decreased in the anterior cingulate cortex of schizophrenia

Human neuronal protein 22 (hNP22) is a novel neuron-specific protein featuring numerous motifs previously described in cytoskeleton-associating and signaling proteins. Because previous studies have supported abnormalities in neuronal cytoarchitecture and/or development in the schizophrenia brain, we examined the expression of hNP22 in the anterior cingulate cortex, the hippocampus and the prefrontal cortex of schizophrenic and normal control postmortem brains using high-sensitive immunohistochemistry. Seven schizophrenic and seven age- and sex-matched control brains were examined. The ratio of hNP22-immunopositive cells/total cells was significantly reduced in layer V (p=.020) and layer VI (p=.022) of the anterior cingulate cortex of schizophrenic brain compared with controls. In contrast, there were no significant changes observed in the hippocampus and the prefrontal cortex. These results suggest that altered expression of hNP22 may be associated with modifications in neuronal cytoarchitecture leading to dysregulation of neural signal transduction in the anterior cingulate cortex of the schizophrenia brain.

Neurochemical markers for schizophrenia, bipolar disorder, and major depression in postmortem brains

BACKGROUND

Previous studies of postmortem neurochemical markers in severe psychiatric disorders have been carried out on different brain collections, making it difficult to compare results.

METHODS

One hundred RNA, protein, and other neurochemical markers were assessed in a single set of 60 postmortem brains (15 each with schizophrenia, bipolar disorder, major depression without psychosis, and unaffected control subjects) in relation to seven neurochemical systems. Quantitative measures of continuous variables for prefrontal, hippocampus, anterior cingulate, superior temporal cortex, or a combination of these were analyzed from published and unpublished studies by 56 research groups.

RESULTS

Before correcting for multiple comparisons, 23% of markers (23/100) were abnormal in one or more regions, with most indicating decreased expression. The largest percentage were associated with the developmental/synaptic (10/22) and gamma-aminobutyric acid (GABA; 3/7) systems. Bipolar disorder (20) and schizophrenia (19) had the most abnormalities, with a 65% overlap. When all brain areas were considered together and corrected for multiple comparisons, reelin, parvalbumin, and GAD67 were the most abnormal.

CONCLUSIONS

Confirming other studies, the GABA and developmental/synaptic neurochemical systems are promising areas for research on schizophrenia and bipolar disorder. Research should include tissue from both diseases, and additional brain areas should be assessed.

Neurodevelopment, neuroplasticity, and new genes for schizophrenia

Schizophrenia is a complex, debilitating neuropsychiatric disorder. Epidemiological, clinical, neuropsychological, and neurophysiological studies have provided substantial evidence that abnormalities in brain development and ongoing neuroplasticity play important roles in the pathogenesis of the disorder. Complementing these clinical studies, a range of cytoarchitectural, morphometric, ultrastructural, immunochemical, and gene expression methods have been applied in investigations of postmortem brain tissues to characterize the cellular and molecular profile of putative developmental and plastic abnormalities in schizophrenia. While findings have been diverse and many are in need of replication, investigations focusing on higher cortical and limbic brain regions are increasingly demonstrating abnormalities in the structural and molecular integrity of the synaptic complex as well as glutamate-related receptors and signal transduction pathways that play critical roles in brain development, synaptogenesis, and synaptic plasticity. Most exciting have been recent associations of schizophrenia with specific genes, such as neuregulin-1, dysbindin-1, and AKT-1, which are vital to synaptic development, neurotransmission, and plasticity.

Validation of semiautomated methods for quantifying cingulate cortical metrics in schizophrenia

This paper validates semiautomated methods for reconstructing cortical surfaces of the cingulate gyrus from high-resolution magnetic resonance (MR) images. Bayesian segmentation was used to delineate the image voxels into five tissue types: cerebrospinal fluid (CSF), gray matter (GM), white matter (WM), and partial volumes of CSF/GM and GM/WM; the tissues were then recalibrated as CSF, GM, and WM via the Neyman-Pearson Likelihood Ratio Test. To generate cortical surfaces at the interface of GM and WM, the thresholds between the tissue types were first used to reassign partial volume voxels to CSF, GM, and WM with minimum error (that varied from 0.06 to 0.15 for the 10 subjects). Next, topology-correct cortical surfaces were generated and validated with almost all surface vertices lying within one voxel (0.5 mm) of hand contours. Dynamic programming was used to delineate and extract the cingulate gyrus from the cortical surfaces based on its gyral and sulcal boundaries. The intraclass correlation coefficient for surface area obtained by two raters for all 10 surfaces was 0.82. In addition, by repeating the entire procedure three times in one subject, we obtained a coefficient of variation of 0.0438 for surface area.

Automated image analysis of disturbed cytoarchitecture in Brodmann area 10 in schizophrenia

To detect cytoarchitectonic abnormalities in the Brodmann area 10 (BA10) of schizophrenic patients, we applied a newly modified variant of the gray-level index (GLI) method as fully automated image analysis method providing cytoarchitectonic profiles of the whole cortex as a scanning tool. Microscopic images of silver-stained sections of 20 schizophrenic brains compared to 20 control brains were automatically scanned and binarized at an adaptive threshold. In 30 measuring fields through the whole cortical depth, the dependent measure of gray-level index (GLI) as the area-percentage covered by perikarya in a measuring field was obtained providing a cytoarchitectonic profile. GLI is an estimate of the volume density of perikarya. A statistical analysis of mean GLI values was performed for six compartments, separately, approximately corresponding to cortical layers. Results revealed significant GLI reductions in schizophrenic brains in all six compartments suggesting either a decreased perikarya fraction or an increased neuropil fraction. The described automated image analysis method providing cytoarchitectonic profiles can be applied as a fast and observer-independent scanning tool to detect cytoarchitectonic abnormalities in multiple brain regions.

Expression of Fyn, a non-receptor tyrosine kinase in prefrontal cortex from patients with schizophrenia and its correlation with clinical onset

Fyn is a member of the non-receptor tyrosine kinase family, which is known to be closely involved in signal transduction in neurons and has an important role in the development and organisation of the central nervous system. In order to explore the possible role of Fyn in schizophrenia, the expression of Fyn messenger RNA (mRNA) and protein were investigated in the postmortem prefrontal cortex of brains from normal and 'schizophrenic' cases. There was an increase in both total area Fyn mRNA signal (17.7%, P<0.05) and cellular mRNA content (15.7%, P<0.05) in the schizophrenic group relative to controls. In parallel the content of Fyn protein detected by immuno-autoradiography was also increased in the schizophrenic cases (21.8% P<0.05). In addition, the cellular Fyn mRNA signal was negatively correlated with the age of onset (r=-0.94, P=0.0026). These results suggest that an increase in Fyn expression may contribute to the pathophysiology of schizophrenia.

The cognitive neuropsychiatric approach to investigating the neurobiology of schizophrenia and other disorders

In this paper, we examine a cognitive neuropsychiatric approach to understanding neuropsychiatric disorders by examining recent data in schizophrenia. By understanding and applying this approach, we suggest that the processes underlying the neurobiology of a range of other psychiatric disorders can be understood. Further, an assessment of the brain-behaviour relationships through this emerging discipline provides testable models for further study, using a range of techniques including functional and other imaging techniques.

Multimodal neuroimaging studies and neurodevelopment and neurodegeneration hypotheses of schizophrenia

The interpretation of the huge number of results in schizophrenia research using neuroimaging is uncertain. However, the simultaneous use of complimentary data obtained with these techniques may yield more relevant information in this regard. In this paper we present a series of studies performed by our group in two schizophrenic samples with the use of structural (magnetic resonance imaging, MRI), functional [glucose positron emission tomography (PET) and N-acetyl-aspartate (NAA) magnetic resonance spectrocopy] and neurophysiological techniques (the P300 event-related potential). Transversal and longitudinal measurements were performed.The integrated vision of the results so obtained allows us to propose the hypothesis of a neurodevelopmentally determined state of prefrontal disinihibition, in which the degree of atrophy would directly relate to the metabolic rate. This state would already be present in the first stages of illness and could have neurotoxic consequences in the long term. This would explain the findings of an association between sulcal cerebrospinal fluid (CSF) and illness duration and decreased NAA levels in chronic but not in recent-onset cases. The prefrotnal disinhibition would overstimulate the limbic system and the hippocampus would become overactivated, the metabolic rate at this level being inversely related to P300 amplitude. Clozapine showed a more selective and intense action on that hyperactive metabolic tone than haloperidol.

Modulation of brain and serum glutamatergic concentrations following a switch from conventional neuroleptics to olanzapine

BACKGROUND

Recent evidence suggests that effects upon glutamatergic transmission may contribute to the therapeutic action of certain atypical antipsychotic agents.

METHODS

Glutamate concentrations were measured in serum and were estimated (Glx/Cr) in cingulate cortex by proton magnetic resonance spectroscopy (MRS) in schizophrenia patients while they were being treated with conventional neuroleptics and then 8 weeks after switching to olanzapine. Serum glutamate concentrations were obtained from 11 subjects, and MRS estimates of Glx/Cr were available from 10 subjects at both time points.

RESULTS

Serum glutamate concentrations significantly increased after the switch from conventional agents to olanzapine; brain glutamate (Glx/Cr) did not change significantly; however, brain glutamate (Glx/Cr) concentrations increased significantly in patients who exhibited an improvement in negative symptoms with olanzapine compared with patients with no change or worsening of negative symptoms.

CONCLUSIONS

Comparisons performed following the switch from conventional agents to olanzapine are consistent with previous studies of clozapine and provide additional preliminary evidence supporting the hypothesis that effects on excitatory amino acid activity may contribute to olanzapine's efficacy for treating negative symptoms.

The density and spatial distribution of GABAergic neurons, labelled using calcium binding proteins, in the anterior cingulate cortex in major depressive disorder, bipolar disorder, and schizophrenia

BACKGROUND

There is strong evidence for the presence of a deficit in cortical gamma aminobutyric acid (GABA) neurotransmission in schizophrenia. In this investigation we have used the calcium binding proteins (CBPs) parvalbumin (PV), calretinin (CR), and calbindin-D28K (CB) as markers of these neuronal populations, and have characterized their pattern and density in schizophrenia, bipolar disorder (BPD), and major depressive disorder (MDD).

METHODS

We examined the anterior cingulate cortex (ACC) in four groups of 15 brains each from subjects with schizophrenia, MDD, and BPD, and from control subjects. Using immunocytochemistry to identify these distinct neuronal populations, we quantified their areal density and spatial pattern organization.

RESULTS

There were reductions in the density of CB-labeled neurons in layer 2 in schizophrenia (34%; p =.04) and BPD (33%; p =.05) compared with control subjects; however, after correction for multiple comparisons these findings no longer attained formal statistical significance. We observed no differences in the density of the neuronal populations labeled by CR or PV in any layer of the cortex in any disorder compared with control subjects. There was increased clustering among PV-labeled neurons in BPD compared with control subjects but no significant differences in the spatial organization of the other neuronal subpopulations in any disorder.

CONCLUSIONS

The study provides some support for the presence of a deficit in GABAergic neurons in schizophrenia and shows that these changes are not specific to schizophrenia. The findings indicate that there may be a pathophysiological condition, shared by subjects with schizophrenia and BPD, which operates to selectively reduce the number or protein expression of CB-immunoreactive neurons.