Meta-analysis of postmortem studies of Alzheimer's disease-like neuropathology in schizophrenia

Synaptic loss in schizophrenia: a meta-analysis and systematic review of synaptic protein and mRNA measures

Although synaptic loss is thought to be core to the pathophysiology of schizophrenia, the nature, consistency and magnitude of synaptic protein and mRNA changes has not been systematically appraised. Our objective was thus to systematically review and meta-analyse findings. The entire PubMed database was searched for studies from inception date to the 1st of July 2017. We selected case-control postmortem studies in schizophrenia quantifying synaptic protein or mRNA levels in brain tissue. The difference in protein and mRNA levels between cases and controls was extracted and meta-analysis conducted. Among the results, we found a significant reduction in synaptophysin in schizophrenia in the hippocampus (effect size: -0.65, p < 0.01), frontal (effect size: -0.36, p = 0.04), and cingulate cortices (effect size: -0.54, p = 0.02), but no significant changes for synaptophysin in occipital and temporal cortices, and no changes for SNAP-25, PSD-95, VAMP, and syntaxin in frontal cortex. There were insufficient studies for meta-analysis of complexins, synapsins, rab3A and synaptotagmin and mRNA measures. Findings are summarised for these, which generally show reductions in SNAP-25, PSD-95, synapsin and rab3A protein levels in the hippocampus but inconsistency in other regions. Our findings of moderate-large reductions in synaptophysin in hippocampus and frontal cortical regions, and a tendency for reductions in other pre- and postsynaptic proteins in the hippocampus are consistent with models that implicate synaptic loss in schizophrenia. However, they also identify potential differences between regions and proteins, suggesting synaptic loss is not uniform in nature or extent.

The effectiveness of postoperative intervention in patients after rhinoplasty: a meta-analysis

Rhinoplasty is the most common facial plastic surgical procedure, and the occurrence of periorbital edema and ecchymosis is normal after rhinoplasty. The goal of this study was to perform a systematic review with meta-analysis of the efficacy of postoperative care of edema and ecchymosis following rhinoplasty. Two authors independently searched the databases (PubMed, SCOPUS, Embase, Web of Science, and the Cochrane database) from inception to September 2016. We included studies that compared postoperative care methods (intervention groups) with no treatment (control group) where the outcomes of interest were edema, ecchymosis, and satisfaction rate of patients on postoperative days. Sufficient data for meta-analysis were retrieved for 11 trials with a total of 627 patients. Eyelid edema and ecchymosis during the first 7 days postoperatively were statistically decreased in the arnica administration groups versus the control group. Eyelid edema and ecchymosis during the first 24 h postoperatively were statistically decreased in the cold compression group versus the control group. The ratio of patient satisfaction was statistically higher in the tapping application group than in the control group. However, the analysis indicated that surgeons had a significant tendency to decrease intranasal packing. The administration of arnica, cold compression, and tape could reduce eyelid edema and ecchymosis. Intranasal packing was associated with more adverse effects in terms of postoperative ecchymosis compared to non-packing. However, additional trials with thorough research methodologies should be conducted to confirm the results of this study.

Β-Amyloid Burden is Not Associated with Cognitive Impairment in Schizophrenia: A Systematic Review

Current literature suggests that the pathology of schizophrenia (SCZ) has developmental origins. However, the neurodevelopmental theory of SCZ cannot solely explain progressive neurodegenerative processes in the illness. There is evidence of accelerated cognitive decline and increased risk of dementia in elderly patients with SCZ. Investigating β-amyloid (Aβ), we conducted a systematic review focusing on Aβ in patients with SCZ. An OVID literature search using PsychINFO, Medline, and Embase databases was conducted, looking for studies that compared Aβ levels between patients with SCZ and either elderly control subjects, patients with Alzheimer disease (AD), or patients with other psychiatric illnesses. Among 14 identified studies, 11 compared Aβ between SCZ and elderly control subjects, 7 between SCZ and AD, and 3 between SCZ and other psychiatric illnesses. As a result, no evidence was found suggesting that Aβ levels differ in patients with SCZ from elderly control subjects or patients with other psychiatric illnesses. All seven studies reported lower cortical Aβ in patients with SCZ than patients with AD. Furthermore, three of the four studies, which investigated the relationship between Aβ and cognitive impairment in SCZ, observed no association between two factors. The limitations of the included studies are small sample sizes, the inclusion of cerebrospinal fluid Aβ or postmortem plaques rather than cortical Aβ assessment in vivo, and the investigation of different brain regions. In conclusion, Aβ deposition is not associated with cognitive decline in late-life SCZ. Future studies should investigate other neurodegenerative indicators in SCZ to better understand the pathophysiologic mechanisms underlying this illness.

How Non-Diagnostic Listening Led to a Rapid “Recovery” from Paranoid Schizophrenia: What is Wrong with Psychiatry?

An experimental interview with a young woman diagnosed with paranoid schizophrenia led to her rapid recovery. This incident and questions raised about psychiatric practices suggest that something is seriously wrong with psychiatry. It lacks insight into its own behavior, invalidates constructive criticism, avoids the kind of selfexamination it urges on “patients,” shows little interest in accounts of successes with “schizophrenic” individuals, erroneously lumps all the schizophrenias (plural) together in research studies, feels helpless and hopeless about schizophrenia, dismisses evidence that contradicts its inaccurate beliefs, and misrepresents what is known about “schizophrenia” to the public and to patients. The argument is put forward that research should begin to focus on the mind of the beholder. It is time for researchers to examine the cognitive processes, personality traits, and motives of “mental health” professionals who perceive schizophrenia in others and insist that schizophrenia is an incurable brain disease.

Neuropsychology, autobiographical memory, and hippocampal volume in "younger" and "older" patients with chronic schizophrenia

Despite a wide range of studies on neuropsychology in schizophrenia, autobiographical memory (AM) has been scarcely investigated in these patients. Hence, less is known about AM in older patients and hippocampal contribution to autobiographical memories of varying remoteness. Therefore, we investigated hippocampal volume and AM along with important neuropsychological domains in patients with chronic schizophrenia and the respective relationships between these parameters. We compared 25 older patients with chronic schizophrenia to 23 younger patients and an older healthy control group (N = 21) with respect to AM, additional neuropsychological parameters, and hippocampal volume. Personal episodic and semantic memory was investigated using a semi-structured interview. Additional neuropsychological parameters were assessed by using a battery of standard neuropsychological tests. Structural magnetic resonance imaging data were analyzed with an automated region-of-interest procedure. While hippocampal volume reduction and neuropsychological impairment were more pronounced in the older than in the younger patients, both groups showed equivalent reduced AM performance for recent personal episodes. In the patient group, significant correlations between left hippocampal volume and recent autobiographical episodes as well as personal semantic memories arose. Verbal memory and working memory were significantly correlated with right hippocampal volume; executive functions, however, were associated with bilateral hippocampal volumes. These findings underline the complexity of AM and its impairments in the course of schizophrenia in comparison to rather progressive neuropsychological deficits and address the importance of hippocampal contribution.

1H-MRS at 4 tesla in minimally treated early schizophrenia

We investigated glutamate-related neuronal dysfunction in the anterior cingulate (AC) early in schizophrenia before and after antipsychotic treatment. A total of 14 minimally treated schizophrenia patients and 10 healthy subjects were studied with single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) of the AC, frontal white matter and thalamus at 4 T. Concentrations of N-acetylaspartate (NAA), glutamate (Glu), glutamine (Gln) and Gln/Glu ratios were determined and corrected for the partial tissue volume. Patients were treated with antipsychotic medication following a specific algorithm and (1)H-MRS was repeated after 1, 6 and 12 months. There were group x region interactions for baseline NAA (P=0.074) and Gln/Glu (P=0.028): schizophrenia subjects had lower NAA (P=0.045) and higher Gln/Glu (P=0.006) in the AC before treatment. In addition, AC Gln/Glu was inversely related to AC NAA in the schizophrenia (P=0.0009) but not in the control group (P=0.92). Following antipsychotic treatment, there were no further changes in NAA, Gln/Glu or any of the other metabolites in any of the regions studied. We conclude that early in the illness, schizophrenia patients already show abnormalities in glutamatergic metabolism and reductions in NAA consistent with glutamate-related excitotoxicity.

Cholinesterase inhibitors as adjunctive therapy in patients with schizophrenia and schizoaffective disorder: a review and meta-analysis of the literature

BACKGROUND

Cognitive deficits have been described in patients with schizophrenia from the first descriptions of dementia praecox to current concepts of cognitive dysmetria. Nevertheless, little is known about how to deal with them. In Alzheimer disease, cholinergic deficit is found and cholinesterase inhibitors have been used to delay the progression of memory and cognitive dysfunction. Several lines of evidence suggest that the cholinergic system may be disrupted in schizophrenia.

OBJECTIVE

To evaluate cognitive and clinical effects of adjunctive cholinesterase inhibitors in patients with schizophrenia and schizoaffective disorder.

METHOD

We conducted a literature search on PubMed and EMBASE (up to December 2008) for articles that investigated adjunctive cholinesterase inhibitors in patients with schizophrenia. The terms 'schizophrenia', 'acetylcholinesterase inhibitors', 'rivastigmine', 'donepezil', 'galantamine' and 'cognitive deficit' were searched with restriction for English language and without a year limit. All articles that presented original data from randomized, double-blind, placebo-controlled trials with donepezil, rivastigmine or galantamine in patients with schizophrenia or schizoaffective disorder were included in the meta-analysis. Studies were excluded for the following reasons: (i) case study/letter/correspondence/review; (ii) animal study; (iii) molecular/genetic investigation; and (iv) inclusion of patients with schizophrenia and co-morbid dementia. Few appropriate data for meta-analysis were found because of the large heterogeneity of the assessment instruments used. Nevertheless, effects of cholinesterase inhibitors in some cognitive domains (executive function, memory and language), psychopathology (using the Positive and Negative Syndrome Scale) and extrapyramidal symptoms could be analysed.

RESULTS

Six open-label and 24 double-blind studies were found. In five open-label studies there was an improvement in memory, attention and executive functions. Thirteen double-blind studies (four with rivastigmine, six with donepezil and three with galantamine) contributed to the meta-analysis. Significant improvement was found in this analysis for memory and the Trail Making test part A.

CONCLUSIONS

The reviewed studies suggest that specific cognitive deficits (memory, and the motor speed and attention part of executive function) of patients with schizophrenia and schizoaffective disorder are responsive to rivastigmine, donepezil and galantamine as adjunctive therapy. Confirmatory studies are needed to determine the clinical utility of this treatment strategy.

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.

Proton magnetic resonance spectroscopy during initial treatment with antipsychotic medication in schizophrenia

Reduced brain N-acetyl-aspartate (NAA) has been repeatedly found in chronic schizophrenia and suggests neuronal loss or dysfunction. However, the potential confounding effect of antipsychotic drugs on NAA has not been resolved. We studied 32 minimally treated schizophrenia patients and 21 healthy subjects with single-voxel proton magnetic resonance spectroscopy ((1)H-MRS) of the frontal and occipital lobes, caudate nucleus, and cerebellum. Concentrations of NAA, Choline, and Cre were determined and corrected for the proportion of cerebrospinal fluid (CSF) in the voxel. Patients were treated in a randomized-controlled double-blind manner with either haloperidol or quetiapine. (1)H-MRS was repeated every 6 months for up to 2 years. There was a group main effect for baseline NAA with lower global NAA in schizophrenia subjects before treatment compared to healthy controls. Global NAA was directly related to measures of global cognitive performance in the whole subject sample. Following treatment with haloperidol or quetiapine, there were no changes in NAA in any of the regions studied. Early in the illness, schizophrenia patients already demonstrate subtle reductions in NAA. Treatment with typical or atypical antipsychotic medications for several months does not result in NAA changes.

How a neuropsychiatric brain bank should be run: a consensus paper of Brainnet Europe II

The development of new molecular and neurobiological methods, computer-assisted quantification techniques and neurobiological investigation methods which can be applied to the human brain, all have evoked an increased demand for post-mortem tissue in research. Psychiatric disorders are considered to be of neurobiological origin. Thus far, however, the etiology and pathophysiology of schizophrenia, depression and dementias are not well understood at the cellular and molecular level. The following will outline the consensus of the working group for neuropsychiatric brain banking organized in the Brainnet Europe II, on ethical guidelines for brain banking, clinical diagnostic criteria, the minimal clinical data set of retrospectively analyzed cases as well as neuropathological standard investigations to perform stageing for neurodegenerative disorders in brain tissue. We will list regions of interest for assessments in psychiatric disorder, propose a dissection scheme and describe preservation and storage conditions of tissue. These guidelines may be of value for future implementations of additional neuropsychiatric brain banks world-wide.

Attenuation of Abeta deposition in the entorhinal cortex of normal elderly individuals associated with tobacco smoking

Investigating correlates of tobacco smoking provides the only currently available opportunity of examining effects of long-term exposure of nicotinic receptors on a specific nicotinic agonist in human. Alzheimer-type pathology (Abeta and abnormally phosphorylated tau assessed on the basis of AT8 immunoreactivity) together with vascular markers has been compared in age-matched groups of normal elderly smokers and non-smokers in the entorhinal cortex, an area of noted age-related pathology. The density of total Abeta and diffuse Abeta immunoreactivity, together with formic acid-extractable Abeta42 but not Abeta40, was reduced in smokers (n = 10-18) compared with non-smokers (n = 10-20) (P < 0.05). There was also a reduced percentage of cortical and leptomeningeal vessels with associated Abeta immunoreactivity in smokers (n = 13) compared with non-smokers (n = 14) (P < 0.005 and 0.05, respectively). There was a significant inverse correlation between formic acid-extractable Abeta42 and pack years (n = 34, r = -0.389, P = 0.025), with a similar trend for total Abeta immunoreactivity which did not reach statistical significance (n = 30, r = -0.323, P = 0.082). In contrast, there were no significant group differences for vascular markers (collagen IV, alpha-actin or glucose transporter 1), AT8 immunoreactivity or phosphate-buffered saline-soluble Abeta peptides, and no significant associations with gender for any of the measured parameters. These findings are consistent with previously reported reductions in histologically assessed amyloid plaques in aged human brain associated with tobacco use and dramatic lessening of Abeta deposits in APPsw mice after nicotine treatment. Development of nicotinic drugs to protect against beta-amyloidosis as one of the principal pathological hallmarks of brain ageing and Alzheimer's disease is indicated.

Older people with chronic schizophrenia

Older people with chronic schizophrenia are a numerically small but important group with complex clinical and service needs. Along with a reduction in positive schizophrenic symptoms with increasing age, a majority suffer from negative symptoms, cognitive deficits, depression, side effects due to long-term use of antipsychotics and co-morbid medical problems. They may have social disabilities making them vulnerable to poverty, isolation and poor quality of life. Evidence suggests that judicious use of antipsychotics combined with psychotherapy and psychosocial interventions are effective. There are shortcomings in the standard of both hospital and community care, and the cost implications of providing adequate services are high.

Schizophrenia genes, gene expression, and neuropathology: on the matter of their convergence

This review critically summarizes the neuropathology and genetics of schizophrenia, the relationship between them, and speculates on their functional convergence. The morphological correlates of schizophrenia are subtle, and range from a slight reduction in brain size to localized alterations in the morphology and molecular composition of specific neuronal, synaptic, and glial populations in the hippocampus, dorsolateral prefrontal cortex, and dorsal thalamus. These findings have fostered the view of schizophrenia as a disorder of connectivity and of the synapse. Although attractive, such concepts are vague, and differentiating primary events from epiphenomena has been difficult. A way forward is provided by the recent identification of several putative susceptibility genes (including neuregulin, dysbindin, COMT, DISC1, RGS4, GRM3, and G72). We discuss the evidence for these and other genes, along with what is known of their expression profiles and biological roles in brain and how these may be altered in schizophrenia. The evidence for several of the genes is now strong. However, for none, with the likely exception of COMT, has a causative allele or the mechanism by which it predisposes to schizophrenia been identified. Nevertheless, we speculate that the genes may all converge functionally upon schizophrenia risk via an influence upon synaptic plasticity and the development and stabilization of cortical microcircuitry. NMDA receptor-mediated glutamate transmission may be especially implicated, though there are also direct and indirect links to dopamine and GABA signalling. Hence, there is a correspondence between the putative roles of the genes at the molecular and synaptic levels and the existing understanding of the disorder at the neural systems level. Characterization of a core molecular pathway and a 'genetic cytoarchitecture' would be a profound advance in understanding schizophrenia, and may have equally significant therapeutic implications.

The hippocampus in schizophrenia: a review of the neuropathological evidence and its pathophysiological implications

This paper puts the case for the hippocampus as being central to the neuropathology and pathophysiology of schizophrenia. The evidence comes from a range of approaches, both in vivo (neuropsychology, structural and functional imaging) and post mortem (histology, morphometry, gene expression, and neurochemistry). Neuropathologically, the main positive findings concern neuronal morphology, organisation, and presynaptic and dendritic parameters. The results are together suggestive of an altered synaptic circuitry or "wiring" within the hippocampus and its extrinsic connections, especially with the prefrontal cortex. These changes plausibly represent the anatomical component of the aberrant functional connectivity that underlies schizophrenia. Glutamatergic pathways are prominently but not exclusively affected. Changes appear somewhat greater in the left hippocampus than the right, and CA1 is relatively uninvolved compared to other subfields. Hippocampal pathology in schizophrenia may be due to genetic factors, aberrant neurodevelopment, and/or abnormal neural plasticity; it is not due to any recognised neurodegenerative process. Hippocampal involvement is likely to be associated with the neuropsychological impairments of schizophrenia rather than with its psychotic symptoms.

Neuropsychological differentiation of late-onset schizophrenia and dementia of the Alzheimer's type

Late-onset schizophrenia and dementia of the Alzheimer's type (DAT) often present with some pathological and behavioral commonalities. Specifically, both illnesses may involve varying degrees of delusional manifestation, apathy, lateral/third-ventricular enlargement, reduced frontal lobe activity, and hippocampal atrophy. Moreover, patients with either disease have shown comparable cognitive impairment on standardized neuropsychological tests. As such, a differential diagnosis of the 2 disorders on the basis of such testing can prove to be difficult. This study evaluated the neuropsychological test results of 32 patients with late-onset schizophrenia and 32 patients with DAT to distinguish the tests that best differentiate the 2 disorders. Results indicate that the Wechsler Adult Intelligence Scale-Revised Similarities subtest and the California Verbal Learning Test (both short- and long-delay free recall) correspond to sensitive diagnostic neuropsychological measures. This investigation was preliminary in nature, and should aid in the development of a definitive differential profile.

Does schizophrenia result from developmental or degenerative processes?

The debate as to whether schizophrenia is a neurodevelopmental or a neurodegenerative disorder has its roots in the latter part of the 19th century when authorities such as Clouston (1891) posited that at least some insanities were "developmental" in origin. These views were soon eclipsed by Kraepelin's (1896) concept of dementia praecox as a degenerative disease, and the latter view carried not only the day but also much of the 20th century. Then, in the 1980s several research groups again began to speculate that schizophrenia might have a significant developmental component (Feinberg, 1982-1983; Schulsinger et al., 1984; Murray et al., 1985; Murray and Lewis, 1987; Weinberger et al., 1987). What became known as the "neurodevelopmental hypothesis" received support from neuropathological studies implicating anomalies in early brain development such as aberrant migration of neurons. Unfortunately, these studies proved difficult, if not impossible, to replicate (Harrison, 1999). The pendulum, therefore, began to swing again, and in the latter part of the 1990s came renewed claims that the clinical progression of the illness was accompanied by continued cerebral ventricular enlargement and reduction in the volumes of certain brain structures. Nevertheless, since few doubt that there is a developmental component to schizophrenia, the question which we will address in this paper is whether schizophrenia is a) simply the final consequence of a cascade of increasing developmental deviance (Bramon et al., 2001), or b) whether there is an additional brain degeneration following onset of psychosis which is superimposed on the developmental impairment (Lieberman, 1999).

Neuropathological studies of synaptic connectivity in the hippocampal formation in schizophrenia

Cytoarchitectural changes in the hippocampal formation have been prominent among the various neuropathological abnormalities reported in schizophrenia. Replicated positive findings include decreased neuronal size and alterations in presynaptic and dendritic markers. These findings, in the absence of neurodegenerative changes, suggest that there are alterations in the neural circuitry in schizophrenia. These may represent the anatomical correlate of the aberrant functional connectivity described in neuroimaging studies, which in turn contributes to the psychotic and cognitive symptomatology of the disorder. The identity of the affected hippocampal circuits remains unclear; there is evidence for both glutamatergic and GABAergic involvement, and perhaps for a gradient of pathology in which changes are most apparent in CA4 and the subiculum, and least in CA1. The data, their interpretation, and their limitations are discussed, with particular emphasis upon molecular and immunological studies of synaptic protein gene expression.

Postmortem studies in schizophrenia

For over a century, postmortem studies have played a central part in the search for the structural and biochemical pathology of schizophrenia. However, for most of this time, little progress has been made. Recently, the situation has begun to change, helped by the emergence of more powerful methodologies and research designs, and by the availability of brain imaging to provide complementary information. As a result, it can now be clearly concluded that there are structural cerebral abnormalities in schizophrenia that are intrinsic to the disorder. The neuropathological process is not primarily degenerative, but involves a change in the normal cytoarchitecture of the brain, probably originating in development. Neurochemically, there is postmortem evidence for alterations in several transmitter systems including dopamine, glutamate, serotonin, and γ-aminobutyric acid (GABA). The cardinal findings are reviewed here, together with a consideration of the conceptual and methodological issues that face postmortem studies of schizophrenia.

The neuropathology of schizophrenia. A critical review of the data and their interpretation

Despite a hundred years' research, the neuropathology of schizophrenia remains obscure. However, neither can the null hypothesis be sustained--that it is a 'functional' psychosis, a disorder with no structural basis. A number of abnormalities have been identified and confirmed by meta-analysis, including ventricular enlargement and decreased cerebral (cortical and hippocampal) volume. These are characteristic of schizophrenia as a whole, rather than being restricted to a subtype, and are present in first-episode, unmedicated patients. There is considerable evidence for preferential involvement of the temporal lobe and moderate evidence for an alteration in normal cerebral asymmetries. There are several candidates for the histological and molecular correlates of the macroscopic features. The probable proximal explanation for decreased cortical volume is reduced neuropil and neuronal size, rather than a loss of neurons. These morphometric changes are in turn suggestive of alterations in synaptic, dendritic and axonal organization, a view supported by immunocytochemical and ultrastructural findings. Pathology in subcortical structures is not well established, apart from dorsal thalamic nuclei, which are smaller and contain fewer neurons. Other cytoarchitectural features of schizophrenia which are often discussed, notably entorhinal cortex heterotopias and hippocampal neuronal disarray, remain to be confirmed. The phenotype of the affected neuronal and synaptic populations is uncertain. A case can be made for impairment of hippocampal and corticocortical excitatory pathways, but in general the relationship between neurochemical findings (which centre upon dopamine, 5-hydroxytryptamine, glutamate and GABA systems) and the neuropathology of schizophrenia is unclear. Gliosis is not an intrinsic feature; its absence supports, but does not prove, the prevailing hypothesis that schizophrenia is a disorder of prenatal neurodevelopment. The cognitive impairment which frequently accompanies schizophrenia is not due to Alzheimer's disease or any other recognized neurodegenerative disorder. Its basis is unknown. Functional imaging data indicate that the pathophysiology of schizophrenia reflects aberrant activity in, and integration of, the components of distributed circuits involving the prefrontal cortex, hippocampus and certain subcortical structures. It is hypothesized that the neuropathological features represent the anatomical substrate of these functional abnormalities in neural connectivity. Investigation of this proposal is a goal of current neuropathological studies, which must also seek (i) to establish which of the recent histological findings are robust and cardinal, and (ii) to define the relationship of the pathological phenotype with the clinical syndrome, its neurochemistry and its pathogenesis.