Schizophrenia as an anomaly of development of cerebral asymmetry. A postmortem study and a proposal concerning the genetic basis of the disease

Defining the course of brain structural change and plasticity in schizophrenia

Recent evidence from controlled CT and MRI longitudinal studies suggests that some cerebral ventricular enlargement and hemispheric volumetric reductions (e.g. cerebral atrophy) may have a progressive component in patients with schizophrenia. These studies vary in cohort composition, stage of illness examined, duration of follow-up interval, imaging techniques used, and specific brain regions with findings. They also conflict with earlier evidence suggesting that schizophrenia is a neurodevelopmental disorder with brain pathological deviance occurring prior to the illness onset. The newer brain imaging reports may be detecting subtle brain plasticity that results from a continuing cortical disruptive process, may be epi-phenomena caused by scanning and image analysis artifacts or may possibly reflect systemic physiological fluctuations. Future longitudinal studies of subjects at all stages of illness using a variety of new technologies are needed to clarify these findings.

Regional brain volume change over the life-time course of schizophrenia

The concept that schizophrenia has its antecedents in neurodevelopment has long been debated and has been at the forefront of research on this disorder over the last decade. However new recent evidence from controlled longitudinal studies indicates that some of the structural brain anomalies observed in schizophrenia may continue to progress sporadically after the onset of clinical illness. The studies vary in cohort composition, stage of illness studied, duration of follow-up interval, and specific brain regions with findings. Nevertheless, the findings as a whole suggest that the brain changes in size throughout the lifespan of an individual and to a greater extent in schizophrenia. While the detected abnormalities could be explained by various technical artifacts, or physiological epi-phenomena, that they result from an ongoing neurochemical, physiological or morphological process characteristic of the underlying basis for the disorder is an intriguing possibility that lends itself to possible future intervention.

Schizophrenic patients and their first-degree relatives show an excess of mixed-handedness

An excess of mixed-handedness in schizophrenia has been reported. However, it is not established whether this excess is manifest in non-schizophrenic psychoses, nor whether the underlying etiology is genetic or environmental. We investigated these issues in a group of patients with schizophrenia (n=94), affective psychosis (n=63), other psychosis (n=26); their respective first-degree relatives (total n=183) and a control group (n=85). A narrow definition of mixed-handedness was used corresponding to groups 5 and 6 as defined by the Annett Handedness Questionnaire. We found an excess of mixed-handedness in the schizophrenic group compared with controls (OR=5.2, 1.4-18.6, p<0.006). There was no difference between the other psychotic groups and controls. There was a trend for an excess of mixed-handedness in the first-degree relatives (n=99) of schizophrenic patients (p=0.055), but not in the relatives of affective or other psychotic patients. There was a striking linear trend in the proportion of mixed-handedness between controls, the relatives and the schizophrenic patients (chi2=7.0, p=0.008). There was no association between mixed-handedness and a history of pregnancy or birth complications in the schizophrenic group. There was some evidence for impaired sociability in the mixed-handed schizophrenic patients. Our results indicate that the excess of mixed-handedness in schizophrenia may have a genetic basis.

The evolutionary genetic underpinnings of schizophrenia: the developmental instability model

The importance of genes in the etiology of schizophrenia is well known, but the manner in which the relevant genomic factors influence neural development and the nature of selection forces operating on these factors are poorly understood. In several prominent papers, Crow has provided a unique and comprehensive theory that attempts to deal with these issues. A central aspect of his theory is that a single gene leads to reduced cerebral lateralization, increased ventricular size, and risk for developing schizophrenia. He relies greatly on Annett's right shift theory of individual variation in handedness. An alternative approach, based on the construct of developmental instability, provides a different way to conceptualize genetic influences, selection forces, and atypical lateralization in schizophrenia. We suggest that the developmental instability model has stronger empirical support and is better grounded in contemporary evolutionary genetics.

Commentary on Annett, Yeo et al., Klar, Saugstad and Orr: cerebral asymmetry, language and psychosis--the case for a Homo sapiens-specific sex-linked gene for brain growth

Annett, Yeo et al. and Klar have each proposed theories that relate the genetics of cerebral lateralization to predisposition to psychosis. These theories are considered in relation to the central paradox that psychosis is associated with a substantial biological disadvantage. Annett's heterozygote advantage hypothesis critically identified lateralization as a major determinant of ability, but it appears that what is inherited is degrees (as suggested by Yeo et al.) rather than (or as well as) direction of lateralization. Relative hand skill has been shown (Crow, T.J., Crow, L.R., Done, D.J., Leask, S.J., 1998. Relative hand skill predicts academic ability: global deficits at the point of hemispheric indecision. Neuropsychologia 36, 1275-1282.) to be a powerful predictor (interacting with sex) of academic ability but the greatest region of vulnerability (that includes reading disability and predisposition to psychosis) is close to the point of equal hand skill ('hemispheric indecision'). In contrast with Annett's single locus, Yeo's polygenic and Klar's strand-segregation hypotheses, each of which postulates an autosomal locus or loci, the hypothesis of a single gene for asymmetry located in a sex-specific region of homology on both X and Y chromosomes can account for sex differences, as observed in age of onset, and premorbid precursors of psychosis, as well as differences in the general population in relation to degrees of hand skill, verbal ability and cerebral asymmetry. The evolutionarily recent transposition to, and subsequent paracentric inversion in, the Y chromosome short arm of a 4-Mb block from Xq21.3 (the proximal long arm of the X) are candidates for speciation events in the lineage that led to Homo sapiens. A gene associated with a range of variation (that may be due to a high mutation site, or perhaps to epigenetic modification) on the Y that overlaps with, but differs quantitatively from, that on the X may explain the sex differences associated with psychosis, and may be relevant to its persistence. Such a gene could be the principal determinant in Man of the rate of brain growth, as suggested by Saugstad and by the findings of a recent study of adolescent onset psychosis (James, A., Crow, T.J., Renowden, S., Wardell, M., Smith, D.M., Anslow, P., in press. Is the course of brain development in schizophrenia delayed? Evidence from onsets in adolescence. Schizophr. Res.).

The theory of an agnosic right shift gene in schizophrenia and autism

The right shift (RS) theory (Annett, M., 1972. The distribution of manual asymmetry. Br. J. Psychol. 63, 343-358; Annett, M., 1985. Left, Right, Hand and Brain: The Right Shift Theory. Lawrence Erlbaum, London) suggests that the typical pattern of human cerebral and manual asymmetries depends on a single gene (RS+) which impairs speech-related cortex of the right hemisphere. The theory offers solutions to several puzzles, including the distribution of handedness in families (Annett, M., 1978. A Single Gene Explanation of Right and Left Handedness and Brainedness. Lanchester Polytechnic, Coventry; Annett, M., 1996. In defense of the right shift theory. Percept. Motor Skills 82, 115-137), relations between handedness and cerebral speech laterality (Annett, M., 1975. Hand preference and the laterality of cerebral speech. Cortex 11, 305-328; Annett, M., Alexander, M.P., 1996. Atypical cerebral dominance: predictions and tests of the right shift theory. Neuropsychologia 34, 1215-1227) and handedness and dyslexia (Annett, M. et al., 1996. Types of dyslexia and the shift to dextrality. J. Child Psychol. Psychiatry 37, 167-180). If Crow's (Crow, T.J. et al., 1989. Schizophrenia as an anomaly of development of cerebral asymmetry. A postmortem study and a proposal concerning the genetic basis of the disease. Arch. Gen. Psychiatry 46, 1145-1150; Crow, T.J., 1997. Is schizophrenia the price that Homo sapiens pays for language? Schizophr. Res. 28, 127-141) theory that schizophrenia is due to an anomaly of cerebral dominance is correct, and if the RS theory is correct, schizophrenia could be due to an anomaly of the RS+ gene. If the RS+ gene were at risk for a mutation which caused a loss of directional coding, the mutant could be described as 'agnosic' for left and right. Such a gene would impair either hemisphere at random. When paired with another RS+ gene, both hemispheres would be impaired in 50% of cases. The other 50% and people in whom the agnosic gene is paired with an RS-allele (neutral for asymmetry and not giving hemisphere impairment) would have one unaffected hemisphere and, thus, normal development. Quantitative predictions based on the RS genetic theory as previously developed, plus an agnosic mutant with frequency required to give schizophrenia in 1% of the population, are consistent with estimates of concordance for schizophrenia in relatives. Homozygotes of the agnosic mutant would occur at about the rate estimated for autism.

Structural brain imaging in schizophrenia: a selective review

Structural neuroimaging studies have provided some of the most consistent evidence for brain abnormalities in schizophrenia. Since the initial computed tomography study by Johnstone and co-workers, which reported lateral ventricular enlargement in schizophrenia, advances in brain imaging technology have enabled further and more refined characterization of abnormal brain structure in schizophrenia in vivo. This selective review discusses the major issues and findings in structural neuroimaging studies of schizophrenia. Among these are evidence for generalized and regional brain volume abnormalities, the specificity of anatomic findings to schizophrenia and to men versus women with schizophrenia, the contribution of genetic influences, and the timing of neuroanatomic pathology in schizophrenia. The second section reviews new approaches for examining brain structure in schizophrenia and their applications to studies on the pathophysiology of schizophrenia.

Schizophrenia and temporal lobe asymmetry. A post-mortem stereological study of tissue volume

BACKGROUND

A previous report by Crow of a left-sided increase in temporal horn volume in schizophrenia implies a left-sided loss of tissue.

AIMS

To elucidate the structural nature of schizophrenia.

METHOD

The volume of grey matter in the temporal pole and inferior, middle and superior temporal gyri was measured, in addition to the total volume of grey and white matter, in the temporal lobes of the brains of 29 patients with schizophrenia and 27 controls.

RESULTS

We found a significant left-sided reduction in the superior temporal gyrus in both males and females with schizophrenia, which was related to increasing age of onset in the males. The total volume of temporal lobe grey and white matter was also significantly reduced. Although being more marked on the left than the right, the lateralisation for these total grey and white measures (by contrast with the superior temporal gyrus alone) did not attain formal statistical significance.

CONCLUSIONS

Confirmation of a lateralised reduction in the superior temporal gyrus, which is differentially related to age of onset according to gender, adds to evidence that the changes in schizophrenia are in systems that are lateralised. The findings implicate language as the relevant function.

Dementia praecox to schizophrenia: the first 100 years

The historical roots of dementia praecox and schizophrenia are described in the context of current nosology and continuing controversies surrounding this nosology. Relevant books and journal articles were reviewed. The information was obtained through computer searches and cross-references from previously published papers. If English translations of foreign language articles were available, they were used; if not, the cross-references were consulted. The psychoses have existed as diagnostic categories from ancient times although their names have changed. Initially, these disorders were considered diseases of the brain, a concept that was swept aside in the United States, influenced by European-derived psychodynamic theories. American clinicians and investigators simply accepted these theories, showing little interest in testing their underlying principles. In contrast, a narrower Kraepelinian approach was adopted outside the United States, and attempts were made to refine its nosology. Because current data supports a central nervous system aetiology for schizophrenia, the concept of dementia praecox warrants resurrection. The authors suggest abandoning the term schizophrenia in favour of the more broad and generic term dementia praecox. Replacing 'schizophrenia' with 'dementia praecox' in the 21st century will facilitate further research and help clarify the nosology of various brain disorders currently included in the schizophrenias.

Schizoaffective disorder: evidence for reversed cerebral asymmetry

BACKGROUND

Schizoaffective disorder is one of the most severe of the affective psychoses, but its pathophysiology is poorly understood. Because cerebral lateralization may be disturbed in psychotic disorders generally, studies examining cerebral asymmetry may improve understanding of the neurobiology specific to schizoaffective disorder. This study examines cerebral lateralization in this patient population using magnetic source localization.

METHODS

We studied 16 subjects with schizoaffective disorder and 16 controls. Magnetic source localization was used to identify the location of the 20 msec latency somatosensory evoked field component (M20).

RESULTS

In control subjects, the source location was further anterior in the right hemisphere. The subjects with schizoaffective disorder were reverse lateralized.

CONCLUSIONS

The findings of a reversed asymmetry of the M20 in patients with schizoaffective disorder suggest an anatomical shift in the placement of the post central gyrus in this disorder, compatible with a disorder of cerebral lateralization. Whether this finding converges or diverges with measurement of the M20 in other psychotic disorders will require further investigation.

Reduction of the parahippocampal gyrus and the hippocampus in patients with chronic schizophrenia

BACKGROUND

There have been many studies reporting reduced volume of the hippocampus or other limbic structures in patients with schizophrenia, but the literature is inconsistent.

AIMS

To compare patients with either first-episode or chronic schizophrenia with controls using high-resolution volumetric magnetic resonance imaging (MRI) scans.

METHOD

Thirteen patients with first-episode schizophrenia, 27 with chronic schizophrenia and 31 controls had 1.5 mm coronal slices taken through the whole brain using a spoiled-grass MRI acquisition protocol.

RESULTS

The parahippocampal gyrus was reduced significantly on the left side in patients with chronic schizophrenia compared with controls for both male and female patients, whereas the hippocampus was reduced significantly on both sides only in female patients. There were no significant reductions in any structure between patients with first-episode schizophrenia and controls.

CONCLUSIONS

Volumetric reduction seen in patients with chronic schizophrenia may be due to an active degenerative process occurring after the onset of illness.

Neurological signs and psychomotor performance in patients with schizophrenia, their relatives and healthy controls

Schizophrenic patients (DSM-III-R) were consecutively recruited and 39 were included. Twenty-one were first-episode and 18 were chronic schizophrenic patients. Thirty of the patients were on neuroleptic medication. Thirty-three parents were included, of whom nine were classified as 'family history positive' and 22 as 'family history negative' of a disposition to psychosis. Fifty-five healthy controls volunteered. The subjects were investigated according to a protocol divided into neurological signs and psychomotor performance (finger-tapping rate, Purdue pegboard test, pronation-supination test, gait and hand-grasp strength). Seventy-eight percent of the patients and 7% of the controls were classified as globally aberrant in signs. The patients and their parents, classified as 'family history positive', exhibited a similar laterality pattern in a finger-tapping test improving performance with the preferred hand, significantly different from the performance of the 'family history negative' parents and normal subjects. Duration of illness, neuroleptic medication and negative symptoms were not related to the occurrence of neurological signs and psychomotor performance. These findings indicate that neurological aberrations are present at the onset of illness and that hereditary factors are associated with motor laterality.

Cognition and neuropathology in schizophrenia

Clinical, neuropsychological and neuropathological avenues of research have advanced in concert to increase our understanding of schizophrenia. Progress in four general areas of investigation will be reviewed: (i) fronto-temporal-limbic dysfunction; (ii) abnormal connectivity or 'miswiring'; (iii) aberrant neurodevelopment; and (iv) neurodegeneration and neural injury. The challenge for post-mortem research is to identify the molecular pathways in which abnormalities culminate in the highly diverse features of the disorder. Candidate pathways must be able to account for the developmental and deteriorative clinical profiles and the global and focal neuropsychological deficits, as well as the various patho-anatomical abnormalities that indicate aberrant cytoarchitecture and connectivity in the absence of neurodegeneration or other obvious evidence of postmaturational neural injury.

MRI anatomy of schizophrenia

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

The size and fiber composition of the anterior commissure with respect to gender and schizophrenia

BACKGROUND

In light of evidence for deviations in asymmetry and alterations in the anatomy of the corpus callosum in schizophrenia, this study examined the anterior commissure in post mortem brains (n = 14 female control patients, 15 male control patients, 11 female schizophrenic patients, 15 male schizophrenic patients).

METHODS

Measures were made of the cross-sectional area of the anterior commissure in the midsagittal plane. In addition, the fiber density and fiber number were measured in a subset of cases (n = 10 female control subjects, 10 male control subjects, 8 female schizophrenic patients, 9 male schizophrenic patients), using the Palmgren silver stain and stereological methods.

RESULTS

In control subjects, fiber numbers were greater (p = .024) in women than men. In schizophrenia, the cross-sectional area was unaffected, but for fiber density there was a significant gender x diagnosis interaction (p = .026), corresponding to a reduction in female, but not male patients with schizophrenia.

CONCLUSIONS

The reduction in density of fibers in the anterior commissure is consistent with an alteration of interhemispheric connectivity in schizophrenia, but the restriction of the finding to women emphasizes the relevance of gender to understanding the nature of the hemispheric interaction.

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.

Delayed neuronal loss after administration of intracerebroventricular kainic acid to preweanling rats

Excitotoxins, such as kainic acid (KA), have been shown to produce both immediate and delayed neuronal degeneration in adult rat brain. While preweanling rats have been shown to be resistant to the immediate neurotoxicity of KA, the presence of delayed neuronal loss has not been investigated in such animals. To determine whether intracerebroventricular (i.c.v.) administration of KA would produce delayed neuronal loss, preweanling rats were administered 5 nmol or 10 nmol KA i.c.v. on postnatal day 7 (P7) and then examined at P14, P45, and P75. Using three-dimensional, non-biased cell counting, neuronal loss was observed in the CA3 subfield of the hippocampal formation at P45 and P75 in animals administered 10 nmol KA, as compared to animals administered 5 nmol KA or artificial cerebrospinal fluid. Further, the amount of immunoreactivity to jun, the protein product of the immediate early gene, c-jun, adjusted for the number of remaining neurons was increased in the same brain areas. Antibody labeling of inducible heat shock protein and glial fibrillary acidic protein was not similarly increased in animals administered i.c.v. KA. The data suggest that while i.c.v. KA does not produce immediate neuronal loss in preweanling rats, the hippocampus is altered so that neuronal loss occurs after a delay, perhaps through apoptosis. These findings may be relevant to the pathogenesis of neuropsychiatric disorders, such as schizophrenia, that are characterized by early limbic-cortical deficits but onset of illness in young adulthood.

The size and fibre composition of the corpus callosum with respect to gender and schizophrenia: a post-mortem study

In this study the cross-sectional area (in n = 14 female controls, 15 male controls, 11 female patients with schizophrenia, 15 male patients with schizophrenia) and fibre composition (in n = 11 female controls, 10 male controls, 10 female patients with schizophrenia, 10 male patients with schizophrenia) of the corpus callosum in post-mortem control and schizophrenic brains was examined. A gender x diagnosis interaction (P = 0.005) was seen in the density of axons in all regions of the corpus callosum except the posterior midbody and splenium. Amongst controls, females had greater density than males; in patients with schizophrenia this difference was reversed. A reduction in the total number of fibres in all regions of the corpus callosum except the rostrum was observed in female schizophrenic patients (P = 0.006; when controlling for brain weight, P = 0.053). A trend towards a reduced cross-sectional area of the corpus callosum was seen in schizophrenia (P = 0.098); however, this is likely to be no more than a reflection of an overall reduction in brain size. With age, all subregions of the corpus callosum except the rostrum showed a significant reduction in cross-sectional area (P = 0.018) and total fibre number (P = 0.002). These findings suggest that in schizophrenia there is a subtle and gender-dependent alteration in the forebrain commissures that may relate to the deviations in asymmetry seen in other studies, but the precise anatomical explanation remains obscure.

Three-dimensional magnetic resonance-based morphometrics and ventricular dysmorphology in schizophrenia

BACKGROUND

Recent methodological refinements in magnetic resonance (MR) imaging have led to brain averaging and morphometric approaches that are sensitive to subtle anatomical distinctions in schizophrenia.

METHODS

Using a novel morphometric technique for surface analysis, 48 selected landmarks of the rendered ventricular system were extracted and compared between the ventricles of 20 patients with schizophrenia and 20 normal subjects.

RESULTS

There was no significant difference in ventricular shape between groups, but significant (p = .015) and highly localized shape deformity was detected at the foramen of Monro and at the proximal temporal horn of the lateral ventricle of male (but not female) patients relative to controls.

CONCLUSIONS

Three-dimensional MR-based morphometrics complements established volumetric approaches and can detect minute shape deformities that may be associated with schizophrenia.

The reduced neuropil hypothesis: a circuit based model of schizophrenia

In recent years, quantitative studies of the neuropathology of schizophrenia have reignited interest in the cerebral cortex and focused attention on the cellular and subcellular constituents that may be altered in this disease. Findings have ranged from compromised circuitry in prefrontal areas to outright neuronal loss in temporal and cingulate cortices. Herein, we propose that a reduction in interneuronal neuropil in the prefrontal cortex is a prominent feature of cortical pathology in schizophrenia and review the growing evidence for this view from reports of altered neuronal density and immunohistochemical markers in various cortical regions. The emerging picture of neuropathology in schizophrenia is one of subtle changes in cellular architecture and brain circuity that nonetheless have a devastating impact on cortical function.

Anomalies of cerebral asymmetry in schizophrenia interact with gender and age of onset: a post-mortem study

In a post-mortem study of cerebral asymmetry in schizophrenia it was found that asymmetry of the length from the frontal pole to the central sulcus measured dorsally over the external surface of the brain on both hemispheres, showed a gender x diagnosis interaction (p = 0.002). Female controls had a left-greater-than-right asymmetry, and the male controls had a right-greater-than-left asymmetry. This pattern was reversed in schizophrenia. The converse effect was observed on a similar measure of the occipito-parietal lobes (p = 0.028). Significant changes were not seen in measures taken around the lateral surface of the hemispheres. Further, within the patient group, the frontal lobe asymmetry was related to age of onset such that leftward asymmetrical brains were associated with a later age of onset than rightward asymmetrical brains (p = 0.0463 for the females; p = 0.0162 for the males). The occipito-parietal asymmetry was not related to age of onset. We conclude that the asymmetry of the relative distribution of tissue between frontal and posterior regions of the hemispheres is altered in schizophrenia. The findings also suggest that there is an interaction between gender and cerebral asymmetry that is critical in determining age of onset.

Temporal horn enlargement is present in schizophrenia and bipolar disorder

BACKGROUND

Ventricular enlargement and temporal lobe volume deficits have been demonstrated in patients with affective disorder as well as those with schizophrenia. This study compares quantitative measures of temporal lobe, hemispheric, and ventricular volumes in a group of patients with chronic schizophrenia and bipolar disorder and seeks to determine if the groups can be differentiated on the basis of measured brain abnormalities.

METHODS

A series of coronal magnetic resonance imaging sections were acquired and analyzed for each of 22 patients with chronic schizophrenia, 14 patients with bipolar disorder, and 15 community volunteers. Eleven regions of interest for each brain were defined, which included temporal lobe, superior temporal gyrus, hemisphere, lateral ventricle, third ventricle, and temporal horn measures. Tissue measures were obtained by tracing, and cerebrospinal fluid measures were obtained by fluid-tissue thresholding using specialized computer software.

RESULTS

Both patient groups had significantly larger temporal horn volumes in comparison with the control group both before and after correction for intracranial volume. The two patient groups did not differ from each other or controls on any other tissue or fluid measure.

CONCLUSIONS

This study confirms the findings of increased temporal horn volume in patients with schizophrenia and suggests that this structural abnormality does not differentiate the structural neuropathology of schizophrenia from that of bipolar disorder.

Hemispheric asymmetry of frontal and temporal gray matter and age of onset in schizophrenia

BACKGROUND

Investigators have reported lack of normal asymmetry of lateralization in some schizophrenic patients, as measured postmortem and by preference and/or performance. It has been suggested that this lack of asymmetry is related to early onset of schizophrenia. The present study extends the inquiry by magnetic resonance imaging (MRI) measurement of volumetric asymmetry.

METHODS

Hemispheric asymmetry of volume in regional gray matter was examined in 16 schizophrenic patients who had undergone MRI of brain volume.

RESULTS

Low levels of hemispheric asymmetry in the frontal and temporal areas were strongly associated with early onset of schizophrenia, the association with frontal volume being more marked than with temporal volume. No relationship was found in the other brain areas that were scanned. The findings were not artifacts of chronological age, nor of extreme scores in a small sample.

CONCLUSIONS

These findings are consistent with the hypothesis that failure to develop asymmetry is an important component of the pathology underlying some forms of schizophrenia.

Hemispheric specialization in schizophrenics with perceptual aberration

Higher rates of left-handedness and atypical lateralization in schizophrenics paired with findings of morphological abnormalities in cerebral asymmetry suggest that the normal patterns of hemisphere specialization for processing verbal and spatial information may be anomalous in schizophrenics. The small number of studies that have addressed this question have produced inconsistent findings and varied with subtype diagnosis, gender, type of task employed, task difficulty, and control of handedness. Conflicting research findings also may be due to confounding from the heterogeneity of the schizophrenic construct and variability in clinical symptoms across patients. The present study was designed to control for factors that may have confounded earlier studies. Because the study used perceptual measures, the relationship between symptoms of perceptual aberration and hemisphere advantages was examined using Chapman et al.'s (1978) Perceptual Aberration Scale (PAS). Fifteen male schizophrenic patients and 14 male controls were administered tachistoscopic letter and facial recognition go/no-go reaction time tasks. Left hemisphere advantages were found for both controls and schizophrenics on the letter task. Right hemisphere advantages were found for controls on the facial task but not schizophrenics. Instead, a strong negative correlation was found between schizophrenics' PAS scores and hemisphere advantages (r = -0.685, p < 0.007). Further analysis identified a subgroup of schizophrenics with perceptual aberration who exhibited reversed left hemisphere advantages that increased as the PAS scores increased. Additional research is needed to determine whether this subgroup of schizophrenics constitutes a meaningful subtype with a distinct disease process that disrupts the development of normal cerebral lateralization. The findings provide further evidence for the importance of examining relationships between schizophrenics' performance on cognitive measures and their symptom patterns.

Ventricular enlargement in poor-outcome schizophrenia

BACKGROUND

A subset of patients with schizophrenia, defined on the basis of longitudinal deficits in self-care, may show a classic ("Kraepelinian") degenerative course. An independent validator of the phenomenologically defined Kraepelinian subtype might be provided by a structural indicator of possible brain degeneration: ventricular size as measured by computed tomography (CT).

METHODS

To examine whether Kraepelinian patients would show a differential increase in ventricular size over time, two CT scans were conducted at intervals separated by > 4 years, an average of 5 years. Fifty-three male patients with DSM-III-R diagnoses of chronic schizophrenia were subdivided into Kraepelinian (n = 22; mean age = 42 +/- 6 years) and non-Kraepelinian (n = 31; mean age = 38 +/- 12.2 years) subgroups. Kraepelinian patients were defined on the basis of longitudinal criteria: > 5 years of complete dependence on others for life necessities and care, lack of employment, and sustained symptomatology. Thirteen normal elderly volunteers (mean age = 60 +/- 17.8) were also scanned at 4-year intervals. CT measurements were made by raters without knowledge of subgroup membership. A semiautomated computer program was used to trace the anterior horn, lateral ventricles, and temporal horns for each slice level on which they were clearly seen.

RESULTS

The ventricles showed a bilateral increase in size over the 4-year interval in the Kraepelinian subgroup, more marked in the left hemisphere than the right. By contrast, neither the non-Kraepelinian subgroup nor the normal volunteers showed significant CT changes from scan 1 to scan 2.

CONCLUSIONS

Thus, the longitudinal dysfunctions in self-care that characterize the Kraepelinian patients were associated with an independent indicator of brain abnormality.

Methylazoxymethanol acetate-induced abnormalities in the entorhinal cortex of the rat; parallels with morphological findings in schizophrenia

It has been suggested repeatedly that the non-heritable factors in the pathogenesis of schizophrenia involve abnormalities of prenatal neurodevelopment. Furthermore, post-mortem studies show neuropathology of apparently developmental origin in the entorhinal cortex and other brain regions of schizophrenic subjects. In an attempt to model a developmental defect of the entorhinal region in the rat, cerebrocortical proliferation was briefly interrupted during its earliest stages, when the entorhinal area is thought to undergo major cell division. Specifically, the experimental set-up involved the administration of methylazoxymethanol acetate (MAM) on 1 of 4 consecutive days of embryonal development, from E9 to E12. Analysis of the forebrain in adult animals shows reduction of the entorhinal cortex in rats treated on each of these days. This effect shifts from lateral to medial divisions of the entorhinal cortex with later administration of MAM, following a known developmental gradient. Morphological consequences of MAM administration appear to be largely confined to the entorhinal cortex in the groups treated on E9 to E11, although slight reductions of the frontal and occipital neocortex were also observed in these animals. MAM treatment on E12 produces relatively more widespread damage, as reflected among other in a small reduction of brain weight. The described brain abnormalities are not accompanied by obvious phenotypical changes in any, but the E12-treated group. They, moreover, involve cortical thinning, disorganised cortical layering, and abnormal temporal asymmetries. These finding bare some similarity to observations in brains of schizophrenic subjects. The possible relevance of this approach in modeling neurodevelopmental aspects of schizophrenia is discussed.

Reversal of cerebral asymmetry in schizophrenia measured with magnetoencephalography

It has been suggested that schizophrenic patients fail to develop left-hemisphere dominance because of an early disturbance in neuronal development. This hypothesis has been supported by some post-mortem. CT and magnetic resonance imaging (MRI) studies, while other in-vivo studies have given contradicting results. We used 122-channel whole-head magnetoencephalography and MRI to locate the sources of auditory evoked responses in 19 schizophrenic patients and in 20 healthy controls. Auditory evoked responses were detected in all subjects. The left-right hemisphere asymmetry of cerebral sources for auditory evoked responses was markedly dispersed among patients when compared with controls. The source locations for left auditory cortex were clearly anterior with respect to the right hemisphere in 32% of the patients, while the corresponding prevalence of this abnormal asymmetry was 0% in controls (p = 0.008. Fisher's exact test). The reversed asymmetry appeared to be associated with a shorter anterior-posterior distance between the auditory cortex and the anterior tip of the temporal lobe in the left side when compared with the right side. The reversed asymmetry was associated with higher PANSS general psychopathological score, and especially with higher guilt feelings and motor retardation scores. The large 2.5-fold standard deviation in the inter-hemispheric anterior posterior difference in the location of the auditory cortex among patients (p 0.001 for the difference in the magnitude of variance between controls and patients) clearly reflects the dispersion of the left right asymmetry into both direction, and three of the patients with 'normal asymmetry' had a greater left-right asymmetry than any of the controls. Markedly greater reversal of hemispheric asymmetry among patients implies that regulation of the development of brain asymmetry is disturbed among schizophrenic patients. Abnormality in the cerebral asymmetry may be a crucial factor in the development of schizophrenic disorder in a substantial proportion of patients. The results suggest that the reversed asymmetry is associated with the higher severity of general psychopathological symptoms.

Decreases in peripheral-type benzodiazepine receptors in postmortem brains of chronic schizophrenics

We measured the peripheral-type benzodiazepine receptors (PBRs), a marker of gliosis, in 26 brain areas (cerebral cortex, thalamus and extrapyramidal system) of the postmortem brains of 13 chronic schizophrenics and 10 controls, using [3H] PK 11195 as a ligand for the receptor assay. The specific [3H] PK 11195 binding was significantly decreased in three brain areas (superior parietal cortex, primary visual area and putamen) of schizophrenics, although there were no changes in the binding in the other brain areas. Scatchard analysis revealed that there were decreases in both the Bmax and Kd of [3H] PK 11195 binding in the brain areas. These results were almost in accordance with a number of neuropathological studies reporting that there was no change or reduction in glial cells in the brain regions of schizophrenics and suggested that the decreased density of PBRs in the brain may be involved in the pathophysiology of schizophrenia, associated with reduced production of neurosteroids coupled to PBRs.

Brain torque and sex differences in schizophrenia

The opposing asymmetry of the frontoparietal brain regions has been referred to as 'torque' and may be used as an index of speed of neurodevelopment. It has been recently suggested that torque is minimized in male schizophrenia, reflecting anomalous neurodevelopment. This study examined volumetric and linear torque in a group of 20 schizophrenia patients and 20 healthy individuals; all were right-handed and under the age of 46 years. None of the main or interaction effects on torque were statistically significant, although the sex difference in torque among schizophrenia patients (male larger than female) was more than seven times that in healthy subjects. Torque was significantly associated with years of education and age of illness onset (schizophrenia). These findings support the hypothesis that slowed neurodevelopment may be associated with male schizophrenia and may contribute to earlier age of onset and fewer years of education.

Schizophrenia as a transcallosal misconnection syndrome

Schizophrenic symptoms are conceived as arising from inter-individual variability in the distribution of those fibres that connect asymmetrical regions of the hemispheres related to language. Language (a bihemispheric phenomenon) arose as a result of a genetic change that allowed the two hemispheres to develop with a degree of independence. One component, the phonological output sequence, became localised to the dominant hemisphere, interacting through the corpus callosum with other component functions, including the associated meanings, in the non-dominant hemisphere. Nuclear symptoms are a consequence of failure of segregation of these two functions. This failure is associated with abnormal connectivity between the hemispheres and relates particularly to those regions that are late developing and differ between the sexes.

Does dysplasia cause anatomical dysconnectivity in schizophrenia?

Evidence is reviewed that dysplastic brain development in the second half of pregnancy predisposes to schizophrenia. We suggest that an important corollary of aberrant development at this stage of ontogenesis is abnormal afferentation of the cortical plate, and that this may be macroscopically measurable in terms of abnormal correlational structure in adult brain imaging data. This prediction is tested by analysis of multiple cortical volume measures on magnetic resonance imaging data acquired from 35 male right-handed schizophrenics and 35 matched controls. There are no significant differences between groups in global, intra-hemispheric or inter-hemispheric correlational structure; but schizophrenics are shown to have significantly reduced dependencies between frontal and temporal lobe volumes, and frontal and hippocampal volumes, in the left hemisphere. We conclude that anatomical dysconnectivity (between frontal and temporal cortex) in schizophrenia may be caused by dysplasia.

Frontal lobe of children with schizophrenia spectrum disorders: a proton magnetic resonance spectroscopic study

BACKGROUND

Schizophrenia is commonly considered a neurodevelopmental disorder. Our aim was to determine whether the proton magnetic resonance spectroscopic (1H-MRS) changes seen in adults with schizophrenia are displayed in children at risk for developing schizophrenia.

METHODS

Children with symptoms of schizophrenia-spectrum disorders (n = 16; mean age = 132 months) and a comparison group (n = 12; mean age 130 months) took part in a 1H-MRS study of the left frontal lobe. Areas of peaks from N-acetylaspartate (NAA), choline (Cho), and creatine (Cre) were determined and ratios of NAA/Cre and Cho/Cre calculated and compared between groups.

RESULTS

The mean ratio of NAA/Cre was significantly lower in schizophrenia-spectrum subjects than the comparison group (1.67 vs. 1.92; p < .05). Medication status did not affect results in schizophrenia-spectrum subjects.

CONCLUSIONS

Our findings suggest that the metabolic changes associated with adult schizophrenia are observed in children with some or all of the symptoms of schizophrenia, supporting a neurodevelopmental theory for schizophrenia.

The genetics of schizophrenia: past, present, and future concepts

Although a genetic susceptibility for schizophrenia has been long established and even noted by Kraepelin in 1907, the mechanisms for its inheritance remains unknown. No candidates have proven to be correct and while many weakly positive chromosomal linkages have been reported, none have yet been consistently replicated. The following review examines the present status of these findings. The conclusion is that the field must move on to finding a consistently replicable mutation segregating with schizophrenia in families, before any of the present linkage results can be resolved.

Is schizophrenia the price that Homo sapiens pays for language?

The dichotomy between schizophrenia and manic-depressive illness is, as E. Kraepelin suspected, flawed; no unequivocal separation can be achieved. There are no categories of psychosis, but only continua of variation. However, the definition of nuclear symptoms by K. Schneider reveals the fundamental characteristics of the core syndrome--it is independent of the environment and constant in incidence across populations that have been separated for thousands of years. The associated genetic variation must be as old as Homo sapiens and represent a component of diversity that crosses the population as a whole. The fecundity disadvantage that accompanies the syndrome requires a balance in a substantial and universal advantage; this advantage, it is proposed, is the speciation characteristic of language; language and psychosis have a common evolutionary origin. Language, it is suggested, originated in a critical change on the sex chromosomes (the 'speciation event'--the genetic change that defined the species) occurring in East Africa between 100 and 250 thousand years ago that allowed the two hemispheres to develop with a degree of independence. Language can be understood as bi-hemispheric with one component function--a linear output sequence--confined to the dominant hemisphere--and a second--parallel distributed sampling occurring mainly in the non-dominant hemisphere. This mechanism provides an account of the generativity of language. The significance of nuclear symptoms is that these reflect a breakdown of bi-hemispheric coordination of language, perhaps specifically of the process of 'indexicalisation' (the distinction between 'I' and 'you') of self- versus other-generated references. Nuclear symptoms can be described as 'language at the end of its tether'; the phenomena and population characteristics of the nuclear syndrome of schizophrenia thus yield clues to the origin of the species.

The dysplastic net hypothesis: an integration of developmental and dysconnectivity theories of schizophrenia

Two separate theories that attempt to explain different aspects of schizophrenia have recently attracted much attention. The first, the neurodevelopmental hypothesis, postulates that deviations in early development establish a neuronal phenotype that predisposes to, or, in some versions, determines the later onset of schizophrenia. The second theory proposes that schizophrenic symptoms arise from abnormalities in neuronal connectivity. Here, we suggest that the findings from these two separate lines of inquiry can be integrated into a unitary framework: the dysplastic net hypothesis. In essence, this proposes that anatomical and physiological dysconnectivity of the adult schizophrenic brain is determined by dysplastic fetal brain development. We also indicate how abnormal connectivity between brain regions constituting large-scale neurocognitive networks is expressed in both the prepsychotic and psychotic phases of schizophrenia, and we examine possible risk factors (genetic and environmental) for dysplastic formation of these networks.

The relation of planum temporale asymmetry and morphology of the corpus callosum to handedness, gender, and dyslexia: a review of the evidence

Asymmetry of the planum temporale in relation to handedness, gender, and dyslexia is reviewed. The frequency of rightward asymmetry is rather higher than are estimates of the proportion of right hemisphere speech representation in the general population. Conversely, the frequency of leftward asymmetry is lower than the proportion of the population with left hemisphere speech. Neuro-anatomic asymmetry may relate more to handedness than to language lateralization. There are suggestions that neuroanatomic asymmetry is reduced in females compared to males but the data are inconclusive. Reports concerning handedness and gender differences in callosal structure are conflicting but, as with planum asymmetry, any effect of handedness is as likely to relate to degree as to direction of handedness. It has been reported that the plana are more often symmetrical in size or larger on the right side among dyslexics than controls but this has not always been found. However, greater frequency of atypical (a)symmetry of the planum in dyslexia would be consistent with the absence of a factor which, when present, biases the distribution of planum asymmetry toward the left (and handedness towards the right) as hypothesized by Annett (1985). Studies of the size of the corpus callosum in dyslexia have produced conflicting findings.

Superior temporal gyrus and planum temporale in schizophrenia: a selective review

1. The normal structure of the superior temporal gyrus (STG) has been elucidated from human and non-human primate research. This brain region is structurally complex, contains several distinct cellular regions and the area known as the planum temporale. 2. The STG connects with heteromodal neocortical regions and temporolimbic areas. 3. Functional studies of the normal STG in animals and in humans, using electrophysiology and PET/fMRI, emphasize the STG's role as part of a cortical network important in the interpretation, production and self-monitoring of language. 4. There is evidence for structural abnormalities of the STG in schizophrenia including both volume reductions and disturbances of normal asymmetries. 5. Functional studies of this region in schizophrenic patients, including measurements of evoked potentials and of bloodflow, are abnormal, especially when patients perform language tasks or experience hallucinations. 6. This structural and functional pathology in the STG probably represents one example of a more general disruption in schizophrenia of the neocortical network of which this region is an essential part. This disturbance may be closely associated with the symptoms of formal thought disorder and of auditory hallucinations commonly seen in the disorder.

Lateralized hemispheric dysfunction in the major psychotic disorders: historical perspectives and findings from a study of motor asymmetry in older patients

Differences in functioning between the two cerebral hemispheres have been reported for more than a century. In recent decades, issues related to lateralized dysfunction have been raised in psychiatric illnesses such as schizophrenia and bipolar disorder. In particular, evidence suggests that schizophrenia may be particularly associated with left hemisphere dysfunction and bipolar disorder with right hemisphere dysfunction. We discuss these issues, along with a conceptual framework for integrating hypotheses about the relationship between the major psychotic illnesses based on a two-dimensional continuum. We also present new findings from our study of motor asymmetry in older patients with psychosis that support this framework. Our results indicate that schizophrenia may be associated with left hemisphere pathology to a greater extent than right, whereas the reverse may occur in bipolar disorder.

Ventricular volume and asymmetry in schizotypal personality disorder and schizophrenia assessed with magnetic resonance imaging

Magnetic resonance imaging (MRI) was performed in 12 patients with schizotypal personality disorder (SPD), 11 patients with chronic schizophrenia, and 23 age- and sex-matched normal volunteers. MRI slices were acquired in the axial plane at 1.2-mm intervals, and the ventricles were traced on every other slice. The lateral ventricular system was divided into the anterior horn, temporal horn, and dorsal lateral ventricle. Schizophrenic patients had larger left anterior and temporal horns than the normal volunteers. Size of the left anterior and temporal horn in SPD patients was intermediate between those of normal volunteers and schizophrenic patients and differed significantly from schizophrenic patients. The left-minus-right difference was larger in schizophrenic patients than in normal volunteers or SPD patients. Thus, in their structural brain characteristics, as well as in their clinical symptomatology, SPD patients evidence, in attenuated form, abnormalities resembling those found in full-fledged schizophrenia. The findings suggest that decreased left hemispheric volume, in frontal and temporal regions, may characterize both psychotic and non-psychotic disorders of the schizophrenia spectrum.

Erotomania associated with temporal lobe abnormalities following radiotherapy

OBJECTIVE

The aetiology of primary erotomania is usually discussed in terms of psychological disturbance in the patient. A case associated with demonstrable left temporal lobe abnormalities is described.

CLINICAL PICTURE

An elderly female patient presented with the delusion of being loved by a physician who had treated her previously. She had received radiotherapy to her left periorbital area in childhood. Structural and functional neuroimaging revealed medial temporal lobe damage.

TREATMENT AND OUTCOME

She was treated with haloperidol with moderate improvement in her distress.

CONCLUSIONS

This case illustrates the contribution of both cerebral injury and psychosocial factors in the eventual development of this unusual psychiatric syndrome.

Morphology according to cranial computed tomography of first-episode cycloid psychosis and its long-term-course: differences compared to schizophrenia

Cranial computed tomography (CCT) findings for 37 patients with cycloid psychosis and 19 patients with DSM-III-R schizophrenia were compared with findings for age- and sex-matched controls. Schizophrenic patients showed enlarged ventricles compared both to controls and to patients suffering from cycloid psychosis. In patients with cycloid psychosis, neither at the first episode nor after many years (mean 16.6 years) of disease were significant differences found compared to control subjects. Over the course of the illness, patients with cycloid psychosis showed ventricular enlargement which was correlated with age but not with the duration of illness. The morphological differences provide further evidence for the proposed nosological distinction between cycloid psychosis and schizophrenia.

Reduced auditory P300 amplitude, medial temporal volume reduction and psychopathology in schizophrenia

Twenty-five schizophrenic patients diagnosed by DSM-III-R underwent event-related potentials and magnetic resonance imaging scans. Latency and amplitude of P300 waveform were measured using an auditory odd-ball paradigm. Anterior and posterior volumes of the superior temporal gyrus and medial temporal structure were measured from contiguous coronal images using the level of the mammillary body as an anatomical landmark. Principal component analysis of P300 latency and amplitude disclosed two orthogonal independent factors each: overall latency and residual, and amplitudes from posterior and anterior recordings, respectively. Structural volumes consisted of four orthogonally independent factors: left superior temporal volume, anterior medial temporal volume, right superior temporal volume, and posterior medial temporal volume. The factor score of the P300 amplitude from posterior recordings correlated with the factor score of volumetric changes in the anterior medial temporal structures. The present study failed to replicate a previously reported association between auditory P300 amplitude and superior temporal volume. Furthermore, the factor score of the P300 amplitude was correlated with the severity of clinical ratings of attentional impairments and positive thought disorder. These findings demonstrate that the information processing dysfunction of schizophrenia indicated by reduced P300 amplitude is associated with structural abnormality in the medial temporal lobe.

Alterations in hippocampal non-phosphorylated MAP2 protein expression in schizophrenia

Microtubule-associated proteins (MAPs) are central to the development of normal neuronal cytoarchitecture and have been suggested in previous studies to be altered in schizophrenia. We investigated hippocampal phosphorylated and non-phosphorylated MAP2 expression in schizophrenia in relation to neuronal orientation and interneuronal distance. One paraffin embedded mid-hippocampal block was obtained from each of 8 schizophrenic and 11 control postmortem brains and immunohistochemistry for the phosphorylated and non-phosphorylated forms of MAP2 performed. Within the corona ammonis (CA) subregions and the subiculum, we assessed densitometry readings for non-phosphorylated MAP2-positive neurones (MAP2-NP), and counted the number of neurones immunopositive for phosphorylated MAP2 (MAP2-P). Using image analysis computer software we measured interneuronal distances and neuronal orientation. While there were no overall alterations in densitometric density of MAP2-NP neurones in any hippocampal subregions, we found a left-sided increase in densitometric density of MAP2-NP neurones within the subiculum (F = 8.740, P < 0.021), and the CA1 (F = 7.044, P < 0.033) of schizophrenic subjects which were unrelated to age, postmortem interval or neuroleptic exposure. There was no accompanying alteration of interneuronal distances, neuronal orientation. The findings support previous work demonstrating altered subicular MAP2 expression in schizophrenia and indicate that the finding may be lateralised. However, in contrast to previous investigations, we have demonstrated this alteration in MAP2 expression is due to an increase in the non-phosphorylated form of MAP2, rather than a decrease in total MAP2 expression. These findings suggest that cytoskeletal assembly is abnormal in schizophrenia and generate testable hypotheses regarding the developmental basis of the disorder.

Schizophrenia and autism considered as the products of an agnosic right shift gene

Crow (1995a) has argued that schizophrenia is caused by a gene associated with the evolution of human language and cerebral specialisation. This paper suggests a mechanism for Crow's theory which requires only one new assumption for the right shift genetic model of handedness and cerebral dominance (Annett, 1978). The proposal is that the RS+ allele, whose normal function is to induce the left hemisphere to serve speech by impairing speech-related cortex in the right hemisphere, tends to lose its directional coding. It becomes agnosic (RS+ a) for right versus left and impairs the left or right hemisphere at random. Schizophrenia is likely to develop when the RS+ a gene is paired with a normal RS+ gene but only in the 50% of cases where both hemispheres are affected. In the 50% where RS+ a affects the right hemisphere, development is normal as in the RS+ RS+ genotype. The risks for schizophrenia in monozygotic and dizygotic twins and other relatives are as expected for 50% expression of a Mendelian gene which is paired with a particular allele, but not alternative alleles at the same locus. The frequency of homozygotes for the agnosic gene is about 4 in 10,000, the rate observed for autism. A random pattern of double hemisphere deficits would give scope for a range of developmental strengths and weaknesses as observed within the spectrum of autistic disorders. Tests of the model require brain-imaging studies sensitive to individual differences in hemisphere lateralisation and a search for a genetic locus with human and nonhuman primate alleles, together with a mutant of the human form with a frequency of about 2%.

Schizophrenia as a chronic active brain process: a study of progressive brain structural change subsequent to the onset of schizophrenia

Brain structural deviation is known to be present in chronic patients with schizophrenia when compared with normal age-matched individuals. While the assumption is that these differences are based on a neurodevelopmental disturbance, whether they are static or continue to change throughout the disease process remains unknown. The following report describes a prospective follow-up study of first episode cases of schizophrenic illness. Analyses of MRI evaluations on an approximate annual basis for a minimum of four years are presented on 50 patients and 20 controls. Computer-assisted image analysis measuring the volume of several brain regions, using the program ANALYZE (Mayo Clinic), was performed on all scans. Patients were compared with controls for the rate of change over time in size of structures. No differences were found for the volumes of the caudate nucleus, temporal lobes, or hippocampus; and no changes in the degree of cerebral laterality were detected. However, there was a significant difference in the rate of change in the overall volumes of left and right hemispheres (P < 0.0004 and 0.001, respectively), right cerebellum (P < 0.02) and area of the isthmus of the corpus callosum (P < 0.05). The left cerebral ventricle had significantly greater enlargement over time when measured on coronal slice sequences (P < 0.02), but was not detected by axial views. These findings suggest that a subtle active brain process may be continuing through the first few years of a schizophrenic illness causing greater than the normal adult cortical deterioration. Further studies using other methods of image analysis and over a longer period of time are needed to determine the course and nature of this biologic process.

Schizophrenia in people with intellectual disability: the role of pregnancy and birth complications

The literature suggests that mental illness is more common in people with intellectual disability than in the general population. Having reviewed the literature, Turner (1989) [Psychological Medicine 19, 301-14] suggested that about 3% of people with intellectual disability also have schizophrenia. As pregnancy and birth complications (PBCs) occur more commonly in people with intellectual disability than in the general population and are also implicated in the aetiology of schizophrenia, it is possible that these conditions share a common aetiology. This study reports on the occurrence of PBCs in those people with intellectual disability who develop schizophrenia. Fifty people with intellectual disability and schizophrenia were matched for age, sex, degree of intellectual disability and presence of epilepsy with a control group who did not suffer from schizophrenia or a schizophreniform psychosis. The obstetric history was obtained and events rated on a scale specifically designed for this study. This PBCs scale consists of six sub-scales covering areas of general maternal health, pregnancy, delivery, medication in labour, total medication score and neonatal score, as well as an overall total score. The study found that people with intellectual disability who develop schizophrenia have significantly higher rates of PBCs than controls. All of the sub-scales on the PBCs scale were significantly higher in people with schizophrenia, with the exception of the medication scales. Only five out of the 50 people with schizophrenia had not had a major obstetric complication, compared to 13 subjects from the control group. A number of abnormalities were specifically higher in people who later developed schizophrenia. These included: abnormally long or short labour; maternal episiotomy; maternal preeclamptic toxaemia; induction of labour; dysmaturity; maternal smoking in pregnancy; and a delay in neonatal crying. The results suggest that PBCs are important in the aetiology of schizophrenia in people with intellectual disability.

Brain morphometric comparison of first-episode schizophrenia and temporal lobe epilepsy

BACKGROUND

Converging evidence has suggested that the abnormalities in brain morphology observed in schizophrenia are similar to those seen in temporal lobe epilepsy (TLE). The purpose of this study was to compare the features of these groups directly with measures of the brain using magnetic resonance (MR) morphometry.

METHOD

Morphometric measures of ventricular and hippocampal volumes obtained from FLASH MR images were studied in 32 patients with first-episode schizophrenia (FES), 39 patients with TLE (21 left, 18 right), and 42 healthy controls.

RESULTS

Ventricular volumes in the FES and TLE groups were both significantly larger that those seen in controls and did not differ from each other. The FES group showed significantly larger temporal horns, while the TLE group had relatively larger frontal horns. Analyses of hippocampal volumes revealed a significant group by hemisphere effect. The FES group showed relative reductions in left hippocampal volume that were comparable only to TLE patients with seizures originating from the left hemisphere.

CONCLUSION

The results indicate that FES and TLE groups both show evidence of ventricular enlargement. Lateralised morphological abnormalities of the hippocampal formation in FES and left TLE are comparable, and may be specific to temporolimbic regions.

Cortical abnormality in schizophrenia: an in vivo application of the gyrification index

To investigate the hypothesis that patients with schizophrenia exhibit gross cortical abnormalities of developmental origin, we utilized the gyrification index (GI) (ratio of inner to outer cortical contours), a measure of overall cortical folding, in an in vivo magnetic resonance imaging study of young, strongly right-handed male patients and controls. The two groups did not differ with respect to whole-brain volume, age, or handedness. In an examination confined to the left hemisphere, mean GI values were significantly reduced in the patient group in both anterior and posterior regions. Neither age nor length of illness were found to be significant predictors of GI variance in the patients group, suggesting that GI reductions do not result from an ongoing atrophic process. Rather, these results are consistent with the hypothesis of neurodevelopmental abnormalities in schizophrenia that result in an overall reduction in cortical folding.