Postmortem evidence of structural brain changes in schizophrenia. Differences in brain weight, temporal horn area, and parahippocampal gyrus compared with affective disorder

Anatomical abnormalities in the brains of monozygotic twins discordant for schizophrenia

Recent neuroradiologic and neuropathological studies indicate that at least some patients with schizophrenia have slightly enlarged cerebral ventricles and subtle anatomical abnormalities in the region of the anterior hippocampus. Using magnetic resonance imaging (MRI), we studied 15 sets of monozygotic twins who were discordant for schizophrenia (age range, 25 to 44 years; 8 male and 7 female pairs). For each pair of twins, T1-weighted contiguous coronal sections (5 mm thick) were compared blindly, and quantitative measurements of brain structures were made with a computerized image-analysis system. In 12 of the 15 discordant pairs, the twin with schizophrenia was identified by visual inspection of cerebrospinal fluid spaces. In two pairs no difference could be discerned visually, and in one the twin with schizophrenia was misidentified. Quantitative analysis of sections through the level of the pes hippocampi showed the hippocampus to be smaller on the left in 14 of the 15 affected twins, as compared with their normal twins, and smaller on the right in 13 affected twins (both P less than 0.001). In the twins with schizophrenia, as compared with their normal twins, the lateral ventricles were larger on the left in 14 (P less than 0.003) and on the right in 13 (P less than 0.001). The third ventricle also was larger in 13 of the twins with schizophrenia (P less than 0.001). None of these differences were found in seven sets of monozygotic twins without schizophrenia who were studied similarly as controls. We conclude that subtle abnormalities of cerebral anatomy (namely, small anterior hippocampi and enlarged lateral and third ventricles) are consistent neuropathologic features of schizophrenia and that their cause is at least in part not genetic. Further study is required to determine whether these changes are primary or secondary to the disease.

Left handedness in an identical twin discordant to his co-twin for handedness and schizophrenia, with neurological and psychometric evidence of left hemisphere damage

A left handed, monozygotic, male twin developed schizophrenia, whilst his right handed brother was free of psychopathology. There was no family history of mental illness or left handedness. The affected twin had left side motor weakness and an EEG showed scattered irregularities, particularly on the left. Psychometry indicated left sided tempero-parietal dysfunction. The relationship between left temporal lobe damage and schizophrenia is considered.

Psychiatry and the frontal lobes

The frontal lobes of the brain have long been regarded as enigmatic in their function and perhaps should be considered even more so in states of dysfunction. Observed associations between structural lesions and psychiatric symptoms and the demonstration of disturbed function and morphology in the frontal lobes of individuals suffering from major psychiatric disorders have led to increased interest in this brain area. Psychiatrists have been particularly concerned with seeking the aetiogenesis of common diagnostic entities and this article attempts to synthesize the available facts. A brief overview of relevant biological data precedes a description of methods of neuropsychological testing and the clinical features arising from frontal lobe damage. A discussion of the role of the frontal lobes in some aspects of personality function follows. Neuropsychiatric features associated with known frontal lobe pathology are described, prefacing a discussion of those psychiatric conditions where an aetiological role for frontal lobe dysfunction has been proposed.

Unification of the findings in schizophrenia by reference to the effects of gestational zinc deficiency

The hypothesis presented here suggests that schizophrenia is caused by the action of gestational zinc deficiency on genetically susceptible foetuses. The psychosis seen is suggested to be due to a combination of dietary or otherwise induced zinc deficiency and lack of zinc releasing capacity in the hippocampus. A non genetic but transmissable immune defect is suggested to be relevant to psychosis and to the nonmendelian pattern of inheritance of the disorder.

Notes from the graveyard: neuropathology and schizophrenia

Schizophrenia is commonly regarded as a 'functional' psychosis, the implication being that the delusions, hallucinations and cognitive impairment characteristic of the disease have no organic basis. This view is due in no small way to the failure of pathologists to find convincing pathological changes associated with the disease in the first seven decades of the century. Over the last 10 years things have changed considerably. Recent CT and MRI scan studies have provided convincing evidence of significant ventricular enlargement in the brains of schizophrenics and post-mortem studies have shown that schizophrenic brains are about 6% lighter than controls and have a reduced volume and reduced antero-posterior length. Planimetric studies on post-mortem material and a recent MRI study show that medial temporal lobe structures (parahippocampal gyrus, hippocampus and amygdala) are preferentially affected. Although other brain regions (e.g. cingulate gyrus, frontal cortex) also show alterations they appear to be 'downstream' from the regions primarily affected. Morphological studies show that there is a loss of neurons from medial temporal lobe structures and indicate irregularities in their cytoarchitectonic arrangement. The alterations in structure are not associated with degenerative, inflammatory, or abnormal vascular processes. There has been much debate as to the possible causes of the structural changes and whether they are limited to particular 'types' or sub-groups of schizophrenics. At present it seems simpler to suppose that all schizophrenics have a degree of structural abnormality which may differ in degree but not in kind. It has been proposed that the changes in brain structure in schizophrenia are the result of an anomaly of brain development. In the last year CT and MRI studies have shown that ventricular enlargement precedes clinical symptoms and is not progressive. These studies support the developmental interpretation. Future studies will need to focus on (a) the mechanisms (probably genetic) which can cause such developmental anomalies, (b) the neurochemical perturbations occurring as a result of such anomalies and (c) how both relate to clinical symptoms.

Reduced temporal lobe areas in schizophrenia: preliminary evidences from a controlled multiplanar magnetic resonance imaging study

Seventeen young patients with relapsing schizophrenia and 13 normal controls matched for age, gender, and educational level underwent magnetic resonance imaging (MRI) scans. Three sagittal, eight axial, and seven coronal images were obtained for all subjects. Schizophrenic patients showed a reduction of brain tissue in the temporal lobes. Among the several brain structures identified, left temporal lobe area, but not ventricular brain ratio (VBR), discriminated between the two groups. As VBR has been reported to be increased in the more severe forms of schizophrenia, temporal lobe abnormalities may characterize the less severe cases of schizophrenia.

Quantitative autoradiographic analysis of glutamate binding sites in the hippocampal formation in normal and schizophrenic brain post mortem

Using quantitative autoradiography, the anatomical distribution of the binding sites (kainate, N-methyl-D-aspartate and quisqualate) for the excitatory neurotransmitter glutamate has been established in the hippocampal formation from control and schizophrenic brains, post mortem. There is a loss of the kainate subtype particularly in schizophrenic hippocampi mainly from the CA4/CA3 mossy fibre termination zone of the cornu ammonis (CA4 and CA3; control and schizophrenic left hippocampus, respectively, 54.2 and 66.6 pmol/g; 18.3 and 17.9 pmol/g), as well as bilateral losses in the dentate gyrus (left 14.2 pmol/g and right 28.0 pmol/g; left 9.5 pmol/g and right 7.9 pmol/g, control and schizophrenic, respectively) and parahippocampal gyrus (left 50.8 pmol/g and right 41.7 pmol/g, left 27.7 pmol/g and right 25.3 pmol/g, control and schizophrenic, respectively). There is complete preservation of N-methy-D-aspartate sites in schizophrenic hippocampi, and a marginally significant loss of the quisqualate binding site in CA4/CA3 regions (left 249 fmol/g and right 306 fmol/g, left 157 fmol/g and right 148 fmol/g, control and schizophrenic, respectively). These findings reflect the possible importance of glutamate in the pathophysiology of schizophrenia and represent novel targets for therapeutic manipulation in schizophrenia.

Reduced GABA uptake sites in the temporal lobe in schizophrenia

The binding of [3H]nipecotic acid, a ligand for labelling GABA uptake sites in brain, was measured in left and right frontal cortex, polar temporal cortex, hippocampus and amygdala from control and schizophrenic postmortem brains. In schizophrenic brains, single concentration [3H]nipecotic acid binding was reduced bilaterally in amygdala and hippocampus and on the left side only in polar temporal cortex. These data suggest that GABA neurones are involved in the cerebral atrophy of schizophrenia and, in agreement with other studies, that this process is most pronounced in left temporal cortex.

Monoclonal antibodies to study the brain in schizophrenia

Twelve monoclonal antibodies were developed which show selective reactivity with brain tissue homogenates from 4 patients with schizophrenia compared to 4 normal controls. Certain antibodies were more reactive with tissue from cases with schizophrenia, others with control tissue. Patterns of reactivity also depended on brain region tested. Differences in reactivity generally ranged from 2- to as much as 8-fold. This panel of monoclonal antibodies may be useful to investigate the pathophysiology of schizophrenia.

Beyond the dopamine hypothesis. The neurochemical pathology of schizophrenia

The dopamine hypothesis still provides a valuable approach to the study of schizophrenia and its treatment by drugs. Although the neuroleptic drugs appear to act via an inhibition of dopamine receptors, measurements of dopamine metabolites in vivo, or of the transmitter and its receptors in post-mortem brain tissue, do not provide unequivocal evidence of a hyperactivity of dopaminergic neurotransmission in the disease. Nevertheless, increased dopamine function might be a consequence of a primary neuronal abnormality in another system. Recent imaging studies and neuropathological reports suggest that, in some patients, there may be a deficit and/or disturbance of neurons in certain temporal limbic regions, and this is supported by some neurochemical investigations, particularly of neuropeptide and amino-acid transmitter systems. A loss of such neurons could conceivably lead to a disinhibition of limbic dopamine neurons, providing the means whereby neuroleptic drug treatment might ameliorate the effects of a neuronal deficit in schizophrenia.

Gross and Histological Criteria for Developmental Disorders in Brains of Schizophrenics

Autopsy findings and examination of histological sections from 12 schizophrenic patients and from age-matched, non-schizophrenic controls were enlarged and confirmed our previous study. Four subgroups were differentiated with gross abnormalities, in most cases with asymmetry of the temporal sulcal gyral pattern. Two types of macroscopical deviations are described. Different periods of developmental termination, concerning the sulcal gyral pattern of the temporal lobe, suggest a period in which the disturbance of the development originated which coincides with a probably genetically-induced disturbed migration in the entorhinal region toward the end of the fifth month. It is thought that the parahippocampal or entorhinal area develops differently, space- and time-wise. This may explain why migratory disturbances particularly occur in this precisely limited area. The findings in the ventral insular area are discussed, together with factors which also suggest a developmental disorder.

Shape analysis of the middle cranial fossa of schizophrenic patients. A computerized tomographic study

Recent morphometric studies indicate that both right and left temporal lobe volumes are reduced in schizophrenic patients. Subsequent studies suggested that this volumetric reduction is the result of focal or multifocal gray matter abnormalities. Since in early life brain growth or lack thereof influences the overlying skull configuration, we attempted to elucidate the time of onset of the temporal lobe lesion in schizophrenic patients by quantifying both the volume and shape of their middle cranial fossa. Computerized tomographic scans of 17 schizophrenic patients and an equal number of age-matched controls were digitized using a LOATS image analysis system. The middle cranial fossa was manually outlined and software routines allowed the quantification of volume and shape parameters. Our results showed that no significant differences were present between schizophrenic patients and controls. If the bilateral reduction in temporal lobe volumes in schizophrenic patients is the result of an early onset (e.g., developmental) lesion, the resultant foci of gray matter abnormality may occur distant to the base of the skull. Alternatively, tissue loss may be insufficient to alter the development of the overlying skull or to be detected by our methods.

Frontal cortical and left temporal glutamatergic dysfunction in schizophrenia

Glutamatergic mechanisms have been investigated in postmortem brain samples from schizophrenics and controls. D-[3H]Aspartate binding to glutamate uptake sites was used as a marker for glutamatergic neurones, and [3H]kainate binding for a subclass of postsynaptic glutamate receptors. There were highly significant increases in the binding of both ligands to membranes from orbital frontal cortex on both the left and right sides of schizophrenic brains. The changes are unlikely to be due to antemortem neuroleptic drug treatment, because no similar changes were recorded in other areas. A predicted left-sided reduction in D-[3H]aspartate binding was refuted at 5% probability, but not at 10%. Previously reported high concentrations of dopamine in left amygdala were strongly associated with low concentrations of D-[3H]aspartate binding in left polar temporal cortex in the schizophrenics. The findings are compatible with an overabundant glutamatergic innervation of orbital frontal cortex in schizophrenia. The results also suggest that schizophrenia may involve left-sided abnormalities in the relationship between temporal glutamatergic and dopaminergic projections to amygdala.

Temporal lobe structure as determined by nuclear magnetic resonance in schizophrenia and bipolar affective disorder

Temporal lobe structure has been assessed by magnetic resonance imaging in groups of patients with schizophrenia (n = 21) bipolar affective disorder (n = 20) and normal controls (n = 21). In the temporal lobe area a significant (p less than 0.05) diagnosis by side interaction was present, the area being less on the left than on the right side in patients with schizophrenia in contrast to findings in the two other groups. Lateral ventricular and temporal horn area did not distinguish the groups as a whole. However, there was a significant (p less than 0.05) relationship between lateral ventricular area and poor outcome, and in an analysis confined to males, patients with schizophrenia (n = 15) were found to have significantly (p less than 0.05) enlarged temporal horns.

Gender differences in the brain: are they relevant to the pathogenesis of schizophrenia?

Gender differences are present in the clinical expression of schizophrenia, age of onset, course of illness, and response to pharmacologic treatment. These differences are not surprising in view of the normal gender differences in brain growth, differentiation, adult brain structure, and neurochemistry. The present review examines what is presently known about brain gender differences, and whether this information is consistent with the published reports of brain functional and morphological abnormalities in schizophrenia. Whether gender differences in the brain can explain the gender differences in clinical aspects of the disorder remains unknown.

Increased temporal lobe glucose use in chronic schizophrenic patients

Temporal lobe glucose metabolic rate was assessed in 21 off-medication patients with schizophrenia and 19 normal controls by positron emission tomography with 18F-deoxyglucose. Patients with schizophrenia had significantly greater metabolic activity in the left than the right anterior temporal lobe, and the extent of this lateralization was in proportion to the severity of psychopathology.

Correlations between abnormal auditory P300 topography and positive symptoms in schizophrenia: a preliminary report

P300 component amplitude in the left temporal scalp region, shown in three previous studies to differentiate normals from schizophrenics, was found to be significantly correlated with the Thought Disorder Index (TDI) and the Scale for the Assessment of Positive Symptoms (SAPS). These correlations occurred primarily in the P300 waveform derived from the Goodin paradigm. These findings suggest a brain processing disturbance in positive symptom schizophrenia that may be reflected by electrophysiological abnormalities detectable in the temporal scalp region.

Hand preference in psychotic twins

In an attempt to replicate the influential study of Boklage (1977), hand preference for writing was examined in a new series of 30 monozygotic (MZ) and 30 dizygotic (DZ) twin pairs in whom the proband had suffered a functional psychosis. In contrast to the original report, no increased rate of left-handedness was found in MZ compared to DZ twins, or psychotic compared with nonpsychotic twins. In particular, no relationship between within-pair left-handedness and discordance for psychosis emerged. Possible reasons for the disagreement between the two studies are examined.

P300 abnormality in schizophrenic subtypes

P300 and other long latency event-related potentials were recorded in 65 schizophrenic subjects and results were compared to findings in 119 healthy controls. Highly significant differences in P300 latency and amplitude were found between the two groups. Forty six per cent of schizophrenics had P300 latency more than two standard deviations longer than the mean for controls, 35% had a P300 amplitude smaller than the mean for controls by the same amount, and 24% were more than two standard deviations outside the mean for controls on both measures. These differences were independent of chronicity of illness, clinical subtype, family psychiatric history or the effects of neuroleptic medication. They confirm that P300 abnormality is present as a stable trait in a high proportion of schizophrenics. The status of abnormal P300 as a biological vulnerability factor for major mental illness is discussed.

Spatiotemporal memory and rate of forgetting in acute schizophrenics

Some schizophrenics show anomalies in the frontal and temporal lobes. It is uncertain whether the cognitive deficits shown by Type I schizophrenics are caused directly by such anomalies, or by a deficit in the exertion of attentional effort. In this study, 16 acute schizophrenics, who broadly fitted the Type I characterization and their controls were given a battery of cognitive tests. The patients were impaired on effort-demanding tasks such as the Wisconsin Card Sorting Test, a verbal fluency test and the WAIS, which are susceptible in varying degrees to frontal, temporal and parietal lobe lesions. Patients were not disproportionately impaired, however, on a test of temporal memory and another of spatial memory, an impairment pattern that selectively reflects frontal and medial temporal lobe lesions respectively, nor were they impaired on a rate of forgetting task sensitive to medial temporal lobe lesions. These tasks were chosen not only because performance on them is selectively sensitive to frontotemporal lobe lesions, but also because it seems to depend on exerting minimum amounts of attentional effort. It is tentatively concluded that the cognitive deficits shown by Type I schizophrenics are caused by a problem in exerting attentional effort of unknown origin.

Neuroanatomical studies of major affective disorders. A review and suggestions for further research

Interest in the long-neglected neuropathology of major affective disorders has recently been rekindled, partly because of the emergence of brain-imaging techniques. We review the literature suggesting that attention be given to the neuroanatomy and neuropathology of primary and secondary affective disorders. Computerised tomography studies show that patients with affective disorders tend to be similar to schizophrenic patients and significantly different from normal control subjects in ventricle:brain ratio, sulcal widening, and cerebellar vermian atrophy. As yet, there are few neuropathological investigations of the brains of patients with primary affective disorders. Suggestions for further research in the neuropathology of affective disorders are offered.

Towards a neuropsychology of schizophrenia

A viable neuropsychology of schizophrenia requires, first, that signs and symptoms be understood in terms of underlying psychological processes and, second, that these underlying processes be related to brain systems. We propose that the negative signs of schizophrenia reflect a defect in the initiation of spontaneous action, while the positive symptoms reflect a defect in the internal monitoring of action. The spontaneous initiation of action depends upon brain systems linking the prefrontal cortex and the basal ganglia. Internal monitoring, carried out in the hippocampus, of spontaneous action, depends upon links between the prefrontal cortex and the hippocampus via the parahippocampal cortex and the cingulate cortex.

Limbic pathology in schizophrenia: the entorhinal region--a morphometric study

The volume of the entorhinal region is significantly reduced in postmortem brains of schizophrenics compared with controls (p less than 0.017). In addition, a significant reduction of neurons (p less than 0.017), but no significant increase in absolute glial cell numbers, is found. These results are consistent with the hypothesis that structural changes in the medial temporal lobe of schizophrenics may be developmental in origin.

A neurodiagnostic approach to schizophrenia

This article presents the perspective that cognitive and sensorimotor abnormalities are as much a part of the pathology of schizophrenia as are the symptoms. It is hypothesized that all these features cluster together in recognizable patterns. The proximate mechanisms of the abnormalities are proposed to involve anatomical and chemical lesions in a variety of locations in the brain. The functioning of widely distributed neuronal systems is thus interrupted. An approach to the assessment and interpretation of neurocognitive abnormalities is outlined. Distinct deficits require differential rehabilitation strategies.

Agenesis of the corpus callosum and schizophrenia: a case report

Clinical, radiological and neuropsychological findings in the first reported case of schizophrenia with complete agenesis of the corpus callosum are described. Although causal inferences were made difficult by the co-existence of a left frontotemporal cyst and a family history of affective disorder, some theories of the role of callosal dysfunction in schizophrenia require revision in the light of this case.

P300 in schizophrenia: confirmation and statistical validation of temporal region deficit in P300 topography

Comparison of normal and medicated schizophrenic groups on the auditory P300 component of the event-related potential confirmed our earlier finding of a left temporal deficit in P300 amplitude in schizophrenia. A difference in P300 topography between groups was evident in both color mapping and in grand-averaged waveforms, which was statistically validated by the presence of a group-by-scalp region interaction (p less than 0.05). The left temporal area in schizophrenics was denoted as the region of greatest deficit and of maximal statistical separation (p less than 0.05) relative to normals by t statistic mapping (SPM), Hotelling's T-squared "protected" contrasts of individual scalp regions, and the relative ratio of left scalp amplitudes to right scalp amplitudes. The left temporal scalp region yielding maximal group separation in the previous study also statistically separated the schizophrenic group from the normal group. This feature correctly differentiated 9 of 11 schizophrenics and 7 of 9 controls. These findings are compatible with other histological, metabolic, and electrophysiological studies suggesting temporal lobe abnormality in schizophrenia.

Differentiation of schizophrenics and normal controls is enhanced by the Goodin subtraction procedure

The P300 event-related potential as calculated by the Goodin subtraction procedure (P300g) combines attentive and inattentive condition waveforms in order to isolate components specifically related to target stimulus processing. The waveform was compared with the more commonly employed unsubtracted P300 waveform associated with attended infrequent stimuli (P300ia). The P300g produced the largest overall schizophrenic and control group differences in mean integrated amplitude compared with the P300ia. A group by scalp region interaction in the P300g, indicative of group topographic alterations, was also noted which was not present in the unsubtracted P300ia. Furthermore, the P300g pinpointed the single best scalp region (left temporal) for maximal group separation. This temporal asymmetry was found to originate in the inattentive condition waveforms, indicating a possible abnormality in "nonvoluntary" processing. We conclude that combining attentive and inattentive condition waveforms to form the P300g enhanced clinically relevant group differences between schizophrenics and normals compared with the P300ia.

Bilateral brain dysfunction during motor activation in type II schizophrenia measured by EEG mapping

In this final electroencephalographic (EEG) mapping study of our series on motor dysfunction in neuroleptic-treated schizophrenic patients, we studied 10 right-handed patients with marked negative symptomatology [type II; raw score on the SANS (Munich version) 31.4 +/- 5.1]. Simple and multisensorimotor tasks involving both the dominant and nondominant hand were used for cortical activation. All tasks were referred to resting states obtained after specially designed relaxation procedures. In contrast to predominantly type I patients (SANS-MV score 12.3 +/- 4.9) of our previous EEG mapping studies, we found for resting states minor evidence (only) of increased power values in the frequency bands delta and theta. Furthermore, in contrast to signs of "left hemisphere dysfunction" and possible "compensatory right hemisphere overactivation" during motor tasks, which we discussed previously for our type I patients, we found for the type II schizophrenics a bilateral brain dysfunction. This consisted of "nonreactivity" in all frequency bands except alpha, in which, on the contrary, a "hyperreactivity" seemed to be present. In combination with evidence of bilateral hemispheric dysfunction in type II patients reported by other authors using EEG, evoked potentials, regional cerebral blood flow (rCBF) and magnetic resonance imaging (MRI) methods, this suggests that marked bilateral brain dysfunction may be correlated in schizophrenia with a clinical syndrome corresponding rather to the "negative pole" of the positive-negative dimension. In contrast, "left hemisphere dysfunction" and "signs of compensatory overactivation" seem to be linked more to a "positive" symptomatology. Finally, discrepancies of our EEG mapping and rCBF findings during motor activity suggest, speculatively, "uncoupling" between electrical and circulatory parameters in schizophrenia involving both hemispheres in type II, and predominantly the left hemisphere in type I, patients.

Is there gliosis in schizophrenia? Investigation of the temporal lobe

Recent studies have described two indicators of pathology in the schizophrenic brain--gliosis and atrophy. The degree of gliosis in the temporal lobe of groups of schizophrenics (with demonstrable atrophy), affectives, and controls was quantified using immunocytochemical techniques and computer-assisted densitometry. Twenty areas within the temporal lobe were assessed. Our data showed no evidence of increased gliosis in the schizophrenic group compared to controls and affectives. This extends and replicates our previous findings, demonstrating that the atrophy/aplasia in schizophrenia is not associated with pathologically significant gliosis. Our observations are consistent with other studies, suggesting that the structural change in schizophrenic brains is due to an embryonic insult or developmental anomaly of an, as yet, undetermined nature.

Altered relationships between metabolic rates of glucose in brain regions of schizophrenic patients

Regional brain glucose metabolism was studied with positron emission tomography (PET) in healthy volunteers (n = 9) and schizophrenic patients (n = 15). The patients were in an acute phase of the disease and drug free. Cerebral metabolic rate with 11C-glucose as the tracer (CMRgl) was determined in both cortical and subcortical structures. In the healthy volunteers significant correlations were found between metabolic rates of some regions, but no relationships were found between CMRgl of limbic cortical areas and that of neocortical or subcortical structures. In the patients, high and significant positive correlations were found between metabolic rates in the neocortical areas, the limbic cortical areas and the subcortical areas. The results indicate differences in the neuronal interplay between regions of healthy and schizophrenic subjects. It is proposed that neuronal systems guiding the specificity and diversity in neuronal functions between different brain regions, are abnormal in schizophrenic patients. Such a disturbance may be the basis for the diversity of psychiatric symptoms in schizophrenics.

Mutation and psychosis: a suggested explanation of seasonality of birth

The persistence of psychosis at a high and relatively constant prevalence in the various populations of the world is rendered difficult to explain by the absence of identified environmental precipitants and by reduced fertility of affected individuals. The problem is not confined to schizophrenia but applies also to affective disorder. The 'virogene' concept attempts to explain this paradox as follows. (1) Psychosis in general is, as suggested by Böök (1953) and Lewis (1958) for schizophrenia, associated with a high rate of mutation. (2) The new mutations occur at a specific site (a 'hot-spot') in the genome and consist of rearrangements (e.g. transpositions or new insertions occurring as a result of unequal recombination) in a sequence which has a degree of potential autonomy, i.e. an integrated pathogen or 'virogene'. (3) The mutations occur specifically in the courses of gametogenesis in the male. By its location in the scrotal sac and its extended time course, gametogenesis in the male is susceptible to insertional mutagenesis as a function of variations in environmental temperature. Such temperature-dependent mutations are reflected in the seasonality of birth seen in both schizophrenic and affective illnesses. The increased likelihood of such mutations occurring with time is held to account for the association of psychosis with increased paternal age. (4) Such new events are held responsible not only for 'sporadic' cases in individuals without a family history of psychosis, but also for increases in severity of illness between generations. Psychosis is viewed as a continuum extending from unipolar through bipolar affective disorder and schizoaffective illness to schizophrenia with increasing degrees of defect.(ABSTRACT TRUNCATED AT 250 WORDS)

The dopamine hypothesis survives, but there must be a way ahead

Karl Popper has taught us that no hypothesis can be regarded as proved-merely as having survived the most stringent tests which have so far been devised. Dinan makes a further attempt to overthrow the dopamine hypothesis of the mechanism of the antipsychotic effect, and provides an alternative suggestion. As one time critic and later advocate of the theory, I think he underestimates its explanatory power and capacity for survival. I doubt that his alternative yet poses a serious challenge. I propose below a second (and perhaps more idiosyncratic) alternative. I do not claim it yet has the explanatory power of the dopamine theory, but I think it generates some new approaches.

Selective decreases in MAO-B activity in post-mortem brains from schizophrenic patients with type II syndrome

The activities of the A and B forms of the enzyme monoamine oxidase (MAO, E.C. 1.4.3.4) have been assessed with the substrates 5-hydroxytryptamine and benzylamine respectively in seven areas of the brains of 39 patients with schizophrenia and 44 control subjects. Whereas previous studies have found the enzyme unchanged in brain in schizophrenia, in this study there was a modest but significant decrease in the activity of MAO-B in frontal and temporal cortices and in amygdala. This decrease could not be accounted for by neuroleptic medication, age, sex or post-mortem variables. In a series of 22 patients who had been assessed in life, the reduction in MAO-B activity was found to be associated specifically with the presence of negative symptoms (flattening of affect and paucity of speech). The findings are therefore consistent with other evidence for structural and neurochemical change in the temporal lobe that have been associated with the type II (defect state) syndrome of schizophrenia. The change in enzyme activity is unlikely to be related to a change in monoamine metabolism but may reflect a disturbance in glial function. The change in MAO-B activity in brain in this study is confined to particular areas of brain and a subgroup of patients; it is thought to be entirely unrelated to earlier reports of reductions of enzyme activity in platelets, which are probably attributable to prolonged neuroleptic medication.

Pathology, phenomenology and the dopamine hypothesis of schizophrenia

The dopamine hypothesis of schizophrenia implies that positive schizophrenic symptoms should be understandable by reference to brain structures receiving a dopamine innervation, or in terms of the functional role of dopamine itself. The basal ganglia, ventral striatum, septo-hippocampal system, and prefrontal cortex, sites of mesotelencephalic dopamine innervation, are examined and it is argued that their dysfunction could form the basis of particular schizophrenic symptom classes. The postulated involvement of dopamine in reinforcement processes might further assist such interpretations. This type of analysis can be extended to other categories of schizophrenic psychopathology.

Late positive component amplitude in schizophrenics and alcoholics in two different paradigms

Abstinent alcoholics, unmedicated schizophrenics, and controls were tested in two paradigms designed to elicit the late positive component. Experiment A used frequent stimuli of differing incentive value and Experiment B used infrequent stimuli of differing perceptual discriminability. Alcoholics and schizophrenics showed late positive components that were significantly reduced in amplitude compared to controls. The patient groups were similar in their late component amplitudes. Control subjects showed a substantially wider response range than the patient groups. The narrow response range in both patient groups was manifested in diminished late component amplitudes to both stimuli in both experiments. The intraclass correlation coefficient of late component amplitudes for both patient groups was significantly greater than that of the controls.

Hypofrontality in schizophrenia: a review of the evidence

This paper reviews the possible role of frontal lobe dysfunction in the pathophysiology of schizophrenia. Pathological, computerized axial tomography (CAT) scan and magnetic resonance imaging (MRI) studies have indicated that a substantial number of schizophrenic patients show structural abnormalities in the frontal lobe areas and other parts of the brain. In some cases, these changes can be correlated with negative symptoms. Attempts to study frontal lobe function with neuropsychological tests, topographic EEG, cerebral blood flow (CBF) and positron emission tomography (PET) scans have also indicated that a substantial number of schizophrenics show abnormalities compared to normal controls. However, these abnormalities can be seen to some degree in other conditions. As well, patients early in the course of their illness tend not to show frontal lobe functional abnormalities. The implications of these findings for current theories of schizophrenia are discussed.

Neuroleptic-induced parkinsonism in older schizophrenics

The association of neuroleptic drug-induced parkinsonism (DIP) with factors related to brain structure and function are poorly understood. Twenty-one medicated schizophrenics over age 55 years were evaluated for parkinsonism, tardive dyskinesia, psychiatric symptoms, ventricular/brain ratio (VBR), and neuropsychological function. Sixteen (76%) of the patients had DIP, whereas 10 (48%) had tardive dyskinesia. Increased severity of parkinsonism was significantly associated with larger VBR and the severity of negative symptoms. Severity of parkinsonism predicted poor visual-spatial function, whereas negative symptoms were modestly predictive of impairment in both verbal ability and cognitive flexibility. These findings suggest that brain atrophy may be a risk factor for DIP. The pattern of cognitive dysfunction associated with DIP in this sample is similar to that found in idiopathic Parkinson's disease. Dopaminergic dysfunction may underlie the pattern of pathology described in this report.