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

Hippocampal underactivation in an fMRI study of word and face memory recognition in schizophrenia

Schizophrenia is a major mental disorder which is characterized by several cognitive deficits. Investigations of the neural basis of memory dysfunctions using neuroimaging techniques suggest that the hippocampus plays an important role in declarative memory impairment. The goal of this study was to investigate possible dysfunctions in cerebral activation in schizophrenic patients during both word and face recognition memory tasks. We tested 22 schizophrenics and 24 controls matched by gender, age, handedness and parental socioeconomic status. Compared to healthy volunteers, patients with schizophrenia showed decreased bilateral hippocampal activation during word and face recognition tasks. The whole brain analysis also showed a pattern of cortical and subcortical hypoactivation for both verbal and non-verbal recognition. This study provides further evidence of hippocampal involvement in declarative memory impairments of schizophrenia.

Conception season and cerebral asymmetries among American baseball players: implications for the seasonal birth effect in schizophrenia

People with schizophrenia and children born with neural tube defects both tend to be conceived most often in May-June, about a month before the summer solstice, and least often in November-December, a month before the winter solstice. Such timings, coupled with evidence of cerebral asymmetry deficits in schizophrenia, and evidence that asymmetry development and neural tube closure represent concurrent fourth-embryonic-week processes both sensitive to oxidant stress, led us to the hypothesis that pro-oxidant sunlight actions capable of affecting the mother's blood could result in a peri-June peak of inhibition and a peri-December peak of facilitation of both processes. Here, using birth and hand preference data from baseball statistics, we tested the hypothesis's prediction that, as a group representing minimal cerebral lateralization, left-handed players would show the same conception rhythm as that observed in the above disorders. We found that not only strict left-handers (those both batting and throwing left) were most often conceived in May-June but that also strict right-handers and other players denoting more extreme levels of cerebral lateralization were most often conceived in November-December.

Superior temporal gyrus volume change in schizophrenia: a review on region of interest volumetric studies

Imaging studies of schizophrenia (SCZ) have repeatedly demonstrated volume differences in superior temporal gyrus (STG) and its subregions. Among them, some studies employed the Region of Interest (ROI) method. We carried out a systematic review of the published literature on STG volumetry MRI studies to examine the potential of ROI method for identifying specific structural differences and correlations with clinical variables including hallucinations and thought disorder symptoms in SCZ. Forty-six studies were identified as suitable for review and analysis including 1444 patients with SCZ and 1327 controls. Female and left-handed subjects are under-represented in the literature and insight from sex and handedness differences may be lost. Thirty-five studies reported significant differences in STG or subregional volumes including bilateral or unilateral ROI, and volume reduction was the most common change in SCZ. Thirty studies reported correlations between volume changes and clinical symptoms or syndromes and 18 found positive results. Among them, left STG or subregions appear to be more involved in the generation of hallucinations and thought disorder than right side. The majority of five follow-up studies found evidence of progressive changes in volumes. Clinical heterogeneity, MRI acquisition parameters, anatomical landmarks for ROI, and sample characteristics, are likely to be the main factors leading to heterogeneous results. Clearly this research links pathophysiological changes in the STG with the development of hallucinations and thought disorder in patients with SCZ, especially in the left side. There is a suggestion that these changes may be progressive but this requires more thorough and comprehensive assessment.

Schizophrenia and epilepsy: is there a shared susceptibility?

Individuals with epilepsy are at increased risk of having psychotic symptoms that resemble those of schizophrenia. More controversial and less searched is if schizophrenia is a risk factor for epilepsy. Here we review overlapping epidemiological, clinical, neuropathological and neuroimaging features of these two diseases. We discuss the role of temporal and other brain areas in the development of schizophrenia-like psychosis of epilepsy. We underline the importance of ventricular enlargement in both conditions as a phenotypic manifestation of a shared biologic liability that might relate to abnormalities in neurodevelopment. We suggest that genes implicated in neurodevelopment may play a common role in both conditions and speculate that recently identified causative genes for partial complex seizures with auditory features might help explain the pathophysiology of schizophrenia. These particularly include the leucine-rich glioma inactivated (LGI) family gene loci overlap with genes of interest for psychiatric diseases like schizophrenia. Finally, we conclude that LGI genes associated with partial epilepsy with auditory features might also represent genes of interest for schizophrenia, especially among patients with prominent auditory hallucinations and formal thought disorder.

Application of a multifractal analysis to study brain white matter abnormalities of schizophrenia on T2-weighted magnetic resonance imaging

Multifractal analysis provides a precise quantitative description of the structural complexity of white matter (WM) on magnetic resonance imaging (MRI). To test this new technique as an aid to elucidating the pathology of schizophrenia, we examined a multifractal dimension (i.e. Deltaalpha) of WM in schizophrenia patients and their relations to clinical variables. We examined 16 patients with schizophrenia and 16 controls matched for age, sex and handedness. Delta alpha value of WM in the prefrontal and frontoparietal lobes and the corpus callosum (genu and splenium) on T2-weighted MRI was calculated. Delta alpha was not significantly different between groups in either region of interest. However, group-by-side interaction for Deltaalpha was found in the frontoparietal WM; post-hoc analysis revealed normal left dominant asymmetry in Deltaalpha for frontoparietal WM in control subjects, which was absent in schizophrenia patients. Furthermore, the patients with schizophrenia had a lower asymmetry coefficient ([R-L]/[R+L]) for Deltaalpha in frontoparietal WM. Relations to clinical symptoms from the Positive and Negative Syndrome Scale, Deltaalpha in corpus callosum, and the asymmetry coefficient in prefrontal WM were correlated with negative and general psychopathology symptom scores. Our results support the left-sided dysfunction hypothesis of schizophrenia and its relation to schizophrenic symptoms. Multifractal analysis reveals abnormal patterns of WM structures in schizophrenia that could be implicated in the disorder's etiology.

Schizophrenia as failure of left hemispheric dominance for the phonological component of language

Background

T. J. Crow suggested that the genetic variance associated with the evolution in Homo sapiens of hemispheric dominance for language carries with it the hazard of the symptoms of schizophrenia. Individuals lacking the typical left hemisphere advantage for language, in particular for phonological components, would be at increased risk of the typical symptoms such as auditory hallucinations and delusions.

Methodology/Principal Findings

Twelve schizophrenic patients treated with low levels of neuroleptics and twelve matched healthy controls participated in an event-related potential experiment. Subjects matched word-pairs in three tasks: rhyming/phonological, semantic judgment and word recognition. Slow evoked potentials were recorded from 26 scalp electrodes, and a laterality index was computed for anterior and posterior regions during the inter stimulus interval. During phonological processing individuals with schizophrenia failed to achieve the left hemispheric dominance consistently observed in healthy controls. The effect involved anterior (fronto-temporal) brain regions and was specific for the Phonological task; group differences were small or absent when subjects processed the same stimulus material in a Semantic task or during Word Recognition, i.e. during tasks that typically activate more widespread areas in both hemispheres.

Conclusions/Significance

We show for the first time how the deficit of lateralization in the schizophrenic brain is specific for the phonological component of language. This loss of hemispheric dominance would explain typical symptoms, e.g. when an individual's own thoughts are perceived as an external intruding voice. The change can be interpreted as a consequence of “hemispheric indecision”, a failure to segregate phonological engrams in one hemisphere.

Inverse relationship between adult hippocampal cell proliferation and synaptic rewiring in the dentate gyrus

Adult neurogenesis is a key feature of the hippocampal dentate gyrus (DG). Neurogenesis is accompanied by synaptogenesis as new cells become integrated into the circuitry of the hippocampus. However, little is known to what extent the embedding of new neurons rewires the pre-existing network. Here we investigate synaptic rewiring in the DG of gerbils (Meriones unguiculatus) under different rates of adult cell proliferation caused by different rearing conditions as well as juvenile methamphetamine treatment. Surprisingly, we found that an increased cell proliferation reduced the amount of synaptic rewiring. To help explain this unexpected finding, we developed a novel model of dentate network formation incorporating neurogenesis and activity-dependent synapse formation and remodelling. In the model, we show that homeostasis of neuronal activity can account for the inverse relationship between cell proliferation and synaptic rewiring.

Diffusion tractography of the fornix in schizophrenia

BACKGROUND

White matter fiber tracts, especially those interconnecting the frontal and temporal lobes, are likely implicated in pathophysiology of schizophrenia. Very few studies, however, have focused on the fornix, a compact bundle of white matter fibers, projecting from the hippocampus to the septum, anterior nucleus of the thalamus and the mamillary bodies. Diffusion Tensor Imaging (DTI), and a new post-processing method, fiber tractography, provides a unique opportunity to visualize and to quantify entire trajectories of fiber bundles, such as the fornix, in vivo. We applied these techniques to quantify fornix diffusion anisotropy in schizophrenia.

METHODS

DTI images were used to evaluate the left and the right fornix in 36 male patients diagnosed with chronic schizophrenia and 35 male healthy individuals, group matched on age, parental socioeconomic status, and handedness. Regions of interest were drawn manually, blind to group membership, to guide tractography, and fractional anisotropy (FA), a measure of fiber integrity, was calculated and averaged over the entire tract for each subject. The Doors and People test (DPT) was used to evaluate visual and verbal memory, combined recall and combined recognition.

RESULTS

Analysis of variance was performed and findings demonstrated a difference between patients with schizophrenia and controls for fornix FA (p=0.006). Protected post-hoc independent sample t-tests demonstrated a bilateral FA decrease in schizophrenia, compared with control subjects (left side: p=0.048; right side p=0.006). Higher fornix FA was statistically significantly correlated with DPT and measures of combined visual memory (r=0.554, p=0.026), combined verbal memory (r=0.647, p=0.007), combined recall (r=0.516, p=0.041), and combined recognition (r=0.710, p=0.002) for the control group. No such statistically significant correlations were found in the patient group.

CONCLUSIONS

Our findings show the utility of applying DTI and tractography to study white matter fiber tracts in vivo in schizophrenia. Specifically, we observed a bilateral disruption in fornix integrity in schizophrenia, thus broadening our understanding of the pathophysiology of this disease.

The volumes of the fornix in schizophrenia and affective disorders: a post-mortem study

Structural and functional pathology of limbic structures including the hippocampus are frequently replicated in schizophrenia. Although the fornix is the main afferent system of the hippocampus to the septal nuclei and the hypothalamus (especially the mammillary bodies), relatively few studies have investigated structural changes of the fornix in schizophrenia. We measured the volume of the fornix in post-mortem brains in 19 patients with schizophrenia, 9 patients with bipolar disorder, 7 patients with unipolar depression, and 14 control subjects by planimetry of serial sections. The volumes, the mean cross-sectional areas, and the anterior to posterior distances of the fornix did not differ among patients with schizophrenia, bipolar disorder, unipolar depression, and control subjects. No lateralization existed between the right and the left fornices in among patients in the diagnostic groups and the control subjects. The fornix does not show morphometrical abnormalities in patients with schizophrenia, bipolar disorder and unipolar depression compared with control subjects, which might indicate that the fornix is not a primary focus of structural changes in these diseases.

Tract-specific analysis of the superior occipitofrontal fasciculus in schizophrenia

Diffusion tensor imaging has been highlighted as a non-invasive tool to explore neural connectivity in vivo. Several studies have suggested disorganization of the neural network (circuitry) including the thalamo-prefrontal connection in schizophrenia. Recent research using post-mortem brains showed that the superior occipitofrontal fasciculus (SOFF) fibers extended to the thalamus. We postulated that the SOFF has some relationship with the anatomical structural components of the thalamo-prefrontal circuitry. We quantitatively assessed the diffusion abnormalities of the SOFF using diffusion tensor tractography (DTT) in schizophrenia. Nineteen male patients with schizophrenia and 20 age-matched normal controls were studied. DTT of the SOFF (DTT-SOFF) was visualized using free software (dTV II/VOLUME-ONE), and we performed tract-specific measurement of the fractional anisotropy (FA), then calculated the apparent diffusion coefficient (ADC) of the DTT-SOFF. Tractography and tract-specific analysis of the SOFF were successfully performed in all subjects. All tracts appeared to be connecting the prefrontal area to the thalamus. The mean FA value of patients with schizophrenia [0.376 (S.D. 0.030)] was significantly lower than that of controls [0.432 (S.D. 0.032)], and the ADC value of patients with schizophrenia [0.771 (x10(-3) mm(2)/s) (S.D. 0.041)] was significantly higher than that of controls [0.726 (x10(-3) mm(2)/s) (S.D. 0.027)]. Our results suggest that the so-called SOFF may be a structural component connecting the prefrontal area to the thalamus and that it is deteriorated in schizophrenia.

Altered metabolic integrity of corpus callosum among individuals at ultra high risk of schizophrenia and first-episode patients

BACKGROUND

The disconnectivity hypothesis as part of the neurodevelopmental model of schizophrenia states that an abnormality in brain development causing impaired corticocortical or interhemispheric connectivity leads to cognitive deficits and symptoms of the illness. Previous studies showed the altered morphology of corpus callosum in patients with schizophrenia. We investigated the metabolic integrity of corpus callosum of individuals at ultra high risk (UHR) of developing schizophrenia and first-episode patients.

METHODS

We studied 17 individuals at UHR of developing schizophrenia, 14 first-episode schizophrenia patients, and 30 healthy control subjects. We measured the absolute concentrations of neurometabolites and T2 relaxation time of tissue water (T2(B)) in the genu region of corpus callosum by using proton magnetic resonance spectroscopy.

RESULTS

N-acetylaspartate (NAA) concentrations were decreased and T2(B) values were prolonged in the UHR cases as well as in the first-episode patients, compared with the control subjects. The difference between the NAA concentrations of the UHR cases and first-episode patients was also significant. The NAA concentrations of the UHR cases and first-episode patients were correlated with the severity of negative symptoms.

CONCLUSIONS

We demonstrated the disrupted metabolic integrity of corpus callosum among individuals at UHR of schizophrenia and the first-episode patients.

Reduced cortical inhibition in first-episode schizophrenia

Disturbances in cortico-cortical and cortico-subcortical circuits in schizophrenia have been described by previous neuroimaging and electrophysiological studies. Transcranial magnetic stimulation (TMS) provides a neurophysiological technique for the measurement of cortical excitability, especially of the motoneural system. Previous studies using paired-pulse TMS to investigate short-interval cortical inhibition (SICI) and intracortical facilitation (ICF), mainly involving chronic schizophrenia patients, have been inconsistent and only one study in first-episode patients has been conducted so far. We assessed SICI (interstimulus interval, ISI, 3 milliseconds, ms) and ICF (ISI 7 ms) in 29 first-episode schizophrenia patients (FE-SZ) with limited exposure to antipsychotic treatment against measures of 28 healthy controls (HC). Amplitudes of motor evoked potentials (MEPs) were measured from the left and right first dorsal interosseus muscle (FDI). The conditioning stimulus was set at 80% intensity of resting motor threshold (RMT) and the test stimulus (TS) was set at an intensity that produced an MEP amplitude of about 1 mV. For SICI conditions, FE-SZ demonstrated significantly higher MEP amplitudes from left motor cortex (right FDI) compared to HC, and for MEPs from right motor cortex (left FDI) a similar trend was observable (FE-SZ 41% vs. HC 21% of TS, p=0.017 for left motor cortex, and FE-SZ 59% vs. HC 31% of TS, p=0.059 for right motor cortex; Mann-Whitney U-test). No significant difference in MEPs could be detected for ICF on either hemisphere. In addition, there was no difference in left and right RMT comparing patients and control subjects. Our result of a reduced SICI in a large sample of well characterized first-episode schizophrenia patients suggests that a GABAergic deficit may be involved in schizophrenic pathophysiology, already early in the disease course, supporting the intracortical dysconnectivity hypothesis.

Handedness and schizotypal features in healthy subjects

BACKGROUND

An excess of mixed-handedness has been repeatedly reported in schizophrenia and schizotypy. Handedness is a measure of atypical cerebral lateralization, which is considered as a risk factor for schizophrenia. Several studies have attempted to identify correlations between handedness and dimensions of psychosis but the results obtained so far remain inconclusive.

OBJECTIVE

To explore a possible link between mixed-handedness and the three classical dimensions of psychosis. As speech and language disorders may be associated with cerebral lateralization, we predicted a correlation between mixed-handedness and disorganized dimension.

METHODS

We used the Schizotypal Personality Questionnaire (SPQ) and the Edinburgh Handedness Inventory (EHI) to study the correlation between mixed-handedness scores and positive, negative or disorganized dimensions in a sample of 62 healthy subjects.

RESULTS

We found a negative correlation between mixed-handedness and the disorganized dimension of schizotypy, as individuals with prominent mixed-handedness showed more severe disorganization.

CONCLUSION

We have identified a link between mixed-handedness and the disorganized dimension that may help to identify genetic vulnerability factors involved in psychosis.

Middle-ear disease and schizophrenia: case-control study

BACKGROUND

One hundred years ago psychiatrists thought that ear disease could cause insanity by irritation of the brain. Current understanding of the role of the temporal lobes in schizophrenia and their proximity to the middle ear supports this hypothesis.

AIMS

To establish the rate of middle-ear disease pre-dating the onset of schizophrenia.

METHOD

Eighty-four patients with schizophrenia were each matched to four non-psychiatric controls by age, gender and season of birth. History of ear disease was obtained from general practice records. Additional information on symptoms was collected for participants in the case group, who also had audiometry.

RESULTS

The odds ratio of recorded middle-ear disease pre-dating schizophrenia was 3.68 (95% CI 1.86-7.28). This excess was particularly marked on the left (OR=4.15, 95% CI 2.08-8.29). Auditory hallucinations were associated with middle-ear disease but not with hearing loss.

CONCLUSIONS

There is an association between middle-ear disease and schizophrenia which may have aetiological significance.

Craddock & Owen vs Kraepelin: 85 years late, mesmerised by "polygenes"

The case for replacing the binary Kraepelinian system with a continuum concept originated with Kraepelin [Kraepelin, E. (1920) Die Erscheinungsformen des Irreseins (translated by H Marshall as: Patterns of mental disorder. In: Themes and Variations in European Psychiatry. Eds S.R. Hirsch & M. Shepherd. Wright, Bristol, pp7-30, l974). Zeitschrift Gesamte Neurologie Psychiatrie, vol. 62, 1-29.], and is based upon studies of familial aggregation and phenomenology. Craddock and Owen's [Craddock, N.J., Owen, M.J. (2007) Rethinking psychosis: the disadvantages of a dichotomous classification now outweigh the advantages. World Psychiatry 6: 20-27.] claim for the "beginning of the end for the Kraepelinian dichotomy" on the basis of linkage and association is undermined by un-replicability of findings across studies (Crow, T.J. (2007) How and why genetic linkage has not solved the problem of psychosis: review and hypothesis. American Journal of Psychiatry, 164, 13-21). Absence of evidence of linkage is consistent with the concept that the variation is epigenetic in form rather than DNA sequence-based. But what are the dimensions that underly the continuum? The BBC Internet survey (Peters, M., Reimers, S., Manning, J.T. (2006) Hand preference for writing and associations with selected demographic and behavioral variables in 255,100 subjects: the BBC internet study. Brain and Cognition 62, 177-189), reinforces the concept that lateralisation is a major and sex-dependent dimension of human variation in verbal and spatial ability: twin studies indicate that inter-individual variation in dominance for language is epigenetic and the paternal age effect can be similarly explained. Thus an epigenetic imprint, arising in relation to the sapiens specific torque and persisting over one or two generations is a better fit to the genetics of the psychotic continuum than Craddock and Owen's elusive "polygenic" variations.

Schizophrenia, "Just the Facts": what we know in 2008 part 1: overview

For every disorder, there is a set of established findings and accepted constructs upon which further understanding is built. The concept of schizophrenia as a disease entity has been with us for a little more than a century, although descriptions resembling this condition predate this conceptualization. In 1988, for the inaugural issue of Schizophrenia Research, at the invitation of the founding editors, a senior researcher, since deceased (RJ Wyatt) published a summary of generally accepted ideas about the disorder, which he termed "the facts" of schizophrenia. Ten years later, in conjunction with two of the authors (MSK, RT), he compiled a more extensive set of "facts" for the purpose of evaluating conceptual models or theoretical constructs developed to understand the nature of schizophrenia. On the 20th anniversary of this journal, we update and substantially expand our effort to periodically summarize the current body of information about schizophrenia. We compile a body of seventy-seven representative major findings and group them in terms of their specific relevance to schizophrenia -- etiologies, pathophysiology, clinical manifestations, and treatments. We rate each such "fact" on a 0-3 scale for measures of reproducibility, whether primary to schizophrenia, and durability over time. We also pose one or more critical questions with reference to each "fact", answers to which might help better elucidate the meaning of that finding for our understanding of schizophrenia. We intend to follow this paper with the submission to the journal of a series of topic-specific articles, critically reviewing the evidence.

The concept of progressive brain change in schizophrenia: implications for understanding schizophrenia

Kraepelin originally defined dementia praecox as a progressive brain disease, although this concept has received various degrees of acceptance and rejection over the years since his famous published textbooks appeared. This article places an historical perspective on the current renewal of Kraepelin's concept in brain imaging literature that supports progressive brain change in schizophrenia from its earliest stages through its chronic course. It is concluded that a great deal of future research is needed focusing on the longitudinal course of change, the extent to the regions of change within each individual and the underlying mechanism and implications of brain change through functional and neurochemical imaging, combined with structural studies in the same individuals.

fMRI study of language activation in schizophrenia, schizoaffective disorder and in individuals genetically at high risk

BACKGROUND

Structural and functional abnormalities have been found in language-related brain regions in patients with schizophrenia. We previously reported findings pointing to differences in word processing between people with schizophrenia and individuals who are at high-risk for schizophrenia using a voxel-based (whole brain) fMRI approach. We now extend this finding to specifically examine functional activity in three language related cortical regions using a larger cohort of individuals.

METHOD

A visual lexical discrimination task was performed by 36 controls, 21 subjects at high genetic-risk for schizophrenia, and 20 patients with schizophrenia during blood oxygenation level dependent (BOLD) fMRI scanning. Activation in bilateral inferior frontal gyri (Brodmann's area 44-45), bilateral inferior parietal lobe (Brodmann's area 39-40), and bilateral superior temporal gyri (Brodmann's area 22) was investigated. For all subjects, two-tailed Pearson correlations were calculated between the computed laterality index and a series of cognitive test scores determining language functioning.

RESULTS

Regional activation in Brodmann's area 44-45 was left lateralized in normal controls, while high-risk subjects and patients with schizophrenia or schizoaffective disorder showed more bilateral activation. No significant differences among the three diagnostic groups in the other two regions of interest (Brodmann's area 22 or areas 39-40) were found. Furthermore, the apparent reasons for loss of leftward language lateralization differed between groups. In high-risk subjects, the loss of lateralization was based on reduced left hemisphere activation, while in the patient group, it was due to increased right side activation. Language ability related cognitive scores were positively correlations with the laterality indices obtained from Brodmann's areas 44-45 in the high-risk group, and with the laterality indices from Brodmann's areas 22 and 44-45 in the patient group.

CONCLUSIONS

This study reinforces previous language related imaging studies in high-risk subjects and patients with schizophrenia suggesting that reduced functional lateralization in language related frontal cortex may be a vulnerability marker for schizophrenia. Future studies will determine whether it is predictive of who develops illness.

Quantitative proton MR spectroscopy findings in the corpus callosum of patients with schizophrenia suggest callosal disconnection

BACKGROUND AND PURPOSE

The callosal disconnectivity theory was previously proposed to explain the pathophysiology of schizophrenia. The goal of this study was to investigate the metabolic integrity of the corpus callosum in patients with schizophrenia by proton MR spectroscopy.

MATERIALS AND METHODS

Twelve first-episode and 16 chronic patients meeting the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for schizophrenia and 28 age- and sex-matched control subjects were enrolled in the study. We measured the absolute concentrations of neurometabolites and T2 relaxation times of tissue water (T2B) in the genu of the corpus callosum by using the internal water-reference method. The severity of symptoms in patients was rated by means of psychopathology scales. Differences in neurometabolite concentrations and T2B values between the patients and control subjects were assessed. We also investigated the correlation of metabolite concentrations with the severity of symptoms.

RESULTS

N-acetylaspartate (NAA) concentrations were significantly lower in the first-episode as well as in chronic patients, compared with respective control subjects (P < .001). NAA concentrations in the first-episode and chronic patient groups were negatively correlated with both the Brief Psychiatry Rating Scale and the Scale for Assessment of Negative Symptoms scores (P < .001). There was a significant negative correlation between the NAA concentrations and the Scale for Assessment of Positive Symptoms scores in all patients (P = .028). T2B values were significantly higher in the patients, compared with the control subjects (P < .001).

CONCLUSION

Decreased NAA concentration in the corpus callosum correlates with psychopathology in schizophrenia. This finding, together with prolonged T2B values of the corpus callosum, supports the previously proposed callosal disconnection theory concerning the pathophysiology of schizophrenia.

The role of white matter for the pathophysiology of schizophrenia

Inter- and intra-hemispheric connectivity disturbances have been suggested to play a major role in schizophrenia. To this extent, diffusion weighted imaging (DWI) is a relatively new technique examining subtle white matter microstructure organization. DWI studies in schizophrenia strongly suggest that white matter communication is disrupted. This supports the hypothesis that there is a cortico-cortical and transcallosal altered connectivity in schizophrenia, which may be relevant for the pathophysiology and the cognitive disturbances of the disorder. Future longitudinal diffusion and functional imaging studies targeting brain communication together with genetic investigations should further characterize white matter pathology in schizophrenia and its relevance for the development of the illness.

Callosal misconnectivity and the sex difference in psychosis

The sex difference in age of onset in schizophrenia is paradoxical in the sense that the brain is developing faster in females but onsets are earlier in males. Therefore if schizophrenia, as widely believed, is a disorder of development, the difference is in the wrong direction. Here we attempt to resolve the paradox with the hypothesis that psychosis is an anomaly of development of cerebral asymmetry and the following assumptions: (1) asymmetry (the torque) confers directionality on the 'language circuit'--failure to develop asymmetry leads to the risk of reverse transmission, a putative mechanism of psychotic symptoms; (2) the corpus callosum goes on developing in an antero-posterior direction into the third and fourth decades of life; (3) a sex difference in structure and development of the corpus callosum (with some anterior components greater in males and posterior components greater in females) reflects stronger, faster lateralization in females; (4) because of the inverse relationship between asymmetry and interhemispheric connections, females, by developing faster, avoid the misconnectivity phenomena in the frontal lobes that males, developing more slowly, may encounter at a younger age with particular risk of negative symptoms.

Cerebral atrophy and white matter disruption in chronic schizophrenia

Several magnetic resonance imaging (MRI) studies have shown cerebral atrophy in established schizophrenia, although not in all reports. Discrepancies may mostly be due to population and postprocessing differences. Recently, disruption of cortical white matter integrity has also been reported in chronic patients with schizophrenia. In this study we explored tridimensional (3D) cerebral volumes and white matter microstructure in schizophrenia with structural and diffusion magnetic resonance. Twenty-five patients with established schizophrenia and 25 1:1 matched normal controls underwent a session of MRI using a Siemens 1.5T-scanner. 3D brain volume reconstruction was performed with the semi-automatic software Amira (TGS, San Diego, CA), whereas the apparent diffusion coefficients (ADCs) of cortical white matter water molecules were obtained with in-house developed softwares written in MatLab (The Mathworks-Inc., Natick, MA). Compared to controls, patients with schizophrenia had significantly smaller gray matter intracranium and total brain volumes, increased 4th ventricle volumes, and greater temporal and occipital ADCs. Patients treated with typical antipsychotic medication (N = 9) had significantly larger right lateral and 4th ventricles compared to those on atypical antipsychotic drugs. Intracranial volumes significantly inversely correlated with left temporal ADC in patients with schizophrenia. Also, age correlated directly with right, left, and 3rd ventricle volumes and inversely with gray matter intracranium volumes in individuals with schizophrenia. This study confirmed the presence of cortical atrophy in patients with schizophrenia, especially in those on typical antipsychotic drugs, and the existence of white matter disruption. It also suggested that physiological aging effects on brain anatomy may be abnormally pronounced in schizophrenia.

Asymmetry in dopamine D(2/3) receptors of caudate nucleus is lost with age

Molecular and functional imaging techniques reveal evidence for lateralization of human cerebral function. Based on animal data, we hypothesized that asymmetry in dopamine neurotransmission declines during normal aging. In order to test this hypothesis, we measured dopamine D2/3 receptor availability with [18F]desmethoxyfallypride-PET (DMFP) in putamen and caudate nucleus (NC) of 21 healthy, right-handed males (24-60 years; 35+/-10). For volumetric analysis, high-resolution T1-weighted MR-images were obtained in 18 of the PET-subjects in order to assess possible age-related decreases in NC and putamen volume. The calculated DMFP binding potentials (BP) showed a right-ward asymmetry in NC of young subjects that decreased with age (r = 0.577, p = 0.006; Pearson correlation; two-tailed). An age-independent analysis showed a right-ward asymmetry in NC of the whole subject group (left: 1.49+/-0.35; right: 1.65+/-0.43 [mean+/-S.D.]; p = 0.020). No such side lateralization or age-effects could be found in the putamen. Volumes tended to be asymmetric in the putamen (right: 4.85+/-0.56 cm3; left: 4.64+/-0.86 cm3 [mean+/-S.D.]; p = 0.063), but not in NC. The decline of putamen volume during aging was significant in the right putamen (r = -0.613; p = 0.007; Pearson correlation; two-tailed). There were no other significant correlations between striatal volumes and age or BP. Because ventral striatal dopamine neurotransmission is involved in cognitive processes, this loss of physiological asymmetry in NC dopamine transmission during aging might be involved in age-related declines of cognitive performance.

Mixed handedness is associated with the Disorganization dimension of schizotypy in a young male population

Within the ASPIS (Athens Study of Psychosis Proneness and Incidence of Schizophrenia) we sought out to examine in accordance with previous reports if a deviation from dextrality is associated with an augmented endorsement of self rated schizotypal personality traits in a large population of 1129 young male army recruits. Schizotypal traits were assessed using the Schizotypal Personality Questionnaire and hand preference membership was determined by applying stringent criteria derived from the Annett Handedness Questionnaire and the Porac-Coren questionnaire of lateral preferences. By adopting three different definitions of hand preference membership, we confirmed an association between mixed handedness and increased schizotypal personality traits, and in particular with Disorganization schizotypy that encompasses aspects of self perceived difficulties in verbal communication. Non-verbal cognitive ability, as indexed by measurement of non-verbal IQ, sustained attention and working memory was not associated with hand preference. We argue that a deviation from normal cerebral lateralization, as indexed by mixed handedness, is associated with mild sub clinical language dysfunction, rather than non-verbal cognitive ability, and this might be relevant to the expression of psychosis phenotype.

Morphologic alterations of the parcellated superior temporal gyrus in schizophrenia spectrum

Morphologic abnormalities of the superior temporal gyrus (STG) as well as its sub-regions such as Heschl's gyrus (HG) or planum temporale (PT) have been reported in schizophrenia patients, but have not been extensively studied in schizotypal subjects. In the present study, magnetic resonance images were acquired from 65 schizophrenia patients, 39 schizotypal disorder patients, and 72 healthy controls. Volumetric analyses were performed using consecutive 1-mm coronal slices on the temporal pole (TP) and superior temporal sub-regions [planum polare (PP), HG, PT, rostral STG, and caudal STG]. The HG was significantly smaller in schizophrenia patients compared with controls but not in schizotypal patients, while volume reductions of the left PT and bilateral caudal STG were common to both disorders. The TP gray matter was larger in female schizotypal patients compared with female schizophrenia patients. There were no significant group differences in the PP and rostral STG volume. In the subgroup of early phase schizophrenia patients (illness duration <1.0 year), smaller volumes for the left PP and rostral STG were correlated with hallucinations and delusions. Our findings suggest that morphologic changes in the posterior regions of the STG are common to the schizophrenia spectrum, whereas less involvement of the HG, and possibly the PP and rostral STG might be related to the sparing of schizotypal patients from developing overt psychosis.

Hippocampal and parahippocampal volumes in schizophrenia: a structural MRI study

Smaller medial temporal lobe volume is a frequent finding in studies of patients with schizophrenia, but the relative contributions of the hippocampus and three surrounding cortical regions (entorhinal cortex, perirhinal cortex, and parahippocampal cortex) are poorly understood. We tested the hypothesis that the volumes of medial temporal lobe regions are selectively changed in schizophrenia. We studied 19 male patients with schizophrenia and 19 age-matched male control subjects. Hippocampal and cortical volumes were estimated using a three-dimensional morphometric protocol for the analysis of high-resolution structural magnetic resonance images, and repeated measures ANOVA was used to test for region-specific differences. Patients had smaller overall medial temporal lobe volumes compared to controls. The volume difference was not specific for either region or hemisphere. The finding of smaller medial temporal lobe volumes in the absence of regional specificity has important implications for studying the functional role of the hippocampus and surrounding cortical regions in schizophrenia.

Decreased numerical density of kainate receptor-positive neurons in the orbitofrontal cortex of chronic schizophrenics

We utilised postmortem brain tissue to quantify sections of left and right orbitofrontal cortex (area 11) from nine schizophrenic and eight control patients from the Charing Cross Prospective Schizophrenia Study immunostained for the presence of the kainate receptor (GluR5/6/7). The numerical density of neurons immunopositive for kainate receptor was measured. Other sections from the same blocks were stained with cresyl violet to determine the total neuronal numerical density. All measurements were made blind: diagnoses were only revealed by a third party after measurements were completed. There was a significant reduction (21%) in numerical density of kainate receptor-positive neurons in both cortices in the schizophrenic group (488 cells/mm2) compared to that in the control group (618 cells/mm2) (P=0.033). Nissl-stained tissue showed no significant difference in total neuronal numerical density between control and schizophrenic groups. These observations suggest that there are actually fewer kainate receptor-positive neurons in schizophrenic orbitofrontal cortex. There was no correlation of reduced kainate receptor-positive cell number with age at death, postmortem interval, or other possibly confounding neuropathology. Our results support the concept of there being reduced glutamatergic activity in frontal cortex in schizophrenia.

Neuroprotective effects of olanzapine in a rat model of neurodevelopmental injury

Recent clinical studies have suggested that treatment with atypical antipsychotic drugs, such as olanzapine, may slow progressive changes in brain structure in patients with schizophrenia. To investigate the possible neural basis of this effect, we sought to determine whether treatment with olanzapine would inhibit the loss of hippocampal neurons associated with the administration of the excitotoxin, kainic acid, in neonatal rats. At post-natal day 7 (P7), rats were exposed to kainic acid via intracerebroventricular administration. Neuronal loss within the CA2 and CA3 subfields of the hippocampus and neurogenesis within the dentate gyrus of the hippocampus were then assessed at P14 by Fluoro-Jade B and BrdU labeling, respectively. Daily doses of olanzapine (2, 6, or 12 mg/day), haloperidol (1.2 mg/kg), melatonin (10 mg/kg), or saline were administered between P7 and P14. Melatonin is an anti-oxidant drug and was included in this study as a positive control, since it has been observed to have neuroprotective effects in a variety of animal models. The highest dose of olanzapine and melatonin, but not haloperidol, ameliorated the hippocampal neuronal loss triggered by kainic acid administration. However, drug administration did not have a significant effect on the rate of neurogenesis. These results suggest that olanzapine has neuroprotective effects in a rat model of neurodevelopmental insult, and may be relevant to the observed effects of atypical antipsychotic drugs on brain structure in patients with schizophrenia.

Synaptic differences in the patch matrix compartments of subjects with schizophrenia: a postmortem ultrastructural study of the striatum

The striatum processes motor, cognitive, and limbic circuitry. Striatal patch and matrix compartments are organized differently in many aspects including connectivity. Abnormalities in either compartment could have different functional consequences. The present study compares the synaptic organization in the patches and matrix in subjects with schizophrenia (SZ, n = 14) versus normal controls (NC, n = 8). Postmortem striatal tissue was processed for calbindin immunocytochemistry to identify the patch versus matrix compartments, prepared for electron microscopy, and analyzed using stereology. Several synaptic changes were observed in the SZ subjects vs. NCs including a higher density of cortical-type synapses in the putamen patch (44% higher) and in the caudate matrix (36% higher) in SZ cases on typical antipsychotic drugs. These changes appeared to be normalized rather than caused by treatment. The abnormal connectivity may represent a failure of normal synaptic pruning and may play a role in limbic or cognitive dysfunction in schizophrenia.

Arm folding, hand clasping, and Luria's concept of "latent left-handedness"

Luria (1947/1970) proposed left-top positions in arm folding (AF) and hand clasping (HC) to be signs of "latent left-handedness". However, research since has revealed that (1) left-top positions are canonical for European right-handers and (2) combined AF/HC measures may provide more information about cerebral laterality than either measure considered alone. We tested whether AF and HC or AF/HC combinations predicted diminished right-handedness for 12 handedness items. Results from 509 healthy participants showed that (1) left-top positions in AF and HC were dominant across participants, as was right-handedness, and a right-top position in HC was associated with attenuated right-handedness, (2) right-hand preference was more frequently associated with congruent AF/HC combinations, especially of the LL type (AF: left-top / HC: left-top), and (3) non-right-hand preference was associated with non-congruent, predominantly LR combinations. We conjecture that the LL type combination indicates left hemispheric dominance for motor actions, whereas the LR combination, in which HC as the distally innervated posture deviates from the canonical pattern, indicates attenuated hemispheric asymmetry. Our data support Luria's proposition that a left-top preference in AF points to "latent" left-handedness, but only if associated with a right-top preference in HC. Consistent left-top preference for the combined AF/HC measure appears to predict right-handedness.

Episodic memory-related activation in schizophrenia: meta-analysis

BACKGROUND

Numerous studies have examined the neural correlates of episodic memory deficits in schizophrenia, yielding both consistencies and discrepancies in the reported patterns of results.

AIMS

To identify in schizophrenia the brain regions in which activity is consistently abnormal across imaging studies of memory.

METHOD

Data from 18 studies meeting the inclusion criteria were combined using a recently developed quantitative meta-analytic approach.

RESULTS

Regions of consistent differential activation between groups were observed in the left inferior prefrontal cortex, medial temporal cortex bilaterally, left cerebellum, and in other prefrontal and temporal lobe regions. Subsequent analyses explored memory encoding and retrieval separately and identified between-group differences in specific prefrontal and medial temporal lobe regions.

CONCLUSIONS

Beneath the apparent heterogeneity of published findings on schizophrenia and memory, a consistent and robust pattern of group differences is observed as a function of memory processes.

Increased proportion of high-affinity dopamine D2 receptors in rats with excitotoxic damage of the entorhinal cortex, an animal model of schizophrenia

Excitotoxic lesions of the left entorhinal cortex (EC) cause dopamine supersensitivity. In order to determine if these lesions selectively alter the high-affinity state of dopamine D2 receptors (D2(High)), these high-affinity states were measured by competition between dopamine and [3H]domperidone in striata from lesioned rats and sham-operated animals. The proportion of D2(High) sites was significantly elevated by 200% in the EC-lesioned rats while that of the D1(High) sites, measured by dopamine/[3H]SCH23390 competition, was unaltered. These results provide a biochemical basis for behavioral supersensitivity in rats with EC lesions.

Reduced auditory M100 asymmetry in schizophrenia and dyslexia: applying a developmental instability approach to assess atypical brain asymmetry

Although atypical structural and functional superior temporal gyrus (STG) asymmetries are frequently observed in patients with schizophrenia and individuals with dyslexia, their significance is unclear. One possibility is that atypical asymmetries reflect a general risk factor that can be seen across multiple neurodevelopmental conditions--a risk factor whose origins are best understood in the context of Developmental Instability (DI) theory. DI measures (minor physical anomalies (MPAs) and fluctuating asymmetries (FAs)) reflect perturbation of the genetic plan. The present study sought to assess whether the presence of peripheral indices of DI predicts anomalous functional auditory cortex asymmetry in schizophrenia patients and dyslexia subjects. The location of the auditory M100 response was used as a measure of functional STG asymmetry, as it has been reported that in controls (but not in subjects with schizophrenia or dyslexia) the M100 source location in the right hemisphere is shifted anterior to that seen for the left hemisphere. Whole-brain auditory evoked magnetic field data were successfully recorded from 14 male schizophrenia patients, 21 male subjects with dyslexia, and 16 normal male control subjects. MPA and FA measures were also obtained. Replicating previous studies, both schizophrenia and dyslexia groups showed less M100 asymmetry than did controls. Schizophrenia and dyslexia subjects also had higher MPA scores than normal controls. Although neither total MPA nor FA measures predicted M100 asymmetry, analyses on individual MPA items revealed a relationship between high palate and M100 asymmetry. Findings suggest that M100 positional asymmetry is not a diagnostically specific feature in several neurodevelopmental conditions. Continued research examining DI and brain asymmetry relationships is warranted.

A 4.0-T fMRI study of brain connectivity during word fluency in first-episode schizophrenia

OBJECTIVE

To use functional magnetic resonance imaging (fMRI) to investigate functional connectivity, and hence, underlying neural networks, in never-treated, first-episode patients with schizophrenia using a word fluency paradigm known to activate prefrontal, anterior cingulate, and thalamic regions. Abnormal connectivity between the prefrontal cortex (PFC) and other brain regions has been demonstrated in chronic, medicated patients in previous positron emission tomography (PET) studies, but has not to our knowledge, previously been demonstrated using both first-episode, drug-naïve patients and fMRI technology.

METHODS

A 4.0-Tesla (T) fMRI was used to examine activation and functional connectivity [psychophysiological interactions (PPIs)] during a word fluency task compared to silent reading in 10 never-treated, first-episode patients with schizophrenia and 10 healthy volunteers of comparable age, sex, handedness, and parental education.

RESULTS

Compared to healthy volunteers, the schizophrenia patient group exhibited less activation during the word fluency task, mostly in the right anterior cingulate and prefrontal regions. Psychophysiological interactions between right anterior cingulate and other parts of the brain revealed a localized interaction with the left temporal lobe in healthy volunteers during the task and a widespread unfocussed interaction in patients.

CONCLUSION

These findings suggest anterior cingulate involvement in the neuronal circuitry underlying schizophrenia.

Handedness in schizophrenia: a quantitative review of evidence

OBJECTIVE

The prevalence of various anomalous handedness subtypes in schizophrenia patients remains ambiguous. Although current literature favours the notion that the shift in lateral preferences seen is because of an increase of mixed-handedness, several studies suggest that exclusive left handedness is more prevalent than in the general population.

METHOD

Over 40 studies with reported prevalence data on various handedness subtypes in a schizophrenia population were evaluated by meta-analysis. Combined odds ratios for the three common handedness subtypes (left, mixed, and right) were separately calculated.

RESULTS

Each of the three atypical hand dominance patterns were significantly greater in schizophrenia patients than in control subjects, showing that the leftward shift in handedness distribution is not entirely because of an increase in mixed-handedness alone.

CONCLUSION

An increase of exclusive left-handedness is at variance with the prevailing assertion that the handedness shift in schizophrenia patients is because of a diffuse and bilateral hemispheric insult.

Macroscopic brain asymmetry is changed along the antero-posterior axis in schizophrenia

BACKGROUND

Anatomical asymmetry may be altered in schizophrenia, but the changes are subtle and in some studies undetected perhaps due to methodological limitations.

METHODS

In a postmortem MRI study (23 patients, 20 controls), we used a geometric mesh technique to define the cortical surface and to separate two components of brain asymmetry: hemisphere shift, conceived as the position of an entire hemisphere relative to the other (which may be reversed in situs inversus), and the distribution of tissue within the hemisphere along the antero-posterior axis ("volume torque").

RESULTS

Only volume torque was changed in schizophrenia-in comparison subjects, the coronal section of maximal left hemisphere volume was more anteriorly placed than on the right [and correlated with left superior temporal gyrus (STG) volume], and, in patients, it was more posterior (showing a reversed correlation with left STG volume).

CONCLUSIONS

The findings validate a new approach to cerebral asymmetry. Assessments of cerebral asymmetry in psychosis should account for, or exclude, hemisphere shift, which is not changed, and focus on the second component, A-P volume distribution; the findings point to an anomaly of relative hemispheric development that may have pathophysiological significance.

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

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

Postnatal maturation of cortical serotonin lateral asymmetry in gerbils is vulnerable to both environmental and pharmacological epigenetic challenges

Long-term effects of postnatal differential rearing conditions and/or early methamphetamine (MA) application on serotonin (5-HT) fibre density were investigated in several cortical areas of both hemispheres of gerbils. The aim of this study was twofold: (1) Is the 5-HT fibre innervation of the cerebral cortex lateralised, and (2) if so, do postnatal environmental conditions and/or an early drug challenge interfere with development of 5-HT cerebral asymmetries? For that purpose, male gerbils were reared either under semi-natural or restricted environmental and social conditions, under both conditions once (on postnatal day 14) being treated with either a single dose of MA (50 mg/kg, i.p.) or saline. On postnatal day 110, 5-HT fibres were immunohistochemically stained and innervation densities quantified in prefrontal cortex, insular cortex, frontal cortex, parietal cortex, and entorhinal cortex. It was found that (1) 5-HT innervation in the cerebral cortex was clearly lateralised; (2) direction and extent of this asymmetry were not uniformly distributed over the different areas investigated; (3) both early methamphetamine challenge and rearing condition differentially interfered with adult 5-HT cerebral asymmetry; (4) combining MA challenge with subsequent restricted rearing tended to reverse the effects of MA on 5-HT cerebral asymmetry in some of the cortical areas investigated; and (5) significant responses in 5-HT cerebral asymmetry only occurred in prefrontal and entorhinal association cortices. The present findings suggest that the ontogenesis of cortical laterality is influenced by epigenetic factors and that disturbances of the postnatal maturation of lateralised functions may be associated with certain psychopathological behaviours.

Neurological soft signs and dermatoglyphic anomalies in twins with schizophrenia

Schizophrenia is associated with altered neural development. We assessed neurological soft signs (NSS) and dermatoglyphic anomalies (total a-b ridge count (TABRC) and total finger ridge count) in 15 pairs of twins concordant and discordant for schizophrenia. Within-pair differences in both NSS and TABRC scores were significantly greater in discordant compared to concordant monozygotic pairs. There was no significant difference in NSS and TABRC scores between subjects with schizophrenia and their co-twins without the illness. However, monozygotic discordant twins with schizophrenia had higher ABRCs on their right hands compared to their co-twins without the illness. These findings suggest that an unidentified environmental event acting between weeks 6 and 15 of gestation affects the development of monozygotic twins who go on to develop schizophrenia but does not have a corresponding effect on their co-twins who do not develop the illness. The effect of such an event on dermatoglyphic profiles appears lateralised to the right hand in affected twins.

[Neurodevelopmental hypothesis in schizophrenia]

The hypothesis for a neurodevelopmental basis to the underlying physiopathological disorder leading to schizophrenia has been proposed by many investigators for more than two decades. This hypothesis is supported by -several lines of evidence. Pregnancy and delivery complications, particularly those with known or presumed impact on fetal neurologic development, result in increased risk for psychotic disorders. Other possible etiologic candidates include viral infections. Minor physical anomalies, manifesting as slight anatomical defects of the head, hair, eyes, mouth, hands and feet, as dematoglyphic fluctuating asymmetries, are due to some injury occurring during the first or second trimester of fetal life, and are more common among patients with schizophrenia and in their unaffected siblings than in the general population. But a major Issue in a such neurodevelopmental model theory is the delayed onset of the schizophrenic disorder. Although early signs and prodromal symptoms can be defined retrospectively in patients who have developed schizophrenia, they do have to be confirmed as early predictors in prospective and longitudinal studies. Abnormalities in brain development and maturation seem to begin prenatally, but may continue throughout childhood and the observed changes during these periods must have -consequences for the neuronal circuitry and connectivity. Advances in brain imaging have now led to the identification of a great number of brain abnormalities in schizophrenia. The most consistently replicated structural anomaly present in the brains of patients with chronic schizophrenia is ventricular enlargement. These findings also include medial temporal lobe structures (which include the amygdala, hippocampus, and parahippocampal gyrus), and neocortical temporal lobe regions (superior temporal gyrus). There is also some evidence for frontal lobe abnormalities, particularly prefrontal gray matter and orbitofrontal regions. Similarly, there are findings for parietal lobe abnormalities (particularly of the inferior parietal lobule which includes both supramarginal and angular gyri) and subcortical abnormalities (basal ganglia, corpus callosum, and thalamus) but more equivocal evidence for cerebellar abnormalities. However, it is possible that the brain structural abnormalities observed in schizophrenia are not only due to neurodevelopmental anomalies, but also to an alteration in cortical plasticity and maturation processes that occurs over the long course of the disease. The genetic predisposition for schizophrenia has been confirmed in many studies. It is utterly disappointing that molecular genetic approaches have so far not yielded conclusive evidence for vulnerability or protection genes in schizophrenia. Future studies will likely benefit from: 1) studying more homogeneous patient groups, 2) studying high risk populations such as biological relatives of patients with schizophrenia, 3) using longitudinal and prospective methodological design in order to confirm the predictive validity of neurodevelopmental clues found in patients with schizophrenia, 4) applying newer strategies such as composite phenotypes of developmental origin, in combination with new genetic methods.

Enhanced locomotor activity in rats with excitotoxic lesions of the entorhinal cortex, a neurodevelopmental animal model of schizophrenia: Behavioral and in vivo microdialysis studies

In order to examine the construct validity of rats with excitotoxic damage of the left entorhinal cortex (EC) as an animal model of schizophrenia, we measured dopamine (DA)-related behaviors and methamphetamine (MAP)-induced DA release in the accumbens nucleus (NAC) in these animals. Quinolinic acid (lesion group) or phosphate buffer (sham group) was infused into the left EC of adolescent (postnatal 7 weeks) male Wistar rats. On the 14th and 28th postoperative day, spontaneous and MAP (1 mg/kg, i.p.)-induced locomotor activities, as well as MAP-induced stereotypy, were measured. The lesioned rats exhibited significantly greater spontaneous or MAP-induced locomotor activity on both of the postoperative days than did sham-operated animals, while EC lesions did not affect MAP-induced stereotypy on either occasion. MAP (1 mg/kg, i.p.)-induced DA release in NAC was measured by in vivo microdialysis on the 28th postoperative day. Lesioned rats did not show a significant change in MAP (1 mg/kg, i.p.)-induced DA release in NAC compared to sham-operated animals. These results suggest that excitotoxic damage of the left EC produces behavioral changes consistent with altered mesolimbic dopaminergic transmissions, possibly mediated by postsynaptic supersensitivity.

A study of hippocampal shape anomaly in schizophrenia and in families multiply affected by schizophrenia or bipolar disorder

Hippocampal shape anomaly (HSA), characterised by a rounded hippocampus, has been documented in congenital malformations and epileptic patients. Subtle structural hippocampal abnormalities have been demonstrated in patients with schizophrenia. We tested the hypothesis that HSA is more frequent in schizophrenia, particularly in patients from families multiply affected by schizophrenia, and that HSA is transmitted within these families. We also aimed to define the anatomical features of the hippocampus and other cerebral structures in the HSA spectrum and to determine the prevalence of HSA in a control group. We reviewed the magnetic resonance imaging of a large number of subjects with schizophrenia and bipolar disorder, many of who came from multiply affected families, relatives of the affected probands, and controls. Quantitative measures of hippocampal shape and position and other qualitative anatomical measures were performed (including depth of dominant sulcus cortical cap, angle of dominant sulcus and hippocampal fissure, bulk of collateral white matter, prominence of temporal horn lateral recess and blurring of internal hippocampal architecture) on subjects with HSA. A spectrum of mild, moderate and severe HSA was defined. The prevalence of HSA was, 7.8% for the controls (n=218), 9.3% for all schizophrenic subjects (n=151) and 12.3% for familial schizophrenic subjects (n=57). There was a greater prevalence of moderate or severe forms of HSA in familial schizophrenics than controls. However, there was no increase in the prevalence of HSA in the unaffected first-degree relatives of schizophrenic patients or in patients with familial bipolar disorder. HSA was rarely transmitted in families. HSA was frequently associated with a deep, vertical collateral/occipito-temporal sulcus and a steep hippocampal fissure. Our data raise the possibility that HSA is linked to disturbances of certain neurodevelopmental genes associated with schizophrenia. However, the lack of any increase in prevalence in the unaffected relatives of patients and the lack of clustering within individual pedigrees argues against this developmental anomaly being commonly associated with genetic predisposition to the illness.

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

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

Spatial memory deficits induced by perinatal treatment of rats with PCP and reversal effect of D-serine

It has been suggested that perinatal treatment with the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist phencyclidine (PCP) induces transient neurodegeneration in the limbic and cortical structures of rats. Since dysfunction of these structures is associated with cognitive deficits in patients with schizophrenia, we studied the effects of subchronic treatment with PCP in perinatal rats with respect to spatial reference, reversal, and spatial working memories using the Morris water maze task in adulthood. In addition, we investigated the effect of D-serine, which has clinical relevance for the treatment of cognitive deficits in patients with schizophrenia. Our goal was to develop a neurodevelopmental model with predictive validity for the cognitive dysfunction described in patients with schizophrenia. Male and female Sprague-Dawley rats were treated with either saline or PCP (8.7 mg/kg s.c.) on days 7, 9, and 11, postnatal, and the long-term behavioral effects were investigated in adulthood. Male PCP-treated rats were slightly impaired during the spatial reference memory task, but strongly impaired during the reversal and spatial working memory tasks. Female rats were not significantly affected by this treatment. This cognitive deficit was reversed by chronic treatment with D-serine. We suggest that this model mimics some of the cognitive deficits of patients with schizophrenia and might be appropriate for the screening of putative antipsychotic agents for the treatment of these cognitive deficits.