Disturbances of corticogenesis in schizophrenia: morphological findings provide new evidence for the maldevelopmental hypothesis

GABA through the ages: regulation of cortical function and plasticity by inhibitory interneurons

Inhibitory interneurons comprise only about 20% of cortical neurons and thus constitute a clear minority compared to the vast number of excitatory projection neurons. They are, however, an influential minority with important roles in cortical maturation, function, and plasticity. In this paper, we will highlight the functional importance of cortical inhibition throughout brain development, starting with the embryonal formation of the cortex, proceeding by the regulation of sensory cortical plasticity in adulthood, and finishing with the GABA involvement in sensory information processing in old age.

Isolation rearing or methamphetamine traumatisation induce a "dysconnection" of prefrontal efferents in gerbils: implications for schizophrenia

A miswiring of prefrontal efferents is generally discussed by the name of "dysconnection" as the anatomical substrate of schizophrenia. Since direct histological confirmation of this hypothesis can hardly be obtained in humans, we used an animal model of schizophrenia to trace prefrontal efferents to distal cortical fields. Mongolian gerbils were intoxicated with a single high dose of methamphetamine on postnatal day 14 and reared in isolation after weaning (day 30). Controls received a saline injection and/or were reared under enriched conditions. Upon reaching adulthood (day 90), biocytin was injected into the medial prefrontal cortex into either deep or superficial laminae. The density of passing fibres and terminal fields in the frontal, parietal and insular cortices was assessed by digital image analysis. Isolation rearing or methamphetamine treatment alone reduced the projections from lamina V/VI to the frontal and from lamina III to the insular cortex, and from both laminae to the parietal cortex. In contrast, isolation rearing of methamphetamine-intoxicated gerbils significantly increased the projections from the deep laminae to the frontal and parietal cortices, compared to isolation-reared controls, with no difference in the efferents from superficial laminae. These results are the first to demonstrate a miswiring of prefrontal efferents in response to adverse systemic influences. They might give a hint at the anatomical basis of "dysconnection" in schizophrenia.

New evidence for involvement of the entorhinal region in schizophrenia: a combined MRI volumetric and DTI study

Postmortem examinations and magnetic resonance imaging (MRI) studies suggest involvement of the entorhinal cortex (EC) in schizophrenic psychoses. However, the extent and nature of the possible pathogenetical process underlying the observed alterations of this limbic key region for processing of multimodal sensory information remains unclear. Three-dimensional high-resolution MRI volumetry and evaluation of the regional diffusional anisotropy based on diffusion tensor imaging (DTI) were performed on the EC of 15 paranoid schizophrenic patients and 15 closely matched control subjects. In schizophrenic patients, EC volumes showed a slight, but not significant, decrease. However, the anisotropy values, expressed as inter-voxel coherences (COH), were found to be significantly decreased by 17.9% (right side) and 12.5% (left side), respectively, in schizophrenics. Reduction of entorhinal diffusional anisotropy can be hypothesized to be functionally related to disturbances in the perforant path, the principal efferent EC fiber tract supplying the limbic system with neuronal input from multimodal association centers. Combinations of different MRI modalities are a promising approach for the detection and characterization of subtle brain tissue alterations.

Frontal lesions do not alter the differential extinction of taste aversion conditioning in rats, when using two methods of sucrose delivery

The frontal cortex is involved in the planning of behavioural responses and in the processing of their outcomes. Thus it contributes to several learning mechanisms, including those of conditioned taste aversion (CTA). A solution of sucrose drunk freely by a rat from a drinking tube-self-drinking protocol (SD)-was used as a conditioned stimulus in CTA. The intake of this solution was followed by gastric malaise. It produced an aversion to sucrose that withstood extinction over a week of repetitive tests. But, when the sucrose was perfused intra-orally (IO), i.e. not depending on any specific action by the rat, the extinction of aversion was much faster. Several factors may explain this differential extinction including the contribution of contextual factors linked to the achievement of an action and/or the enhancement of the attention towards the outcome of the action (the taste). The processing of such factors is usually believed to require the prefrontal cortex or the cingulate cortex (CgC). In our first experiment, the frontal cortex was totally transected. In the second experiment, the CgC was removed by aspiration. None of these lesions elicited any change in CTA, either in IO or in SD conditions, meaning that the differential extinction remained. The surprising absence of a frontal lesion effect was thought to indicate the low attentional demand required in both CTA protocols.

Cell-type specific alterations of cortical interneurons in schizophrenic patients

In the human brain, cortical GABAergic interneurons represent an important population of local circuit neurons responsible for the intrinsic modulation of neuronal information and have been supposed to be involved in the pathophysiology of schizophrenia. We conducted a quantitative study on the differentiated three-dimensional morphological structure of two types of parvalbumin-immunoreactive interneurons in the anterior cingulate cortex (ACC) of schizophrenic patients versus controls. While type A interneurons ('small bipolar cells') showed a significant reduction of their soma size in schizophrenics, type B interneurons ('small multipolar cells') of schizophrenic patients exhibited a marked decrease in the extent of their dendritic system. These results further support the assumption of a considerable significance of the ACC, an important limbic relay centre, for the etiopathogenesis of schizophrenic psychoses.

Vulval disease in pre-pubertal girls

Children present with vulval complaints less frequently than do adults; although there are many similarities between paediatric and adult groups of patients with vulval disease, there are also important differences. In both groups, dermatitis, psoriasis and lichen sclerosus are the most frequently seen dermatoses. Birthmarks and congenital abnormalities presenting for the first time are more of an issue in children than in adults. Fusion of the labia and streptococcal vulvovaginitis are conditions seen only in the paediatric group. Sexually transmitted diseases such as genital warts and genital herpes are not common in this group and should always raise the possibility of child sexual abuse. Chronic vulvovaginal candidiasis, although a very common problem in adult patients, is not seen in the prepubertal group.

Synaptic pathology in the anterior cingulate cortex in schizophrenia and mood disorders. A review and a Western blot study of synaptophysin, GAP-43 and the complexins

There are several reports of ultrastructural and protein changes affecting synapses in the anterior cingulate cortex in schizophrenia. Altered cytoarchitecture has also been described in this region in schizophrenia as well as in mood disorders. In this paper we review the literature and present a new study investigating synaptic abnormalities in the anterior cingulate cortex (area 24) in the Stanley Foundation brain series. We used Western blotting to assess four synaptic proteins: synaptophysin, growth-associated protein-43 (GAP-43), complexin I and complexin II, which inform about somewhat different aspects of the synaptic circuitry. Synaptophysin, complexin II and GAP-43 were reduced in bipolar disorder. The decreases correlated with the duration of illness and tended to be greater in subjects without a family history. Complexin II was also reduced in major depression. Complexin I and the housekeeping protein beta-actin did not differ between groups. None of the proteins changed significantly in schizophrenia. The results indicate the presence of a synaptic pathology in the anterior cingulate cortex in mood disorders, especially bipolar disorder. The abnormalities may contribute to the dysfunction of cingulate neural circuits. The loss of synaptophysin is suggestive of decreased synaptic density whilst the decrease in GAP-43 may denote impaired synaptic plasticity and the reduction of complexin II but not complexin I implies that the alterations particularly affect excitatory connections. The reductions may be progressive.

The dendritic architecture of prefrontal pyramidal neurons in schizophrenic patients

Despite a considerable number of investigations revealing the prefrontal cortex (PFC) to be a major site of pathological changes in schizophrenia, the neuronal basis of these alterations is still unknown. We used a 3-D image analysis technique to investigate the dendritic arborization of Golgi-impregnated prefrontal pyramidal neurons in schizophrenic patients and controls. While the apical dendrites were found to be unchanged in schizophrenics, the basilar dendritic systems were markedly reduced in the patient group. A segment analysis showed that the observed alterations were mainly confined to distal dendritic segments. The dendritic changes are likely to be associated with specific dysfunctions of prefrontal circuitry and point to the pathogenetical relevance of pre- and perinatal disturbances of PFC maturation in schizophrenic patients.