Quantitative shape analysis of the temporal and prefrontal lobes of schizophrenic patients: a magnetic resonance image study

Impairments in dendrite morphogenesis as etiology for neurodevelopmental disorders and implications for therapeutic treatments

Dendrite morphology is pivotal for neural circuitry functioning. While the causative relationship between small-scale dendrite morphological abnormalities (shape, density of dendritic spines) and neurodevelopmental disorders is well established, such relationship remains elusive for larger-scale dendrite morphological impairments (size, shape, branching pattern of dendritic trees). Here, we summarize published data on dendrite morphological irregularities in human patients and animal models for neurodevelopmental disorders, with focus on autism and schizophrenia. We next discuss high-risk genes for these disorders and their role in dendrite morphogenesis. We finally overview recent developments in therapeutic attempts and we discuss how they relate to dendrite morphology. We find that both autism and schizophrenia are accompanied by dendritic arbor morphological irregularities, and that majority of their high-risk genes regulate dendrite morphogenesis. Thus, we present a compelling argument that, along with smaller-scale morphological impairments in dendrites (spines and synapse), irregularities in larger-scale dendrite morphology (arbor shape, size) may be an important part of neurodevelopmental disorders' etiology. We suggest that this should not be ignored when developing future therapeutic treatments.

Fractal dimension analysis of the cortical ribbon in mild Alzheimer's disease

Fractal analysis methods are used to quantify the complexity of the human cerebral cortex. Many recent studies have focused on high resolution three-dimensional reconstructions of either the outer (pial) surface of the brain or the junction between the gray and white matter, but ignore the structure between these surfaces. This study uses a new method to incorporate the entire cortical thickness. Data were obtained from the Alzheimer's Disease (AD) Neuroimaging Initiative database (Control N=35, Mild AD N=35). Image segmentation was performed using a semi-automated analysis program. The fractal dimension of three cortical models (the pial surface, gray/white surface and entire cortical ribbon) were calculated using a custom cube-counting triangle-intersection algorithm. The fractal dimension of the cortical ribbon showed highly significant differences between control and AD subjects (p<0.001). The inner surface analysis also found smaller but significant differences (p<0.05). The pial surface dimensionality was not significantly different between the two groups. All three models had a significant positive correlation with the cortical gyrification index (r>0.55, p<0.001). Only the cortical ribbon had a significant correlation with cortical thickness (r=0.832, p<0.001) and the Alzheimer's Disease Assessment Scale cognitive battery (r=-0.513, p=0.002). The cortical ribbon dimensionality showed a larger effect size (d=1.12) in separating control and mild AD subjects than cortical thickness (d=1.01) or gyrification index (d=0.84). The methodological change shown in this paper may allow for further clinical application of cortical fractal dimension as a biomarker for structural changes that accrue with neurodegenerative diseases.

Corpus Callosum Shape Analysis with Application to Dyslexia

Morphometric studies of the corpus callosum suggest its involvement in a number of psychiatric conditions. In the present study we introduce a novel pattern recognition technique that offers a point-by-point shape descriptor of the corpus callosum. The method uses arc lengths of electric field lines in order to avoid discontinuities caused by folding anatomical contours. We tested this technique by comparing the shape of the corpus callosum in a series of dyslexic men (n = 16) and age-matched controls (n = 14). The results indicate a generalized increase in size of the corpus callosum in dyslexia with a concomitant diminution at its rostral and caudal poles. The reported shape analysis and 2D-reconstruction provide information of anatomical importance that would otherwise passed unnoticed when analyzing size information alone.

Characterization of Atrophic Changes in the Cerebral Cortex Using Fractal Dimensional Analysis

The purpose of this project is to apply a modified fractal analysis technique to high-resolution T1 weighted magnetic resonance images in order to quantify the alterations in the shape of the cerebral cortex that occur in patients with Alzheimer's disease. Images were selected from the Alzheimer's Disease Neuroimaging Initiative database (Control N=15, Mild-Moderate AD N=15). The images were segmented using a semi-automated analysis program. Four coronal and three axial profiles of the cerebral cortical ribbon were created. The fractal dimensions (D(f)) of the cortical ribbons were then computed using a box-counting algorithm. The mean D(f) of the cortical ribbons from AD patients were lower than age-matched controls on six of seven profiles. The fractal measure has regional variability which reflects local differences in brain structure. Fractal dimension is complementary to volumetric measures and may assist in identifying disease state or disease progression.

Shape changes in prefrontal, but not parieto-occipital regions: brains of schizophrenic patients come closer to a circle in coronal and sagittal view

There is some evidence for prefrontal (PF) lobe changes in schizophrenia while the parieto-occipital (PO) region seems to be unaffected. This magnetic resonance imaging (MRI) study was performed to examine shape differences as part of the spectrum of structural abnormalities in schizophrenia. The measurements were done on families affected with schizophrenia to identify the influence of genetic and environmental factors on these changes. The sample under study consisted of 164 subjects including 45 family members (FM) suffering from schizophrenia, 27 FM with other psychiatric disorders and 51 FM without psychiatric disorders based on ICD-10 criteria. In addition, 41 nonpsychiatric control subjects were included in the study. On defined planes at the corpus callosum boundary of the PF and the PO, brain width, height and length were measured on coronal slices. Ratios of these linear measurements were also calculated based on the idea that a plane can be approximated by a circle if the concerning ratio comes close to 1. It was hypothesized that these relative brain shape parameters, especially the PF ratio width/height, would show differences between schizophrenic patients and control subjects. For all members from families with schizophrenia compared with control subjects, there were significant differences in the PF, but not in the PO region. PF height was increased. PF ratios of width/height and height/(2 x length) were closer to 1 in affected families than in control subjects. The results can be interpreted as an indication for PF brain shape changes in subjects with a disposition for schizophrenia. On coronal and sagittal planes situated at the corpus callosum, their PF could be approximated by a circle better than in control subjects. As the frontal lobe takes shape late in brain development, underlying genetic mechanisms may be dysregulated in schizophrenic patients and subjects at risk to develop the disorder.

GAD67 and GAD65 mRNA and protein expression in cerebrocortical regions of elderly patients with schizophrenia

Gamma-Aminobutyric acid (GABA), the principal inhibitory neurotransmitter of CNS, has been consistently implicated in the pathophysiology of schizophrenia. GABA is synthesized from glutamate by the enzyme glutamic acid decarboxylase (GAD). Two isoforms of GAD have been identified and have been named GAD65 and GAD67 based on their apparent molecular weights. In this study, GAD65 and GAD67 mRNA and protein levels were measured by using real-time RT-PCR and immunoblotting, respectively, in post-mortem brain tissue from the dorsolateral prefrontal cortex (DLPFC) and the occipital cortex of the elderly persons with schizophrenia and matched normal controls. In addition, the mRNA expression of GAT-1, one of the principal transporters of GABA, was also studied in the same subjects. Expression of GAD65 and GAD67 mRNA in the DLPFC and in the occipital cortex was significantly elevated in patients with schizophrenia, whereas the expression of the corresponding proteins and GAT-1 mRNA was unchanged. Although the levels of GAD65 and GAD67 messages were increased in schizophrenia subjects, the proportion of the two GAD isoforms remained constant in controls and schizophrenics. In the human DLPFC, GAD65 mRNA was found to be expressed significantly less than the message for GAD67, approximately 16% of that observed for GAD67. On the contrary, the abundance of GAD65 protein in the DLPFC was about 350% of that observed for GAD67. The results suggest a substantial dysregulation of GAD mRNA expression in schizophrenia and, taken together with the results of protein expression studies, raise the possibility that both cortical and subcortical GABA function may be compromised in the disease.

Senile plaques exert no mass lesion effect on surrounding neurons

Since the turn of the century studies have suggested that clinical deterioration in Alzheimer's disease (AD) is accompanied by a gradual increase in both the size and numbers of senile plaques (SP's). Our study investigated the 'mass effect' of SP's on the morphometry of adjacent neurons. For this purpose, we used a computerized image analysis system to study pyramidal cells from the hippocampus of ten AD patients, ten demented schizophrenic (SC) patients and ten cognitively impaired non-AD/non-SC control patients with. We examined cell shape, area and disarray and quantitated the number of SP's and neurofibrillary tangles (NFT's) in the CA1 subfield of the hippocampus. Our results indicated no significant differences between groups for measurements of neuronal shape, size, or disarray. Contrary to earlier reports, our results noted no evidence of pyramidal cell disarray in schizophrenic patients. Our results suggest that SP's incorporate, rather than displace, their surrounding neuropil.

Superior temporal gyrus in schizophrenia: a volumetric magnetic resonance imaging study

The left superior temporal gyrus (STG) has been reported to be smaller in patients with schizophrenia. The volume of the STG has been found to correlate negatively with severity of hallucinations and thought disorder. In this study, we measured the STG volume of 20 normal controls and 20 patients with schizophrenia using 3 mm contiguous coronal T1 magnetic resonance images. We found that patients had a significantly smaller left anterior STG, and that the volume of this region negatively correlated with the severity of hallucinations. The left posterior STG was not significantly smaller in patients than in controls, but its volume negatively correlated with severity of thought disorder. We also found that the left anterior STG was smaller than the right STG in patients but not in controls. The STG has at least three histologically distinct areas, each with different connections to the rest of the brain. These data are consistent with the proposition that dysfunction of the primary auditory cortex in the anterior and middle STG and auditory association cortex in the posterior STG may play a role in the production of auditory perceptual abnormalities and poor organization of thought respectively.

Structural brain imaging in schizophrenia: a selective review

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

Computer analysis of magnetic resonance imaging of the brain in children and adolescents after treatment of diabetic ketoacidosis

Cerebral vascular accidents are one of the causes of morbidity and mortality in children with diabetic ketoacidosis. We investigated the possible occurrence of asymptomatic cerebrovascular infarcts and the course of subclinical brain edema in six patients. Neurologic examinations and computer analysis of magnetic resonance imaging were performed immediately after, and again at 14 days after, correction of DKA. None of the patients had clinical evidence of a neurologic deficit. Neither radiologic evaluation nor computer analysis of MRI identified changes indicating asymptomatic ischemic events. However, a computer analysis of the MRI identified a significant increase of the total ventricle area between Day one and Day 14. Our study does not establish whether this change is a return to the baseline prior to DKA or a new baseline, representing an early manifestation of diabetic encephalopathy.

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

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

Abnormal cholecystokinin mRNA levels in entorhinal cortex of schizophrenics

Limbic cortical regions, including anterior cingulate cortex (ACC), prefrontal cortex (PFC) and entorhinal cortex (ERC), have been implicated in the neuropathology of schizophrenia. Glutamate projection neurons connect these limbic cortical regions to each other, as well as to the terminal fields of the striatal/accumbens dopamine neurons. Subsets of these glutamate projection neurons, and of the GABA interneurons in cortex, contain the neuropeptide cholecystokinin (CCK). In an effort to study the limbic cortical glutamate projection neurons and GABA interneurons in schizophrenia, we have measured CCK mRNA with in situ hybridization histochemistry in postmortem samples of dorsolateral (DL)PFC, ACC and ERC of seven schizophrenics, nine non-psychotic suicides and seven normal controls. CCK mRNA is decreased in ERC (especially layers iii vi) and subiculum in schizophrenics relative to controls. Cellular analysis indicates that there is a decrease in density of CCK mRNA in labelled neurons. In so far as ERC CCK mRNA is not reduced in rats treated chronically with haloperidol, this decrease in schizophrenics does not appear to be related to neuroleptic treatment. In contrast, in DLPFC, where schizophrenics do not differ from normals, the suicide victims have elevated CCK mRNA (especially in layers v and vi), and increased cellular density of CCK mRNA, relative to both normals and schizophrenics. These results lend further support for the involvement of ERC and hippocampus in schizophrenia, suggesting that neurons that utilize CCK may be particularly important. Similarly, an increase in CCK mRNA levels in the PFC of suicides adds to a growing body of evidence implicating this structure in this pathological state. In so far as CCK is co-localized with GABA or glutamate in cortical neurons, both of these neuronal populations need to be studied further in schizophrenia and suicide.

Posterior superior temporal gyrus in schizophrenia: grey matter changes and clinical correlates

We report an MRI morphometric study of the posterior segment of the superior temporal gyrus (STG) in twenty young male schizophrenics and their individually matched normal controls. In particular the more posterior segment of STG was examined, since it has been identified as the approximate site of Wernicke's language area and is a marker for the planum temporale, a region believed to be abnormal in schizophrenia. Total volumes and grey and white matter volumes were measured in middle and posterior STG in each hemisphere. STG grey matter volumes and percentages were significantly reduced bilaterally in both regions in schizophrenic subjects. No significant differences between patients and controls were noted in STG white matter volumes. A significant correlation was detected between delusion scores in schizophrenics and the total volume of the left dominant posterior STG. Replicating the findings of a recent study (Shenton et al., 1992), we found an inverse correlation between thought disorder scores and grey matter reduction in the left posterior STG in schizophrenia.

Fractal analysis of the boundary between white matter and cerebral cortex in magnetic resonance images: a controlled study of schizophrenic and manic-depressive patients

This paper reports development of a computerized ('box-counting') method for estimation of fractal dimension (FD) of the magnetic resonance image (MRI) boundary between cerebral cortex and white matter; and the application of this method to MRIs of 39 schizophrenics (SZs), 23 manic-depressives (MDs) and 31 controls (CONs). Mean FD across all diagnostic groups was 1.402; 95% confidence interval (CI) 1.399 to 1.406. Mean FD was greater in boundaries extracted from manic-depressive patients than in boundaries extracted from controls (difference between MD and CON mean FDs = 0.008; 95% CI -0.002 to +0.018); and less in schizophrenics than in controls (difference between SZ and CON mean FDs = -0.003; 95% CI -0.011 to +0.005). Mean FD was positively correlated with subcortical volume and anterior cerebral volume, and negatively correlated with sulcal cerebrospinal fluid volume. Significant differences in mean FD between diagnostic groups were demonstrated by analysis of covariance (ANCOVA; P < 0.01), with age and volumetric measures of brain size as covariates; and manic-depressive boundaries were shown to have significantly greater values for residual FD (after controlling for effects of brain size) than boundaries extracted from controls (t test; P < 0.05). It is proposed that FD is a useful measure of clinically relevant differences in the complexity of MRI boundaries.

Computed tomography measurements of brain density in Schizophrenia

Although previous studies have reported differences in computed tomography (CT) scan attenuation values between patients with schizophrenia and controls, interpretation of these findings has been hindered by methodological shortcomings such as the failure to control for head size, scanner calibration differences, and other confounding variables. In the present study of CT attenuation values in multiple brain regions in 20 patients with chronic schizophrenia and an equal number of age- and sex-matched normal subjects we controlled for head size and normalized the attenuation values for each scan to an internal standard. No significant differences emerged between the patients with schizophrenia and the controls. However, in the controls only, the mean density of white matter in the left frontal area was significantly higher (t = -2.83, p = 0.01) than that in the right. The results, although possibly suggestive of deviant lateralization in schizophrenia, raise questions about the sensitivity and validity of regional CT attenuation values in detecting subtle anatomic abnormalities in patients with this illness.