Anterior thalamic radiation integrity in schizophrenia: a diffusion-tensor imaging study.

The anterior limb of the internal capsule (ALIC) is a white matter structure, the medial portion of which includes the anterior thalamic radiation (ATR) carrying nerve fibers between thalamus and prefrontal cortex. ATR abnormalities have a possible link with cognitive abnormalities and negative symptoms in schizophrenia. We aimed to study the fiber integrity of the ATR more selectively by isolating the medial portion of the ALIC using region-of-interest based methodology. Diffusion-tensor imaging was used to measure the anisotropy of total ALIC (tALIC) and medial ALIC (mALIC) in 39 schizophrenia and 33 control participants, matched for age/gender/handedness. Relationships between anisotropy, psychopathology, and cognitive performance were analyzed. Compared with controls, schizophrenia participants had 4.55% lower anisotropy in right tALIC, and 5.38% lower anisotropy in right mALIC. There were no significant group anisotropy differences on the left. Significant correlations were observed between right ALIC integrity and relevant domains of cognitive function (e.g., executive function, working memory). Our study suggests an asymmetric microstructural change in ALIC in schizophrenia involving the right side, which is only minimally stronger in mALIC, and which correlates with cognitive impairment. Microstructural changes in the ALIC may be linked to cognitive dysfunction in schizophrenia.

Abnormalities of cingulate gyrus neuroanatomy in schizophrenia.

OBJECTIVE AND METHODS: Abnormalities of the neuroanatomy of the gray matter of the cingulate gyrus, especially its anterior segment, have been suggested to be an important characteristic of schizophrenia. In this study, T1-weighted magnetic resonance scans were collected in 53 individuals with schizophrenia and 68 comparison subjects matched for age, gender, race and parental socioeconomic status. We applied Labeled Cortical Mantle Distance Mapping to assess the volume, surface area and thickness of the cortical mantle within the anterior (AC) and posterior (PC) segments of the cingulate gyrus, excluding the paracingulate gyrus, and related these anatomical measures to measures of psychopathology and illness duration. RESULTS: After covarying for total cerebral volume, individuals with schizophrenia showed smaller AC gray matter volume (p=0.024), thickness (trend, p=0.081), but not surface area (p=0.16), than comparison subjects. Similar group differences were found for PC gray matter volume (p=0.0005) and thickness (trend, p=0.055), but not surface area (p=0.15). Across both groups, there was a significant L>R asymmetry in thickness of the AC, and a significant L>R asymmetry in the surface area of the PC. However, there were no significant group-by-hemisphere interactions. In the individuals with schizophrenia, thinning of the AC, but not the PC, was correlated with a longer duration of illness and a greater severity of psychotic symptoms. CONCLUSIONS: Individuals with schizophrenia showed smaller gray matter volumes across the entire cingulate gyrus, mostly due to a reduction in cortical mantle thickness. However, structural measures of the AC were more closely related to clinical features of the illness.

Abnormalities of thalamic activation and cognition in schizophrenia.

OBJECTIVE: Functional and structural magnetic resonance imaging (MRI) was used to investigate relationships among structure, functional activation, and cognitive deficits related to the thalamus in individuals with schizophrenia and healthy comparison subjects. METHOD: Thirty-six schizophrenia subjects and 28 healthy comparison subjects matched by age, gender, race, and parental socioeconomic status underwent structural and functional MRI while performing a series of memory tasks, including an N-back task (working memory), intentional memorization of a series of pictures or words (episodic encoding), and a yes/no recognition task. Functional activation magnitudes in seven regions of interest within the thalamic complex, as defined by anatomical and functional criteria, were computed for each group. RESULTS: Participants with schizophrenia exhibited decreased activation within the whole thalamus, the anterior nuclei, and the medial dorsal nucleus. These nuclei overlap with subregions of the thalamic surface that the authors previously reported to exhibit morphological abnormalities in schizophrenia. However, there were no significant correlations between specific dimensions of thalamic shape variation (i.e., eigenvectors) and the activation patterns within thalamic regions of interest. Better performance on the working memory task among individuals with schizophrenia was significantly associated with increased activation in the anterior nuclei, the centromedian nucleus, the pulvinar, and the ventrolateral nuclei. CONCLUSIONS: These results suggest that there are limited relationships between morphological and functional abnormalities of the thalamus in schizophrenia subjects and highlight the importance of investigating relationships between brain structure and function.

Inter-rater reliability of manual segmentation of the superior, inferior and middle frontal gyri.

Precise rules for locating the anatomical boundaries of the dorsolateral prefrontal cortex (DLPFC) or its subdivisions, i.e., superior, inferior and middle frontal gyri (SFG, IFG and MFG) on magnetic resonance images (MRI), have not been defined. The present study describes the inter-rater reliability of manual segmentation of the SFG, IFG and MFG using guidelines based on sulcal-gyral anatomical boundaries as well as the cytoarchitectonic features of the sub-regions of the prefrontal cortex (PFC). Variations in the application of these guidelines in different subjects to account for normal sulcal variability were developed using the atlas of Ono et al. (Ono, M., Kubik, S., Abernathey, C.D., 1990. Atlas of the Cerebral Sulci. Georg Thieme Verlag, New York). Based on previous cytoarchitectonic studies, the coronal plane of the anterior termination of olfactory sulcus (ATOS) was used as a landmark for delimiting the boundary between the frontal pole (FP) and the frontal gyri. The left hemisphere gray-matter volumes of the SFG, IFG and MFG were determined using a set of 10 MRIs (5 normal and 5 schizophrenia subjects) by two trained raters independently. The intra-class correlation coefficients (ICC) for the SFG, IFG and MFG volumes by the two raters were 0.97, 0.94 and 0.93, respectively. Thus, we describe a reliable method of parcellating the SFG, IFG and MFG, which constitute the DLPFC, a brain region involved in a variety of neuropsychiatric conditions.

Untreated depression and hippocampal volume loss.

OBJECTIVE: The purpose of this study was to investigate the effect of antidepressant treatment on hippocampal volumes in patients with major depression. METHOD: For 38 female outpatients, the total time each had been in a depressive episode was divided into days during which the patient was receiving antidepressant medication and days during which no antidepressant treatment was received. Hippocampal gray matter volumes were determined by high resolution magnetic resonance imaging and unbiased stereological measurement. RESULTS: Longer durations during which depressive episodes went untreated with antidepressant medication were associated with reductions in hippocampal volume. There was no significant relationship between hippocampal volume loss and time depressed while taking antidepressant medication or with lifetime exposure to antidepressants. CONCLUSIONS: Antidepressants may have a neuroprotective effect during depression.

High-dimensional mapping of the hippocampus in depression.

OBJECTIVE: Abnormalities of the hippocampus may play a role in the pathophysiology of depression, but efforts to identify a structural abnormality in this brain structure among depressed patients have produced mixed results. Previous research may have been limited by exclusive reliance on measures of hippocampal volume. High-dimensional brain mapping is a new analytic method that quantitatively characterizes the shape as well as volume of a brain structure. In this study, high-dimensional brain mapping was used to evaluate hippocampal shape and volume in patients with major depressive disorder and healthy comparison subjects. METHOD: By using magnetic resonance imaging, brain scans were obtained from 27 patients with major depressive disorder and 42 healthy comparison subjects. High-dimensional brain mapping generated a series of 10 variables (components) that represented hippocampal shape, and hippocampal volumes were also computed. Analysis of variance techniques were used to compare depressed patients and comparison subjects on hippocampal shape and volume. RESULTS: While the depressed patients and comparison subjects did not differ in hippocampal volume, there were highly significant group differences in hippocampal shape. The two groups did not overlap on a discriminant function computed from a model comprising the 10 components. The pattern of hippocampal surface deformation in the depressed patients suggested specific involvement of the subiculum. CONCLUSIONS: Patients with major depression may have structural abnormalities of the hippocampus that can be detected by analysis of hippocampal shape but not volume. A specific defect in the subiculum could have widespread effects throughout neurocircuits that appear to be abnormal in depression.

Feasibility of geometric-intensity-based semi-automated delineation of the tentorium cerebelli from MRI scans.

This paper describes a feasibility study of a method for delineating the tentorium cerebelli in magnetic resonance imaging (MRI) brain scans. The tentorium cerebelli is a thin sheet of dura matter covering the cerebellum and separating it from the posterior part of the temporal lobe and the occipital lobe of the cerebral hemispheres. Cortical structures such as the parahippocampal gyrus can be indistinguishable from tentorium in magnetized prepared rapid gradient echo and T1-weighted MRI scans. Similar intensities in these neighboring regions make it difficult to perform accurate cortical analysis in neuroimaging studies of schizophrenia and Alzheimer's disease. A semi-automated, geometric, intensity-based procedure for delineating the tentorium from a whole-brain scan is described. Initial and final curves are traced within the tentorium. A cost function, based on intensity and Euclidean distance, is computed between the two curves using the Fast Marching method. The initial curve is then evolved to the final curve based on the gradient of the computed costs, generating a series of intermediate curves. These curves are then used to generate a triangulated surface of the tentorium. For 3 scans, surfaces were found to be within 2 voxels from hand segmentations.

Progressive deformation of deep brain nuclei and hippocampal-amygdala formation in schizophrenia.

BACKGROUND: Progressive decreases in cortical gray matter volume have been reported in schizophrenia. However, studies of progressive change in deep brain nuclei and hippocampal-amygdala formation have not yielded consistent findings. METHODS: Two high-resolution, T1-weighted magnetic resonance images were collected 2 years apart in 56 schizophrenia and 62 control subjects. Large-deformation high-dimensional brain mapping was used to generate surfaces for deep brain nuclei and hippocampal-amygdala formation at baseline and follow-up. Repeated-measures analysis of variance was used to test for longitudinal changes in volume and shape. RESULTS: The pattern of progressive changes in the deep brain nuclei and hippocampal-amygdala formation in schizophrenia and control subjects was variable. Of the structures that receive direct projections from the cortex, the thalamus, caudate nucleus, nucleus accumbens, and hippocampus showed changes specific to subjects with schizophrenia, and changes in the amygdala and putamen were similar in both groups. Although different at baseline, no progressive change was observed in the globus pallidus, which does not receive direct projections from the cortex. CONCLUSIONS: These findings suggest that the disease process of schizophrenia is associated with progressive effects on brain structure and that brain structures that receive direct, excitatory connections from the cortex may be more likely to show progressive changes, compared with brain structures that receive indirect, inhibitory connections from the cortex. These findings are also somewhat consistent with the hypothesis that overactivity of excitatory pathways in the brain may contribute to the neural degeneration that occurs in at least a subgroup of individuals with schizophrenia.

Abnormalities of hippocampal surface structure in very mild dementia of the Alzheimer type.

To better define the pattern of hippocampal deformity early in the course of Alzheimer's disease, we compared the pattern of hippocampal surface variation in subjects with very mild dementia of the Alzheimer type (DAT) and nondemented subjects. The surface of the hippocampus was divided a priori on a neuroanatomical template into three zones approximating the locations of underlying subfields [Csernansky, J.G., Wang, L., Swank, J., Miller, J.P., Gado, M., McKeel, D., Miller, M.I., Morris, J.C., 2005. Preclinical detection of Alzheimer's disease: hippocampal shape and volume predict dementia onset in the elderly. NeuroImage 25, 783--792]; i.e., a lateral zone (LZ) approximating the CA1 subfield, a superior zone (SZ) approximating the combined CA2, CA3, CA4 subfields and the gyrus dentatus (GD), and an inferior-medial zone (IMZ) approximating the subiculum. Large-deformation high-dimensional brain mapping (HDBM-LD) was used to generate the hippocampal surfaces of all subjects and to register the surface zones across subjects. Average variations within each zone were calculated for the subjects with very mild DAT as compared to the average of the nondemented subjects. After correcting for multiple comparisons, the very mild DAT subjects showed significant inward variation in the left and right LZ, the left and right IMZ, but not in the left and right SZ as compared to nondemented subjects. In logistic regression analyses, inward variation of the left and right LZ or IMZ by 0.1 mm relative to the average of the nondemented subjects increased the odds of the subject being a very mild DAT subject (range-1.18 to 1.57) rather than being a nondemented subject. The odds ratios for the left and right SZ were not significant. These results represent a replication of our previous findings [Csernansky, J.G., Wang, L., Joshi, S., Miller, J.P., Gado, M., Kido, D., McKeel, D., Morris, J.C., Miller, M.I., 2000. Early DAT is distinguished from aging by high-dimensional mapping of the hippocampus. Neurology 55, 1636--1643.] and suggest that inward deformities of the hippocampal surface in proximity to the CA1 subfield and subiculum can be used to distinguish subjects with very mild DAT from nondemented subjects.

Changes in hippocampal volume and shape across time distinguish dementia of the Alzheimer type from healthy aging.

Rates of hippocampal volume loss have been shown to distinguish subjects with dementia of the Alzheimer type (DAT) from nondemented controls. In this study, we obtained magnetic resonance scans in 18 subjects with very mild DAT (CDR 0.5) and 26 age-matched nondemented controls (CDR 0) 2 years apart. Large-deformation high-dimensional brain mapping was used to quantify and compare changes in hippocampal shape as well as volume in the two groups of subjects. Hippocampal volume loss over time was significantly greater in the CDR 0.5 subjects (left = 8.3%, right = 10.2%) than in the CDR 0 subjects (left = 4.0%, right = 5.5%) (ANOVA, F = 7.81, P = 0.0078). We used singular-value decomposition and logistic regression models to quantify hippocampal shape change across time within individuals, and this shape change in the CDR 0.5 and CDR 0 subjects was found to be significantly different (Wilks's lambda, P = 0.014). Further, at baseline, CDR 0.5 subjects, in comparison to CDR 0 subjects, showed inward deformation over 38% of the hippocampal surface; after 2 years this difference grew to 47%. Also, within the CDR 0 subjects, shape change between baseline and follow-up was largely confined to the head of the hippocampus and subiculum, while in the CDR 0.5 subjects, shape change involved the lateral body of the hippocampus as well as the head region and subiculum. These results suggest that different patterns of hippocampal shape change in time as well as different rates of hippocampal volume loss distinguish very mild DAT from healthy aging.