Biomedical subjects

Paul M Thompson

Publications and source records attributed to Paul M Thompson.

97 records · Page 6Linked to original sources

PubMed2002

Mapping cortical gray matter asymmetry patterns in adolescents with heavy prenatal alcohol exposure.

Here we report on detailed three-dimensional quantitative maps of brain surface and gray matter density asymmetry patterns during normal adolescent development and show how these anatomical features of the brain are disrupted as a result of prenatal exposure to large quantities of alcohol. We studied two independent samples of normally developing children, adolescents, and young adults, totaling 83 subjects from two different research groups, and compared them to 21 individuals with heavy prenatal alcohol exposure. Surface-based image analysis techniques allowed us to match cortical anatomy across subjects and between hemispheres based on manually delineated sulcal landmarks. Quantitative maps of brain surface asymmetry reveal prominent peri-Sylvian hemispheric differences in which the superior temporal and inferior parietal cortices are shifted backward in the left relative to the right hemisphere in both normal and alcohol-exposed subjects. Cortical surface gray matter asymmetry, mapped here in adolescent populations, is most prominent in the posterior inferior temporal lobes (right greater than left), and this effect does not differ between groups of normally developing children, adolescents, or young adults. Alcohol-exposed individuals show a significant reduction in this asymmetry, whether studied with surface-based or more traditional volumetric region of interest analyses. This region of cortex, near the junction of Brodmann's areas 21, 22, and 37, primarily subserves language functions that are known to be impaired on average in the alcohol-exposed subjects. Our findings elucidate regional patterns of brain surface and gray matter asymmetry during normal development and may contribute to a more comprehensive understanding of the neural substrates of cognitive dysfunction after heavy prenatal alcohol exposure.

Adolescent↗

PubMed2002

Mapping sulcal pattern asymmetry and local cortical surface gray matter distribution in vivo: maturation in perisylvian cortices.

Previous in vivo morphometric studies of human brain maturation between childhood and young adulthood have revealed a spatial and temporal pattern of progressive brain changes that is consistent with the post mortem cytoarchitectonic and cognitive developmental literatures. In this study, we mapped age differences in structural asymmetries at the cortical surface in groups of normally developing children (7-11 years), adolescents (12-16 years) and young adults (23-30 years) using novel surface-based mesh modeling image analytic methods. We also assessed relationships between cortical surface sulcal asymmetry and the local density of the underlying cortical gray matter. Results from this study reveal that perisylvian sulcal asymmetries are much more prominent in the adults than in the children studied. The superior posterior extent of the Sylvian fissure in the right hemisphere is approximately 7 mm more superior in the average adult than in the average child studied, whereas little difference is observed during this age range in the location of this anatomical structure in the left hemisphere. Age-related differences in Sylvian fissure asymmetry were significant (P = 0.0129, permutation test), showing increased asymmetry with increasing age. We also show age-related increases in local gray matter proportion bilaterally in the temporo-parietal cortices that are anatomically and temporally related to the sulcal asymmetries. Results from this cross-sectional study imply that asymmetries in the Sylvian fissure are dynamically changing into young adulthood and show that variability in brain tissue density is related to asymmetry in this region. These morphological differences may be related to changing cognitive abilities and are relevant in interpreting results from studies of abnormal brain development where perisylvian brain regions are implicated.

Adolescent↗

PubMed2002

Regional brain shape abnormalities persist into adolescence after heavy prenatal alcohol exposure.

We assessed regional brain shape abnormalities and spatial relationships between brain shape and abnormalities observed in the underlying tissue in children and adolescents prenatally exposed to large quantities of alcohol. We used high resolution, 3-D, structural magnetic resonance imaging data and novel, whole-brain, surface-based image analysis procedures to study 21 subjects with heavy prenatal alcohol exposure (8-22 years, mean age 12.6 years) and 21 normally developing control subjects (8-25 years, mean age 13.5 years). Significant brain size and shape abnormalities were observed in the alcohol-exposed subjects in inferior parietal/ perisylvian regions bilaterally, where their brains appeared to be narrower than those of the controls in the same general location where they also had increased gray matter density. Highly significant decreased brain surface extent or reduced brain growth was also observed in the ventral aspects of the frontal lobes most prominent in the left hemisphere. For the first time in this report we have mapped brain morphologic abnormalities to the cortical surface in subjects with prenatal alcohol exposure and have shown that the size and shape of the brain is altered in these individuals. The results imply that brain growth continues to be adversely affected long after the prenatal insult of alcohol exposure to the developing brain and the brain regions most implicated, frontal and inferior parietal/ perisylvian, may be consistent with behavioral deficits characteristic of individuals prenatally exposed to alcohol.

Adolescent↗

PubMed2002

Quantitative comparison and analysis of brain image registration using frequency-adaptive wavelet shrinkage.

In the field of template-based medical image analysis, image registration and normalization are frequently used to evaluate and interpret data in a standard template or reference atlas space. Despite the large number of image-registration (warping) techniques developed recently in the literature, only a few studies have been undertaken to numerically characterize and compare various alignment methods. In this paper, we introduce a new approach for analyzing image registration based on a selective-wavelet reconstruction technique using a frequency-adaptive wavelet shrinkage. We study four polynomial-based and two higher complexity nonaffine warping methods applied to groups of stereotaxic human brain structural (magnetic resonance imaging) and functional (positron emission tomography) data. Depending upon the aim of the image registration, we present several warp classification schemes. Our method uses a concise representation of the native and resliced (pre- and post-warp) data in compressed wavelet space to assess quality of registration. This technique is computationally inexpensive and utilizes the image compression, image enhancement, and denoising characteristics of the wavelet-based function representation, as well as the optimality properties of frequency-dependent wavelet shrinkage.

Brain↗

PubMed2002

Adaptive elastic segmentation of brain MRI via shape-model-guided evolutionary programming.

This paper presents a fully automated segmentation method for medical images. The goal is to localize and parameterize a variety of types of structure in these images for subsequent quantitative analysis. We propose a new hybrid strategy that combines a general elastic template matching approach and an evolutionary heuristic. The evolutionary algorithm uses prior statistical information about the shape of the target structure to control the behavior of a number of deformable templates. Each template, modeled in the form of a B-spline, is warped in a potential field which is itself dynamically adapted. Such a hybrid scheme proves to be promising: by maintaining a population of templates, we cover a large domain of the solution space under the global guidance of the evolutionary heuristic, and thoroughly explore interesting areas. We address key issues of automated image segmentation systems. The potential fields are initially designed based on the spatial features of the edges in the input image, and are subjected to spatially adaptive diffusion to guarantee the deformation of the template. This also improves its global consistency and convergence speed. The deformation algorithm can modify the internal structure of the templates to allow a better match. We investigate in detail the preprocessing phase that the images undergo before they can be used more effectively in the iterative elastic matching procedure: a texture classifier, trained via linear discriminant analysis of a learning set, is used to enhance the contrast of the target structure with respect to surrounding tissues. We show how these techniques interact within a statistically driven evolutionary scheme to achieve a better tradeoff between template flexibility and sensitivity to noise and outliers. We focus on understanding the features of template matching that are most beneficial in terms of the achieved match. Examples from simulated and real image data are discussed, with considerations of algorithmic efficiency.

Algorithms↗

PubMedDate not supplied

3D mapping of mini-mental state examination performance in clinical and preclinical Alzheimer disease.

The Mini-mental State Examination (MMSE) is a brief cognitive screening instrument frequently used to track Alzheimer disease (AD) progression. We investigated the structural neuroimaging correlates of MMSE performance in patients with clinical and preclinical AD. We analyzed structural magnetic resonance imaging data from 29 probable AD and 5 MCI patients who later converted to probable AD using an advanced 3D cortical mapping technique. MMSE scores were entered as covariates in a general linear model that predicted the gray matter density at each cortical surface point. The results were corrected for multiple comparisons by permutation testing. The global permutation-corrected significance for the maps linking gray matter loss and cognitive decline was P=0.005 for the left and P=0.012 for the right hemisphere. Strongest correlations between MMSE score and gray matter integrity were seen in the entorhinal, parahippocampal, precuneus, superior parietal, and subgenual cingulate/orbitofrontal cortices. Significant correlations were also seen bilaterally in the temporal, the middle frontal and the left angular and supramarginal gyri. As a global cognitive measure, MMSE depends on the integrity of widely distributed cortical areas in both brain hemispheres with left-sided predominance.

Aged↗

PubMedDate not supplied

New approaches in brain morphometry.

The complexity and variability of the human brain across subjects is so great that reliance on maps and atlases is essential to effectively manipulate, analyze, and interpret brain data. Central to these tasks is the construction of averages, templates, and models to describe how the brain and its component parts are organized. Design of appropriate reference systems for human brain data presents considerable challenges because these systems must capture how brain structure and function vary in large populations, across age and gender, in different disease states, across imaging modalities, and even across species. The authors introduce the topic of brain maps as applied to a variety of questions and problems in health and disease and include a brief survey of the types of maps relevant to mental disorders, including maps that capture dynamic patterns of brain change in dementia.

Brain↗