Correction of eddy current distortions in high angular resolution diffusion imaging.

Purpose: To correct distortions caused by eddy currents induced by large diffusion gradients during high angular resolution diffusion imaging without any auxiliary reference scans.

Materials And Methods: Image distortion parameters were obtained by image coregistration, performed only between diffusion-weighted images with close diffusion gradient orientations. A linear model that describes distortion parameters (translation, scale, and shear) as a function of diffusion gradient directions was numerically computed to allow individualized distortion correction for every diffusion-weighted image.

Risky decision-making in older adults without cognitive deficits: an fMRI study of VMPFC using the Iowa Gambling Task.

Some older adults without neurological disease exhibit impaired decision-making in risky, nontransparent situations, like the Iowa Gambling Task (IGT). The prefrontal cortices are particularly vulnerable to age-related decline, and numerous studies implicate the ventromedial prefrontal cortex (VMPFC) in successful IGT performance. However, the relationship between IGT performance and VMPFC function in older adults has not yet been tested by fMRI.

Mapping brain abnormalities in boys with autism.

Children with autism spectrum disorder (ASD) exhibit characteristic cognitive and behavioral differences, but no systematic pattern of neuroanatomical differences has been consistently found. Recent neurodevelopmental models posit an abnormal early surge in subcortical white matter growth in at least some autistic children, perhaps normalizing by adulthood, but other studies report subcortical white matter deficits. To investigate the profile of these alterations in 3D, we mapped brain volumetric differences using a relatively new method, tensor-based morphometry.

Working memory in Parkinson's disease patients: clinical features and response to levodopa.

Objective: To evaluate the clinical features of the working memory (WM) in Parkinson's disease (PD) patients and to test the effect of levodopa on WM.

Method: The paradigm was based on the 'n-back' tasks, which enables to study the level of executive demand (three levels of difficulty) and the domain of the information being processed (spatial items, faces and letters). The effect of levodopa was studied by testing PD patients in "on" and "off" states.

Three-dimensional mapping of the lateral ventricles in autism.

In this study, a computational mapping technique was used to examine the three-dimensional profile of the lateral ventricles in autism. T1-weighted three-dimensional magnetic resonance images of the brain were acquired from 20 males with autism (age: 10.1+/-3.

Detection and mapping of hippocampal abnormalities in autism.

Brain imaging studies of the hippocampus in autism have yielded inconsistent results. In this study, a computational mapping strategy was used to examine the three-dimensional profile of hippocampal abnormalities in autism. Twenty-one males with autism (age: 9.

Mapping corpus callosum deficits in autism: an index of aberrant cortical connectivity.

Background: Volumetric studies have reported reductions in the size of the corpus callosum (CC) in autism, but the callosal regions contributing to this deficit have differed among studies. In this study, a computational method was used to detect and map the spatial pattern of CC abnormalities in male patients with autism.

Methods: Twenty-four boys with autism (aged 10.

Dynamically spreading frontal and cingulate deficits mapped in adolescents with schizophrenia.

Context: We previously detected a dynamic wave of gray matter loss in childhood-onset schizophrenia that started in parietal association cortices and proceeded frontally to envelop dorsolateral prefrontal and temporal cortices, including superior temporal gyri.

Objective: To map gray matter loss rates across the medial hemispheric surface, including the cingulate and medial frontal cortex, in the same cohort studied previously.

Design: Five-year longitudinal study.

Detecting disease-specific patterns of brain structure using cortical pattern matching and a population-based probabilistic brain atlas.

The rapid creation of comprehensive brain image databases mandates the development of mathematical algorithms to uncover disease specific patterns of brain structure and function in human populations. We describe our construction of probabilistic atlases that store detailed information on how the brain varies across age and gender, across time, in health and disease, and in large human populations. Specifically, we introduce a mathematical framework based on covariant partial differential equations (PDEs), pull-backs of mappings under harmonic flows, and high-dimensional random tensor fields to encode variations in cortical patterning, asymmetry and tissue distribution in a population-based brain image database (N =94 scans).