Magnetic Resonance Imaging (MRI)

OBJECTIVE: To test the hypotheses 1) that whole-brain volume decline begins in early adulthood, 2) that cross-sectional and longitudinal atrophy estimates agree in older, nondemented individuals, and 3) that longitudinal atrophy accelerates in the earliest stages of Alzheimer disease (AD).

Young adults typically deactivate specific brain regions during active task performance. Deactivated regions overlap with those that show reduced resting metabolic activity in aging and dementia, raising the possibility of a relation. Here, the magnitude and dynamic temporal properties of these typically deactivated regions were explored in aging by using functional MRI in 82 participants.

Controversy persists regarding whether Alzheimer's disease (AD) is a distinct entity or instead exists on a continuum with nondemented aging. To explore this issue, volumetric analyses of callosal and hippocampal regions were performed on 150 participants aged 18-93 years. Group-level analyses revealed that nondemented age-related differences were greater in anterior than posterior callosal regions and were not augmented by early-stage AD. In contrast, early-stage AD was associated with substantial reduction in hippocampal volume.

Spelling performance across a common set of stimuli was examined in young adults, healthy older adults, individuals with early stage dementia of the Alzheimer's type (DAT), and four individuals with a primary semantic impairment (PSI). The stimuli included homophones and low-frequency sound-to-spelling consistent (i.e. words with more predictable spellings) and inconsistent words (i.e. words with less predictable spellings).

The application of advances in biomedical computing to medical imaging research is enabling scientists to conduct quantitative clinical imaging studies using data collected across multiple sites to test new hypotheses on larger cohorts, increasing the power to detect subtle effects. Given that many research groups have valuable existing (legacy) data, one goal of the Morphometry Biomedical Informatics Research Network (BIRN) Testbed is to assess the feasibility of pooled analyses of legacy structural neuroimaging data in normal aging and Alzheimer's disease.

Alzheimer's disease (AD) is associated with neurodegeneration in vulnerable limbic and heteromodal regions of the cerebral cortex, detectable in vivo using magnetic resonance imaging. It is not clear whether abnormalities of cortical anatomy in AD can be reliably measured across different subject samples, how closely they track symptoms, and whether they are detectable prior to symptoms. An exploratory map of cortical thinning in mild AD was used to define regions of interest that were applied in a hypothesis-driven fashion to other subject samples.

This article describes a large multi-institutional analysis of the shape and structure of the human hippocampus in the aging brain as measured via MRI. The study was conducted on a population of 101 subjects including nondemented control subjects (n = 57) and subjects clinically diagnosed with Alzheimer's Disease (AD, n = 38) or semantic dementia (n = 6) with imaging data collected at Washington University in St.

Functional magnetic resonance imaging (fMRI) can provide maps of brain activation with millimeter spatial resolution but is limited in its temporal resolution to the order of seconds. Here, we describe a technique that combines structural and functional MRI with magnetoencephalography (MEG) to obtain spatiotemporal maps of human brain activity with millisecond temporal resolution. This new technique was used to obtain dynamic statistical parametric maps of cortical activity during semantic processing of visually presented words.

Patients with schizophrenia consistently show deficient performance on tasks requiring volitional saccades. We previously reported reduced fractional anisotropy in the white matter underlying right dorsal anterior cingulate cortex in schizophrenia, which, along with lower fractional anisotropy in the right frontal eye field and posterior parietal cortex, predicted longer latencies of volitional saccades.

Cognitive functions such as memory retrieval involve a combination of state- and item-related processes. State-related processes are sustained throughout a task (e.g., "retrieval mode" associated with ongoing goals), whereas item-related processes are transient and allied to individual stimuli (e.g., "retrieval success" associated with the recovery of information from memory). The present study employed a mixed "blocked and event-related" experimental design to identify neural mechanisms that support state- and item-related processes during a recognition memory task.