Joseph A. Frank

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A fundamental characteristic of working memory is that its capacity to handle information is limited. While there have been many brain mapping studies of working memory, the physiological basis of its capacity limitation has not been explained. We identified characteristics of working memory capacity using functional magnetic resonance imaging (fMRI) in(More)
Low frequency drift (0.0-0.015 Hz) has often been reported in time series fMRI data. This drift has often been attributed to physiological noise or subject motion, but no studies have been done to test this assumption. Time series T*2-weighted volumes were acquired on two clinical 1.5 T MRI systems using spiral and EPI readout gradients from cadavers, a(More)
Magnetic resonance (MR) tracking of magnetically labeled stem and progenitor cells is an emerging technology, leading to an urgent need for magnetic probes that can make cells highly magnetic during their normal expansion in culture. We have developed magnetodendrimers as a versatile class of magnetic tags that can efficiently label mammalian cells,(More)
Functional magnetic resonance imaging (fMRI) is a potential paradigm shift in psychiatric neuroimaging. The technique provides individual, rather than group-averaged, functional neuroimaging data, but subtle methodological confounds represent unique challenges for psychiatric research. As an exemplar of the unique potential and problems of fMRI, we present(More)
Recently, there have been several reports using various superparamagnetic iron oxide (SPIO) nanoparticles to label mammalian cells for monitoring their temporal and spatial migration in vivo by magnetic resonance imaging (MRI). The purpose of this study was to evaluate the efficiency and toxicity of labeling cells using 2 commercially available Food and(More)
Diffusion tensor imaging is highly sensitive to the microstructural integrity of the brain and has uncovered significant abnormalities following traumatic brain injury not appreciated through other methods. It is hoped that this increased sensitivity will aid in the detection and prognostication in patients with traumatic injury. However, the pathological(More)
Monoaminergic neurotransmitters are known to have modulatory effects on cognition and on neurophysiological function in the cortex. The current study was performed with BOLD fMRI to examine physiological correlates of the effects of dextroamphetamine on working-memory performance in healthy controls. In a group analysis dextroamphetamine increased BOLD(More)
MRI methods are widely used to follow the pathological evolution of multiple sclerosis in life and its modification by treatment. To date, measures of the number and volume of macroscopically visible lesions have been studied most often. These MRI outcomes have demonstrated clear treatment effects but without a commensurate clinical benefit, suggesting that(More)
Steady-state arterial spin tagging approaches can provide quantitative images of CBF, but have not been validated in humans. The work presented here compared CBF values measured using steady-state arterial spin tagging with CBF values measured in the same group of human subjects using the H(2)(15)O IV bolus PET method. Blood flow values determined by(More)
Positron emission tomography (PET) functional imaging is based on changes in regional cerebral blood flow (rCBF). Functional magnetic resonance imaging (fMRI) is based on a variety of physiological parameters as well as rCBF. This study is aimed at the cross validation of three-dimensional (3D) fMRI, which is sensitive to changes in blood oxygenation, with(More)