Peter A. Hardy

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PURPOSE To test the hypothesis that the T2 shortening observed on MR images of the brain in patients with Parkinson and Huntington diseases is due to tissue iron deposition. METHODS Tissue iron and ferritin assays were performed on postmortem putamen and globus pallidus samples from subjects with Huntington and Parkinson disease. The assays were(More)
Three-dimensional (3D) MR imaging of the knee is useful to detect cartilage abnormalities, although the tissue contrast in 3D gradient-recalled echo (GRE) sequences such as gradient-recalled acquisition in the steady state (GRASS) or fast low-angle shot (FLASH) is poor. T2 contrast can be added to a GRASS sequence by combining the signals from the first and(More)
Changes in the nigrostriatal system may be involved with the motor abnormalities seen in aging. These perturbations include alterations in dopamine (DA) release, regulation and transport in the striatum and substantia nigra, striatal atrophy and elevated iron levels in the basal ganglia. However, the relative contribution of these changes to the motor(More)
PURPOSE To estimate the relationship between R2 = 1/T2 as measured with a double echo spin echo sequence and total iron concentration in gray matter structures in the brains of aging rhesus monkeys. MATERIALS AND METHODS Using a 1.5-T magnetic resonance (MR) imager, we collected double echo spin echo images of the brains of 12 female rhesus monkeys aged(More)
Speed of visual word recognition is an important variable affecting linguistic competence. Although speed of visual word recognition varies widely between individuals, the neural basis of reaction time (RT) differences is poorly understood. Recently, a magnetic resonance technique called diffusion tensor imaging (DTI) has been shown to provide information(More)
Fast spin-echo (FSE) sequences are becoming popular for T2-weighted clinical imaging because they result in a severalfold reduction in imaging time and because they provide conventional spin-echo contrast for most tissues. Fat, however, has been observed to have anomalously high signal intensity on FSE images. The present study shows that the brighter fat(More)
Functional imaging of the non-human primate brain in awake animals is now feasible because of recent methodological advances. Here we detail our procedures for conducting functional MRI (fMRI) studies in rhesus monkeys. Our emphasis has been on analyzing drug-evoked responses within and across test groups, meaning that techniques have had to be developed(More)
Because short-term limb immobilization produces selective adaptations in the neuromuscular system that probably interact with the task-dependent expression of muscle fatigue, the purpose of this study was to determine the effects of limb immobilization on the ability of human subjects to sustain isometric contractions at low and moderate submaximal forces.(More)
There is a great need for the development of noninvasive, highly sensitive, and widely available imaging methods that can potentially be used to longitudinally monitor treatment of Parkinson's disease (PD). Here we report the monitoring of GDNF-induced functional changes of the basal ganglia in hemiparkinsonian monkeys via pharmacological MRI measuring the(More)
Visual cortical surface area varies two- to threefold between human individuals, is highly heritable, and has been correlated with visual acuity and visual perception. However, it is still largely unknown what specific genetic and environmental factors contribute to normal variation in the area of visual cortex. To identify SNPs associated with the(More)