This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The overall goal of Dr. Hillis's research is to identify impairments of specific cognitive processes in hyperacute stroke that predict concurrent dysfunction of specific brain regions and that will be potentially useful in guiding and evaluating acute stroke intervention. The assumption underlying this research is that any given behavioral task (e.g., naming a picture) entails a number of component cognitive processes that are each subserved by relatively focal areas within a network of brain regions responsible for carrying out the task. Thus, dysfunction of any of the relevant focal brain regions may result in disruption of selective components of the task. As such, several developments in TRD1, TRD2 and TRD3 are of importance for Dr. Hillis' research. These are the development of absolute flow measurements using arterial spin tagging and the use of T2* for studying oxygen extraction ratios in TRD1. The development of fast MRSI technology should allow the use of MRSI durin g the hyperacute phase of stroke, which is now prohibited due to the restricted treatment window. The proposed research in TRD3 and 4 is important for stroke rehabilitation in the more chronic phase of stroke (Days 3 and 90), when reperfusion treatment is no longer an option under present guidelines. The technology developments in TRD3 should allow the detection of relationships between impaired cognitive skills and remote regions suffering from stroke through the imaging of the connecting fibers and the evaluation of these fiber properties. The development of dynamic fiber tracking in TRD4 aids both TRD3 and Dr. Hillis' research. In addition to this, it is our intention to include fMRI in this evaluation of more chronic patients, which would benefit from most of the developments in TRD1 and TRD4 related to fMRI improvements. TRD 3 has been very active: For patients who suffer from stroke, it is very important to know the prognosis and to properly prescribe rehabilitation. Characterization of the location and size of primary stroke lesions by MRI is one of the most important steps toward this goal. Conventional T2-weighted MR images can delineate gray and white matter regions that are involved in the stroke. The gray and white matter consists of various areas with different functionalities, which cannot be differentiated by conventional MRI. Because there is accumulated knowledge about the relationship between gray matter areas and brain functions, it is possible to deduce impacts of stroke lesions on the gray matter and related brain functions from the locations of the stroke observed by MRI. However, such a location-function relationship has not been well established in the white matter. Furthermore, the conventional MRI cannot differentiate various functional units (white matter tracts) in the white matt er. Diffusion tensor imaging (DTI) is a technique that can identify and assess the status of individual white matter tracts. Our hypothesis is that the DTI provides detailed neuroanatomy of brain white matter, which will be crucial information for prognosis and prescription of rehabilitation. In this grant year, we focused on setting up DTI imaging protocols using a group of healthy volunteers (n = 10) and one stroke patient. The results indicated that the technique could delineate specific degeneration of white matter tracts.
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