Over the last 2 years, my laboratoary has been deeply involved in the development of new MRI techniques for the study of human brain anatomy and function. During 2001-2002, significant progress was made in the development of new techniques for multi-channel MRI, resulting in improved spatial and temporal resolution. In addition to the design of multi-channel MRI signal detectors, a receiver system was developed to allow signal reception simultaneously through 16 channels. This system is currently being tested for 3.0T magnets, and will also be adapted for the 7.0T system. Preliminary results with 4-channel signal detection show that sensitivity gains allow the detection of cortical layers in human V1. Multi-channel technology was combined with parallel imaging techniques to facilitate image acquisition. Novel parallel imaging strategies were designed and evaluated in BOLD fMRI studies, demonstrating the feasibility of improving temporal or spatial resolution, or alternatively reduce acoustic noise and hardware stress during the MRI acquisition process. A technique to measure perfusion and BOLD changes during brain activation was evaluated and used to perform high resolution somatotopy and retinotopy studies. These studies indicated that the ultimately achievable functional resolution in V1 and S1 is limited by vascular artifacts, suggesting that additional methodologies need to be developed to remove these artifacts. One possibility is that the attenuation of vessels at higher magnetic field (7.0T) will be adequate to accomplish this. A new method to investigate temporal aspects of brain activation was developed in collaboration with NHLBI. Non-linear system analysis was performed in the human visual system to investigate non-linear aspects of temporal summation. This required separation of neuronal and hemodynamic effects. We found that, despite the seconds-long temporal blurring of the fMRI contrast mechanism, temporal non-linearities on neuronal time-scales of 10's of millisecond could be detected and mapped.
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