Functional Magnetic Resonance Imaging (fMRI) has revolutionized neuroscience by mapping activity throughout the brain without the use of radioactive tracers, electrical probes or other invasive procedures. The dominant method for fMRI, Blood Oxygenation Level Dependent (BOLD) imaging, is sensitive to changes in blood oxygenation that occur in response to brain activity. While BOLD imaging represents a major advance in brain mapping, this method has a number of significant limitations including poor spatial resolution, low signal levels, limited contrast and severe image artifacts. These limitations derive from the fact that BOLD contrast is slow to develop, resulting in a loss of signal and a sensitivity to image artifacts. Our group has developed a new steady-state fMRI method that has the potential to overcome these limitations by sensing changes in blood oxygenation more directly. The steady-state signal can be made intrinsically sensitive to oxygenation, allowing data to be gathered under significantly better imaging conditions. Steady-state fMRI is expected to produce artifact-free images with high spatial resolution, and provide high signal levels with excellent functional contrast. The work described in this proposal will take the first steps in transforming this nascent method into a practical tool for neuroscience experiments. Development of the imaging methodology will be accompanied by analysis of the spatial and temporal characteristics of the functional signal, as well as comparison with standard BOLD imaging. This proposal will focus on the visual system as a well-characterized testbed of widespread interest in the neuroscience community. Development will be guided by the specific goals of spatial and temporal characterization in the visual cortex.
