CNT Seminar: Prof. Jonathan R. Polimeni

CNT Seminar

Abstract:

Accelerated image encoding and the increased sensitivity afforded by highly-parallel receive arrays and Ultra-High Field (≥7T) systems have recently enabled sub-second, sub-millimeter isotropic resolution studies of the functional architecture of the human brain with fMRI, the spatial and temporal accuracy of which is increasingly limited by the biological point-spread of the BOLD signal. In this presentation, I will review recent work investigating the limits of spatial and temporal accuracy of fMRI. I will present studies designed to characterize the specificity of the BOLD signal by combining subsecond or submillimeter isotropic voxels and a surface-based analysis approach that together allow the BOLD signal to be measured over large extents of the folded cortical surface. With such small voxels and rapid sampling times, the characteristics of the BOLD signal become increasingly influenced by the details of the vascular anatomy and physiology. I will present recent results from our laboratory showing cortical columnar imaging simultaneously over multiple visual cortical areas, and the detection of oscillations up to the delta-band frequencies in human visual cortex and sub-cortical regions using high spatiotemporal resolution EPI at 7 and 9.4 T. I will also survey recent methodological work into “high-performance accelerated EPI” aimed at increasing the imaging resolution and time-series signal-to-noise ratio for future high-resolution UHF fMRI studies. Lastly, I will present new work demonstrating biases in the BOLD fMRI signal as a function of cortical orientation relative to the B0 axis direction up to 70% at 7T, and how similar cortical orientation effects induce tSNR biases and across-subject tSNR variability in the 3T HCP dataset.