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Abstract:
Functional MR imaging in monkeys promises to build a bridge between brain research in humans and the large body of systems neuroscience work in animals. Simultaneous fMRI and
electrophysiology was recently used in the anesthetized monkey to elucidate the neural activity underlying the fMRI BOLD signal [1]. Perfusion-based MRI measures cerebral blood flow (CBF) at the capillary level and can be used for functional studies based on the tight spatial coupling between brain activity and blood flow. From CBF changes and interleaved-acquired BOLD data, changes in oxygen consumption can be calculated. Obtaining functional CBF maps with high spatial resolution is a major challenge, because the CBF signal is intrinsically low and the signal-to-noise ratio is critical. In this study, high-resolution CBF maps were obtained with voxel sizes as small as 0.5 x 0.5 x 3 mm3 in the Macaca mulatta for the first time. High sensitivity was made possible by signal-to-noise gains at the high magnetic field of 7 Tesla and by using a customized RF combination coil design. In first experiments, CBF maps and functional CBF data were acquired and compared with functional BOLD data in the primary visual
cortex. For CBF, large contrast-to-noise gains were obtained at high spatial resolution similar as previously reported in humans [2]. These first results demonstrate that the sensitivity gains at high field can be used to study CBF changes in primate brain with spatial dimensions well below the cortical thickness. This is significant for the understanding of localized brain function and the physiological basis of functional neuroimaging.
