Claire Stevenson1, Matthew Brookes1, Peter Morris1, Susan Francis1
1SPMMRC School of Physics and Astronomy, The University of Nottingham, Nottingham, Nottinghamshire, UK
ASL techniques provide a quantitative measurement of local tissue blood flow, and this may be more directly related to neuronal activation, as measured by MEG, than BOLD. The correlation between MEG phenomena and the changes in cerebral blood flow (CBF), T2* and BOLD, are investigated for a graded visual stimulus. Spatial separation of ASL and BOLD peaks and differences in stimulus related modulations suggest a decoupling of local perfusion and activity measured with BOLD. CBF shows a monotonic increase in amplitude with increasing stimulus contrast, similar to the visual evoked field and γ activity, however β activity is not modulated.