Yuji Shen1, Ida Mengyi Pu2, Y-C L. Ho3, R Vidyasagar4, Xavier Golay5, Risto A. Kauppinen6
1School of Medicine, University of Birmingham, Birmingham, UK; 2Department of Computing, Goldsmiths, University of London, London, UK; 3Department of Neuroradiology, National Neuroscience Institute, Singapore; 4MARIARC, University of Liverpool, Liverpool, UK; 5Department of Brain Repair and Rehabilitation, Institute of Neurology, University College London, London, UK; 6Biomedical NMR Research Center, Dartmouth Medical School, Hanover, NH 03755, USA
Grey matter nulled (GMN) and VASO fMRI methods were used to measure CBV and T2* changes associated with brain activation in different parenchymal compartments, i.e., blood and extravascular tissues. fMRI experiments were performed in normoxia and mild hypoxic hypoxia. It was observed that while the CBV-weighted signal changes to visual stimulation remain similar in both normoxia and hypoxia, the activated areas are significantly reduced by 7222% in GMN and 6623% in VASO fMRI in hypoxia. Interestingly, T2* decreased in GMN active volume during hypoxia in contrast to increased T2* in normoxia, while T2* in VASO-activated areas increased in both conditions.