Functional imaging methods and biophysics.
My lab focuses on three major inter-related research themes; (a) the development of in vivo brain imaging techniques, (b) the examination of biophysical and physiological sources of in vivo imaging techniques, and (c) the linkage of functional imaging with electrophysiological activities. For understanding human brain function, non-invasive brain imaging techniques, including fMRI and intrinsic optical imaging, have been extensively utilized. However, underlying signal sources of fMRI are not well-understood, and its intrinsic limit of spatial temporal and spatial resolution is not well-characterized. For investigating these issues, novel magnetic resonance imaging and spectroscopy techniques have been developed to obtain various physiological information such as cerebral blood flow, cerebral blood volumes, oxygen consumption, and synaptic activity. Using these newly developed methodologies, a chain of events from neural activity and hemodynamic-based fMRI is being investigated. Intrinsic limits of spatial and temporal resolution of hemodynamic-based brain mapping techniques have been examined using sub-millimeter visual orientation columns and cortical layers as a model. My lab has a 9.4 Tesla/31-cm diameter MRI scanner, an intrinsic optical imager with continuous sampling capability, and an electrophysiological recording unit.
Park, S.-H., Masamoto, K., Hendrich, K., Kanno, I. and Kim, S.-G. Imaging brain vasculature with BOLD microscopy: MR detection limits determined by in vivo two-photon microscopy, Magn. Reson. Med., 59: 855–865, 2008.
Moon, C.-H., Fukuda, M., Park, S.-H. and Kim, S.-G. Neural Interpretation of Blood Oxygenation Level Dependent fMRI maps at submillimeter columnar resolution, J of Neurosci, 27: 6892-90, 2007.
Kim, T., Masamoto, K., Hendrich, K. and Kim, S.-G., Arterial versus Total Blood Volume Changes during Neural Activity-induced Cerebral Blood Flow Change: Implication for BOLD fMRI, J. Cerebral Blood Flow and Metabolism, 27(6): 1235-47, 2007.
Masamoto, K., Kim, T., Fukuda, M., Wang, P. and Kim, S.-G. Relationship between Neural, Vascular and BOLD Signals in Isoflurane-anesthetized rat somatosensory cortex, Cerebral Cortex, 17(4): 942-50, 2007.
Fukuda, M., Moon, C.-H., Wang, P. and Kim, S.-G. Mapping iso-orientation columns by contrast agent-enhanced functional magnetic resonance imaging: reproducibility, specificity and evaluation by optical imaging of intrinsic signal, J of Neurosci, 26(46): 11821–11832, 2006.
Zhao, F., Wang, P., Hendrich, K., Ugurbil, K. and Kim, S.-G. Cortical layer-dependent BOLD and CBV responses measured by spin-echo and gradient-echo fMRI: Insights into hemodynamic regulation, NeuroImage, 30, 1149-1160, 2006.