FUNCTIONAL MRI OF HUMAN BRAIN ACTIVATION COMBINING HIGH SPATIAL AND TEMPORAL RESOLUTION BY A CINE FLASH TECHNIQUE

Functional mapping of human brain activation has been accomplished at high spatial and temporal resolution (voxel size 4.9 mu l, temporal in crement 100 ms), The approach was based on oxygenation-sensitive long- echo time FLASH MRI sequences synchronized to multiply repeated cycles of visual stimulation in a CINE acquisition mode, This high temporal resolution revealed that stimulus-related signal intensity changes in human visual cortex display an initial latency followed by increases e xtending over several seconds. Furthermore, the temporal characteristi cs of the complete CINE MRI signal time course depended on the absolut e and relative durations of activation and control periods and, for ex ample, caused an apparent absence of a poststimulation ''undershoot'' phenomenon. Complementing hyperoxygenation due to rapid hemodynamic ad justments, these results suggest signal intensity modulation by enhanc ed oxygen consumption and concomitant deoxygenation during prolonged a nd/or repetitive stimulation.