INCREASE OF CREATINE-KINASE ACTIVITY IN THE VISUAL-CORTEX OF HUMAN BRAIN DURING VISUAL-STIMULATION - A P-31 NMR MAGNETIZATION-TRANSFER STUDY

P-31 magnetic resonance spectroscopy was used to investigate changes i n high energy phosphate levels and creatine kinase (CK) kinetics induc ed in the human visual cortex during photic stimulation. CK kinetics w as evaluated by measuring the apparent unidirectional rate constant (k (f)) in the ''forward'' direction (i.e., in the direction of ATP synth esis from phosphocreatine). k(f) increased 34% in the visual cortex ar eas during stimulation without significant changes of steady-state con centration of high energy phosphate compounds, indicating that CK turn over is elevated during increased neuronal activity.