sentences:  In the spring of 1991 he performed his first human experiments showing that large MRI signal changes were observable in the human brain following exposure to simple visual stimuli, using both blood oxygenation (BOLD) and flow contrast.The first dynamic video images of human brain activity appeared first at a meeting of the Society for Magnetic Resonance in Medicine in August 1991 in San Francisco in a plenary session by colleague Tom Brady, and was subsequently published in 1992 in the Proceedings of the National Academy of Sciences.