INCREASED OXYGEN-CONSUMPTION IN HUMAN VISUAL-CORTEX - RESPONSE TO VISUAL-STIMULATION

To test whether a sufficiently complex visual stimulus causes the cons umption of oxygen to rise in the human visual cortex, we used positron emission tomography (PET) to measure the cerebral metabolic rate of o xygen (CMRO2) during visual stimulation in 6 healthy normal volunteers . A yellow-blue checkerboard, reversing its contrast at a frequency of 8 Hz, was presented for a period of 7 min, beginning 4 min before the onset of a 3-min scan. In the baseline condition, subjects fixated a cross-hair from 30 s before until the end of the 3-min scan. The CMRO2 was calculated with the two-compartment weighted integration method ( 1). The checkerboard minus baseline subtraction yielded statistically significant increases in CMRO2 in the primary (V1) and higher order vi sual cortices (V4 and V5). The significant CMRO2 increases were detect ed in these regions in both the group average and in each individual s ubject.