Effects of check size on visual cortex activation studied by functional magnetic resonance imaging

We studied functional magnetic resonance imaging (fMRI) of visual cortex du ring checkerboard visual stimulation with three standard check sizes to exa mine whether activation in the visual cortex varied among these sizes. We a cquired fMRI at 1.5 T in 8 normal subjects, each receiving the best refract ive correction. Each subject underwent an experiment consisting of four con ditions: black and white checkerboards with three check sizes (0.25-, 0.5-, and 1.0-degree) flickering at 8 Hz, and a black screen. SPM96 was used for a group data analysis with a random effects model after each of the subjec t's data was motion-corrected and spatially normalized to a standard brain. The activation in the visual cortex showed the greatest signal changes wit h the 0.5-degree check among the th ree check sizes. When standard check si zes are used to stimulate visual cortex in fMRI experiments, our results su ggest that 0.5-degree checks flickering at 8 Hz produce the most vigorous a ctivation in visual cortex. Copyright (C) 2001 S. Karger AG, Basel.