Rate dependence of human visual cortical response due to brief stimulation: An event-related fMRI study

The human brain response to a wide range of visual stimulus rates presented over a prolonged time period has been investigated by various neuroimaging techniques. However, to date, no imaging study has been performed to study the dynamic human brain response to various stimulus rates when presented in a short time. This report describes activation in the human brain due to brief visual stimulus presentation (1 s) for stimulus rates varying from 1 to 20 Hz using event-related functional MRI (fMRI). Our results show that the amplitude of the fMRI response increases with the stimulus frequency an d plateaus at 6 Hz. This finding differs slightly from the results of previ ous blocked task paradigm experiments (with a longer time of stimulus prese ntation), in which the response peaks at approximately 8 Hz and then decrea ses. Our results are in close agreement with previously published psychophy sical studies, suggesting that the fMRI signal in this experiment is indica tive of cortical activity related to visual processing. (C) 2001 Elsevier S cience Inc. All rights reserved.