Due to their rapid acquisition and high contrast-to-noise-ratio, MRI sequences based on gradient-echo (GE) schemes, e.g., gradient-echo echo-planar-imaging (GE-EPI), are the most commonly used method in human functional MRI. However, their enhanced sensitivity to veins restricts their use in laminar fMRI due to poor signal localization, i.e., venous bias. Here, we investigated the spatial specificity of high-resolution GE signals, pre-processed with ten different approaches. Removal of motion parameters, physiological signals and non-GM tissue contributions, as well as regression of the pre-processed phase image from the magnitude image, significantly increased the spatial specificity of GE-fMRI in resting-state and task paradigms.
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