Functional magnetic resonance imaging in white matter using 3 T gradient-echo-planar imaging

White matter structures make up functional connectivity of the brain. The ability to observe white matter in action will provide insight into both normal brain function, as well as diseases characterized by loss of white matter integrity. Detection of functional magnetic resonance imaging (fMRI) activation in white matter is has been increasingly reported despite historically being controversial. The majority of development work to-date has used high-field MRI and specialized pulse sequences. In the current study, we utilized 3T MRI and a commonly applied gradient echo (GRE) echo-planar imaging (EPI) sequence to probe the robustness of fMRI activation using conventional clinical conditions. Functional activity was stimulated in target regions of interest within the corpus callosum, using an established visual-motor interhemispheric transfer task. The results confirmed that it was possible to detect white matter fMRI activation at the group level (N = 13, healthy individuals). Individual analyses revealed that 8 of the 13 individuals showed white matter activation in the body of the corpus callosum. Overall, the group results replicated prior 4 T MRI studies, but showed a lower percentage of individuals with activation. The findings support the concept that while white matter activation is detectable, the activation levels are close to thresholds used for routine 3 T MRI studies. Furthermore, by applying alternate hemodynamic response functions during analysis, larger clusters of activation were seen at the group-level