Spatial heterogeneity of cerebral cortical-depth response profiles in gradient-echo BOLD fMRI: neuronal or vascular origins?

Motivation: Large draining veins bias gradient-echo BOLD signal towards the pial surface. However, since the cerebral cortex in only sparsely covered by blood vessels, the cortical-depth activation profile varies with position across the cortex. Goal(s): To determine if distinct cortical-depth profiles can be observed across hemodynamic responses of both vascular and neuronal origin. Approach: We applied k-means clustering of the cortical-depth profiles in gradient-echo BOLD data during visual stimulation and breath-hold. Results: Spatio-temporal characteristics of the cortical-depth BOLD fMRI response profiles for visual- and breath-hold task show similarities and differences, likely due to interplay of vascular and neuronal factors. Impact: Comparison of cortical-depth profiles in visual-task and breath-hold task induced BOLD fMRI responses revealed an interplay of vascular and neuronal components, which could be exploited to develop novel data-driven approaches for vascular bias mitigation and improved neuronal specificity.