Model-free detection of task-evoked neural activity in the whole brain with structurally constrained synchronization of fMRI signals

Motivation: The nonlinear nature of neurovascular coupling and background brain activities that are unrelated to extrinsic stimuli in tasks could result in an inadequate mapping of the task-evoked brain activations with the conventional-GLM in fMRI. Goal(s): The aim of this study is to propose a new approach to map task-evoked brain activation without the linear assumption. Approach: we proposed a model-free approach to map task-evoked activation in the whole brain by measuring increases in BOLD signal synchronization within anatomical structures. Results: Compared to the GLM approach, the model-free approach could detect regions of brain activations beyond the conventional-GLM's characterization, especially in the white matter. Impact: The model-free approach detects task-evoked brain activations by measuring changes in BOLD signal synchronization within local anatomical structures, which is expected to serve as a standardized tool to measure neural activities with nonlinear hemodynamic responses.