Hemodynamic Deconvolution Demystified: Sparsity-Driven Regularization at Work
Date
2023Author
Uruñuela, Eneko
Bolton, Thomas A.W.
Van De Ville, Dimitri
Caballero-Gaudes, César
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Aperture Neuro
Abstract
Deconvolution of the hemodynamic response is an important step to access short timescales of brain activity recorded by functional
magnetic resonance imaging (fMRI). Albeit conventional deconvolution algorithms have been around for a long time (e.g., Wiener
deconvolution), recent state-of-the-art methods based on sparsity-pursuing regularization are attracting increasing interest to in-
vestigate brain dynamics and connectivity with fMRI. This technical note revisits the main concepts underlying two main methods,
paradigm free mapping and total activation, in the most accessible way. Despite their apparent differences in the formulation,
these methods are theoretically equivalent as they represent the synthesis and analysis sides of the same problem, respectively. We
demonstrate this equivalence in practice with their best-available implementations using both simulations, with different signal-to-
noise ratios, and experimental fMRI data acquired during a motor task and resting state. We evaluate the parameter settings that
lead to equivalent results and showcase the potential of these algorithms compared to other common approaches. This note is
useful for practitioners interested in gaining a better understanding of state-of-the-art hemodynamic deconvolution and aims to
answer questions that practitioners often have regarding the differences between the two methods.