Poro-Viscoelastic Effects During Biomechanical Testing of Human Brain Tissue

Brain tissue is one of the softest tissues in human body and quantification its mechanical properties has challenged scientists over past decades. Associated experimental results literature have been contradictory as characterizing response brain not only requires well-designed setups that can record ultrasoft response, but also appropriate approaches to analyze corresponding data. Due extreme complexity behavior, nonlinear continuum mechanics proven an expedient tool testing data predict using a combination hyper-, visco-, or poro-elastic models. Such models allow for personalized predictions through finite element simulations, help comprehensively understand physical mechanisms underlying response. Here, we use poro-viscoelastic computational model evaluate effect different intrinsic material (permeability, shear moduli, nonlinearity, viscosity) on during quasi-static biomechanical measurements, i.e., large-strain compression tension well indentation experiments. We show permeability viscoelastic solid largely control fluid flow within out sample. This reveals close coupling between viscous porous effects behavior. Strikingly, our simulations explain why experiments yield white matter stiffer than gray matter, while opposite trend. These observations be attributed loading boundary conditions assumptions made analysis. The present study provides important step better previously published improve analysis future.