Investigating the Regional, Directional, and Rate-Dependent Mechanical Response of Fixed Human Brain Tissue Under Compression.

Assuming homogeneous mechanical properties for all brain tissue in computational simulations may lead to inaccurate predictions of response, affecting conclusions about brain injury mechanisms, prevention, and treatment. This study investigated the effect of tissue location, loading direction, and strain rate on the mechanical properties of brain tissue. Digital Image Correlation (DIC) analysis was used to quantify the stress response, Poisson's Ratio (PR), and volume ratio of human brain tissue under uniaxial compression. The directional, regional, and strain rate dependent properties of white matter from the corpus callosum and gray matter from the temporal lobe cortex were investigated. Higher strain rate and compression magnitude increased the tissue stress response across all brain regions and loading directions. The PR of all tissues varied with compression magnitude. The temporal lobe exhibited isotropic deformation behavior, aligning with homogeneous incompressible material behavior. In the corpus callosum, directionally dependent PR suggested transverse isotropy. For both tissue locations, the volume ratio investigation showed deviations from incompressibility as strain rate and compressive strain magnitude increased; these deviations can result in large stored-energy penalties due to the high bulk modulus of brain tissue. Integrating region- and direction-specific mechanical properties into brain tissue models could improve insights into complex load transfer mechanisms within the brain, potentially refining clinical strategies for brain injury intervention and prevention.