GFAP and Alzheimer disease: The current study addressed this question by examining the association of CP macrostructure/volume and CP microstructure (assessed using T1 or T2) with plasma biomarkers of AD (Aß42/40 ratio; pTau181), neuronal injury (neurofilament light chain [NfL]), and reactive astrogliosis (glial fibrillary acidic protein [GFAP]), a maker of astrocyte-mediated neuro-inflammation.