There is a need for non-invasive biomarkers that enable accurate tracking of early, pre-symptomatic phases of Alzheimer’s disease (AD). Previous fMRI studies have differentiated AD patients from healthy controls. However, it is unknown whether the accumulation of tau or amyloid pathology is driving the fMRI irregularity. This is the first study to investigate whether tau pathology alone can modulate task-based BOLD fMRI. We observed stronger BOLD responses to visual stimulation in lateral geniculate nucleus and superior colliculus in the tau cohort, mirroring observations in mild AD and MCI patients.