MAPT and red-green color blindness: The primary tauopathies progressive supranuclear palsy (PSP) or corticobasal degeneration (CBD) are characterized by an abnormal aggregation of tau isoforms with four‐repeat binding domains within neurons and glial cells typically in brainstem regions and subcortical nuclei, which manifest as atypical parkinsonian syndromes with oculo‐motor symptoms, gait disturbance, and falls in PSP, as well as asymmetric hypokinetic rigid syndrome, limb dyspraxia, and alien limb phenomenon in CBD.5