MAPT and tauopathy: Finally, acknowledging the transformative impact of amyloid and tau PET on AD research and drug development, there remains a huge unmet need to develop molecular imaging markers for other protein aggregates, such as non-AD tauopathies, α-synuclein, and TDP-43, to truly capture the complexity of brain pathologies that contribute to neurodegeneration and dementia (see Appendix C).