MAPT and dementia: While diagnostic criteria have traditionally focused on the clinical syndrome, typically a predominately amnestic phenotype for AD and a pre-dementia phase called Mild Cognitive Impairment (MCI), recently there has been increasing effort to define AD biologically based on the presence of biomarkers for amyloid deposition (A), tau deposition (T), and neurodegeneration (N), each characterized typically dichotomously as either absent (−) or present (+) and, thus, defining the AT(N) framework7.