MAPT and Cognitive impairment: Alzheimer’s disease (AD) is a neurodegenerative disorder and the most common cause of dementia.1  Ad is characterized by pathological depositions of amyloid-β (A) and hyperphosphorylated tau (T) in the brain, which can be detected in vivo by abnormal CSF levels of these proteins.2,3 Individuals with mild cognitive impairment (MCI) and abnormal amyloid (A+) are at increased risk of developing dementia,4,5 but individuals vary in their rates of cognitive decline.