MAPT and early-onset autosomal dominant Alzheimer disease: In Alzheimer’s disease, tau accumulation in the LC precedes volume loss, with a decrease of more than 55% of LC neurons during the progression from prodromal to severe dementia.8,9 Neuronal loss may be more prominent in the rostral/middle portion of the LC,9,10 and has been shown to correlate with decreased cognitive function,11–13 post-mortem neuropathology8 and reduced NA levels in the neocortex and hippocampus.14