MAPT and Alzheimer disease: According to our analysis, none of the clinical trials [14, 15, 18, 41] reported biomarkers for neurofibrillary tangles (FDDNP-PET) or amyloid deposition (PiB-PET) [60] to keep track of any stimulation-induced benefits as well as potential deterioration.10 Recently, a study using optogenetics showed that neuronal activity enhances tau propagation and tau pathology in vivo in a mice model of AD.