Although, at this time, there are no data showing that increasing M-neurons gives functional benefit, the issue is relevant to the present article because TGF-β drives E-to-M, and the levels of TGF-β become reduced after the transition from MCI to AD; it seems possible that the consequent reduction of E-to M relates to why MCI is often spontaneously reversed but that never happens once AD occurs. Here, TGFB1 is linked to Alzheimer disease.