PET scans prove that neurons like estrogen

We now have several lines of evidence, from independent parts of the brain, that estrogen is actually protective in a manner that is related to aging and dementia.
---Daniel Silverman, MD, head of neuronuclear imaging at UCLA

Scads of research evidence already support this conclusion. Reports from brain cells in petri dishes, as well as testimonials from aging gerbils, mice, rats, and women attest to the beneficial effects of estrogen with respect to forming new memories, learning new tasks, finding the right word at the right time, and completing a multi-step task(1) from start to finish.

UCLA scientists used functional brain imaging to visualize how well postmenopausal brains worked with estrogen compared to their activity after estrogen is withdrawn(2). PET scanning involves administration of 'tagged glucose' molecules. When busy little neurons put on their thinking caps in your brain, they suck up and metabolize sugar at an accelerated rate. The labeled glucose glows like a light bulb on subsequent scanning, identifying those parts of the brain that are successively at work.

81 women considered to be at high risk for Alzheimer's disease (AD) based on family history or genetic testing entered the study. All were initially on estrogen for menopausal symptoms. Baseline PET scans were performed, then the subjects were randomly assigned to continue estrogen or go on placebo over 2 years of follow-up. Intial "findings from the first 25 women to undergo baseline and follow-up scans were highly consistent for a neuroprotective effect of estrogen," per Dr. Silverman.

The initial scans showed that the longer the woman had been exposed to her own estrogen (defined as years from onset of menstruation to the end of the line at menopause), the higher the metabolism in the precuneus area of the posterior medial cortex. Don't knock the precuneus area just because you--and me!--haven't a clue where or what it is. Significantly diminished blood flow to this area is one of the earliest signs of Alzeimer's disease.

By study's end, women on estrogen continued to light up brain regions known to be most affected by AD whereas lights were dimming for the estrogenless group. Activity in the right inferior parietal lobe decreased twice as fast for this befuddled group. Research suggests that the right IPL is involved in the "what" (...did I come for) and "where" (...did I put it) of working memory. In fact, again per Silverman: "In [some] women who stayed on estrogen, metabolic activity in the frontal part of the cortex actually increased."
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(1)Such as walking from one room to another to get something, grabbing that something, and returning with it to the original room with the thought intact as to why you wanted that thing
(2)Silverman, D et al. Society of Nuclear Medicine 2008 Annual Meeting: Abstract 973. Presented June 16, 2008.