From the article:
“We saw no beneficial effect of estrogen in the animals in cognitively and physically stimulating environments (also known as enriched environments),” said Karyn Frick, assistant professor of psychology and principal investigator on the study. “This fits in nicely with human data and might help to explain why studies of hormone replacement therapy (HRT) do not show beneficial effects for all women. Most studies of HRT use very well-educated women. These results might spur researchers to include a broader population with a greater variation in education and socioeconomic status.”
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“Animals [that had their ovaries removed to simulate menopause] raised in standard conditions showed significant spatial and object memory improvement when treated with a high dose of estrogen, whereas memory in animals in the enriched environment were unaffected or impaired by estrogen treatment,” Frick said. “Among mice not treated with estrogen, enrichment treatment alone significantly improved spatial memory. The behavioral changes were also associated with alterations in a part of the brain critical for memory. These data suggest that estrogen benefits mice raised in un-stimulating environments more than those raised in cognitively and physically stimulating environments.”