Just moderate walking several times a week can improve the memory and brain function in seniors...http://www.webmd.com/healthy-aging/news/20080902/walking-boosts-brainpower
It sure does work. In fact, I think any form of exercise in general makes one's brain a bit sharper.
the university study they referenced maintained that slow walking is NOT fitness - that it only qualifies when you bring your heart rate up to some stated cardio level. Anything below that level, they swore, was NOT exercise and was useless.
I get the impression it was written by a bunch of 18-year-old first-year psych students who couldn't Google anything better to write about.