Mushrooms, it would seem, have been reported to improve cognitive abilities and motor performance before. But the people studied in one such trial also consumed a high level of fruit and vegetables. With this is mind, researchers from Tufts University, Boston set about studying the effect of diets in which 0.5, 1, 2 or 5% of the food was mushroom.
First off, it was in rats not humans this time, but the findings were interesting nonetheless. They found that supplementation with A. Bisporus mushroom (the most commonly consumed one) led to improved motor performance, specifically balance. They also found that small amounts improved cognition, but, larger quantities paradoxically, seemed to have a negative effect.
There was also no weight gain seen in the groups consuming the mushrooms even though the food intake was higher.
So, not quite compelling enough to convince me to start eating them every day, but I might make my intake little and often and start avoiding mushroom stroganoff the day before I really need to engage my brain in the lab.