Riding a motorcycle every day might actually keep your brain functioning at peak condition, or so says a study conducted by the University of Tokyo.
(...)
Scientists believe that the extra concentration needed to successfully operate a motorcycle can contribute to higher general levels of brain function, and it’s that increase in activity that’s surely a contributing factor to the appeal of the motorcycles as transportation. It’s the way a ride on a bike turns the simplest journey into a challenge to the senses that sets the motorcyclist apart from the everyday commuter.

"This Is Your Brain on a Motorcycle" (Motorcycle Insurance, 15/02/2012)