Jim, I've always heard about exercise increasing neurogenesis and synaptic plasticity.
But... You could interpret that as being more susceptible to propaganda or just having more neurons.
I would want to see that the specific neural changes actually produce a cognitive benefit in controlled behavioral tests.
Mostly because neural systems are highly degenerate. (See Eve Marders work). Several different neural configurations (in terms if parameters like connection strength and potassium conductance) can lead to the same functional result.