"When, at last, adequate slow wave signals from the hippocampus were recorded, their relation to behavior became very obvious. Gross movements such as walking, struggling to escape from my hand, or rearing up on the hind legs were invariably accompanied by rhythmical potentials potentials of about 8-9 Hz but a more irregular pattern punctuated at irregular intervals by large spike-like potentials (sharp waves), occurred whenever the rat stood still. However, it also became apparent that a number of smaller movements such as turning the head, changing posture while resting, or moving a forepaw in isolation, were also reliably accompanied by rhythmical waves but both the amplitude and frequency (6-7 Hz) of these waves was less than it was during walking or struggling."
This information was obtained on rats, but humans and rats share mammalian brain structures. Walking sounds like a good thing to do for the hippocampus - make big waves so the 10,000 new baby neurons that form in there every day get some big wave stimulation.