Chakotay's medicine wheel
A medicine wheel was a medical tool, described as a talisman, in use by Chakotay's Native American tribe. It incorporated animal remains.
When a person was sleeping or on a vision quest, they were said to be walking the wheel. Being in a coma or near death indicated the person had gotten lost. Locations on the wheel might indicate realms, including the fifth and sixth one. stones might be placed as signposts to help point the way back to the soul (that is, their consciousness).
As a practical example, placing the Coyote Stone on the crossroads between the fifth and sixth realm diverted the soul to the Mountains of the Antelope Women.
USS Voyager's EMH was fully versed in tribal healing practices and the therapeutic properties they could provide. (VOY: "Cathexis")