For in that sleep of death what dreams may come.

[William Cloud Hicklin]

Well, not osanwe, which was a transferance of verbal or pre-verbal thought, experienced by the recipient as a 'voice.' Osanwe didn't transmit sense-data.

Tolkien it seems viewed body and soul in incarnates as partaking somewhat of each other's nature, being made for each other; in Elves, ultimately their faded hroar would exist merely as memories imprinted on their fear. I think it not unlikely that, under the magic of the barrow, a corpse would retasin some imprint of its last living thoughts, and that these would have been picked up by the animating wight, perhaps passed on through a series of possessed bodies- of which Merry perhaps was targeted to be the next.

Of course T had thought none of this through when he wrote this chapter (which was never really revised); one thought he had at the time that Black Riders were Barrow-wights, or closely related