5 Years ago Claire Wineland was in a medically induced coma for 2 weeks. On her Youtube channel she recounts what she remembers, which is a surprising amount. Conversations that happened around her were melded into her dreams, and ice packs put around her made her dream of being in Alaska.
Recently a man awoke from a 12 year coma and said that he was aware of everything. Others report not remembering anything at all from their coma experiences. The variety of sensations seem to be as varied as the people themselves.