I went down a few years ago. Riding with one other cyclist, had a vague recollection of clearing his rear wheel but nothing after that. Was knocked out for a minute, asked the same questions repeatedly, got a ride home from a nearby railway worker. Didn't remember the ride home but was cognizant enough to give him directions to my place. Not too coordinated in the shower and still asking same questions of my wife. Went to a movie (near a hospital) that afternoon with the family and they kept an eye on me. Didn't have any further symptoms but memory of the incident never came back. To this day I have no idea what happened. Took the next day off and then rode again. Don't recall how I felt but checked my diary and noticed I took 4 days off the bike which is unusual.