My first ride on my then-three-year-old (some Arabians grow slowly, but that leaves time for a solid basis in groundwork. I suspect Saddlebreds do too, but I'd be guessing. I never knew any baby Saddlebreds) went smooth as buttah. In fact every first ride I've taken on a horse I'm starting out went as smooth as buttah. Dude, work don't rush the ground-work!
But yeah, I gotta feel for him. I got a concussion the same way. I was even wearing a helmet and it just flew off. I still remember that day, but strangely, not the same way everyone else does. I was dumb enough to put the saddle on my horse for the first time... with an arm broken in two places. Luckily that went well, but it was dumb. And I thought that I kept having to be woken up and that I missed three days of school because of pain killers.
Years later, mom told me I wasn't on any strong pain killers. I just had a concussion. I never knew that. Apparently I was told, but I wasn't in my head at the time.
So a performer going on auto-pilot after a concussion? Sure! Why not? It frakked me up for a few days. I seem to remember he was pretty funny, but that was back in high school.