Chin blow carries mechanical force from mandible directly to the skull with no soft tissue shock absorption along the way--and the direct mechanical force of the blow translates to fore-and-aft movement of the skull WITHOUT any rotation absorbing the energy---skull imparts blows force directly to soft tissue of the brain as the inertial mass of the brain leaves it standing in place, being sloshed through the normally cushioning layer of cerebral spinal fluid to make direct mechanical contact with the inside of the skull (albeit through the layers of the pia, mater and dura) ----forebrain and probably including midbrain structures---and then whipsaws backwards with a contra-coup impact on the back the brain as the head snaps back. (occiput/visual centers)

The mechanical impact of the brain tissue on the inside wall of the brain probably causes (now I'm guessing, but it's an informed guess) the neurons to respond to the blow with a mass ionic depolarization/electrical potential trigger---and concussion.

If he's only averagely unlucky, he'll also have a intra-cerebral/parenchymal micro bleeding---and if he's really unlucky, he'll keep getting in that ring and he'll end up like the NFL players with serial concussions or like Muhammed Ali. A demented, Parkinsonian cripple.

Don't get hit in the head.

I've got immense respect for Gazzaniga, but he's got one thing wrong here. He's implicitly equating consciouness with linguistic awareness. It's odd, too, because he's clearly demonstrating conscious awareness of the items in subject's left visual field. I'm guessing he's basically just simplifying things for the audience. Is this from Nova? What year?

Even though everyone in the neuroscience community calls it split-brain, it's really a misnomer, because there remains a lot of communication between the hemispheres via the amygdala and other midbrain structures. There's a lot of neat studies demonstrating this, in particular using highly emotional content.

If you want to go to the beginning though, look up Sperry's groundbreaking split-brain studies from the 60s - for which he won the Nobel Prize.