Synesthesia is a process by which the brain associates colors and visuals with feelings, smells and sounds, creating a sensory overload that can be very exhilarating.
Sound like something from a drug-induced mind trip? It can actually be as simple as associating the color red with the flavor cherry, or feeling sad when looking at a certain shade of blue. The Synthetic Locked video is a mind-melting display of visuals and noises, attempting to program the viewer's brain to associate various words with certain sounds and sights.
The point of this sensory overload is that once the brain is trained, it will continue to make these types of associations no matter what it is looking at.