Can your eyes still move for 4 seconds after being decapitated?

The answer is: yes

Neuroscientists used to believe that all brain activity stopped immediately when the brain was deprived of oxygen. Now we know that decapitated heads retain much of their power. Brain waves continue for about 20 seconds, just as if the head were still attached to the body. And severed parts of the brain can remain alive and active for hours if nourished with oxygenated fluid. Some experiments have suggested that the head of an executed criminal might even retain the capacity to think and feel for a full minute after separation from the body. Even more startling, severed heads might actually remain conscious for the four seconds or so that it takes for the brain's supply of oxygen to be totally depleted.