You're walking along the river, eating a Big Mac sans pickles, when your heart stops. Hardly noticeable in and of itself, considering it starts right back up again. A lot more noticeable is your sudden hunger. The Big Mac, now forgotten, falls to the ground, the upper bun rolling lopsidedly down the bank and into the water.
Your brain, having stopped at the same time as your heart, is not so quick to reboot. The brain stem starts working first, keeping your heart pumping, keeping your lungs moving. Instinct kicks in, recognizes your body's hunger, seeks to satisfy it.
Your vision is connected to the cerebrum and has not yet begun to work again. Same with your hearing and your memory, stored in the temporal lobes of the upper brain. You stumble about, moaning unintelligibly.
After a few minutes, the blood pumping through your brain manages to conduct an electrical charge to the occipital lobe of the cerebrum, and your sight comes back online. Your eyes, by now nearly glowing they're so bloodshot, begin to work once more.
Food! Motion ahead of you indicates life, and even in your moronic state you recognize an animal as your quarry. You spring forward, loping toward it, hoping to catch it unaware, confident that speed and surprise are your best weapons.
The animal, just about a match for you in terms of size, walks unwittingly into your path. When you jump on its back, it crumples to the ground, and you ecstatically dig your incisors into its shoulder meet, struggling to rip flesh with teeth long unused to such fresh and unwilling food.
The animal is making frantic, piercing noises, your first indication that you can hear once again. The electrical charge in your brain has made its way to your temporal lobe, where hearing and memory are controlled. The first twinge of doubt creeps in as you begin to realize that this animal you're attacking has a body shape all too similar to your own.
Your hypothalamus comes online next and your hunger drops sharply away. You are looking down upon the human writhing in pain, clutching her shoulder as she bucks and twists in an attempt to escape your grasp.