"You can live "normally" with half your brain. In some severe drug resistant epileptic syndrom in young kids, the only option to stop the seizures is to remove a complete brain hemisphere.

After a while, with proper reeducation and all, the children can go on to have a normal life without cognitive deficit. They will have a limping, blindness from one eye and a very weark arm but can lead a normal life and not end up cognitively impaired.

One of the earliest sign of alzheimer's disease, before the memory loss, could be the loss of the sense of smell. It's also the case with Parkinson disease.

Our brain looks wrinkled because it is actually "folded" inside our skull in order to fit a maximum of surface and thus neurons & cell communications. Some animals like rodents have a completely smooth brain."

"The reason it feels weird when you or someone touches the inside of your belly button is because the nerves actually go to your spinal cord. These nerves lie at the same level that relay signals to your urethra and bladder. So when you feel like you have to pee when you touch the inside of your belly button, that's why."