If an epileptic seizure is focused in a particular sweet spot in the temporal lobe, a person won´t have motor seizures, but instead something more subtle. The effect is something like a cognitive seizure, marked by changes of personality, hyperreligiosity (an obsession with religion and feelings of religious certainity), hypergraphia (extensive writing on a subject, usually about religion), the false sense of an external presence, and, often, the hearing voices that are attributed to a god. Some fraction of history´s prophets, martyrs, and leaders appear to have had temporal lobe epilepsy.

Imbalance of reason and emotion may explain the tenacity of religion in societies: world religions are optimized to tap into the emotional networks, and great arguments of reason amount to little against such magnetic pull.

When one part of the brain makes a choice, other parts can quickly invent a story to explain why. If you show the command "Walk" to the right hemisphere (the one without language), the patient will get up and start walking. If you stop him and ask why he's leaving, his left hemisphere, cooking up an answer, will say something like "I was going to get a drink of water."

It turns out that dopamine is a chemical on double duty in the brain. Along with its role in motor commands, it also serves as the main messenger in the reward systems, guiding a person toward food, drink, mates, and all things useful for survival. Because of its role in the reward system, imbalances in dopamine can trigger gambling, overeating, and drug addiction - behaviors that result from a reward system gone awry.

The left hemisphere acts as an "interpreter," watching the actions and behaviors of the body and assigning a coherent narrative to these events. And the left hemisphere works this way even in normal, intact brains. Hidden programs drive actions, and the left hemisphere makes justifications. This idea of retrospective storytelling suggests that we come to know our own attitudes and emotions, at least partially, by inferring them from observations of our own behavior.

I'm using the afterlife as a backdrop against which to explore the joys and complexities of being human - it turns out that it's a great lens with which to understand what matters to us.

As we develop better technologies for probing the brain, we detect more problems.