Why do we sleep? And what does sleep have to do with memory, trauma, and our emotions? From fruit flies to whales, virtually every animal sleeps. But why? Why do we need to spend nearly a third of our lives in such a defenseless state? Scientists are peering more deeply into the sleeping brain than ever before, discovering just how powerful sleep can be, playing a role in everything from memory retention and emotional regulation to removing waste from our brains. So why are we getting so little of it?

In the fifth episode Neil deGrasse Tyson explores questions that have baffled scientists for centuries. Can we know the universe? Are our brains capable of comprehending the cosmos in all of its complexity and splendor?. We don't yet know the answers because our brain remains almost as much of a mystery to that questions as the universe itself. An abandoned orphan's dream opened the way to understanding the architecture of thought.

The nervous system is fundamentally electric. When we move our arm, it moves because a electric signal has been sent to the muscle that controls it. Now, because the brain is electric, we could also use electricity to record what the brain is doing or bypass it entirely, and control a body. That means that we could restore movement to people who are paralyzed, feel through an artificial hand as if it was our own, and even read people's minds.
Michael Stevens explores how electricity can be used to move cockroaches, control other peoples' limbs and even read peoples' thoughts.

Autistic minds provide windows into how we all think, feel, and behave. A complete brain science should be able to account for all kinds of minds and brains. As long as some minds remain a mystery, so too will all minds.
Michael Stevens travels to London to meet a blind, autistic savant with astonishing musical abilities, and volunteers to have his brain's function temporarily disrupted at UCLA's Neuromodulation Lab.

Two and a half thousand years ago, the Greek philosopher Socrates worried that the wide use of writing would have a negative impact on people's minds. He said that writing would create forgetfulness, because people will not use their memories. They would trust the external written characters and not remember themselves. In a world with an ever-growing tech industry, Michael Stevens tries to find out what effect technology has on our brains. He finds Technology isn't just changing our lives, it's changing our brains. In his experiments he tests what just 10 days of gaming does to things like our spatial memory.

When it comes to illusions, optical illusions get all the attention. But the whole body you have can be fooled and can fool the brain. What is touch? Is it real, or is it just in our heads? Michael Stevens decides to find out.