How Your Brain Works & Changes

Andrew Huberman introduces himself as a professor of neurobiology and ophthalmology at Stanford School of Medicine. He frames the episode as a tour of the "parts list of the nervous system." He admits the topic may sound dry, but he argues that these parts together make up "everything about your experience of life," from thinking and feeling to imagining and accomplishing things, from birth to death. He plans to tell the story through history that, in his words, touches on engineering, warfare, religion and philosophy.

He promises some storytelling, a lot about the people behind the discoveries, and some technical language he says cannot be avoided. His goal is for listeners to come away with the equivalent of "an entire semester of learning about the nervous system and how you work."

Before the science, he sets limits on his role. He says he is not a medical doctor and does not prescribe anything. Any tools he discusses should be filtered through the listener's own responsibility for their health, and new tools or practices should be discussed with a healthcare professional. He also says the podcast is a personal effort to offer free information to the public, separate from his role at Stanford University.

Huberman's first claim is that "the brain" is the wrong unit of analysis. The brain is one piece of a larger system that includes the spinal cord, the connections from brain and spinal cord to the body's organs, and, which he stresses, the connections from the organs back to the spinal cord and brain. On this view, everything a person thinks, remembers, feels and imagines comes from constant two-way communication between brain, spinal cord and body.

In fact, we really can't even separate them. It's one continuous loop.

He compares this structure to a Möbius strip, a figure with no clear start or end. He gives two examples of the nervous system working in places people credit to other systems. First, he says it is the nervous system that tells organs like the spleen to release killer cells that hunt down bacterial and viral invaders, a job most people assign to the immune system alone. Second, a stomachache is felt in the stomach, but the "ache aspect of it is a nervous system feature."

From this he concludes that any discussion of experience, or of changing the self, has to start with the nervous system. He describes the relationship as two-way: the nervous system "governs all other biological systems of the body" and is also influenced by them. He then says that "a big loop of wires" is too vague and turns to its actual parts.

Huberman recounts that around the turn from the 1800s to the 1900s, the nervous system was believed to be one giant cell. He credits Ramón y Cajal, a Spaniard, and Camillo Golgi, an Italian, with finding ways to label or stain nervous tissue. Their stains revealed that we are made of what he calls "trillions" of separate nerve cells, or neurons. These cells do not touch one another. They are separated by small gaps called synapses.

He describes signaling in two steps. One neuron releases chemicals into the synapse. The next neuron detects them and passes electricity down its length to the next cell. His overall picture is that body, thoughts and mind are a "flow of electricity" between nerve cells. Which cells are active determines whether you lift or lower your arm, or whether you see something as red or green.

There's nothing mystical about this.

He uses red versus green to make a broader point. Experience makes it feel as if the outside world is happening inside us, but "the language of the nervous system is just electricity." He compares it to Morse code, or to syllables, consonants and vowels, whose meaning depends on how they are assembled and in what order.

His main analogy is a piano. An experience or memory is like keys played in a particular order at a particular intensity. A single key such as A sharp or E flat is not the song, only part of it. He applies this to the hippocampus, which he confirms is involved in memory. Memories are not stored there "as you know, sentences," but as patterns of electrical activity in neurons that, when repeated, give the sense of experiencing something again.

He explains déjà vu the same way. It is "merely" neurons that were active in one circumstance becoming active again in the same circumstance, like hearing the same song played on a classical guitar instead of a piano. He sums up the section with three points: the nervous system includes far more than the brain, it is built from neurons and synapses, and "it's the electrical activity of these neurons that dictates our experience."

One of the more surprising sources of insight into the nervous system, Huberman says, was warfare. In World War I, changes in artillery and bullets meant that bullets often entered and left the body and brain at very discrete points, leaving small exit holes. Earlier weapons, he says, tended to blow out large holes. These narrower wounds destroyed limited, specific pieces of neural tissue, creating what he calls "naturally occurring lesions." He adds that better wound cleaning meant many more of these soldiers survived.