Essentials: Control Your Brain Chemistry for Focus, Motivation & Well-Being

Andrew Huberman, who introduces himself as a professor of neurobiology and ophthalmology at Stanford School of Medicine, opens this Essentials episode by describing the nervous system as two-way. The brain, spinal cord and the rest of the nervous system control the body's organs, and those organs feed back to the nervous system "through chemicals and other means." From there he makes the claim the episode is built on: which neural circuits are more or less active at a given moment is governed by two major categories of chemicals, hormones and neuromodulators.

which neural circuits are active and which neural circuits are likely to be less active at any given moment depends on two major categories of chemicals.

He names four neuromodulators as most important for the listener's goals: dopamine, epinephrine (also called adrenaline), serotonin and acetylcholine. Neuromodulators have many features, but he narrows the discussion to two: fast-acting effects and slower, longer "baseline" effects. He chooses to start with the slow effects, which he notes may be surprising. His reason is that these baseline actions are always running in everyone, and they determine how well any tool for shifting these chemicals will work.

they set the backdrop, the context in which the various tools to manipulate dopamine, epinephrine, serotonin, or acetylcholine will work.

To describe that baseline, Huberman splits the 24 hours after waking into three phases and calls them approximations. He says sleep and wake schedules vary, but nearly everyone follows the same broad pattern no matter when they wake. Phase one runs from waking to about nine hours later. In this window, dopamine and epinephrine are at the highest levels they reach at any point in the 24-hour cycle. Phase two runs from about nine to about 16 hours after waking. Here dopamine and epinephrine "tend to subside a bit" compared with phase one, and serotonin starts to rise. Phase three runs from about 17 to 24 hours after waking. He says that by then you "ought to be deeply asleep," so he sets it aside for this discussion.

Phase one (about 0–9 hours after waking): dominated by dopamine and epinephrine, both at their daily peak. Phase two (about 9–16 hours): dopamine and epinephrine ease off somewhat and serotonin rises, making this the serotonin-dominated part of the day. Phase three (about 17–24 hours): a period when one should be deeply asleep, and not a focus of the episode.

Huberman notes that the timings are rough: "again, about, these are approximates." He also says he has used this phase framework in an earlier episode, "but not in this exact context."

Acetylcholine doesn't fit the clock-based scheme, and Huberman expects listeners to notice. In his account, acetylcholine depends less on time of day and more on what a person is doing at the moment: whether they are focusing and whether they are learning. He also limits his scope. He is talking about acetylcholine in the brain and in thinking, not its role at the nerve-to-muscle synapse. There, he explains, neurons control muscle fiber contraction by releasing acetylcholine. That is how movement happens, but it is outside today's topic.

He ends this section by restating the practical point. Anyone who wants to use tools to change their brain chemistry first needs to understand that baseline neuromodulator levels vary across the day. The tools he describes are framed around what can be done in phase one versus phase two.