Dopamine helps us learn what may be worth pursuing. Serotonin participates in regulation and adaptation. Acetylcholine helps direct attention and translate neural intention into muscular action. Noradrenaline prepares the brain to notice and respond. None of them acts alone. And these four are not the entire chemical orchestra. Glutamate, GABA, histamine, endorphins, endocannabinoids, neuropeptides, hormones and immune signals also contribute to human thought, emotion and b

As a young medical student, I remember sitting in an embryology lecture, staring at a diagram of the early embryo. The notochord sat there like a quiet rod in the middle, a slender axial structure that somehow knew how to orchestrate the rest of the body. From its signaling, the neural plate would arise, fold, and become the neural tube—the future brain and spinal cord. The heart fields were also taking shape, destiny encoded in tissue that only days earlier had been a seemin