Neuromodulators like dopamine, acetylcholine, epinephrine, and serotonin alter brain area activity, making certain neural connections more likely to be active.

“And that is the category of chemicals in the brain and body called the neuromodulators, neuromodulators are different than neuro-transmitters in the sense that neuromodulators modulator or change the activity of brain areas in neural circuits, you can think of them as microphones that are held between particular sets of connections in the brain that make those connections in the brain, more likely to be active relative to others, okay? They make them louder so to speak, there are many neuromodulators, but the ones that are important for sake of today's discussion are the classic ones, dopamine acetylcholine or epinephrin and serotonin.”