As we age, the brain’s production of neuromodulators (brain chemicals that help with learning and remembering) drops sharply. For example, studies suggest that after age 40, with each passing decade people produce an average of 13% less of the critical neuromodulator dopamine than in the previous decade. Neuromodulators – especially dopamine, acetylcholine, norepinephrine, and serotonin – are essential ingredients in the brain’s ability to learn and remember. They are released when something important happens, which signals the brain that the event should be stored and remembered rather than dismissed and forgotten.