Acetylcholine is involved in memory and learning.
Dopamine is involved in sex drive, mood, alertness, and movement.
Norepinephrine is involved in alertness, arousal, and mood. Serotonin is involved in mood, appetite control, emotional balance, and impulse control. GABA is involved in relaxation and sedation. Dozens of natural supplements have been introduced over the past few years that promise to enhance mental function. The whole process is admittedly complicated.