Which neurotransmitters are primarily involved in the modulation of global brain states?

• A. Norepinephrine
• B. Dopamine
• C. Serotonin
• D. Dopamine, Norepinephrine, and Serotonin

Answer: (D)

Global brain states such as wakefulness and arousal are governed by diffuse neuromodulatory systems that broadcast signals broadly across the brain. Norepinephrine, released from the locus coeruleus, sharpens attention, increases alertness, and helps stabilize network activity so the brain can respond to salient stimuli. Serotonin, from the dorsal raphe, influences mood and arousal levels, helps regulate sleep-wake transitions, and modulates sensory processing across many regions. Dopamine, coming from midbrain areas like the ventral tegmental area and substantia nigra, modulates motivational salience and reward, but also affects cortical and thalamic network dynamics that contribute to sustained arousal and exploration. Because these three systems collectively shape the global tone and readiness of large-scale brain networks, they are the best combination for modulating global brain states.