The pattern 'too much dopamine causes basal ganglia symptoms; too little causes frontal cortex symptoms' reflects imbalance in which neurotransmitter?

• A. Dopamine
• B. Serotonin
• C. Norepinephrine
• D. Acetylcholine

Answer: (A)

Dopamine drives distinct brain circuits with different effects on behavior. In the basal ganglia (the nigrostriatal pathway), dopamine regulates movement, so excess dopamine in that circuit tends to produce motor-related symptoms. In the frontal cortex (the mesocortical pathway), dopamine supports executive function and cognition, so too little dopamine there leads to cognitive and negative/cognitive-affective symptoms. The described pattern—basal ganglia problems with too much dopamine and frontal cortex problems with too little—fits dopamine because of these region-specific effects. The other neurotransmitters don’t show this same clear division between motor regulation in the basal ganglia and cognitive control in the frontal cortex.