Summary of neurotransmitter associations with performance on tests of inhibition or impulsivity.

+: Evidence of significant influence of the neurotransmitter on the test score.−: Evidence of probable lack of influence of the neurotransmitter on the test score.+−: Inconsistent or equivocal evidence of influence of the neurotransmitter on the test score.# Lack of evidence of any specific effect of the neurotransmitter on the test score (for details of each test, see Table 2).Citations correspond to studies in PD patients, otherwise marked as,Patients with other diseases;h healthy controls;rodents.