Table 1.

Proposed mechanism of dopaminergic pathway malfunction and their effects.

Systems affected by dopaminergic disfunction.	Proposed behavioral results.	References
Increased ventral striatal response to rewards/reward cues.	Sensitization of ventral striatal circuits to rewards resulting in increased reward seeking.	Steeves et al. [15], O’Sullivan et al. [16], Wu et al. [17]
Low ventral striatal D2/D3 receptor availability	Increased reward seeking/propensity for impulsivity due to blunted transmission of reward signals	Steeves et al. [15], Boileau et al. [19,20], Payer et al. [21]
Low DAT expression in ventral striatum	Functional downregulation (compensating for lower dopamine availability) or susceptibility trait.	Cilia et al. [24], Vriend et al. [25]
Low midbrain dopamine autoreceptor function	Lack of homeostatic control over striatal DA release, causing increased sensitivity to rewards/propensity for impulsivity	Ray et al. [27], Cole et al. [28]
Altered cortical and striatal responses to feedback when on dopamine agonists	Increased learning from reward and decreased learning from punishment, fostering the repetition of maladaptive behaviors	Van Eimeren et al. [29]