Accumbens core dopamine and acquisition of instrumental responding

ACCUMBENS CORE DOPAMINE AND ACQUISITION OF INSTRUMENTAL RESPONDING 

Various studies show that lesion or reversible impairment of excitatory transmision of the NAc core impair acquisition of instrumental responding for food and for drug self-administration. The mechanism of this effect, however, is debated. 

Excitotoxic NAc core lesions slow down the acquisition of first order schedules of heroin self-administration but do not affect already established responding (Alderson et al., 2001 Hutcheson et al., 2001). An impairment of instrumental learning by these lesions has been excluded on the basis of the observation that responding was still sensitive to changes in the outcome value. On the basis of the above studies, Cardinal et al. (2002) maintain that the NAc core is not critical for instrumental learning and interpret the effects of NAc core lesions in acquisition as the result of an impairment of the motivational arousal elicited by drug-conditioned stimuli. Consistent with this explanation is the observation that NAc core lesions prevent acquisition of second-order schedules 

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