title: Differential effects on effort discounting induced by inactivations of the nucleus accumbens core or shell.
abstract: The authors investigated the contribution of the nucleus accumbens (NAc) core and shell to effort-based decision making using a discounting procedure. Selection of 1 lever delivered a smaller, 2-pellet reward immediately, whereas the other lever delivered a 4-pellet reward after a fixed ratio of presses (2, 5, 10, or 20) that increased over 4 blocks of 10 discrete choice trials. Subsequent testing employed an equivalent delays procedure, whereby the relative delay to reward delivery after selection of either option was equalized. In well-trained rats, inactivation of the core, but not the shell, via infusion of GABA A/B agonists muscimol/baclofen reduced preference for the high-effort option under standard conditions and also when rats were tested using an equivalent delays procedure. However, inactivation of the core did not alter preference for 4-pellet versus 2-pellet rewards when the relative costs of each option were the same (1 press). Thus, the NAc core, but not the shell, appears to be part of a neural circuit that biases choice toward larger rewards associated with a greater effort cost. Furthermore, the contributions by the NAc core to this form of decision making can be dissociated from its role in delay discounting.
authors.affiliation: Department of Psychology, University of British Columbia, Vancouver, BC V6T1Z4, Canada.
authors.forename: Sarvin
authors.initials: S
authors.lastname: Ghods-Sharifi
authors.forename: Stan B
authors.initials: SB
authors.lastname: Floresco
mesh_terms: D000818:Animals; D001418:Baclofen / Q000008:administration & dosage / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D003657:Decision Making / Q000187:drug effects; D004338:Drug Combinations; D018755:GABA Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D005082:Physical Exertion / Q000187:drug effects; D051381:Rats; D020318:Rats, Long-Evans; D012055:Reinforcement Schedule; D012201:Reward
chemical_list: D004338:Drug Combinations; D018755:GABA Agonists; D009118:Muscimol; D001418:Baclofen