title: Dorsomedial striatum lesions affect adjustment to reward uncertainty, but not to reward devaluation or omission.
abstract: The dorsomedial striatum (DMS) has been implicated in the acquisition of reward representations, a proposal leading to the hypothesis that it should play a role in situations involving reward loss. We report the results of an experiment in which the effects of DMS excitotoxic lesions were tested in consummatory successive negative contrast (reward devaluation), autoshaping training with partial vs. continuous reinforcement (reward uncertainty), and appetitive extinction (reward omission). Animals with DMS lesions exhibited reduced lever pressing responding, but enhanced goal entries, during partial reinforcement training in autoshaping. However, they showed normal negative contrast, acquisition under continuous reinforcement (CR), appetitive extinction, and response facilitation in early extinction trials. Open-field testing also indicated normal motor behavior. Thus, DMS lesions selectively affected the behavioral adjustment to a situation involving reward uncertainty, producing a behavioral reorganization according to which goal tracking (goal entries) became predominant at the expense of sign tracking (lever pressing). This pattern of results shows that the function of the DMS in situations involving reward loss is not general, but restricted to reward uncertainty. We suggest that a nonassociative, drive-related process induced by reward uncertainty requires normal output from DMS neurons.
authors.affiliation: Department of Psychology, University of Jaén, 23071-Jaén, Spain. Electronic address: mctorres@ujaen.es.
authors.forename: Carmen
authors.initials: C
authors.lastname: Torres
authors.affiliation: Department of Psychology, Texas Christian University, Fort Worth, TX 76129, USA. Electronic address: glueckphd@gmail.com.
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Glueck
authors.affiliation: Department of Psychology, Texas Christian University, Fort Worth, TX 76129, USA. Electronic address: shannon.conrad@tcu.edu.
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Conrad
authors.affiliation: Department of Psychobiology, University of Granada, 18071-Granada, Spain. Electronic address: imoron@ugr.es.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Morón
authors.affiliation: Department of Psychology, Texas Christian University, Fort Worth, TX 76129, USA. Electronic address: m.papini@tcu.edu.
authors.forename: Mauricio R
authors.initials: MR
authors.lastname: Papini
mesh_terms: D000818:Animals; D059031:Anticipation, Psychological / Q000502:physiology; D003342:Corpus Striatum / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D005108:Extinction, Psychological / Q000502:physiology; D006040:Goals; D008297:Male; D023421:Models, Animal; D009043:Motor Activity / Q000502:physiology; D009483:Neuropsychological Tests; D017378:Quinolinic Acid; D011897:Random Allocation; D017208:Rats, Wistar; D012201:Reward; D035501:Uncertainty
chemical_list: D017378:Quinolinic Acid
keywords: extinction spike; partial reinforcement; reward devaluation; reward omission; reward uncertainty; successive negative contrast