title: Stimulus-response learning in long-term cocaine users: acquired equivalence and probabilistic category learning.
abstract: OBJECTIVE
  The purpose of this study was to examine stimulus-response (S-R) learning in active cocaine users.
  
  
  METHODS
  Twenty-two cocaine-dependent participants (20 males and 2 females) and 21 non-drug using control participants (19 males and 2 females) who were similar in age and education were administered two computerized learning tasks. The Acquired Equivalence task initially requires learning of simple antecedent-consequent discriminations, but later requires generalization of this learning when the stimuli are presented in novel recombinations. The Weather Prediction task requires the prediction of a dichotomous outcome based on different stimuli combinations when the stimuli predict the outcome only probabilistically.
  
  
  RESULTS
  On the Acquired Equivalence task, cocaine users made significantly more errors than control participants when required to learn new discriminations while maintaining previously learned discriminations, but performed similarly to controls when required to generalize this learning. No group differences were seen on the Weather Prediction task.
  
  
  CONCLUSIONS
  Cocaine users' learning of stimulus discriminations under conflicting response demands was impaired, but their ability to generalize this learning once they achieved criterion was intact. This performance pattern is consistent with other laboratory studies of long-term cocaine users that demonstrated that established learning interfered with new learning on incremental learning tasks, relative to healthy controls, and may reflect altered dopamine transmission in the basal ganglia of long-term cocaine users.
authors.affiliation: Columbia University, New York, NY 10027-6902, USA. npv2101@columbia.edu
authors.forename: Nehal P
authors.initials: NP
authors.lastname: Vadhan
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Myers
authors.forename: Eric
authors.initials: E
authors.lastname: Rubin
authors.forename: Daphna
authors.initials: D
authors.lastname: Shohamy
authors.forename: Richard W
authors.initials: RW
authors.lastname: Foltin
authors.forename: Mark A
authors.initials: MA
authors.lastname: Gluck
mesh_terms: D000428:Alcohol Drinking / Q000453:epidemiology; D001479:Basal Ganglia / Q000378:metabolism; D019970:Cocaine-Related Disorders / Q000453:epidemiology*; D003214:Conditioning, Classical; D004192:Discrimination, Psychological; D004298:Dopamine / Q000378:metabolism; D005260:Female; D006184:Habits; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D007858:Learning; D007859:Learning Disabilities / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology; D011336:Probability; D011581:Psychological Tests; D013997:Time Factors; D014163:Transfer, Psychology
chemical_list: D004298:Dopamine