title: Automatic recording of mediating behavior in delayed matching- and nonmatching-to-position procedures in rats.
abstract: BACKGROUND
  Delayed matching-to-position and nonmatching-to-position procedures are widely used to model working memory in rodents. Mediating behavior-which enhances performance but is not explicitly required by the task-is generally considered an obstacle to the measurement of memory, but often occurs despite attempts to prevent it. The ubiquitous nature of mediating behavior suggests it might be analogous to rehearsal, an important component of learning and memory in humans.
  
  
  OBJECTIVE
  The aim was to study an easily recordable, rehearsal-like mediating response in rats under baseline conditions and after treatment with amnestic drugs [scopolamine (0.1-0.3 mg/kg) and delta-9-tetrahydrocannabinol (THC; 1-5.6 mg/kg)].
  
  
  METHODS
  Lighted nosepoke holes were used to present position cues and record delayed matching or nonmatching responses. Performance of a distractor task was required to prevent simply waiting at the correct choice, but the nosepoke holes were left accessible during the delay.
  
  
  RESULTS
  Each rat trained with the nonmatching task exhibited one of two mediating "strategies" that increased the odds of a correct choice: responding in the to-be-correct hole during the delay or responding in the opposite hole during the delay. Rats trained with the matching task all showed the former strategy. Treatment with scopolamine disrupted performance of the mediating response. Scopolamine and THC both decreased the effectiveness of the mediating response, increasing errors even on trials when the "appropriate" mediating behavior did occur.
  
  
  CONCLUSIONS
  The procedures and data analysis approach used here provide an objective, automated means of measuring mediating behavior, which might be useful as an animal model of memory rehearsal.
authors.affiliation: Preclinical Pharmacology Section, Behavioral Neuroscience Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, 251 Bayview Blvd., Baltimore, MD 21224, USA. lpanlili@intra.nida.nih.gov
authors.forename: Leigh V
authors.initials: LV
authors.lastname: Panlilio
authors.forename: Sevil
authors.initials: S
authors.lastname: Yasar
authors.forename: Eric B
authors.initials: EB
authors.lastname: Thorndike
authors.forename: Steven R
authors.initials: SR
authors.lastname: Goldberg
authors.forename: Charles W
authors.initials: CW
authors.lastname: Schindler
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003463:Cues; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects; D016017:Odds Ratio; D011619:Psychotropic Drugs / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D012601:Scopolamine / Q000494:pharmacology; D013997:Time Factors
chemical_list: D011619:Psychotropic Drugs; D013759:Dronabinol; D012601:Scopolamine