title: Effects of environmental and pharmacological manipulations on a novel delayed nonmatching-to-sample 'working memory' procedure in unrestrained rhesus monkeys.
abstract: BACKGROUND
  Working memory is a domain of 'executive function.' Delayed nonmatching-to-sample (DNMTS) procedures are commonly used to examine working memory in both human laboratory and preclinical studies.
  
  
  METHODS
  The aim was to develop an automated DNMTS procedure maintained by food pellets in rhesus monkeys using a touch-sensitive screen attached to the housing chamber. Specifically, the DNMTS procedure was a 2-stimulus, 2-choice recognition memory task employing unidimensional discriminative stimuli and randomized delay interval presentations.
  
  
  RESULTS
  DNMTS maintained a delay-dependent decrease in discriminability that was independent of the retention interval distribution. Eliminating reinforcer availability during a single delay session or providing food pellets before the session did not systematically alter accuracy, but did reduce total choices. Increasing the intertrial interval enhanced accuracy at short delays. Acute Δ(9)-THC pretreatment produced delay interval-dependent changes in the forgetting function at doses that did not alter total choices. Acute methylphenidate pretreatment only decreased total choices.
  
  
  METHODS
  All monkeys were trained to perform NMTS at the 1s training delay within 60 days of initiating operant touch training. Furthermore, forgetting functions were reliably delay interval-dependent and stable over the experimental period (∼6 months).
  
  
  CONCLUSIONS
  Consistent with previous studies, increasing the intertrial interval improved DNMTS performance, whereas Δ(9)-THC disrupted DNMTS performance independent of changes in total choices. Overall, the touchscreen-based DNMTS procedure described provides an efficient method for training and testing experimental manipulations on working memory in unrestrained rhesus monkeys.
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Blake A
authors.initials: BA
authors.lastname: Hutsell
authors.affiliation: Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, USA; Institute for Drug and Alcohol Abuse Studies, Virginia Commonwealth University, Richmond, VA, USA. Electronic address: mbanks7@vcu.edu.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Banks
mesh_terms: D000818:Animals; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002755:Choice Behavior / Q000187:drug effects; D003216:Conditioning, Operant / Q000187:drug effects; D013759:Dronabinol / Q000494:pharmacology*; D004777:Environment; D008253:Macaca mulatta; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology; D008774:Methylphenidate / Q000494:pharmacology*; D011619:Psychotropic Drugs / Q000494:pharmacology*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D014110:Touch; D014851:Wakefulness
chemical_list: D000697:Central Nervous System Stimulants; D011619:Psychotropic Drugs; D008774:Methylphenidate; D013759:Dronabinol
keywords: Delayed nonmatching to sample; Methylphenidate; Rhesus monkey; Touchscreen; Working memory; Δ(9)-Tetrahydrocannabinol