Post-training self administration of sugar facilitates cognitive performance of male C57BL/6J mice in two spatial learning tasks.
Spatial memory can be strengthened by adverse stimuli that activate the stress system, and administration of the stress hormone corticosterone in close-context with the learning task. Less is known about modulation of spatial memory by post-training positive reinforcers (reward). Cognitive performance was assessed in male C57BL/6J mice using two learning tasks: the water maze (WM) and circular hole board (CHB). Sugar was chosen as a post-training reinforcer. We expected that the free access to sugar immediately (0 h) after training would facilitate spatial memory; delayed access to sugar (4h after training) or no sugar served as controls. In both tasks, 0 h sugar mice showed superior performance, indicated by shorter latencies and distances to the trained spatial location. The memory facilitating effect of sugar became visible at distinct times during training: on the CHB from the first trial onwards, in the WM on training days 4 and 5. Sugar-rewarded mice kept their superior performance during the free exploration/swim trial, expressed by more persistent search strategies for the exit hole or platform. Post-training sugar reward in close-context with performance strengthens memory via modulation of consolidation. This finding supports the integrative theory of reinforcement and memory. We suggest that our experimental set-up will allow to differentiate between direct effects on memory and alterations in reward processes in animal models of stress-related diseases.
Dalm
Sergiu
S
Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research and Leiden University Medical Center, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
Schwabe
Lars
L
Schachinger
Hartmut
H
Oitzl
Melly S
MS
D000818:Animals; D002241:Carbohydrates / Q000008:administration & dosage*; D003071:Cognition / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology; D005106:Exploratory Behavior / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000502:physiology; D008568:Memory / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D011597:Psychomotor Performance / Q000502:physiology; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D012201:Reward; D012646:Self Administration; D013037:Spatial Behavior / Q000502:physiology*; D013997:Time Factors
D002241:Carbohydrates