Late post-learning participation of entorhinal cortex in memory processes.
Mice of the BALB/c strain were bilaterally implanted with electrodes in the lateral entorhinal cortex (EC) in order to study the influence of post-trial EC stimulation on memory. The learning task was a food reinforced operant conditioning. At one of several time intervals after a first learning session, the experimental groups were stimulated for 80 s with subseizure current intensity. Testing was carried out 24 h later. In the first experiment, a continuous reinforcement schedule was used. EC stimulation had no effect when applied at the 30-s or 3-h intervals, but surprisingly a 30-min delayed stimulation greatly improved retention compared to performance of non-stimulated animals. In the second experiment, the same paradigm was used in a discriminative operant conditioning task. The same facilitation on retention was observed only with the 30-min delayed stimulation. Compared to previous data with hippocampal or hypothalamic stimulation, the present results reveal that EC is lately involved in memory processes.
D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology; D003216:Conditioning, Operant / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology; D004558:Electric Stimulation; D005071:Evoked Potentials; D008032:Limbic System / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D012055:Reinforcement Schedule; D012153:Retention, Psychology / Q000502:physiology