Exposure to retrieval cues improves retention performance and induces changes in ACTH and corticosterone release
Memory retrieval can be facilitated by pretest exposure to cues associated with the original training. The present series of experiments was aimed at investigating whether the effectiveness of the retrieval cues might be due to their emotional value and thus be associated to a particular pattern of activation of stress systems. Therefore, the effects of exposing rats to different cueing conditions were investigated both on retention performance and on the level of different stress hormones (ACTH, corticosterone and glucose; the latter as an indirect index of adrenergic/sympathetic nervous system activation). Rats trained in a brightness avoidance discrimination task exhibited an enhancement of the retention performance following exposure to the light discriminative stimulus when delivered 1-day after training and not after 21 days, while exposure to contextual cues led to opposite effects on the retention performance, confirming our previous results. Analyses of the level of stress hormones at the time of testing indicated that when the retrieval cues were effective at the behavioral level, cued rats exhibited higher ACTH plasmatic levels than controls, but did not differ in their glucose or corticosterone levels. Further experiments showed that one day after training, both ACTH and corticosterone levels were elevated in light-cued rats if hormone samples were taken 15 min after cueing. These results show that exposure to an effective retrieval cue is accompanied by the activation of the hypothalamus-pituitary-adrenal axis. The possible involvement of the Corticotropin Releasing Factor at the level of the hypothalamus and amygdala (particularly the central nucleus) on the facilitating effect on retention performance following exposure to aversive training-associated cues is discussed. The present results strengthen the notion that emotion can interact with retrieval processes.
Keywords: Adrenocorticotropic Hormone/ secretion ; Analysis of Variance ; Animals ; Arousal/ physiology ; Association Learning/physiology ; Avoidance Learning/ physiology ; Blood Glucose/physiology ; Corticosterone/ secretion ; Cues ; Hypothalamo-Hypophyseal System/physiology ; Male ; Mental Recall ; Photic Stimulation ; Pituitary-Adrenal System/physiology ; Rats ; Rats ; Sprague-Dawley ; Retention (Psychology)/ physiology ; Stress ; Psychological/ physiopathology
Author address: Laboratoire de Neurobiologie de l'Apprentissage et de la Memoire et de la Communication, UMR CNRS 8620, Universite Paris-Sud, 91405 Orsay cedex, France. email@example.com
Record created on 2007-01-18, modified on 2016-08-08