PubMed · 16586
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
W Fishbein, B M Gutwein. 1977. Paradoxical sleep and memory storage processes.. https://doi.org/10.1016/s0091-6773(77)91903-4
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Previous studies have shown that in rats the acquisition of a step-through passive avoidance reaction (PAR) in the light-dark box apparatus is disrupted by tetrodotoxin (TTX) inactivation of the parabrachial nuclei (PBN) 24 but not 48 h after the acquisition trial. The present experiment shows that TTX induces retrograde amnesia even when applied to the PBN 48 h after PAR acquisition only if it is preceded by a 30-min confinement (extinction) or by a footshock (retraining) in the dark compartment. These stimuli, independently of their sign, induce quantitatively comparable TTX disrupting effects. This happens notwithstanding the fact that these stimuli are too weak to modify PAR under control conditions. This paradoxical finding suggests that engram vulnerability may not be a simple inverse function of its recency but that it may reflect a reactivation of the neural circuits involved in memory trace formation. Consolidated engrams become again vulnerable only when contextual cue stimuli are presented shortly before the application of the disrupting procedure.
Previous work has demonstrated that in rats post-trial bilateral functional blockade of the parabrachial nuclei by local injection of tetrodotoxin (10 ng in 1 microliter) partially disrupts retention of an overtrained passive avoidance response. The time-course of functional blockade disrupting effects on passive avoidance response has been studied by altering both the acquisition-tetrodotoxin injection interval and footshock intensity as independent variables. When week footshocks (0.8 mA) were delivered, functional ablation of the parabrachial nuclei was still effective when induced up to 8 days after acquisition training. On the other hand, when rats were shocked with the stronger stimuli (1.2 mA), 2 days after acquisition functional ablation was no longer effective. The results are discussed in terms of unconditioned stimulus (US) intensity and engram consolidation.
The role of the amygdala (AM) in the consolidation of the passive avoidance reaction (PAR) has been examined with the tetrodotoxin (TTX)-induced functional block of this structure. Rats were trained in the step-through PAR and anesthetized with ketamine. TTX injected immediately after acquisition into both AM (2 x 10 ng) significantly reduced avoidance of the dark compartment in the retrieval test performed two days later. The amnesic effect was significant when the acquisition--TTX delay was prolonged to 90 min but not to 6 h or 24 h. Earlier research indicated that TTX blockade of the parabrachial nuclei caused similar PAR disruption when elicited 24 h but not 48 h after acquisition. Comparison of the TTX-induced retrograde amnesias indicates that the two structures play different roles in the formation of the PAR engram.