Exploring the absence of episodic memory benefits from post-encoding emotional arousal and novelty manipulations in humans

It is now well-established that a brief period of stress immediately after learning can be beneficial for memory. These results indicate that even after memories have been formed, they can still be enhanced by certain psychological and biological processes. Although this benefit of post-encoding stress is well established, the exact mechanisms and limits of this effect are still debated. Determining the effects of other, non-stressful, post-encoding manipulations such as emotional arousal or novel spatial exploration can provide important data for understanding these effects. To this end, we conducted a series of five experiments using the same stimuli and study designs that have been used in post-encoding stress studies. Experiments 1 and 2 examined memory for neutral and negative pictures and found that emotional arousal after learning did not benefit memory. Experiments 3 and 4 examined whether post-encoding emotional arousal might benefit memory for verbal, rather than visual items, but again there was no benefit of post-encoding arousal on either true or false memory. Experiment 5 examined whether a novel exploration task after learning would provide a memory benefit, but again there was no memory benefit. Taken together, these results suggest that post-encoding periods of arousal and novelty do not appear to produce the same types of memory benefits that are produced by stress, which provides further support for the critical role of glucocorticoids in post-encoding memory benefits.