Mechanisms of Memory Retrieval in Slow-Wave Sleep
- S-Med
- Jul 10
- 2 min read
We carried out two TMR experiments to investigate the cognitive mechanisms by which memories are retrieved for reactivation in SWS. In Experiment 1, verbal and nonverbal TMR with cues that were acoustically identical to training reduced forgetting of respective cued (vs. noncued) speech-word pairs and sound-word pairs to similar extents. In Experiment 2, nonverbal TMR with identical cues also reduced forgetting of
cued (vs. noncued) sound-word pairs, replicating Experiment 1. However, verbal TMR with nonidentical cues (ie, presented in a different voice) appeared to reduce forgetting of both cued and noncued speech-word pairs. We observed no benefit of TMR for the spatial locations of the paired associates in either Experiment 1 or 2.
The findings of Experiment 1 are in keeping with a growing literature, which indicates that TMR delivered in SWS selectively enhances the retention of cued (vs. noncued) memories. Whereas previous studies have investigated separately the memory effects of TMR delivered with nonverbal cues and complex verbal cues, we carried out the first direct comparison of verbal and nonverbal TMR. Interestingly, verbal
TMR reduced forgetting of cued (vs. noncued) paired associates to almost the same extent as nonverbal TMR, demonstrating that the memory benefits of these techniques are equivalent when the reactivation cues are identical to training.
Because spoken words are more abstract and complex stimuli than environmental sounds, with their wakeful perception requiring multiple stages of phonological and semantic analysis, one might have expected the memory benefits of verbal TMR to be of a smaller magnitude to those arising from nonverbal TMR. However, the findings of Experiment 1 suggest that the sleeping brain can exploit verbal and nonverbal materials
for memory retrieval to comparable extents. One possible interpretation of this outcome is that the associations formed before sleep, regardless of whether they involve spoken words or environmental sounds, can be retrieved during sleep via a surface-level matching process that represents the form of the cues in a relatively concrete, unanalyzed acoustic manner. This would fit with a substantial body of evidence suggesting that recently encountered words are stored in an episodic form that
tends to preserve non linguistic detail.
Comments