Wakeful Rest Benefits Recall, but Not Recognition, of Incidentally Encoded Memory Stimuli in Younger and Older Adults

Abstract

Older adults exhibit deficits in episodic memory tasks, which have often been attributed to encoding or retrieval deficits, with little attention to consolidation mechanisms. More recently, researchers have attempted to measure consolidation in the context of a behavioral experiment using the wakeful rest paradigm (i.e., a brief, quiet period of minimal stimulation, which facilitates memory performance, compared to a distractor task). Critically, older adults might not produce this effect, given established age differences in other episodic memory processes and mind-wandering. In three experiments, we directly compared younger and older adults in modified versions of the wakeful rest paradigm. Critically, we utilized incidental encoding procedures (all experiments) and abstract shape stimuli (in Experiment 3) to limit the possibility of retrieval practice or maintenance rehearsal as potential confounding mechanisms in producing the wakeful rest effect. Wakeful rest reliably and equally benefited recall of incidentally encoded words in both younger and older adults. In contrast, wakeful rest had no benefit for standard accuracy measures of recognition performance in verbal stimuli, although there was an effect in response latencies for non-verbal stimuli. Overall, these results suggest that the benefits of wakeful rest on episodic retrieval are preserved across age groups, and hence support age-independence in potential consolidation mechanisms as measured by wakeful rest. Further, these benefits do not appear to be dependent on the intentionality of encoding or variations in distractor task types. Finally, the lack of wakeful rest benefits on recognition performance might be driven by theoretical constraints on the effect or methodological limitations of recognition memory testing in the current paradigm.

Keywords: aging; consolidation; episodic memory; wakeful rest.

Figure 1

Overall design of Experiments 1–3. (A) Diagram of task sequence. (B) Example stimuli. Note that Experiment 3 only included a surprise recognition test since abstract shapes were used as stimuli.

Figure 2

Retrieval task performance measures for auditory word stimuli in younger and older adults in Experiment 1, as a function of delay condition. (A) Proportion recalled. (B) Recognition performance (hits-false alarms). (C) Recognition hit confidence. (D) Recognition hit reaction time (standardized). Bar heights reflect mean values. Points reflect individual participants. Error bars are standard error of the mean.

Figure 3

Retrieval task performance measures for visual word stimuli in younger and older adults in Experiment 2, as a function of delay condition. (A) Proportion recalled. (B) Recognition performance (hits-false alarms). (C) Recognition hit confidence. (D) Recognition hit reaction time (standardized). Bar heights reflect mean values. Points reflect individual participants. Error bars are standard error of the mean.

Figure 4

Retrieval task performance measures for abstract shape stimuli in younger and older adults in Experiment 3, as a function of delay condition. (A) Recognition performance (hits-false alarms). (B) Recognition hit confidence. (C) Recognition hit reaction time (standardized). Bar heights reflect mean values. Points reflect individual participants. Error bars are standard error of the mean.