The Episodic-inhibition hypothesis

Consolidation of Episodic Memories During Sleep: Long-Term Effects of Retrieval Practice
Psychological Science OnlineFirst, published on November 23, 2009 as doi:10.1177/0956797609354074
Mihály Racsmány, Martin A. Conway, and Gyula Demeter

Two experiments investigated the long-term effects of retrieval practice. In the retrieval-practice procedure, selected items from a previously studied list are repeatedly recalled. The typical retrieval-practice effects are considerably enhanced memory for practiced items accompanied by low levels of recall, relative to baseline, for previously studied items that are associated with the practiced items but were not themselves practiced. The two experiments demonstrated that the former effect persisted over 12 hr; the latter effect also persisted over 12 hr, but only if a period of nocturnal sleep occurred during the retention interval. We propose that consolidation processes occurring during sleep, and possibly featuring some form of offline rehearsal, mediate these long-term effects of retrieval practice.

More faithful memories for those experiences

Awake replay of remote experiences in the hippocampus
Nature Neuroscience Volume 12, Number 7, July 2009
Published online at
Mattias P Karlsson & Loren M Frank

Hippocampal replay is thought to be essential for the consolidation of event memories in hippocampal-neocortical networks. Replay is present during both sleep and waking behavior, but although sleep replay involves the reactivation of stored representations in the absence of specific sensory inputs, awake replay is thought to depend on sensory input from the current environment. Here, we show that stored representations are reactivated during both waking and sleep replay. We found frequent awake replay of sequences of rat hippocampal place cells from a previous experience. This spatially remote replay was as common as local replay of the current environment and was more robust when the rat had recently been in motion than during extended periods of quiescence. Our results indicate that the hippocampus consistently replays past experiences during brief pauses in waking behavior, suggesting a role for waking replay in memory consolidation and retrieval.

Growing Older Does Not Mean Sleeping Poorly

Recent Advances in Understanding Sleep and Sleep Disturbances in Older Adults
Growing Older Does Not Mean Sleeping Poorly
Association for Psychological Science Volume 18—Number 6
Michael V. Vitiello

Despite commonly held assumptions, growing older does not necessarily result in disturbed or unsatisfying sleep. There is no reason to assume, a priori, that the sleep of an older adult is necessarily problematic; in fact, many high-functioning older adults are satisfied with their sleep. When the various factors that can disrupt sleep— poor health, primary sleep disorders, poor sleep-hygiene practices (e.g., irregular sleep schedules and poor sleeping environments), and so on—are screened out, ‘‘optimally’’ or ‘‘successfully’’ aging older adults, assuming they remain healthy, can expect to experience little further change in their sleep and are not likely to experience excessive daytime sleepiness and the concomitant need to nap regularly during the day. Nevertheless, the majority of older adults, who are not optimally aging, suffer significant sleep disturbances from a variety of causes. Fortunately, our growing understanding of how sleep changes with aging and of the causes of these changes is informing ever-improving treatments for these disturbances, thereby helping to ensure that growing older does not mean sleeping poorly.