Abstract
ObjectiveTo determine if sleep talkers with REM sleep behavior disorder (RBD) would utter during REM sleep sentences learned before sleep, and to evaluate their verbal memory consolidation during sleep. MethodsEighteen patients with RBD and 10 controls performed two verbal memory tasks (16 words from the Free and Cued Selective Reminding Test and a 220-263 word long modified Story Recall Test) in the evening, followed by nocturnal video-polysomnography and morning recall (night-time consolidation). In 9 patients with RBD, daytime consolidation (morning learning/recall, evening recall) was also evaluated with the modified Story Recall Test in a cross-over order. Two RBD patients with dementia were studied separately. Sleep talking was recorded using video-polysomnography, and the utterances were compared to the studied texts by two external judges. ResultsSleep-related verbal memory consolidation was maintained in patients with RBD (+24±36% words) as in controls (+9±18%, p=0.3). The two demented patients with RBD also exhibited excellent nighttime consolidation. The post-sleep performance was unrelated to the sleep measures (including continuity, stages, fragmentation and apnea-hypopnea index). Daytime consolidation (-9±19%) was worse than night-time consolidation (+29±45%, p=0.03) in the subgroup of 9 patients with RBD. Eleven patients with RBD spoke during REM sleep and pronounced a median of 20 words, which represented 0.0003% of sleep with spoken language. A single patient uttered a sentence that was judged to be semantically (but not literally) related to the text learned before sleep. ConclusionVerbal declarative memory normally consolidates during sleep in patients with RBD. The incorporation of learned material within REM sleep-associated sleep talking in one patient (unbeknownst to himself) at the semantic level suggests a replay at a highly cognitive creative level.
Highlights
After a learning episode, still fragile memory traces are progressively converted over time into more stable representations in long-term memory [1]
Patients with primary insomnia demonstrated a lower sleep-associated memory consolidation of declarative memory tasks, while results are more controversial for procedural memory compared to good sleepers [13]
Brain regions involved in motor skill learning are reactivated during post-training sleep in human function imaging studies [17]. These regional reperfusions could correspond to the replay during sleep of temporallyorganized patterns of neural activity encoding for newly acquired information, or they may reflect other experience-dependent brain processes, such as local homeostasis [18]. We recently addressed this question by studying patients who exhibited overt dreamlike behaviors during two types of parasomnias, non-rapid eye movement (REM) sleep and during REM sleep (REM sleep behavior disorder, RBD) [19]
Summary
Still fragile memory traces are progressively converted over time into more stable representations in long-term memory [1]. Brain regions involved in motor skill learning are reactivated during post-training sleep in human function imaging studies [17] These regional reperfusions could correspond (as observed in animals) to the replay during sleep of temporallyorganized patterns of neural activity encoding for newly acquired information, or they may reflect other experience-dependent brain processes, such as local homeostasis [18]. We recently addressed this question by studying patients who exhibited overt dreamlike behaviors during two types of parasomnias, non-REM sleep (sleepwalkers) and during REM sleep (REM sleep behavior disorder, RBD) [19]. Our second goal was to determine if patients with RBD maintain their ability to consolidate verbal memory during sleep despite the RBD disorder and cognitive impairment
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