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1. ‘Sleep-dependent’ memory consolidation? Brief periods of post-training rest and sleep provide an equivalent benefit for both declarative and procedural memory

   https://doi.org/10.1101/lm.053330.120  

   Wang, Serene Y. ; Baker, Kirsten C. ; Culbreth, Jessica L. ; Tracy, Olivia ; Arora, Madison ; Liu, Tingtong ; Morris, Sydney ; Collins, Megan B. ; Wamsley, Erin J. ( May 2021 , Learning & Memory)

   Sleep following learning facilitates the consolidation of memories. This effect has often been attributed to sleep-specific factors, such as the presence of sleep spindles or slow waves in the electroencephalogram (EEG). However, recent studies suggest that simply resting quietly while awake could confer a similar memory benefit. In the current study, we examined the effects of sleep, quiet rest, and active wakefulness on the consolidation of declarative and procedural memory. We hypothesized that sleep and eyes-closed quiet rest would both benefit memory compared with a period of active wakefulness. After completing a declarative and a procedural memory task, participants began a 30-min retention period with PSG (polysomnographic) monitoring, in which they either slept ( n = 24), quietly rested with their eyes closed ( n = 22), or completed a distractor task ( n = 29). Following the retention period, participants were again tested on their memory for the two learning tasks. As hypothesized, sleep and quiet rest both led to better performance on the declarative and procedural memory tasks than did the distractor task. Moreover, the performance advantages conferred by rest were indistinguishable from those of sleep. These data suggest that neurobiology specific to sleep might not be necessary to induce the consolidation of memory, at least across very short retention intervals. Instead, offline memory consolidation may function opportunistically, occurring during either sleep or stimulus-free rest, provided a favorable neurobiological milieu and sufficient reduction of new encoding. 

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2. Acoustic enhancement of sleep slow oscillations in mild cognitive impairment

   https://doi.org/10.1002/acn3.796  

   Papalambros, Nelly A. ; Weintraub, Sandra ; Chen, Tammy ; Grimaldi, Daniela ; Santostasi, Giovanni ; Paller, Ken A. ; Zee, Phyllis C. ; Malkani, Roneil G. ( July 2019 , Annals of Clinical and Translational Neurology)

   Slow‐wave activity (SWA) during sleep is reduced in people with amnestic mild cognitive impairment (aMCI) and is related to sleep‐dependent memory consolidation. Acoustic stimulation of slow oscillations has proven effective in enhancingSWAand memory in younger and older adults. In this study we aimed to determine whether acoustic stimulation during sleep boostsSWAand improves memory performance in people withaMCI.

   Nine adults withaMCI(72 ± 8.7 years) completed one night of acoustic stimulation (stim) and one night of sham stimulation (sham) in a blinded, randomized crossover study. Acoustic stimuli were delivered phase‐locked to the upstate of the endogenous sleep slow‐waves. Participants completed a declarative recall task with 44 word‐pairs before and after sleep.

   During intervals of acoustic stimulation,SWAincreased by >10% over sham intervals (P < 0.01), but memory recall increased in only five of the nine patients. The increase inSWAwith stimulation was associated with improved morning word recall (r = 0.78,P = 0.012).

   Acoustic stimulation delivered during slow‐wave sleep over one night was effective for enhancingSWAin individuals withaMCI. Given established relationships betweenSWAand memory, a larger or more prolonged enhancement may be needed to consistently improve memory inaMCI.

    

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3. Failure to consolidate statistical learning in developmental dyslexia

   https://doi.org/10.3758/s13423-022-02169-y  

   Ballan, Ranin ; Durrant, Simon J. ; Manoach, Dara S. ; Gabay, Yafit ( January 2022 , Psychonomic Bulletin & Review)

   Statistical learning (SL), the ability to pick up patterns in sensory input, serves as one of the building blocks of language acquisition. Although SL has been studied extensively in developmental dyslexia (DD), much less is known about the way SL evolves over time. The handful of studies examining this question were all limited to the acquisition of motor sequential knowledge or highly learned segmented linguistic units. Here we examined memory consolidation of statistical regularities in adults with DD and typically developed (TD) readers by using auditory SL requiring the segmentation of units from continuous input, which represents one of the earliest learning challenges in language acquisition. DD and TD groups were exposed to tones in a probabilistically determined sequential structure varying in difficulty and subsequently tested for recognition of novel short sequences that adhered to this statistical pattern in immediate and delayed-recall sessions separated by a night of sleep. SL performance of the DD group at the easy and hard difficulty levels was poorer than that of the TD group in the immediate-recall session. Importantly, DD participants showed a significant overnight deterioration in SL performance at the medium difficulty level compared to TD, who instead showed overnight stabilization of the learned information. These findings imply that SL difficulties in DD may arise not only from impaired initial learning but also due to a failure to consolidate statistically structured information into long-term memory. We hypothesize that these deficits disrupt the typical course of language acquisition in those with DD. 

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4. Low acetylcholine during early sleep is important for motor memory consolidation

   https://doi.org/10.1093/sleep/zsz297  

   Inayat, Samsoon ; Qandeel ; Nazariahangarkolaee, Mojtaba ; Singh, Surjeet ; McNaughton, Bruce L. ; Whishaw, Ian Q. ; Mohajerani, Majid H. ( December 2019 , Sleep)

   The synaptic homeostasis theory of sleep proposes that low neurotransmitter activity in sleep optimizes memory consolidation. We tested this theory by asking whether increasing acetylcholine levels during early sleep would weaken motor memory consolidation. We trained separate groups of adult mice on the rotarod walking task and the single pellet reaching task, and after training, administered physostigmine, an acetylcholinesterase inhibitor, to increase cholinergic tone in subsequent sleep. Post-sleep testing showed that physostigmine impaired motor skill acquisition of both tasks. Home-cage video monitoring and electrophysiology revealed that physostigmine disrupted sleep structure, delayed non-rapid-eye-movement sleep onset, and reduced slow-wave power in the hippocampus and cortex. Additional experiments showed that: (1) the impaired performance associated with physostigmine was not due to its effects on sleep structure, as 1 h of sleep deprivation after training did not impair rotarod performance, (2) a reduction in cholinergic tone by inactivation of cholinergic neurons during early sleep did not affect rotarod performance, and (3) stimulating or blocking muscarinic and nicotinic acetylcholine receptors did not impair rotarod performance. Taken together, the experiments suggest that the increased slow wave activity and inactivation of both muscarinic and nicotinic receptors during early sleep due to reduced acetylcholine contribute to motor memory consolidation.

    

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5. Attitudinal Effects of Stimulus Co-occurrence and Stimulus Relations: Sleep Supports Propositional Learning Via Memory Consolidation

   https://doi.org/10.1177/19485506211067673  

   Jin, Rui ; Xia, Tao ; Gawronski, Bertram ; Hu, Xiaoqing ( February 2022 , Social Psychological and Personality Science)

   Adaptive behavior requires that organisms learn not only which stimuli tend to co-occur (e.g., whether stimulus A co-occurs with unpleasant stimulus B) but also how co-occurring stimuli are related (e.g., whether A starts or stops B). In a preregistered study ( N = 200 adults), we investigated whether sleep would promote adaptive evaluative choices requiring joint memories for stimulus co-occurrences and stimulus relations. Participants learned about hypothetical pharmaceutical products that either cause or prevent positive or negative health conditions, followed by measures of evaluative choices and explicit memory. After a 12-hr retention interval including either nocturnal sleep or daytime wake, participants completed the same measures a second time. Results showed that sleep strengthened the impact of causal product–condition relations on choices (revealed by multinomial modeling analyses) and enhanced memories for specific stimulus co-occurrences (revealed by memory preservation analyses). The findings suggest that sleep promotes adaptive evaluative choices via offline memory consolidation.

    

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