Sleep and dreaming improves memory organization, emotion regulation and creativity

Sleep and dreaming are for important matters.
Perogamvros L, Dang-Vu TT, Desseilles M, Schwartz S.
Frontiers in Psychology, 25 July 2013 

Recent studies in sleep and dreaming have described an activation of emotional and reward systems, as well as the processing of internal information during these states. Specifically, increased activity in the amygdala and across mesolimbic dopaminergic regions during REM sleep is likely to promote the consolidation of memory traces with high emotional/motivational value. Moreover, coordinated hippocampal-striatal replay during NREM sleep may contribute to the selective strengthening of memories for important events. In this review, we suggest that, via the activation of emotional/motivational circuits, sleep and dreaming may offer a neurobehavioral substrate for the offline reprocessing of emotions, associative learning, and exploratory behaviors, resulting in improved memory organization, waking emotion regulation, social skills, and creativity. Dysregulation of such motivational/emotional processes due to sleep disturbances (e.g., insomnia, sleep deprivation) would predispose to reward-related disorders, such as mood disorders, increased risk-taking and compulsive behaviors, and may have major health implications, especially in vulnerable populations.

Poor sleep increases desire to eat

The impact of sleep deprivation on food desire in the human brain.
Stephanie Greer, Andrea Goldstein and Matthew Walker.
Nature Communications, August 6, 2013

Epidemiological evidence supports a link between sleep loss and obesity. However, the detrimental impact of sleep deprivation on central brain mechanisms governing appetitive food desire remains unknown. Here we report that sleep deprivation significantly decreases activity in appetitive evaluation regions within the human frontal cortex and insular cortex during food desirability choices, combined with a converse amplification of activity within the amygdala. Moreover, this bi-directional change in the profile of brain activity is further associated with a significant increase in the desire for weight-gain promoting high-calorie foods following sleep deprivation, the extent of which is predicted by the subjective severity of sleep loss across participants. These findings provide an explanatory brain mechanism by which insufficient sleep may lead to the development/maintenance of obesity through diminished activity in higher-order cortical evaluation regions, combined with excess subcortical limbic responsivity, resulting in the selection of foods most capable of triggering weight-gain.

Sleep consolidates memories for competing tasks

Sleep Consolidation of Interfering Auditory Memories in Starlings
Brawn TP, Nusbaum HC, Margoliash D.
Psychological Science 2013, published on Feb 22

Memory consolidation has been described as a process to strengthen newly formed memories and to stabilize them against interference from similar learning experiences. Sleep facilitates memory consolidation in humans, improving memory performance and protecting against interference encountered after sleep. The European starling, a songbird, has also manifested sleep-dependent memory consolidation when trained on an auditory-classification task. Here, we examined how memory for two similar classification tasks is consolidated across waking and sleep in starlings. We demonstrated for the first time that the learning of each classification reliably interferes with the retention of the other classification across waking retention but that sleep enhances and stabilizes the memory of both classifications even after performance is impaired by interference. These observations demonstrate that sleep consolidation enhances retention of interfering experiences, facilitating opportunistic daytime learning and the subsequent formation of stable long-term memories

Get enough sleep - children

Experts recommend that children should get the following amount of sleep at each stage of growth:

• 3 months – 1 year: About 14 to 15 hours a day 
• 1 – 3 years: 12 to 14 hours a day 
• 3 – 5 years: 11 to 12 hours of sleep a day 
• 6 – 12 years: 10 to 11 hours a day 
• 12 – 18 years: 8.5 to 9.5 hours a day

Source: American Academy of Sleep Medicine

Lucidity and consciousness in dreams

Measuring consciousness in dreams: The lucidity and consciousness in dreams scale
Ursula Vossa, Karin Schermelleh-Engela, Jennifer Windtc, Clemens Frenzeld, Allan Hobsone
Consciousness and Cognition, Volume 22, Issue 1, March 2013, Pages 8–21 

Both lucid and non-lucid dreams are an important contrast condition for theories of waking consciousness, giving valuable insights into the structure of conscious experience and its neural correlates during sleep. However, the precise differences between lucid and non-lucid dreams remain poorly understood. The construction of the Lucidity and Consciousness in Dreams scale (LuCiD) was based on theoretical considerations and empirical observations. Exploratory factor analysis of the data from the first survey identified eight factors that were validated in a second survey using confirmatory factor analysis: INSIGHT, CONTROL, THOUGHT, REALISM, MEMORY, DISSOCIATION, NEGATIVE EMOTION, and POSITIVE EMOTION. While all factors are involved in dream consciousness, realism and negative emotion do not differentiate between lucid and non-lucid dreams, suggesting that lucid insight is separable from both bizarreness in dreams and a change in the subjectively experienced realism of the dream.

Long-term fear memory

Neural pattern similarity predicts long-term fear memory
Renée M Visser, H Steven Scholte, Tinka Beemsterboer & Merel Kindt
Nature Neuroscience (2013) 

Although certain changes in the brain may reflect fear learning, there are no known markers that indicate whether an aversive experience will develop into fear memory. We examined the moment-to-moment dynamics of human fear learning by applying multi-voxel pattern analysis to single-trial blood oxygen level–dependent magnetic resonance imaging data. We found that the long-term behavioral expression of fear memory could be predicted from neural patterns at the time of learning.

Good sleep = good memory

Prefrontal atrophy, disrupted NREM slow waves and impaired hippocampal-dependent memory in aging
Bryce A Mander, Vikram Rao, Brandon Lu, Jared M Saletin, John R Lindquist, Sonia Ancoli-Israel, William Jagust & Matthew P Walker
Nature Neuroscience (2013) 

Aging has independently been associated with regional brain atrophy, reduced slow wave activity (SWA) during non–rapid eye movement (NREM) sleep and impaired long-term retention of episodic memories. However, whether the interaction of these factors represents a neuropatholgical pathway associated with cognitive decline in later life remains unknown. We found that age-related medial prefrontal cortex (mPFC) gray-matter atrophy was associated with reduced NREM SWA in older adults, the extent to which statistically mediated the impairment of overnight sleep–dependent memory retention. Moreover, this memory impairment was further associated with persistent hippocampal activation and reduced task-related hippocampal-prefrontal cortex functional connectivity, potentially representing impoverished hippocampal-neocortical memory transformation. Together, these data support a model in which age-related mPFC atrophy diminishes SWA, the functional consequence of which is impaired long-term memory. Such findings suggest that sleep disruption in the elderly, mediated by structural brain changes, represents a contributing factor to age-related cognitive decline in later life.

Sleep-dependent memory processing

Sleep-dependent memory triage: evolving generalization through selective processing
Robert Stickgold & Matthew P Walker
Nature Neuroscience 16, 139–145 (2013) 

The brain does not retain all the information it encodes in a day. Much is forgotten, and of those memories retained, their subsequent evolution can follow any of a number of pathways. Emerging data makes clear that sleep is a compelling candidate for performing many of these operations. But how does the sleeping brain know which information to preserve and which to forget? What should sleep do with that information it chooses to keep? For information that is retained, sleep can integrate it into existing memory networks, look for common patterns and distill overarching rules, or simply stabilize and strengthen the memory exactly as it was learned. We suggest such 'memory triage' lies at the heart of a sleep-dependent memory processing system that selects new information, in a discriminatory manner, and assimilates it into the brain's vast armamentarium of evolving knowledge, helping guide each organism through its own, unique life

Emotions are at the center of our thinking

Protecting recent memories against emotional contextual interference

Sleep unbinds memories from their emotional context
Deliens G, Gilson M, Schmitz R, Peigneux P.
Cerebral Cortex, Dec 2012 

Consistent evidence nowadays indicates that sleep protects declarative memory from lexical interference. However, little is known about its effect against emotional interference. In a within-subject counterbalanced design, participants learned a list of word pairs after a mood induction procedure (MIP), then slept or stayed awake during the post-learning night. After two recovery nights, half of the list was recalled after a similar mood induction than at the encoding session (no interference condition) and the other half after a different mood induction (interference condition). Amongst participants for whom the MIP was effective, an emotional interference effect appeared only in the sleep-deprived condition, with a lower recall of word pairs subjected to contextual interference than of the other pairs. These findings support the hypothesis of a decoupling between memories and their "affective blanket" during post-learning sleep, protecting recent memories against emotional contextual interference.

REM sleep necessary for emotional memory consolidation

The role of REM sleep in the processing of emotional memories: Evidence from behavior and event-related potentials
S. Groch, I. Wilhelm, S. Diekelmann, J. Born
Neurobiology of Learning and Memory, Volume 99, January 2013, Pages 1–9

Emotional memories are vividly remembered for the long-term. Rapid eye movement (REM) sleep has been repeatedly proposed to support the superior retention of emotional memories. However, its exact contribution and, specifically, whether its effect is mainly on the consolidation of the contents or the processing of the affective component of emotional memories is not clear. Here, we investigated the effects of sleep rich in slow wave sleep (SWS) or REM sleep on the consolidation of emotional pictures and the accompanying changes in affective tone, using event-related potentials (ERPs) together with subjective ratings of valence and arousal. Sixteen healthy, young men learned 50 negative and 50 neutral pictures before 3-h retention sleep intervals that were filled with either SWS-rich early or REM sleep-rich late nocturnal sleep. In accordance with our hypothesis, recognition was better for emotional pictures than neutral pictures after REM compared to SWS-rich sleep. This emotional enhancement after REM-rich sleep expressed itself in an increased late positive potential of the ERP over the frontal cortex 300–500 ms after stimulus onset for correctly classified old emotional pictures compared with new emotional and neutral pictures. Valence and arousal ratings of emotional pictures were not differentially affected by REM or SWS-rich sleep after learning. Our results corroborate that REM sleep contributes to the consolidation of emotional contents in memory, but suggest that the affective tone is preserved rather than reduced by the processing of emotional memories during REM sleep.