Posted by: Trudy Prevost | July 27, 2012

Yoga for a Good Sleep and a Good Memory

One of the most frequents comments I hear as people talk about their yoga experience is they sleep better!

I had more than one student tell me they cannot sleep or have trouble falling asleep at the start of the class yet they fell deeply asleep during the relaxation – in some cases the environment was very bright and noisy yet the sense of total relaxation sent them into dreamland.

There are not many studies on yoga and sleep quality but the few that have been done show there is often an improvement especially with regular practice.

In one study from Spain the effects of long-term yoga on Subjective Sleep Quality and on several hormonal parameters of the hypothalamus-pituitary-adrenal axis was  examined. Their conclusion was that long-term yoga practice is associated with significant psycho-biological differences, including better sleep quality as well as a modulatory action on the levels of cortisol.

The results from another study involving 26 elderly patients showed that after 6 months of performing yoga exercises, participants’ overall sleep quality had significantly improved, whereas depression, sleep disturbances, and daytime dysfunction had decreased significantly. In addition, participants in the intervention group had better results on all outcome indicators than those of participants in the control group.

There have been a few other studies done on patients with cancer; osteoarthritis and other ailments and each one found regular yoga practice improved sleep quality and alleviated insomnia.

When we consider that our brain is more efficient at storing long term memories when we have a good quality sleep – this has important implications for potential memory improvement – improve sleep quality and improve long term memory.

Studies from the 1990’s Stanford University research has found disrupting sleep made it harder for animals to recognise familiar objects.

This study looked at sleep that was fragmented, but not shorter or less intense than normal for the mice.

The animals were then placed in a box with two objects, one of which they had encountered before.

Mice would naturally spend more time examining the newer object, and those who had been allowed uninterrupted sleep did just that.

But those whose sleep had been disrupted were equally interested in both objects, suggesting their memories had been affected.

Writing in the journal, the researchers, led by Dr Luis de Lecea, said: “Sleep continuity is one of the main factors affected in various pathological conditions that impact memory, including Alzheimer’s and other age-related cognitive deficits.”

Researchers concluded that regardless of the total amount of sleep or sleep intensity, a minimal unit of uninterrupted sleep is crucial for memory consolidation.”

Independent sleep expert Dr Neil Stanley, a former chairman of the British Sleep Society, said: “During the day, we accumulate all these memories.

“At some point we have to sort through what’s happened during the day.

“There are some things that we need to ‘lock down’ as a permanent hard memory.

That process occurs in deep sleep. So anything that affects sleep will have an effect on that process to a greater or a lesser extent.”

Dr Stanley said there was particularly striking evidence that people with sleep apnoea had particular problems “locking down” memories.

And he added that people with Alzheimer’s often had trouble sleeping, but said: “There is something there. But whether it’s the degeneration of the brain that causes poor sleep, or poor sleep that aids the degeneration of the brain has not been determined.”

Miranda Watson, director of communications at the British Lung Foundation, said: “For patients with the dangerous sleep disorder, obstructive sleep apnoea, this study will come as no surprise.

“Patients regularly stop breathing during the night when their airways become blocked depriving them of a full night’s rest.

“This interrupted sleep can cause extreme day time tiredness and memory loss.”

Arizona University

Scientists are finding new evidence that a good night’s rest plays a crucial role in cementing memories formed during the day.

One new study has identified a brain region involved, along with the hippocampus, in creating memories of the day’s activities during sleep. Another study suggests melatonin, a hormone involved in regulating our day-night cycle, or “circadian rhythm,” acts to suppress the formation of new memories as bedtime nears, perhaps in an effort to give memories made earlier in the day a chance to be prepared for long-term storage.

Both studies are detailed in the Nov. 16 issue of the journal Science.

Prepping for storage

In 1993, scientists learned that the hippocampus “replays” the day’s events during sleep. The process appears to be important for consolidating new memories and preparing them for long-term storage in other brain areas.

In one of the two latest studies, David Euston of the University of Arizona and his colleagues found that the medial prefrontal cortex, a brain region implicated in the retrieval of memories from the distant past, was also active during learning and replayed the day’s events during sleep. And similar to memory replay in the hippocampus, events were speeded up when reviewed.

Euston’s team recorded activity in the medial prefrontal cortices of rats as they ran on a track and afterward while they slept. When the rats were running, brain cells in the medial prefrontal cortex fired off electrical signals in specific patterns over time. The patterns of electrical firing corresponded to memories.

“You see a series of these patterns,” Euston said. “You can imagine at point A there’d be one pattern of cells firing, and at point B there’s another pattern.”

The rats’ brains were scanned again as they rested after performing the task. “When the rats go to sleep, we can continue to monitor the activity of the cells, and we look for a re-expression of those same activity patterns,” Euston told LiveScience.

Memory fast forward

The researchers found the patterns, but discovered they were being replayed about seven times faster than when the rats were actually performing their tasks.

“In the maze, the rat might take 1.5 seconds to get from point A to point B,” Euston said. “When the rat goes to sleep, you see those patterns replaying, and the entire thing takes only 200 milliseconds.”

The researchers say the medial prefrontal cortex’s fast-forward replay of the day’s events could be evidence that our brains can process information much faster when not busy with real-world tasks.

“When you’re awake and performing things, the brain has to go at the pace at which your behavior is unfolding,” Euston said. “If you’re reaching for a cup, the cells in your motor cortex have to be expressing the patterns of activity that will guide your hand to the cup. When you go to sleep you don’t have that constraint anymore.”

Brain-imaging studies involving people have also shown the medial prefrontal cortex to be active during learning, so the same processes could apply to humans as well, Euston said.

Melatonin memories

In order to ensure that memory consolidation proceeds smoothly, our brains might have a built-in mechanism that inhibits the formation of new memories as we get closer to bedtime, the second new study finds.

Gregg Roman at the University of Houston in Texas and his colleagues linked the hormone melatonin to the quality of memories formed in zebrafish . They showed that zebrafish trained to perform a task during the day, when melatonin levels are typically low, remembered what they were supposed to do better than if they were trained at night, when levels of the hormone peak.

As further support for melatonin’s role in memory, the team found that fish administered with melatonin during the day had trouble forming new memories, and that night training which occurred in the presence of constant lights (which inhibits melatonin secretion) yielded strong memories.

Roman speculates melatonin blocks new memory formation so that older experiences accumulated during the day have a chance to solidify.

Melatonin is an important hormone in every creature from cockroaches to humans, so it’s likely the zebrafish findings also apply to humans, Roman said.

So does that mean learning is best done during the day and not at night?

Maybe, Roman said, but he points out that the human memory system is much more complex than that of the zebrafish, and while melatonin should inhibit memory formation at night in us, its effects will be buffered by other hormones and other brain components.

“I would presuppose that learning could occur at night in humans,” Roman said. “We have a much higher capacity for learning than zebrafish

Harvard University

Boston – July 10, 2006 – Researchers from Brigham and Women’s Hospital, Harvard Medical School and the University of Pennsylvania found that sleep benefits an individual’s ability to recall recently learned declarative memories, even when recall of these memories is challenged hours later by competing information. This finding is particularly important for individuals with mentally demanding lifestyles, such as doctors, medical residents and college students, who often do not get adequate amounts of sleep. The study appears in the July 11, 2006 issue of Current Biology.

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