Mind Matters

Part 2 - Sleep:  The Ultimate Memory Enhancer

Everyone wants to have a good memory.  It is essential for career success.  But there are a multitude of factors that impede memory.  Common memory reducers include things like lack of sleep, stress, vitamin deficiency and trauma.  Less common memory cripplers include such factors as illness, diseases such as Alzheimers, poor blood flow to the brain, brain hemorrhages or injuries, and tumors.  Beyond all these, there are a multitude of additional variables – such as ways that the brain works -- that impact memory.  Often memory is affected in ways that neurologists haven’t even begun to understand.  Indeed, scientists agree that memory is one of the functions of brain that is still not well understood.

However, every day, researchers are learning more about memory…. How memory works and how it can be helped to work better.  While memory research had previously been focused on what happens when a memory is first formed and on what happens when a memory is retrieved, it is the in-between time when it appears many aspects of memory storage happens.  Numerous studies are finding that sleep is actually an important tool in the memory retention process.  Here are the latest strategies and research on sleep and how it may be the key to improving memory.

To Sleep, Perchance to Remember?

For those that scoff at sleep and see it as an utter waste of time, think again.  Researchers are concluding that sleep may be the key to the mind’s ability to recall everything that is important, including valuable career information.  The connection between memory and sleep is now fairly well-established.  There have been a number of studies that show the connection between quality sleep and better ability to remember.  

1.  Deep sleep helps the brain store memories.
For instance, one recent study by researchers at the University of California, Berkeley showed that poor sleep causes significant memory loss and brain deterioration among the elderly.  The study involved assessing the memory after sleeping of 18 young adults in their 20s and 15 older adults in their 70s.  The subjects were tested on 120 word sets before they went to bed and a electroencephalographic (EEG) machine monitored their brain activity while they slept. When they woke, they were tested again on the word pairs.  This time, they took the tests while undergoing functional and structural Magnetic Resonance Imaging (MRI) scans. The quality of deep sleep among the older adults was 75% lower than the young adults, and their memory was significantly worse the next day - 55 percent worse.

There was evidence to suggest that deterioration of the frontal lobe was linked with impaired wave activity.  According to Bryce Mander, lead author of the study and a postdoctoral fellow in psychology at UC Berkeley, and sleep researcher Matthew Walker, an associate professor of psychology and neuroscience at UC Berkeley, during sleep important brain waves are produced which play a vital role in storing memories. The brain waves transfer memories from a part of the brain called the hippocampus to the prefrontal cortex, a part of the brain where long term memories are stored.  Poor quality sleep in the adults caused memories to remain ‘stuck’ in the hippocampus unable to reach the prefrontal cortex.  The deteriorated quality of sleep prevented those memories from being saved by the brain at night.  In non rapid-eye movement sleep, the brain produced waves from the middle frontal lobe.  As that part of the brain deteriorates, which happens with age, it undermines the ability to enter deep sleep, crucial for storing memories.  This dysfunctional pathway between sleep, brain deterioration, and memory resulted in forgetfulness and difficulty remembering names. Young people, on the other hand, enjoyed deep sleep which helped the brain transfer, store and retain new facts and information.   

2.  Uninterrupted sleep aids memory.
Another study, conducted by scientists at the University of Stanford in 2011 using new technology to disrupt continuity of sleep, concluded that interrupted sleep impairs memory. They used optogenetics on mice without changing other variables to target specific neurons and found that a minimum amount of continuous sleep is crucial for memory consolidation.  As a result, people with certain neurological and psychiatric conditions that affect sleep continuity, without affecting total sleep or sleep quality, often have memory problems. These conditions include sleep apnea, where the person stops breathing and can experience hundreds of “micro-sleep interruptions” a night.  (Although scientists had suspected for a while that sleep continuity was important for memory, it had not been possible to investigate, because the technology that allowed the manipulation of continuity of sleep without affecting other variables like quality and overall duration had not been available until recently.)

3.  Timed sounds during sleep can improve memory.
A study by Dr Jan Born at the University of Tubingen in Germany, published in the journal Neuron, revealed that specifically timed sounds that rise and fall at the same rate as brain waves during sleep can improve memory.  The researchers conducted tests on 11 people - during which they were exposed to sound stimulations or to fake stimulations.  The participants were then shown 120 pairs of words every night before bed. In the morning they were tested to see what they remembered.  When the subjects were exposed to stimulating sounds that were in sync with the brain's slow oscillation rhythm, they could remember word associations that they had learned the previous night better. Stimulation that was not in line with the brain's slow oscillation rhythm did not work the same way.  This technique might potentially improve people's memory of information learned the day before, and also help those who have memory issues.

How does it work?  Slow oscillations in brain activity happen during slow-wave sleep and are necessary for storing memories. Specific sounds synchronized to the rhythm of the slow brain oscillations of people sleeping improved the oscillations, and in turn, improved their memory.  Born found that the sound stimulation was effective only when the sounds occurred in synchrony with the ongoing slow oscillation rhythm during deep sleep.

4.  Memory reactivation and rehearsal during sleep improves ability to recall.

A study at Northwestern University as recently as April 2013 suggests that memories rehearsed, during either sleep or while awake, can have an impact on memory consolidation and on what is remembered later.  The study showed that when the information that made up a memory had a high value (associated with, for example, making more money), the memory was more likely to be rehearsed and consolidated during sleep and, thus, remembered later.  Through the use of a direct manipulation of sleep, the research also demonstrated a way to encourage the reactivation of low-value memories so they too were better remembered later.

Delphine Oudiette, a postdoctoral fellow in the department of psychology at Northwestern and lead author of the study, and Ken Paller, professor of psychology at Northwestern and co-author of the study, designed the experiment to study how participants remembered locations of objects on a computer screen. A value assigned to each object informed participants how much money they could make if they remembered it later on the test. The pay-off was much higher for some of the objects than for others.  . The value of the memories were manipulated -- just as the things experienced each day vary in how important they are for being remembered the next day. When each object was shown, it was accompanied by a characteristic sound.  For example, a tea kettle would appear with a whistling sound. During both states of wakefulness and sleep, some of the sounds were played alone, quite softly, essentially reminding participants of the low-value items.  Participants remembered the low-value associations better the next day when the sound presentations occurred during sleep.  It appeared that during sleep the information was reactivated.  The researchers provoked the reactivation of the memory by presenting the sounds paired with those low-value items, therefore energizing the low-value memories to get stored better.  Seemingly, whatever caused a person to reactivate and rehearse a particular event from the day during sleep determined what was remembered.  A lot of rehearsal happens during sleep. 

5.  Deeper sleep improves overnight memory.
In yet another sleep study in Germany, scientists were able to effectively enhance deep sleep in adults using electrical stimulation.  The improved sleep helped greatly with overnight memory.   Further studies are planned to see if there is a way of further enhancing sleep among the elderly in order to allow proper storage of memories and reduce overall forgetfulness.

What is the point?  To have a better memory, get a better night’s sleep. Sleep deep.  Sleep uninterrupted.  Sleep long.  Allow your brain to reactivate and rehearse the information gathered during the day.   Let it transfer that information from where it is gathered to where it can be stored.  It is sleep – not more work – which will help the brain retain all that you experience…. so that the next day, your mind is ready to put all that information to good use.  Sleep on it.

QUOTE OF THE WEEK

"Memory is the treasury and guardian of all things." Marcus Tullius Cicero