Generally speaking, you cannot learn from sounds of new information while you sleep, though this was a fad several decades ago. But in an earlier post, I discussed a new line of research where sleep learning can occur. The key is to play sound cues that were associated with learning that occurred during the previous wakefulness period. The explanation I posted was that cue-dependent sleep learning can work because a normal function of sleep is to strengthen memories of new information and that presenting relevant cues during sleep increases the retrieval of these memories and makes them accessible for rehearsal and strengthening.

The latest experiment by a different group shows that this cuing during sleep can modify bad attitudes and habits. The test involved counter stereotype-training of certain biased attitudes during wakefulness, and investigators reactivated that counter-training during sleep by playing a sound cue that had been associated with the wakefulness training.

In the experiment, before a 90-minute nap 40 white males and females were trained to counter their existing gender and racial biases by counter-training. A formal surveyed allowed quantification of each person's level of gender or racial bias before and after counter-training. For example, one bias was that females are not good at math. Subjects were conditioned to have a more favorable attitude about women and math with counter-training that repeatedly associated female faces with science-related words. Similarly, racial bias toward blacks was countered by associating black faces with highly positive words. In each training situation, whenever the subject saw a pairing that was incompatible with their existing bias they pressed a "correct" button, which yielded a confirmatory sound tone that was unique for each bias condition. Subjects were immediately tested for their learning by showing a face (female or black) and the counter-training cue, whereupon they were to drag the appropriate bias-free face on to a screen with the positive word. For example, if the first test screen was that of a woman, accompanied by the sound cue, the subject dragged a woman's face onto a second screen that said "good at math." Results revealed that this conditioning worked: both kinds of bias were reduced immediately after counter-conditioning.

Then during the nap, as soon as EEG signs indicated the presence of deep sleep, the appropriate sound cue was played repeatedly to reactivate the prior learning. When subjects re-took the bias survey a week later, the social bias was reduced in the sound-cued group, but not in the control group that was trained without sound cues.

Experimenters noted that the long-term improvement of bias was associated with rapid-eye-movement (REM) (dream) sleep which often followed the deep sleep during early stages of the nap. That is, the beneficial effect was proportional to the amount of nap time spent in both slow-wave sleep and REM sleep, not either alone. It may be that memories are reactivated by cuing during deep (slow-wave) sleep, but that the actual cell-level storage of memory is provided by REM sleep.

Implications of this approach to enhancing learning and memory show a great deal of promise. Can it be used for enhancing learning in school? Can it be used in rehabilitation of addicts or criminals? But there is a dark side. Now might be a good time to re-read Huxley's Brave New World wherein he actually described conditioning values in young children while they slept. Sleep is a state where people are mentally vulnerable and without conscious control over their thoughts. Malevolent people could impose this kind of conditioning and memory enhancement on others for nefarious purposes.  These techniques may have valid social engineering applications, but they must be guided by ethical considerations.

Dr. Klemm is author of Memory Power 101(Skyhorse), Better Grades, Less Effort(Benecton), and Mental Biology(Prometheus).

Sources:

Klemm, W. R. (2013). New discoveries on optimizing femory formation.  http://thankyoubrain.blogspot.com/2013/05/new-discoveries-on-optimizing-memory.html

Hu, Xiaoqing et al. (2015. Unlearning implicit social biases during sleep. Science. 348(6238), 1013-1015.

In other blog posts I have explained why sleep is good for the brain in general and memory formation in particular. Now a new discovery provides another reason for people to get enough sleep. The study examined a type of support cell in the brain, oligodendrocytes–let’s call them oligos for short. These cells wrap their membranes around nerve cells to form what is called myelin, which forms an electrical insulation in a way that speeds up the propagation of nerve impulses through neural networks. You may have heard about oligos in reading about multiple sclerosis, a disease that impairs nerve communication because oligos die and the myelin insulation degrades.

Speed of transmission is important–it influences IQ for example. As you know from buying a new computer, the faster processor speed gives it new capabilities your old clunker could not do. A similar idea applies to the brain.

Anyway, this new study, from the University of Wisconsin, focused on oligos because other research had shown that sleep promoted the expression of several genes that are involved in synthesis of cell membranes in general and those in oligos in particular. Unlike neurons, oligos die, and are replaced in the brain. Thus, anything that affects their turnover is important for brain function. Sleep has been implicated in this turnover because a common neurotransmitter in the brain, glutamate, is known to increase in wakefulness and decline during sleep. Glutamate  suppresses maturation of oligo precursor cells into formation of myelin insulation.

In this particular study, investigators examined a genome-wide profile of oligo gene expression in mice after a 6-7 hour periods of sleep or spontaneous wakefulness, or four hours of forced wakefulness (sleep deprivation). They found that 357 genes were expressed differently, depending on the time of day, in response to normal daily rhythms. More dramatic was the observation that 714 genes changed expression in conjunction with the sleep/wakefulness cycle, independent of the time of day. Of these genes, 310 were “sleep” genes that were selectively activated during sleep.

Many of the sleep genes contribute to maturation of oligos into myelin. In follow up experiments, mice were injected with a radiolabeled tag that marks the birth of new cells. Injection occurred eight hours before mice spent a long period of either of wakefulness or sleep. The number of newly born oligos was almost double in the sleep group compared to the wake group. More detailed analysis showed that this increase was specifically correlated with the amount of REM sleep (dream sleep in humans).

This REM effect may have particular importance in humans. Most REM sleep occurs in the early morning hours and only after substantial time has been spent in non-REM stages of sleep. Thus, cutting a night’s sleep short by getting up early may decrease the amount of REM time and thus the beneficial effects on oligo proliferation. So don’t feel guilty about “sleeping in” from time to time.

We might also think about how these findings could have special relevance to children, whose brains are incompletely myelinated. Getting children up early in the morning to start school at 8 AM may not be such a good idea. Until school districts get around to changing school hours, you might tell you kids about my learning and memory improvement e-book, Better Grades, Less Effort, available at Smashwords.com.

Source:

Bellesi, M., et al. (2013) Effects of sleep and wake on oligodendrocytes and their precursors. J. Neuroscience. 33 (36), 14288-14300.

As each of us goes through life, we remember a little and forget a lot. The stockpile of what we remember contributes greatly to define us and our place in the world. Thus, it is important to remember and optimize the processes that make that possible.

People who compete in memory contests (“memory athletes”) have long known the value of associational cues (see my Memory Power 101 book). Neuroscientists have known for a long time about memory consolidation (converting short-term memory to long-term form) and the value of associational cues. But now, important new understanding is arising from a research lab at Northwestern that links cueing to “re-consolidation” and reveals new possibilities for optimizing long-term memory formation.

The underlying research approach is based on such well-established memory principles as:

1. When information is first acquired, it is tagged for its potential importance or value.
2. Such tagging is influenced by multiple factors such as repetition, attention, emotion, or purpose.
3. Valuable memories get preferentially rehearsed, either through conscious will or by covert (implicit) brain processes.
4. Rehearsal episodes reactive the memory and enhance long-term remembering because each re-consolidation episode builds on prior ones and strengthens the neural circuits that store the memory.
5. Effectiveness of recall during rehearsal is promoted by use of relevant cues, that is, information that was associated with the original learning material.
6. Such cues are effective, even when delivered during sleep.

The pioneering study involving sleep learning appears to have been done by John Rudoy and colleagues in 2009 [1}. They showed that people recalled locations of memorized objects better if they heard sounds associated with the locations during their sleep that had been earlier associated with the learning of object locations. The basic finding was replicated in a follow-up study [2].

Most recently, a study by another group also confirmed and extended this concept of using cues during sleep to promote memory formation.The study involved 60 people in their early 20s, screened for good memory ability.[3]All subjects participated in a four-hour learning period beginning in late morning. The learning consisted of 72 images placed in specific locations on a tile-like screen and presented one at a time. As each image appeared a corresponding sound was associated, intended to serve as a learning cue. For example, a dog picture would be associated with barking, cat with meow sound, etc. To create a value bias, each image had a superimposed number representing how important it was to remember this item and its location upon later testing. Subjects were given financial reward for how well they remembered, and thus remembering high-value images was a priority. Half of the images had high value assignments, while the rest had low values.

 Subjects were assigned to four groups:  

1. Groups 1 and 2 were tested to see how well they could remember where each object had appeared during the learning phase. They then took a 90 min nap while their EEGs were recorded. Half of these subjects heard white noise while the other have was presented the original sound cues of low-value images during non-REM sleep at a level that did not cause awakening. At the end of the nap, recall was again tested.
2. The procedure in two other groups was similar except that these subjects did not nap. One of these groups watched a movie during the 90 minutes after the learning session, while the other group listed to the low-value sound cues while performing a working memory task.

Not surprisingly, the studies revealed that high-value images were remembered better, irrespective of whether or not a nap was taken. The practical point is that we remember better the things we value and find to have positive reward value. This reminds me of the sage saying that T. Boone Pickens repeated from his basketball coach, who told players after each game: “Don’t dwell on your mistakes. Think about what you did right and do more of that!”

In the study, half of the low-value associations were rescued by cueing during wakefulness and all of them were rescued by cueing during sleep, even though only half of the images were cued. Notably, the best effects occurred during the deepest stage of sleep. No explanation was given to explain the sleep benefit, but I suspect it is because the sleeping brain is not distracting itself with irrelevant thoughts. This is consistent with the finding that low-value memories were not rescued well during REM sleep, when the brain is busily engaged in dreaming. The REM-sleep finding is at variance with other studies that reported a memory consolidating benefit of REM sleep. Apparently, the test conditions make a difference and more research is needed here.

Low-value associations were preferentially forgotten in the group that was not allowed to nap. This likely signifies that a brain busily engaged with other thoughts is less able to selectively consolidate memories, and only high-value items are likely to survive. This accords with the long-held theory that distractions and multi-tasking interfere with memory consolidation.

In summary, memory optimization would seem to require one to:

1.    Create associations that can serve as memory cues.

2.    Place a high value on the cues and their targets.

3.    Repeatedly present the cues and replay the initial information. When awake, present the cues in self-test mode. When asleep, even better results would obtain if cues were presented at a level that does not cause awakening during the early night sleep when sleep is deepest and there is little dreaming.

---

1. Rudoy, J. D., Voss, J. L., Westerberg, C. E., Paller, K. A. (2009). Strengthening individual memories by reactivating them during sleep. Science. 326: 1079.

2.. Antony, J. W, Gobel, E. W., O’Hare, J., K., Reber, P. J., and Paller, K. A. (2012). Cued memory reactivation during sleep influences skill learning. Nat. Neurosci. 15: 1114:1116.

2. Oudiette, D., Antony, J. W., Creery, J. D., and Paller, K. A. (2013) The role of memory reactivation during wakefulness and sleep in determining which memories endure. J. Neurosci. 33(15): 6672-6678.

Don't forget to check my memory e-book, Better Grades, Less Effort, 

for only $2.99 at Smashwords.com.