Lifestyle Matters. Lesson 14b. Exercise

 

Be healthy. Be smart.

Exercise is not only good for the body; it is good for the brain.  The idea that exercise might benefit memory originally came from animal research revealing exercise increases learning and memory capability, presumably because exercise stimulates the birth of new nerve cells in the hippocampus, the part of the brain that is crucial for forming long-term memory. I have posted many articles on the benefits of exercise for the brain  at this blog site (type “exercise” into the search field).

It is now clear that exercise benefits memory capability in humans too, both old and young. In addition, the state of exercise is tied to memory; that is, state-dependent memory can be demonstrated with exercise. For example, in a study of humans exercising on a bicycle, word lists learned during the exercise were recalled best during another exercise episode, while words learned not riding on a bike were recalled best under that same condition. State-dependent learning has been demonstrated in other contexts too, such as with alcohol and with school-room environments.

Even when I was a kid, which was long before the whole notion of aerobic exercise, people said that being physically active could help you perform better in school. But this was mostly anecdotal, with very little research evidence. Now there is much solid evidence. Sadly, it may have come too late. Many schools have done away with or minimize physical education. Many girls think it’s not cool to sweat.

Charles Hillman and colleagues at the University of Illinois recently reported a study on the effects of exercise on cognitive function of 20 children aged 9 to 10. They administered some stimulus discrimination tests and academic tests for reading, spelling and math. On one day, students were tested following a 20-minute resting period; on another day, students walked on a treadmill before testing. The exercise consisted of 20 minutes of treadmill exercise at 60% of estimated maximum heart rate. Mental function was then tested once the heart rate returned to within 10% of pre-exercise levels. Results indicated improved performance on the tests following aerobic exercise relative to the resting session. Tests of brain responses to stimuli suggested the difference was attributable to improved attentiveness after just this one bout of exercise.

Note this is just from a single aerobic exercise experience. How can that be beneficial? The most obvious explanation is that exercise generates more blood supply to the brain, but I don't know that this has been documented. Actually, what is known is that exercise diverts blood to the muscles. The generally accepted view is that the body tightly regulates blood flow to the brain and that the brain always gets what it needs.

A more likely explanation is that single bouts of exercise relieve anxiety and stress, which are known to disrupt attentiveness and learning. Maybe the repetitive discipline of exercises like treadmill-walking help entrain the brain into a more attentive mode, akin perhaps to meditation. We need a study that compares treadmill walking with a different kind of exercise regimen (like a vigorous and competitive basketball game, for example).

As for what goes on in a typical school recess, I doubt that such activities as gossiping, text messaging, or whatever else goes on these days with kids at recess markedly interfere with learning.

There is also the possibility a continuing aerobic exercise program could produce long-lasting beneficial effects in young children. My own prejudice is that schools and parents ought to get serious about requiring aerobic exercise programs. It should not only improve the quality of school work but also help combat the epidemic of obesity and diabetes. One caveat: excessive running to achieve aerobic levels of exercise may not be advisable in children. My own experience with jogging, for example, might have been great for my heart and brain, but I now have two artificial knees and an artificial hip joint to show for it.

Here is another caveat you may have thought about: If exercise is so good for academic performance, why do varsity athletes generally make poorer grades than their classmates? Well, there are many other factors, of course. One prevailing attitude among athletes is that academics are less important to them than their sport. Athletes tend to devote their time and energy to their sport, not school work. They also have more incentive to focus on their sport. Students idolize athletic stars. But students who make all As are not considered heroes; they are often considered nerds or otherwise abnormal. What should be normal is to exercise both body and brain. 

Sources, Exercise

Hillman, C. H., Pontifex, M. B., Raine, L. B.,  Castelli,, D. M., Hall, E. E., and Kramer, A.F. (2009). The effect of acute treadmill walking on cognitive control and academic achievement preadolescent children, Neuroscience, 159 (3), 1044-1054, https://doi.org/10.1016/j.neuroscience.2009.01.057.

Miles, Christopher, and Hardman, Elinoir. (2010). State-dependent memory produced by aerobic exercise. Ergonomics. 41(1), doi.org/10.1080/001401398187297

 

 

Engram Neurons: A New Take on Memory Consolidation

As far back as Plato and Aristotle, people believed that our memories had to be physical somethings that were stored somewhere in the brain. But only in modern times have we learned much about what this something is. First, the something was given a name: memory engram. Then, as knowledge accumulated about what happens in neurons and their synapses as they become active in learning and remembering, it became clear that learning events that could be remembered were causing chemical and physical changes in the junctions (synapses) between neurons that participate in the learning experience. Participating neurons grow new dendritic branches (called spines) and the synapses on those spines enlarge and their neurotransmitter systems become enhanced. These changes constitute the engram. Post-learning reactivation of the synapses holding such an engram can produce recall of the original learning that created the engram.

In the early days of neuroscience, scientists believed that learning experiences assigned or recruited certain parts of the brain to hold the memory. An experimenter, Karl Lashley, taught certain tasks to lab animals, and then under anesthesia, destroyed different parts of the neocortex in the hopes of finding where the memory was stored. He couldn’t find any particular storage location. What he did find was that the more extensive he made the cortical lesions, the more likely he could erase the memory. In other words, memory of a given experience seemed to be deconstructed and parceled out into different regions.

Then came quantitative EEG studies by E. Roy John, in which he tracked the location of brain electrical evoked responses in different parts of the cortex during learning experiences. He saw that a given learning experience would produce electrical responses in several parts of the cortex, again suggesting a deconstruction and distribution of memory engrams. This led him to famously proclaim, “Memory is not a thing in a place, but a process in a population.”  Well, we know that this is a bit of over-statement. There is such a thing as a memory engram that is stored in specific places. Nonetheless, there is a distribution process for creating the engram in multiple locations and for orchestrating them into simultaneous and coordinated activity during recall of the memory.

Modern genetic engineering and neuron staining technology provide powerful new tools to examine neurons that participate in joining the neural circuits involved engrams. There are now ways to image and manipulate engrams at the level of neuronal ensembles.  Several lines of evidence show that engram neurons can be seen histologically and evaluated under various experimental approaches. For example, histological stains revealing neurons that are activated by a learning experience show that they are also active during memory retrieval of that experience. Second, loss-of-function studies show that impairing engram neuron function after an experience impairs subsequent memory retrieval. Third, studies show that memory retrieval can be triggered by optogenic stimulation of engram neurons in the absence of any natural sensory retrieval cues.

The basic approach used by investigators in the lab of Susumu Tonegawa was to teach mice to avoid walking into a chamber in which they would receive a mild electric shock. Neurons that are activated by this fear conditioning fluoresce in immunohistological stains of brain slices in mice that are sacrificed at various times after learning reveal a memory engram that resides in selected neurons in the amgydala (which processes fear information), in the hippocampus (which converts short-term memory to longer-term memory), and in multiple regions of neocortex (which holds long-term memory in the form of enhanced synaptic capability). Some of these cells still fluoresce when examined many days later, indicating that they have become part of an ensemble of engram neurons that hold a relatively lasting representation of the original learned experience.

Other mice were genetically engineered so that engram cells would fluoresce and be activated when exposed to light delivered via micro-fiber optic cables surgically implanted in various regions of neocortex. Such light stimulation of engram cells confirmed their engram status, because light stimulation alone triggered the previously learned behavior (freezing in place, rather than entering the shock chamber). A key finding was that engram neurons in the prefrontal cortex were “silent” soon after learning — they could initiate freezing behavior when artificially activated by light delivered via surgically implanted fiber optic filaments, but they did not fire during natural memory recall. In other words, the memory engram was formed right away in all three places (amygdala, hippocampus, and neocortex), but the engram cells in the neocortex had to mature over time to become fully functional.

Over the next two weeks, the engram neurons in the neocortex gradually matured, as reflected by changes in their anatomy and physiological activity. By the end of that same period, the hippocampal engram cells became silent and were no longer used for natural recall. At this point, the mice could recall the event naturally, without activation of neocortical cells by fiber-optic light. However, traces of the memory remained in the hippocampus, because reactivating those hippocampal neurons with light prompted the animals to freeze.

The past prevailing view was that learning experiences are temporarily held in circuits in the hippocampus and then later exported out to other parts of brain for final storage. Both in the past and now, all the evidence indicates that the hippocampus is crucial for forming lasting memories of experiences that do not involve motor learning, but the mechanisms had been uncertain. 

Neuroscientists did know that long-term memories were stored outside of the hippocampus, because people with hippocampal damage can lose the ability to form new long-term memories, but they are still able to recall old memories.

Now, the new research suggests that memory engrams are not transported from hippocampus to neocortex but are present in both places at the outset of learning. The memory engram in the neocortex just requires maturation for the memory to become more permanent. Moreover, the hippocampus cannot, and need not, hold long-lasting engrams.

Though this is a new way to think about the mechanisms of how temporary memories consolidate into longer-lasting ones, the conventional idea of consolidation remains confirmed. That is, the memory engram must mature over time in the form of biochemical and anatomical changes in the engram cells. Obviously, such maturation process would be disrupted if those same engram cells are recruited to serve other learning purposes before they have finished their maturation as a specific memory engram. This also helps to explain why subsequent rehearsals help make memories last longer, because each rehearsal re-engages engram neurons into the same kind of activity they performed during learning, thus strengthening the relevant synapses.

Once memories were formed in the fear-conditioned mice, the engram cells in the amygdala remained unchanged throughout the course of the experiment. Those cells, which are necessary to evoke the emotions linked with specific memories, like fear of entering the shock chamber in this case, communicate with engram cells in both the hippocampus and the prefrontal cortex.

We don’t know what happens to memory-specific engram cells in the hippocampus. Maybe as they gradually lose their engram status, they become available for processing new kinds of learning experience. Perhaps some traces of engram remain in hippocampus and are accessible for reactivation if highly relevant inputs are received, as could be the case with strong memory cues. Perhaps the important point is that these new techniques for labeling engram cells open the door for new ways to study of memory retrieval, the long-neglected aspect of memory mechanisms.

Another potentially relevant finding of this kind of research is that memory engrams may become damaged but may still exist in a form that cannot be retrieved by natural means. The fact that such “silent” engrams can be retrieved with direct optogenetic stimulation indicates that failures to recall do not necessarily indicate that the memory is lost. The problem may lie in an inadequacy of the natural memory cues used to triggger memory retrieval.

The door is also now open for experiments that might advance our understanding of the maturation of engram neurons in the neocortex. What is known so far is that maturation requires initial communication with engram cells in the hippocampus. Disrupting hippocampal connections between hippocampus and frontal cortex prevents the maturation of neocortical engram cells.

Sources

Takashi Kitamura, Takashi, et al., (2017). Engrams and circuits crucial for systems consolidation of a memory,” Science, 356(6333), 73-78; DOI: 10.1126/science.aam6808

Josselyn, Sheena A., and Tonegawa, Susumu (2020). Memory engrams: Recalling the past and imagining the future. Science. 367 (6473), eaaw4325. Doi: 10.1126science.aaw4325. https://science.sciencemag.org/content/367/6473/eaaw4325

Sleep Away Your Bad Attitudes

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.

What Is the Optimal Spacing for Study?

We have all been told by teachers that learning occurs best when we spread it out over time, rather than trying to cram everything into our memory banks at one time. But what is the optimal spacing? There is no general consensus.

However we do know that immediately after a learning experience the memory of the event is extremely volatile and easily lost. It's like looking up a number in the phone book: if you think about something else at the same time you may have to look the number up again before you can dial it. School settings commonly create this problem. One learning object may be immediately followed by another, and the succession of such new information tends to erase the memory of the preceding ones.

Memory researchers have known for a long time that repeated retrieval enhances long-term retention. This happens because each time we retrieve a memory, it has to be reconsolidated and each such reconsolidation strengthens the memory. Though optimal spacing intervals have not been identified, research confirms the importance of spaced retrieval. No doubt, the nature of the information, the effectiveness of initial encoding, competing experiences, and individual variability affect the optimal interval for spaced learning.

One study revealed that repeated retrieval of learned information (100 Swahili–English word pairs) with long intervals produced a 200% improvement in long-term retention relative to repeated retrieval with no spacing between tests. Investigators compared different-length intervals of 15, 30, or 90 minute spacing that expanded (for example, 15-30-45 min), stayed the same (30-30-30 min) or contracted (45-30-15 min) revealed that no one relative spacing interval pattern was superior to any other.[1]

Another study[2] has revealed that the optimally efficient gap between study sessions depends on when the information will be tested in the future. A very comprehensive study of this matter in 1,350 individuals involved teaching them a set of facts and then testing them for long-term retention after 3.5 months. A final test was given at a further delay of up to one year. At any test delay, increasing the inter-study gap between the first learning and a study of that material at first increased and then gradually reduced final test performance. Expressed as a ratio, the optimal gap equaled 10-20% of the test delay. That is, for example, a one-day gap was best for a test to be given seven days later, while a 21-day gap was best for a test 70 days later. Few of any teachers or students know this, and their study times are rarely scheduled in any systematic way, typically being driven by test schedules for other subjects, convenience, or even the teacher's whim.

The bottom line: the optimal time to review a newly learned experience is just before you are about to forget it. Obviously, we usually don't know when this occurs, but in general the vast bulk of forgetting occurs within the first day after learning. As a rule of thumb, you can suspect that a few repetitions early on should be helpful in fully encoding the information and initiating a robust consolidation process. So, for example, after each class a student should quickly remind herself what was just learned—then that evening do another quick review. Before the next class on that subject, the student should review again. Teachers help this process by linking the next lesson to the preceding one.

Certain practices will reduce the amount of time needed for study and the degree of long-term memory formation. These include:

• Don't procrastinate. Do it now!

• Organize the information in ways that make sense (outlines, concept maps)

• Identify what needs to be memorized and what does not.

• Focus. Do not multi-task. No music, cell phones, TV or radio, or distractions of any kind.

• Association the new with things you already know.

• Associate words with mental images and link images to locations, or in story chains

• Think hard about the information, in different contexts

• Study small chunks of material, in short intervals. Then take a mental break.

• Say out loud what you are trying to remember.

• Practice soon after learning and frequently thereafter at spaced intervals.

• Explain what you are learning to somebody else. Work with study groups later.

• Self-test. Don't just "look over" the material. Truly engage with it.

• Never, never, ever CRAM!

---

[1] Karpicke, J. d., and Bauernschmidt, a. 2011. Spaced retrieval: absolute spacing enhances learning regardless of relative spacing. J. Exp. Psychol. 37 (5) 1250-1257.

[2] Cepeda, N. J. et al. 2008. Spacing effects in learning. A temporal ridgeline of optimal retention. 19  (11): 1095-1102

How Schools Make Learning Harder Than Necessary

Keep your "nose to the grindstone" is the advice we often give as an essential ingredient of learning difficult tasks. An old joke captures the problem with the old bromide for success, "Keep your eye on the ball, your ear to the ground, your nose to the grindstone, your shoulder to the wheel: Now try to work in that position."

Over the years of teaching, I have seen many highly conscientious students work like demons in their study yet don't seem to learn as much as they should for all the effort they put in. Typically, it is because they don't study smart. And sometimes the problem is created by the teachers' method of instruction.

In an earlier post, I described a learning strategy wherein a student should spend repeated short (say 10-15 minutes) of intense study followed immediately by a comparable rest period of "brain-dead" activity where they don't engage with a new learning task. The idea is that memory of the just-learned material is more likely to be consolidated into long-term memory because there are no mental distractions to erase the temporary working memory while it is in the process of consolidation.

Now, new research now suggests that too much nose-to-the-grindstone can impair learning.

Margaret Schlichting, a graduate student researcher, and Alison Preston, an associate professor of psychology and neuroscience at the University of Texas tested the effect of mental rest with a learning task of remembering two sets of a series of associated photo pairs.  Between the two task sets, the participants rested and were allowed to think about whatever they wanted. Not surprisingly, those who used the rest time to reflect on what they had learned earlier were able to remember more upon re-test. Obviously, in this case, the brain is not really resting, as it is processing (that is, rehearsing) the new learning. But the brain is resting in the sense that no new mental challenges are encountered.

The university press release quotes the authors as saying, "We've shown for the first time that how the brain processes information during rest can improve future learning. We think replaying memories during rest makes those earlier memories stronger, not just impacting the original content, but impacting the memories to come." Despite the fact that this concept has been anointed as a new discovery in a prestigious science journal, the principle has been well-known for decades. I have explained this phenomenon in my memory books as the well-established term of "interference theory of memory,"

What has not been well understood among teachers is the need to alter teaching practices to accommodate this principle. A typical class period involves teachers presenting a back-to-back succession of highly diverse learning objects and concepts. Each new topic interferes with memory formation of the prior topics. An additional interference occurs when a class period is disrupted by blaring announcements from the principal's office, designed to be loud to command attention (which has the effect of diverting attention away from the learning material). The typical classroom has a plethora of other distractions, such as windows for looking outside and multiple objects like animals, pictures, posters, banners, and ceiling mobiles designed to decorate and enliven the room. The room itself is a major distraction.

Then, to compound the problem, the class bell rings, and students rush out into the hall for their next class, socializing furiously in the limited time they have to get to the next class (on a different subject, by a different teacher, in a differently decorated classroom). You can be sure, little reflection occurs on the academic material they had just encountered.

The format of a typical school day is so well-entrenched that I doubt it can be changed. But there is no excuse for blaring loudspeaker announcements during the middle of a class period. Classrooms do not have to be decorated. A given class period does not have to be an information dump on overwhelmed students. Short periods of instruction need to be followed by short, low-key, periods of questioning, discussion, reflection, and application of what has just been taught. Content that doesn't get "covered" in class can be assigned as homework—or even exempted from being a learning requirement. It is better to learn a few things well than many things poorly. Indeed, this is the refreshing philosophy behind the new national science standards known as "Next Generation Science Standards."

Give our kids a rest: the right kind of mental rest.

Sources:


Schlichting, M. L., and Preston, A. R. (2014). Memory reactivation during rest supports upcoming learning of related content Proc. Nat. Acad. Science. Published ahead of print October 20, 2014.

http://scicasts.com/neuroscience/2065-cognitive-science/8539-study-suggests-mental-rest-and-reflection-boost-learning/

http://www.nextgenscience.org/

Dr. Klemm's latest book, available at most retail outlets, is "Mental Biology. The New Science of How the Brain and Mind Relate" (Prometheus). 

Memory and Location, Location, Location

When you remember first meeting the love of your life, do you also have a strong memory of where you both were and also where you were in relation to objects in the scene? When I first met my wife, Doris, it was at a party and she was at a piano surround by “bird dog” males, who I saw from an adjacent room. In my mind’s eye, I still see both rooms and where everybody was.

Do you remember where you were on 9/11? I was in the waiting room of a hospital, looking over a series of lounge chairs at a large-screen TV program that was reporting the news.

It seems that many people remember not only events but where they were at the time of the event. But how does this happen? We do know that a new experience may be “consolidated” into a lasting memory, especially if it stirs emotion and you replay it in your mind. That is certainly the case when you meet the love of your life or see a terrible event.

If you were there, you would surely remember what you were doing.

Back in the 1970s I was studying the part of the brain known as the hippocampus, and it was known at the time that this structure is crucial for consolidating memories. I and others were focused on an EEG rhythm (theta rhythm of 4-7 waves per second) that was especially prominent when an animal moves around in an enclosure EEG signals are summed over dozens of neurons, and therefore to get more precise data some investigators put microelectrodes into the hippocampus so they could monitor the nerve impulse activity of single neurons as the animal moved around.

It was quickly discovered that some hippocampal neurons fired impulses selectively when an animal was in a special location within the enclosure. Collectively, these “place” neurons were actually mapping the enclosure space and tracking the animal’s position as it moved around in this space.

New insight on an additional role for place neurons has come from a new research report on human epileptics with electrodes implanted in their hippocampus to locate the diseased tissue. These patients played a virtual-reality game in which their avatar drove through a virtual town and delivered items to stores. Their task was to memorize the layout and what was delivered at each store. Meanwhile, place cells in the hippocampus were monitored and their place coding was noted. Then when participants were asked to recall the memory of what went where, the place-responsive activity was reinstated even though the subjects were not actually playing the game but recalling it from memory. And the activity of place cells was similar to that during the learning stage.

In other words, neural representations of the content of the experience had become linked with the spatial and temporal context. Such evidence provides strong evidence for the theory that memory formation and recall involve association of event with context, especially spatial and temporal context. This linkage creates a mutually reinforcing interaction of event and location. We tend to remember both or neither.

Can we apply these findings to improving everyday learning and memory situations? Of course, we can. The key elements for making it easier to learn something new are to:

1.  Identify a context that stirs emotions, preferably positive emotions like meeting someone you are attracted to.

2.  Be especially aware of where you are at the time and where you are in relation to the location of various objects.

The hippocampus uses these emotional and spatial cues to facilitate the consolidation of memory. We know that memory is promoted by making associations. Emotions and spatial cues are probably the most effective kinds of cues.

Sources: Miller, J. F. et al. (2013) Neural activity in human hippocampal formation reveals the spatial context of retrieved memories. Science. 342, 1111-1114

END NOTE: If you find these posts helpful, you are not alone. I am gratified to have so many readers. My reader views here and at a cross-posting site now total over 800,000. Thank you so much for wanting to read what I write. You might also want to read some of my books: see http://thankyoubrain.com