Sunday, December 01, 2013
When I was in veterinary medical school, I could often be found lounging in the fraternity living room listening to jazz records. My classmates were stunned that I was wasting so much time, when most of them had to study while I seemingly had nothing to do. O.K., so maybe I graduated fifth in my class rather than first, but I was not nearly as stressed as my classmates.
My reason for sacrificing study time was that it bolstered my spirits. Veterinary medicine is a lot harder than most people think. Veterinarians learn the same anatomy, physiology, pharmacology, microbiology, and so on as physicians do. In some schools, human and veterinary medical students take many of the same basic science classes. Moreover, veterinary students have to learn about multiple species, learn more public health, and take a year’s worth of surgery.
But back to the music issue: some people, especially students, think that listening to music helps the memory. Historically, supporters of this practice have referred to this as the “Mozart effect.” Most students, of course, listen to pop music rather than Mozart. Students are notorious for listening to music while studying. Why isn’t music a distraction? I have written before about how extraneous stimuli can prevent memory consolidation, which in the case of studying, consumes cognitive resources and prevents the formation of memory that lasts long enough for the next examination.
Because so many students listen to music while studying, formal experiments were recently reported on whether or not that is a good thing. These experiments, conducted in Finland, had a scientific rationale. Prior research had shown that listening to music that people considered pleasurable increased the release of dopamine in the brain, and dopamine is well known as a “feel good” neurotransmitter. Other research had also shown that dopamine promotes learning to approach rewards, while a deficiency of dopamine promotes learning of punishments.
Seventy three subjects, mean age of 27.1 years, listened to a battery of 14 songs and identified three that they really liked and three that were emotionally neutral. One of each was selected for use in the study, in which subjects were grouped in four different listening patterns involving a positive (P) or neutral (N) song during study and the opposite kind of song during testing. Thus, there were four groups, NN, NP, PP, PN. Each group was formed to have an approximately equal number of musicians and non-musicians.
The learning involved memorizing 54 pairs of Japanese characters, in which one character was arbitrarily given a high reward value (a simple smiley face feedback display during training) and the other character a low reward value (frowning face feedback). In the test phase, pairs were shuffled and thus served as a measure of how well the original learning was generalized.
Results indicated that people with more musical experience
learned better with neutral music but tested better
I looked at their song list and found no jazz–all of it was either concert-type music or pop songs. That is a serious oversight, in my view. What the researchers may have missed is the possible positive effect of the unique rhythms and syncopation of jazz. I am reminded of a study I reported in my book, Memory Power 101, showing that chewing gum helps learning.
I am musically untrained, and maybe my listening to jazz improved my learning in vet school by creating positive emotions. A great deal of research has shown that positive emotions have an indirect enhancing effect on forming memories. Negative emotions impair memory. No solid neuroscience explanation exists, but it is no doubt highly relevant that the same brain structure, the hippocampus, mediates both emotions and memory formation.
Gold, B. P. et al. (2013) Pleasurable music affects reinforcement learning according to the listener. Frontiers in Psychology. Vol. 4 Article 541. Doi: 10.3389/fpsyg.2013.00541
Sunday, November 10, 2013
It’s normal to get depressed. Let’s face it, a lot of life experience IS depressing. Depression that is severe enough to be considered a clinical malady is a state that persists for long periods. It’s not the initial depression that is the problem, but rather its sustained nature.
So, the issue is what sustains the depression. I contend that continual rehearsal of negative emotions, which can be done explicitly or implicitly, is the driver of clinical depression. I don’t know if psychologists agree or not, but as a neuroscientist I know that rehearsal of thoughts and feelings strengthens the mediating synapses and circuits.
Obviously, consciously rehearsing bad events and our depressive response will help to cement depression in neural circuitry. But even implicit rehearsal can have the same effect. This being the case, it seems important to focus on the triggers that activate recall, explicit or implicit, of stored representations of depressed feelings. Bad events and their associated feelings are stored in memory. As long as such memory is stored and not activated in recall, little harm is done. But environmental and mental cues can dredge depression from its hidden stores. Repeated retrieval is what makes depression pervasive and persistent.
So, it would seem important to focus on ways to block the retrieval cues. Yet, part of the problem is in recognizing what these cues are, as they are frequently buried do deep in memory that the cues are no longer available for explicit recognition. Yet, subconsciously, the cues still wrench the sadness from memory storage.
One solution that sometimes works is to change environments. Even if you don’t know what the depression cues are, you know they can somehow be embedded in the current environment and lifestyle. Maybe the problem is with some of the people you run around with. People who drag you down are not all that hard to spot. Avoid them. Maybe the problem is with your career or work environment, which has saddled you with depressing experiences from time to time. Staying in that environment assures that depression triggering cues will be encountered again.
It is not always feasible to change environment or lifestyle. You can’t abandon those you love just because
Common experience and a great deal of formal research have shown the usefulness of “happy thoughts” as a way to boost positive mood. Here, the trick is to enhance recall of the buried memories of happy experiences. The same neural mechanisms involved in rehearsal and recall of depressing experiences are involved. But, you can’t be sad and happy at the same time. Thus, triggers that recall happy experiences do so at the expense of triggers that would trigger depressive feelings.
Recent research emphasizes the importance of memory cues as therapy for depression. In this study, clinically depressed patients were asked to recall 15 positive memories. Patients in one group, the controls, were asked to rehearse these positive experiences by grouping them according to similarities. Patients in the experimental group were taught to use a mnemonic technique to rehearse the positive memories. This technique, the ancient “method-of-loci” method, entails associating a mental image of an item to be remembered to an image of a well-known physical location. For example, to remember a grocery list, you might use location of objects in your car. You might picture a banana in your side view mirror, apples on the steering wheel, bread on the dashboard, cereal in the rear-view mirror. As you drive to the grocery store, you rehearse the items in terms of their mental images and locations within the car. There are many powerful permutations of this method that I explain in my recent book, Memory Power 101.
Results of the experiment showed that both memorization methods were equally effective when recall was tested right after the training. But a week later, experimenters made a surprise phone call to each patient and asked them to recall the happy thoughts again. This time, clearly better recall occurred in the patients who had used the method-of-loci method. If we can generalize these results, it means that patients can alleviate their depression if they train their brains to be more effective at remembering positive events. This can be done at any stage of life, as we all have a past and there typically were some good moments in that past. Whether you use a method-of-loci method to remember happy times or some other memory device, your life should be more satisfying and less depressing when you consciously train your brain to remember the good times.
Dalgleish, T. et al. (2013). Method-of_Loci as a mnemonic device to facilitate access to self-affirming
Sunday, November 03, 2013
The more a woman weighs, the worse her memory. No, I am not a chauvinist pig. This claim comes from actual research—by a woman, no less. Diana Kerwin and her colleagues at Northwestern University studied 8,745 women ages 65 to 79 and found that for every one-point increase in female body mass index, the score on a 100 point memory test dropped by one point.
The problem was greatest in women who had put the weight on around the hips, which is fairly typical for weight gain in women. Nobody knows why this is so. Fat deposits may increase the amount of cytokines, which are hormones that can cause inflammation. In a couple of earlier columns I explained how body inflammation, from sore joints or sore throat, for example, can trigger inflammation in the brain. I explained that brains can get inflamed too, irritated from the release of cytokines and other toxins from the brain’s immune cells in response to inflammation. In both genders, these toxins diminish mental capabilities, especially memory. Remember, everything the brain does affects memory (and everything affecting memory affects the brain).
Another obvious possibility is that excess weight often creates vascular problems, and everybody tends to have a problem with circulation in small arteries as they get older. Excess weight is a risk factor for stroke, as well as Alzheimer’s Disease.
This finding about memory loss is just one of many good reasons to lose weight. There are only two ways to lose weight: eat fewer calories and exercise more. Though exercise doesn’t do much to cause weight loss, it has many other benefits (improved circulation of blood to the brain) that can directly benefit memory and cognitive function.
It is not surprising then to learn of recent studies showing that losing weight can improve thinking and memory, in both men and women. John Gunstad, at Kent State University, compared attentiveness and memory test scores in 150 overweight subjects 109 of whom who had bariatric stomach by-pass surgery and 41 controls who did not. Those who lost weight because of gastric bypass surgery showed mental function improvements within 12 weeks after surgery. Those without hypertension improved more than the bariatric patients who had hypertension. Memory performance of the obese controls actually decreased over this period. Gunstad has a U tube video on his work at www.youtube.com/watch?v=gsFP2zAkStU.
Of course bariatric surgery is not without its problems. This surgery can lead to Wernicke's encephalopathy, a condition associated with thiamin or vitamin B1 deficiency. Symptoms of Wernicke's encephalopathy include loss of short-term memory, vision and muscle coordination. Presumably, vitamin supplements prevent this problem.
Most of us lose weight the old fashioned way: diet and exercise. Will weight loss help mental function, especially in people who are overweight but not to the point of obesity? What Gunstad hopes to test next is the possible mental benefit from losing weight through diet and exercise rather than surgery. I suspect he will see a benefit, but it could come from exercise as such rather than the weight loss. As I have reported in earlier columns, normal-weight people see a mental improvement from aerobic exercise.
But up to a point, you can just sit in your lounge chair and munch potato chips and still improve your memory—if you are learning from my book, Memory Power 101.
Gunstad, J. et al. (2013). Improved memory function 12 weeks after bariatric surgery. Surgery for Obesity and Related Diseases. 7 (4): 465-472. http://www.soard.org/article/S1550-7289%2810%2900688-X/abstract
Kerwin, D. R. et al. 2010. The cross-sectional relationship between body mass index, waist–hip ratio, and cognitive performance in postmenopausal women enrolled in the Women's Health Initiative. Journal of the American Geriatrics Society. 58 (8): 1427–1432.
Neurologic Complications Associated with Novel Influenza A (H1N1) Virus Infection in Children. Center for Disease Control, July 24 2009
Monday, October 21, 2013
In 1913, Ebbinghaus demonstrated that spacing learning out over time creates much more efficient learning than cramming a learning task into a single intense session. Now, a new discovery has been made for a specific spaced-learning strategy that so far is the best of all. In reviewing this new design, Kelley and Whatson (2013) point out experiments showing that this kind of spaced learning is optimal for information encoding and for activation of the genes needed to form long-term memory.
And what is the design? The idea begins with the established notion that a given learning task should be “chunked” so that it can be studied in a short time, on the order say of 20 minutes. What is novel about the new design is that a given chunk is studied three times in a single session, with two intervening “rest” periods of 10 minutes in which there is little mental activity. During the rest periods, physical activity, like shooting hoops or cycling, seem to be ideal. The reason for these intervening rest periods is that thinking about new information or performing mental tasks creates interference with the memory-forming processes already under way.
Of course, like most learning tasks, a single session, even with three repetitions within it, is not likely to be sufficient unless you are really adept at mnemonic techniques (Klemm, 2012). After a day or so, this strategy needs to be repeated one or more times.
This is so simple to do and, if replicated in more studies, should become standard practice in schools. However, very few teachers know about this technique and school curricula are not designed to be taught this way. Changing the educational establishment is probably too much to hope for. But this strategy can be used by all students in homework study. Home schoolers and students taking Internet courses can easily use the technique on their own.
If you try this approach, please add comments to this post to let us know how it works for you.
Kelley, P. and Whatson, T. (2013). Making long-term memories in minutes: a spaced learning pattern from memory research in education. Frontiers in Human Neuroscience. 25 September. Doi: 10.3389/fnhum.2013.00589.
Klemm, W. R. (2012). Memory Power 101. New York: Skyhorse Publishing.
Sunday, October 13, 2013
“Life, liberty, and the pursuit of happiness:” some people might argue that the U.S. Constitution endorses hedonism, and indeed many politicians want to ignore or get rid of the Constitution, but not necessarily because of hedonism. We should not be dismissive about encouraging people to pursue happiness. Happiness can be good for your brain. Depression is surely bad for your brain.
Positive mood states promote more effective thinking and problem solving. A recent scholarly report reviews the literature demonstrating that positive mood broadens the scope of attentiveness, enhances semantic associations over a wide range, improves task shifting, and improves problem-solving capability. The review also documents the changes in brain activation patterns induced by positive mood in subjects while solving problems. Especially important is the dopamine signaling in the prefrontal cortex.
Published studies reveal that a variety of techniques are used to momentarily manipulate mood. These have included making subjects temporarily happy or sad by asking subjects to recall emotionally corresponding past experiences or to view film clips or hear words that trigger happy or sad feelings,
The effect of happiness on broadened attentiveness arises because the brain has better cognitive flexibility and executive control, which in turn makes it easier to be more flexible and creative. Happy problem solvers are better able to select and act upon useful solutions that otherwise never consciously surface. Happiness reduces perseverative tendencies for errant problem-solving strategies. The broadened attentiveness, for example, allows people to attend to more stimuli, both in external visual space and in internal semantic space, which in turn enables more holistic processing. For example, in one cited study, experimenters manipulated subjects’ momentary mood and then measured performance on a task involving matching of visual objects based on their global versus local shapes. Happy moods yielded better global matching.
Other experiments report broader word association performance when subjects are manipulated to be happier. For example, subjects in a neutral mood would typically regard the word “pen” as a writing tool and would associate it with words like pencil or paper. But positive mood subjects would think also of pen as an enclosure and associate it with words like barn or pigs. This effect has been demonstrated with practical effect in physicians, who, when in a happy mood, thought of more disease possibilities in making a differential diagnosis.
The review authors reported their own experiment on beneficial happy mood effects on insightfulness, using a task in which subjects were given three words and asked to think of a fourth word that could be combined into a compound word or phrase. For example, an insightful response to “tooth, potato, and heart” might be “sweet tooth, sweet potato, and sweetheart.” Generating such insight typically requires one to suppress dominant “knee jerk” responses such as associating tooth with pain and recognizing that pain does not fit potato while at the same time becoming capable of switching to non-dominant alternatives.
Other cited experiments showed that happy mood improved performance on “Duncker’s candle task.” Here, subjects are given a box of tacks, a candle, and a book of matches, and are asked to attach a candle to the wall in a way that will burn without dripping wax on the floor. Subjects in a happy mood were more able to realize that the box could be a platform for the candle when the box is tacked to the wall.
Such effects of happy moods seem to arise from increased neural activity in the prefrontal cortex and cingulate cortex, areas that numerous prior studies have demonstrated as crucial parts of the brain’s executive control network. Similar effects have been observed in EEG studies. Other research suggests that the happiness effect is mediated by increased release of dopamine in the cortex that serves to up-regulate executive control.
The review authors described a meta-analysis of 49 positive-psychology manipulation studies showing that momentary happiness is readily manipulated by such strategies as deliberate optimistic thinking, increased attention to and memory of happy experiences, practicing mindfulness and acceptance, and increasing socialization. The effect occurs in most normal people and even in people with depression, anxiety, and schizophrenia. Biofeedback training, where subjects monitor their own fMRI scans or EEGs, might be an even more effective way for people to train themselves to be happier.
The main point is that people can be as happy as they choose to be.
For more on how positive mood influences memory ability,
see my new book, Memory Power 101 (http://skyhorsepublishing.com).
 Subramaniam, K. and Vinogradov, S. (2013). Improving the neural mechanisms of cognition through the pursuit of happiness. Frontiers in Human Neuroscience. 7 August. Doi: 10.3389/fnhum.2013.00452
Friday, October 04, 2013
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.
Bellesi, M., et al. (2013) Effects of sleep and wake on oligodendrocytes and their precursors. J. Neuroscience. 33 (36), 14288-14300.
Tuesday, September 10, 2013
Most people now have been told that mental activity is good for the brain. I have even posted information that it can build “cognitive reserve” that can delay or reduce the symptoms of Alzheimer’s disease. Therefore, it would be no surprise if popularity increased for mentally stimulating games like crossword puzzles, Sudoko, bridge, dominoes, chess, and the like.
In addition to these traditional games, another form of mental stimulation is to learn mnemonic techniques, such as creating associations with mental images, acrostics, acronyms, the method of loci, mental imaging of peg-words, and the like, which I explain in my books, Memory Power 101 and Better Grades, Less Effort. While these techniques are task specific, mastering them can produce benefits that last beyond the time when you are using these mnemonics. For example, when I was in high school, I used to give memory demonstrations using a well-known image-word peg system. Even when I quit doing that, my general capacity for remembering remained better than before because my brain had been trained to be more agile and imaginative in generating images that I could use in making memory associations. My mind was also probably more disciplined.
The scientific basis for such claims is solid. Numerous research reports confirm that even older people can improve their memory skills with instruction and practice. Even with traditional memory training, research has shown that by teaching people multiple strategies, the training benefit can be seen immediately, can endure for up to five years, and even transfer to everyday learning tasks.
The scientific explanation is straightforward. When the brain is challenged to solve problems and enhance memory capability, the neurons have to grow new contact points among neurons. This process requires new protein synthesis, growth of neuron terminals, and boosting of neurotransmitter systems. In other words, mental challenge changes the brain physically. Through training, you can sculpt a more alert, focused, and smarter brain.
As a result of this understanding, a host of mental training options have become available. The hype often seems to sound like snake oil, but some training programs are documentably effective. For example, we know from published research that I have described before that working memory capacity can be extended by formal training and that IQ increases as a result.
A new emphasis seems to be emerging to create training platforms that are cost effective, self-administered, flexible, and easily distributed to wide segments of population. CD, audiotape, and web-based approaches can reduce the need for trainers who work one-on-one or with small groups. The web-based training seems the most feasible, except for the current crop of elderly, many of whom do not use the Internet.
Effective training need not be specifically address memory. Non-specific mental stimulation can improve memory capability, because whatever affects the brain affects the brain’s ability to remember things. Especially promising are training programs that train people to be more attentive, to have more positive attitudes about their memory ability, reduce anxiety and stress, and require learners to apply memory techniques to everyday mental tasks.1 When benefits from memory training persist after the training, researchers assume it is because the trainees are still using the techniques they have learned. Method-of-loci and peg-word systems are extremely powerful, but it is hard to get people to create new habits of thinking and memorization. Even so, memory training produces other lasting effects that benefit memory irrespective of the explicit use of techniques. One of these effects is actual re-wiring of the brain, which intense learning is known to produce.
Many sites on the Web focus on teaching people about mental fitness in general, which as I just said, has collateral benefit on memory capability. One site I recommend, and have posted to, is Sharp Brains (http://sharpbrains.com/). Among the better known Web training programs are Brainware Safari and Lumosity (I have no conflict of interest here). Using “brain fitness” as search words in Google or Bing will identify many other sites that I am not familiar with.
Recently, a new three-dimensional videogame system, “NeuroRacer” that reportedly works even for older adults has been developed at the University of California, San Francisco. In this game, a user navigates a race car along a winding track and hits a button on a controller whenever a green circle appears, making the response as quickly as possible. This task forces concentration and trains the brain to switch operations rapidly and accurately.
In a recently published test of the NeuroRacer’s effects on older adults, people aged 60 to 85 were trained on the game for 12 hours, spread over a month. Without training, the researchers found a clear age-related decline in performance in the game. After training on the game, the seniors performed on the game better than untrained 20-year olds, and the benefit lasted at least six months.
Popular press reports and numerous blogs of this study have attributed the benefit to the value of multi-tasking. I contend that multi-tasking is harmful for memory and, moreover, that the benefit of NeuroRacer is not multi-tasking training as such but rather the training it provides for attentiveness and executive control. It is perhaps not surprising that such good effects were seen in older folks. A typical problem in aging is a loss in ability to focus, and thus training that increases attentiveness would be likely to have conspicuously beneficial effects.
 Rebok, G. W., Carlson, M. c., and Langaum, J. B. S. (2007). Training and maintaining memory abilities in health older adults: traditional and novel approaches. J. Gerontology. 62B (Special Issue): 53-61.
 Anguera, J. A. et al. (2013). Video game training enhances cognitive control in older adults. Nature 501: 97-101.
Wednesday, September 04, 2013
People frequently ask me “What’s the best way to improve my memory? (or … my child’s memory? … my elderly parent’s memory?). The answer most commonly given is to use memory aids, that is, mnemonic devices such as associating mental images of new information with images of already learned images that serve as pegs on which to hang new information. I explain these devices in great detail in both of my books, “Memory Power 101” and “Better Grades, Less Effort.”
Mnemonics are essential if you want to become a “memory athlete” and show off prodigious feats of memory. After you have used such mnemonics for a while, some of the benefit persists long after you quit using such mnemonics because the brain has been trained to be more facile and imaginative in making associations.
But for real-world practicality, it is hard to beat the usefulness of thinking about what you are trying to remember. Thinking unifies the essential elements of learning, which I view as follows:
Knowledge → Understanding → Creative Insight
When people try to acquire knowledge, they of course must remember it, which they usually attempt by mentally repeating it again and again. This rote process is the least effective way to remember. When you think about what you are trying to remember, your efforts to understand it actually constitute rehearsal in meaningful ways. Attempts to understand include associating and cross checking the new with your understanding of what you already know, thinking about what else might be relevant, reflecting on the merits of the new information, and self-examination of your level of understanding. Then, as understanding is gained, you become poised for creative insight, making application of the new information for your own needs and purposes. In the process, you might even think of things about the new information that others have not discerned. This process automatically creates mental associations that not only cement the new information in memory but also integrate it with all the things you already know as well as perhaps even generating ideas that nobody else has thought of.
The biological basis behind this thinking process of memory rehearsal is now being confirmed. The original basis of the idea comes from suggestion some 20 years ago that multiple areas of brain participate in formation of memory. Thinking engages multiple areas of brain and, when performed on what you are trying to remember, strengthens the memory representation in the brain areas that are creating the engram.
Some recent support for multiple-area formation of memory includes a recent brain-scan study of male and female college students during consolidation of a recent fear-induced experience revealed increased activity in multiple brain areas (amygdala, parahippocampus, insula, thalamus, ventromedial prefrontal cortex, and anterior cingulate cortex) during a resting state lasting 10 minutes immediately after the conditioning. “Rest” occurred immediately after responding to the fear-inducing stimulus and probably involved a process of reflection on the learning task or an equivalent subconscious process.
Decreased activity occurred in the striatum (caudate, putamen). This decrease may have occurred because this area of brain includes the positive reinforcement (reward) system, and fear conditioning is aversive, not rewarding.
I should add that the extensiveness of brain areas participating in thinking and its associated memory consolidation was surely under-estimated. MRI brain scans measure metabolism, which is not a direct index of the nerve impulse signaling required for processing learning events.
 Squire, L. R. (1992) Declarative and non-declarative memory: multiple brain systems supporting learning and memory. J. Cognitive Neuroscience. 4 (3):232-243 Posted Online December 13, 2007.(doi:10.1162/jocn.19184.108.40.206)
 Feng, T., Feng. P., and Chen, Z. (2013). Altered resting-state brain activity at functional MRI during automatic memory consolidation of fear conditioning. Brain Res. 2013 Jul 26;1523:59-67. doi: 10.1016/j.brainres.2013.05.039