An Example of Publication Bias - Cognitive Advantage in Bilingualism

MindBlog has done several posts on experiments that reinforce what has become the conventional wisdom regarding bilingualism: that it enhances our executive control faculties. De Bruin et al., noting that they themselves had chosen to report positive results supporting this conclusion, but had not followed through on negative data (the file drawer effect), thought to do a systematic analysis of the publication fate of experiments with positive, mixed, or negative outcomes. They searched for conference abstracts on bilingualism and executive control in 169 conferences (31 different national and international meetings) organized between 1999 and 2012, and identified 128 abstracts (presented at 52 different conferences) that focused on bilingualism and executive control. Their result:

Sixty-eight percent of the studies that clearly found a bilingual advantage were published, compared with 50% of the studies that found mixed results supporting the bilingual-advantage theories, 39% of the studies that found mixed results partly challenging those theories, and 29% of the studies that found no differences between monolinguals and bilinguals or found a bilingual disadvantage. On the whole, 63% of the studies supporting the bilingual advantage were published, compared with only 36% of the studies that challenged it.

From the authors discussion:

This difference in publication percentage based on the outcomes of the study could be the result of a bias during several steps of the publication process: Authors, reviewers, and editors can decide to submit or accept only studies that showed positive results. In the first step of the publication process, the file-drawer problem could play an important role in the observed publication bias. Authors could decide not to publish studies with null or mixed results, or they could choose to submit their results only partially, for example, by leaving out tasks that did not show an effect of bilingualism. The article by Treccani et al. (2009)[Treccani is a co-author of the current paper] is an example of the file-drawer problem, as it excluded the experiments that did not show an effect of bilingualism.

On the next level, reviewers and editors might reject manuscripts reporting null, negative, or mixed results more often than manuscripts reporting positive effects. This rejection is often based on the argument that null effects are difficult to interpret, or the result of poor stimulus design... Mahoney (1977) asked journal reviewers to referee manuscripts reporting positive, negative, mixed, or null results with identical methodological procedures. Although the methodology was the same, reviewers scored the manuscripts reporting positive results as methodologically better than the manuscripts reporting negative or mixed results. For manuscripts with positive results, reviewers usually recommended acceptance with moderate revisions. For manuscripts with negative results, however, their usual recommendation was major revision or rejection. Manuscripts with mixed results were mostly rejected.

Watching brain oscillations drive perception.

Are the electrical oscillations observed in EEG recordings as we perceive images simply correlations, reflecting brain processes driving our visual experience, or are the oscillations themselves causal, driving the visual experience? Helfrich et al. address this basic question in a clever experiment in which they force brain oscillations of the left and right visual hemispheres into synchrony using transcranial alternating current stimulation. This causes human subjects to more often perceive an ambiguous figure in one of its perceptual instantiations, showing that the oscillations are driving the visual experience, not vice versa. Their summary:

Brain activity is profoundly rhythmic and exhibits seemingly random fluctuations across a very broad frequency range (less than 0.1 Hz to greater than 600 Hz). Recently, it has become evident that these brain rhythms are not just a generic sign of the brain-at-work, but actually reflect a highly flexible mechanism for information encoding and transfer. In particular, it has been suggested that oscillatory synchronization between different areas of the cortex underlies the establishment of task-relevant networks. Here, we investigated whether gamma-band synchronization (~40 Hz) is causally involved in the integration between the two brain hemispheres of alternating visual tokens into a coherent motion percept. We utilized transcranial alternating current stimulation (tACS), a novel non-invasive brain stimulation technique, which allows frequency-specific entrainment of cortical areas. In a combined tACS-electroencephalography study, we selectively up- and down-regulated interhemispheric coherence, resulting in a directed bias in apparent motion perception: Increased interhemispheric connectivity sustained the horizontal motion percept, while decreased connectivity reinforced the vertical percept. Thus, our data suggest that the level of interhemispheric gamma-band coherence directly influenced the instantaneous motion percept. From these results, we conclude that synchronized neuronal activity is essential for conscious perception and cognition.

Perceived control promotes persistence and influences brain response to setbacks

From Bhanji et al:

Highlights

•We report two distinct neural mechanisms for persistence through adversity 

•Perceiving control over setbacks increases persistence 

•Striatum activity relates to persisting after setbacks by correcting mistakes 

•Ventromedial prefrontal activity mediates effects of negative affect on persistence

Summary

How do people cope with setbacks and persist with their goals? We examine how perceiving control over setbacks alters neural processing in ways that increase persistence through adversity. For example, a student might retake a class if initial failure was due to controllable factors (e.g., studying) but give up if failure was uncontrollable (e.g., unfair exam questions). Participants persisted more when they perceived control over setbacks, and when they experienced increased negative affect to setbacks. Consistent with previous observations involving negative outcomes, ventral striatum and ventromedial prefrontal (VMPFC) activity was decreased in response to setbacks. Critically, these structures represented distinct neural mechanisms for persistence through adversity. Ventral striatum signal change to controllable setbacks correlated with greater persistence, whereas VMPFC signal change to uncontrollable setbacks mediated the relationship between increased negative affect and persistence. Taken together, the findings highlight how people process setbacks and adapt their behavior for future goal pursuit.

From Whalen and Kelly's review :

The vmPFC is necessary for regulating our emotional responses...in the present study, the negative affect change is the catalyst that kicks vmPFC into a higher gear and effects adaptive change (i.e., persistence)...when negative affect accompanies uncontrollable setbacks, as is often the case, the vmPFC activity is necessary to adapt to the emotional reaction and, in so doing, preserve persistence.

The ventral striatum on the other hand is important for signaling prediction errors when behavioral outcomes do not match our expectations...when we believe we have control over situations, the ventral striatum can use value signals to motivate future behavior...this striatal effect is problem focused compared to the prefrontal effect that is more emotion focused.

A fetching point about Paul Whalen's and William Kelley's review is that it starts with the example of two professors currently employed at Dartmouth College.

One applied, and he was hired on his very first try (we’ll call him Bill in this example). Imagine that the other; well, he needed more chances before his eventual hire (we’ll call him P.W. to protect his identity). What dictates whether someone will persist when they encounter a setback? Is it the person who remains calm in the moment, not letting this single event rattle her? Or is it the person who reacts strongly to defeat and heavily reinvests in the project, determined to change things the next time? To borrow from Shakespeare, tell us where is persistence bred, or in the heart, or in the head (The Merchant of Venice, 3.2)? ...Bhanji and Delgado (2014) provide clear evidence of the latter.

Guess who Bill and P.W. actually are!

Another magic anti-aging compound?

Riluzole is a drug used to treat amyotrophic lateral sclerosis, also studied for use in mood and anxiety disorders, depression and obsessive-compulsive disorder. It also can have some nasty side effects (nausea,weakness, decreased lung function).

 
Pereira et al. now show that it has a dramatic effect in preventing cognitive decline in aged rats:

The dementia of Alzheimer’s disease (AD) results primarily from degeneration of neurons that furnish glutamatergic corticocortical connections that subserve cognition. Although neuron death is minimal in the absence of AD, age-related cognitive decline does occur in animals as well as humans, and it decreases quality of life for elderly people. Age-related cognitive decline has been linked to synapse loss and/or alterations of synaptic proteins that impair function in regions such as the hippocampus and prefrontal cortex. These synaptic alterations are likely reversible, such that maintenance of synaptic health in the face of aging is a critically important therapeutic goal. Here, we show that riluzole can protect against some of the synaptic alterations in hippocampus that are linked to age-related memory loss in rats. Riluzole increases glutamate uptake through glial transporters and is thought to decrease glutamate spillover to extrasynaptic NMDA receptors while increasing synaptic glutamatergic activity. Treated aged rats were protected against age-related cognitive decline displayed in nontreated aged animals. Memory performance correlated with density of thin spines on apical dendrites in CA1, although not with mushroom spines. Furthermore, riluzole-treated rats had an increase in clustering of thin spines that correlated with memory performance and was specific to the apical, but not the basilar, dendrites of CA1. Clustering of synaptic inputs is thought to allow nonlinear summation of synaptic strength. These findings further elucidate neuroplastic changes in glutamatergic circuits with aging and advance therapeutic development to prevent and treat age-related cognitive decline.

Human children conform to peers' behavior, but apes do not.

Haun and collaborators make the interesting observation that two year old human children will change a learned problem solving strategy on observing peers performing an alternative strategy; apes do not show this behavior.

All primates learn things from conspecifics socially, but it is not clear whether they conform to the behavior of these conspecifics—if conformity is defined as overriding individually acquired behavioral tendencies in order to copy peers’ behavior. In the current study, chimpanzees, orangutans, and 2-year-old human children individually acquired a problem-solving strategy. They then watched several conspecific peers demonstrate an alternative strategy. The children switched to this new, socially demonstrated strategy in roughly half of all instances, whereas the other two great-ape species almost never adjusted their behavior to the majority’s. In a follow-up study, children switched much more when the peer demonstrators were still present than when they were absent, which suggests that their conformity arose at least in part from social motivations. These results demonstrate an important difference between the social learning of humans and great apes, a difference that might help to account for differences in human and nonhuman cultures.

Personality and Ideology

I've done a number of posts (for example, here) pointing to work suggesting that differences in basic partially inherited neurocognitive traits (such as flexibility and openness versus caution and rule following) might underlie liberal versus conservative personalities. Malka et al. have done a cross national test, analyzing responses from more than 70,000 people from 51 countries to ask how a conservative personality style actually relates to cultural and economic attitudes. From their review of the work:

...we found that people with a conservative personality did indeed tend to adopt culturally conservative attitudes on matters like abortion, homosexuality and immigration. On this count, the rigidity of the right model seems to be valid.

But when it came to economic matters related to social welfare policy and economic intervention — the central feature of the left-right divide in much of the world — the results were far different. People with a conservative personality tended to lean slightly to the left...a conservative personality might actually pull people in two directions with respect to their economic attitudes. Prioritizing order and stability will lead to a yearning for the security that left-wing economic policies aim to provide.

This left leaning tendency can be extinguished, however, among people who are highly attentive to politics in countries in which left-right conflict is prominent, by political messaging that binds together right wing cultural and economic views under a broad "conservative" banner. This has nothing to do with psychological predispositions, and suggests that changing the packaging or messaging could change behaviors.

Subliminal Strengthening

Levy et al. make the interesting observation that presenting subliminal positive age stereotypes to older people has a greater effect than similar explicit interventions:

Negative age stereotypes that older individuals assimilate from their culture predict detrimental outcomes, including worse physical function. We examined, for the first time, whether positive age stereotypes, presented subliminally across multiple sessions in the community, would lead to improved outcomes. Each of 100 older individuals (age = 61–99 years, M = 81) was randomly assigned to an implicit-positive-age-stereotype-intervention group, an explicit-positive-age-stereotype-intervention group, a combined implicit- and explicit-positive-age-stereotype-intervention group, or a control group. Interventions occurred at four 1-week intervals. The implicit intervention strengthened positive age stereotypes, which strengthened positive self-perceptions of aging, which, in turn, improved physical function. The improvement in these outcomes continued for 3 weeks after the last intervention session. Further, negative age stereotypes and negative self-perceptions of aging were weakened. For all outcomes, the implicit intervention’s impact was greater than the explicit intervention’s impact. The physical-function effect of the implicit intervention surpassed a previous study’s 6-month-exercise-intervention’s effect with participants of similar ages. The current study’s findings demonstrate the potential of directing implicit processes toward physical-function enhancement over time.

The study they cite as showing less effect of exercise than subliminal priming used the same standard "Short Physical Performance Battery" to assess changes in physical ability caused by the interventions. This test assesses strength, gait, and balance by examining (a) time to rise from a chair and return to the seated position five times, (b) time to walk 8 feet, and (c) ability to stand with feet together in the side-by-side, semi-tandem, and tandem positions for 10 s. Possible scores range from 0 to 12, with a higher score indicating better physical performance. Older individuals who receive lower scores on this measure have increased risk of disability, nursing-home placement, and mortality.

Personality and immune system reactivity.

Vedhara et al. have examined the expression of inflammatory genes in 121 people who also took personality tests that rated the generally identified five major dimensions of human personality (Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness). From the author's introduction:

...we hypothesized that pro-inflammatory gene expression would be up-regulated in extraverts and people with high levels of openness to experience (both of whom would be expected to experience elevated risk of injury/infection) and down-regulated in conscientious individuals with comparatively strong behavioural immune responses.

This is in fact what they found. From their discussion:

The present results identified systematic differences in leukocyte gene expression that correlate with individual differences on two major dimensions of human personality: Extraversion and Conscientiousness. Consistent with predictions from behavioural immune response theory, Extraversion was associated with up-regulated expression of pro-inflammatory genes, whereas Conscientiousness was associated with down-regulated expression of pro-inflammatory genes. These effects were independent of major health behavioural factors (BMI, smoking, alcohol consumption, physical activity); independent of variations in leukocyte subset prevalence; independent of negative affect; independent of minor physical symptoms and related medications; and independent of demographic characteristics as well as other major dimensions of human personality. In contrast, none of the major personality dimensions was significantly associated with differential expression of the other primary gene module involved in the CTRA profile – antiviral and antibody-related transcripts. In the context of previous data linking Extraversion and Conscientiousness to health and longevity, the present functional genomics findings may provide new insights into the molecular basis for such relationships.

Their results do not support the model of neuroticism and negative affect generating a 'disease-prone personality.' Numerous other studies have correlated the trait of conscientiousness with longevity.

The unforeseen costs of extraordinary experiences.

Daniel Gilbert and his collaborators at Harvard have come up with yet another fascinating nugget on our human behaviors:

People seek extraordinary experiences—from drinking rare wines and taking exotic vacations to jumping from airplanes and shaking hands with celebrities. But are such experiences worth having? We found that participants thoroughly enjoyed having experiences that were superior to those had by their peers, but that having had such experiences spoiled their subsequent social interactions and ultimately left them feeling worse than they would have felt if they had had an ordinary experience instead. Participants were able to predict the benefits of having an extraordinary experience but were unable to predict the costs. These studies suggest that people may pay a surprising price for the experiences they covet most.

A bit from the introduction:

More than 600 people have paid a minimum of $250,000 for a seat on the world’s first commercial spacecraft, soon to be launched by Virgin Galactic. Their journey will last a few hours, but they will talk about it for years to come...Floating weightless for several minutes while gazing down at Earth is an experience that falls somewhere between delightful and dazzling, which is why so many people are willing to pay so much money to have it. The less obvious consequence is that such experiences can make the people who have them strangers to everyone else on earth—and, as a rule, earthlings do not always treat strangers so nicely. At worst, people may be envious and resentful of those who have had an extraordinary experience, and at best, they may find themselves with little to talk about. Indeed, when people interact, they typically discuss the things they have in common and an afternoon in orbit typically is not one of them. Extraordinary experiences are both different from and better than the experiences that most other people have, and being both alien and enviable is an unlikely recipe for popularity.

In one experiment subjects in groups watched a video (17 groups of 4 participants, each watching in their own cubicle - afterwards they were escorted to a room for 5 min of unstructured conversation. One of the participants in each group watched a video that was superior to the video watched by the others. Participants who had watched the superior movie felt more enjoyment just after the film, but felt excluded during a subsequent social interaction, and this left them feeling worse than participants who had had an ordinary experience instead. A second experiment showed that participants correctly predicted that the extraordinary experience would leave them feeling better than the ordinary experience would before the interaction, but failed to realize that it would leave them feeling worse after the interaction. In a final study participants were asked to estimate how the actual participants in Study 1 felt. The result found was that they did not expect the extraordinary experiencer to be excluded from the interaction, and they expected the extraordinary experiencer to feel better—not worse—than the ordinary experiencers.

From the summary:

Pleasures come in two varieties: the social and the nonsocial. A hallmark of the nonsocial pleasures—whether the cool tingle of Dom Pérignon or the hot snarl of a new Maserati—is that people adapt to them quickly, which is why such experiences are typically best when they are novel or rare. The social pleasures have a different appeal. People crave acceptance, belonging, and camaraderie, and the hallmark of these pleasures is that they come more readily to those who fit in than to those who stand out. The two varieties of pleasure give rise to a pair of incompatible desires: to do what other people have not yet done and to be just like everyone else. Satisfying the first of these desires can frustrate the second. When extraordinary experiences separate a person from others, these experiences may ultimately reclaim more joy than they provide.

Invunerablism

Todd May does a brief essay (coining the world “invulnerabilism”) that is yet another interesting take on an issue central to all our lives: Do what degree is it useful to psychologically armor ourselves from the ‘slings and arrows of outrageous fortune’ - to have a strong psychological immune system, or an emotionally invulnerable self construal? The meditative practices of several traditions offer us a route into our brain’s ‘basement’, a closer approach to and experience of the machinery that generates all the stuff upstairs, our emotionally reactive immersed selves and personas (Buddhism, for example, offering us an end to suffering if we abandon our desires.) May suggests:

..the way to think about these things has less to do with the invulnerability promoted by the official doctrines, and more to do with, one might say, using these doctrines to take the edge off of vulnerability, to allow one to experience life without becoming overwhelmed or depressed or resentful or bitter, except perhaps at the extremity of loss. There is some combination of embedding oneself in the world in a vulnerable way and not being completely undone by that vulnerability that is pointed at, if not directly endorsed, by the official doctrines.

It seems to me that Taoism, Buddhism, Stoicism, etc. work not by making one invulnerable but rather by allowing one to step back from the immediacy of the situation so that the experience of pain or suffering is seen for what it is, precisely as part of a contingent process, a process that could have yielded a very different present but just happened to yield this one.

Another point would be the evolution of our social brain has resulted in a built in bias towards feeling the sort of vulnerability and bonding that sustains and defends social group identity. A group of floating detached Taoists isn't all that useful in intergroup conflicts. Finally, disciplines that result in maintaining emotional distance from others can also let atrophy the evolved neuroendocrine chemistries that can vitalize our physiology and longevity.

Is there a reason for everything? - Teleological reasoning about life events

Banerjee and Bloom  explore the view that the tendency to develop teleological beliefs about life events is a byproduct of certain universal social-cognitive biases, a cognitive byproduct of humans’ natural tendency to view the world in terms of agency, purpose, and design. Their detailed descriptions of the three studies noted in the abstract below (in the journal "Cognition") are difficult to summarize in this brief post, so I pass on just the highlights and abstract. Motivated readers can request a copy of the article from me.

Highlights

• We examine religious believers’ and non-believers’ belief in purpose in life events. 

• Mentalizing ability predicts the tendency to hold teleological beliefs about events. 

• Adults’ teleological beliefs about life events do not depend upon a belief in God. 

• The perception of purpose in events is rooted in universal social-cognitive biases.

Abstract

People often believe that significant life events happen for a reason. In three studies, we examined evidence for the view that teleological beliefs reflect a general cognitive bias to view the world in terms of agency, purpose, and design. Consistent with this hypothesis, we found that individual differences in mentalizing ability predicted both the tendency to believe in fate (Study 1) and to infer purposeful causes of one’s own life events (Study 2). In addition, people’s perception of purpose in life events was correlated with their teleological beliefs about nature, but this relationship was driven primarily by individuals’ explicit religious and paranormal beliefs (Study 3). Across all three studies, we found that while people who believe in God hold stronger teleological beliefs than those who do not, there is nonetheless evidence of teleological beliefs among non-believers, confirming that the perception of purpose in life events does not rely on theistic belief. These findings suggest that the tendency to perceive design and purpose in life events—while moderated by theistic belief—is not solely a consequence of culturally transmitted religious ideas. Rather, this teleological bias has its roots in certain more general social propensities.

Biological explanations for psychopathology decrease clinician empathy.

Lebowitz and Ahn find that clinicians become less, not more, empathetic with patients whose mental disorder is known to have a biological basis:

Mental disorders are increasingly understood in terms of biological mechanisms. We examined how such biological explanations of patients’ symptoms would affect mental health clinicians’ empathy—a crucial component of the relationship between treatment-providers and patients—as well as their clinical judgments and recommendations. In a series of studies, US clinicians read descriptions of potential patients whose symptoms were explained using either biological or psychosocial information. Biological explanations have been thought to make patients appear less accountable for their disorders, which could increase clinicians’ empathy. To the contrary, biological explanations evoked significantly less empathy. These results are consistent with other research and theory that has suggested that biological accounts of psychopathology can exacerbate perceptions of patients as abnormal, distinct from the rest of the population, meriting social exclusion, and even less than fully human. Although the ongoing shift toward biomedical conceptualizations has many benefits, our results reveal unintended negative consequences.

Cerebral coherence between communicators.

Stolk et al. have searched across the whole brain for a cerebral dynamics matching the behavioral dynamics of mutual understanding and note that brain activities in the right temporal lobes of individuals synchronize during communication in a way that reflects conceptualization of a signal's use apart from specific experiences of the signal:

How can we understand each other during communicative interactions? An influential suggestion holds that communicators are primed by each other’s behaviors, with associative mechanisms automatically coordinating the production of communicative signals and the comprehension of their meanings. An alternative suggestion posits that mutual understanding requires shared conceptualizations of a signal’s use, i.e., “conceptual pacts” that are abstracted away from specific experiences. Both accounts predict coherent neural dynamics across communicators, aligned either to the occurrence of a signal or to the dynamics of conceptual pacts. Using coherence spectral-density analysis of cerebral activity simultaneously measured in pairs of communicators, this study shows that establishing mutual understanding of novel signals synchronizes cerebral dynamics across communicators’ right temporal lobes. This interpersonal cerebral coherence occurred only within pairs with a shared communicative history, and at temporal scales independent from signals’ occurrences. These findings favor the notion that meaning emerges from shared conceptualizations of a signal’s use.

Neurobiology and the Humanities

I want to point to this open access article in Neuron by Semir Zeki, a well known visual neuroanatomist who has addressed in particular visual artists - who, in engaging representations of form and color, explore the brain with techniques that are unique to them. Here is an early clip from the relatively brief article, which I think you might enjoy reading, that proceeds to consider the experience, significance, and uses of beauty.:

Paul Cézanne’s preoccupation, and artistic experimentation, with how color modulates form is but a variant of the neurobiological question of how the separate representations of form and color are integrated in the brain to give us a unitary percept of both. The experiments of Picasso and Braque in the early, analytic, phase of cubism—of how a form maintains its identity in spite of wide variations in the context in which it is viewed—resolves itself scientifically into the neurobiological problem of form constancy. The quest of Piet Mondrian for the “constant truths concerning forms” is an artistic version of the question of what the neural building blocks of all forms are (often presumed to be the orientation-selective cells of the visual cortex), while kinetic art, which sought to represent motion artistically, reached conclusions that are consistent with conclusions reached later by neurobiology.

Origins of human altruism.

A number of studies in recent years have shown that 1- and 2-year-olds often provide help to novel individuals, and have generally been interpreted as suggesting that this tendency is innate, and unlikely to result from social interactions. Barragan and Dweck offer observations to the contrary, finding that very simple reciprocal social activities at these ages can elicit high degrees of altruism. The experiments involved reciprocal play (two individuals playing with one set of toys from a bag) or parallel play (two individuals playing separately with identical sets of toys taken from two bags.) Here is their abstract:

A very simple reciprocal activity elicited high degrees of altruism in 1- and 2-y-old children, whereas friendly but nonreciprocal activity yielded little subsequent altruism. In a second study, reciprocity with one adult led 1- and 2-y-olds to provide help to a new person. These results question the current dominant claim that social experiences cannot account for early occurring altruistic behavior. A third study, with preschool-age children, showed that subtle reciprocal cues remain potent elicitors of altruism, whereas a fourth study with preschoolers showed that even a brief reciprocal experience fostered children’s expectation of altruism from others. Collectively, the studies suggest that simple reciprocal interactions are a potent trigger of altruism for young children, and that these interactions lead children to believe that their relationships are characterized by mutual care and commitment.

Exercise and intermittent fasting improve brain plasticity and health

I thought it might be useful to point to this brief review by Praag et al. that references several recent pieces of work presented at a recent Soc. for Neuroscience Meeting symposium. The experiments indicate that exercise and intermittent energy restriction/fasting may optimize brain function and forestall metabolic and neurodegenerative diseases by enhancing neurogenesis, synaptic plasticity and neuronal stress robustness.  (Motivated readers can obtain the article from me.) Here is their central summary figure:

Exercise and IER/fasting exert complex integrated adaptive responses in the brain and peripheral tissues involved in energy metabolism. As described in the text, both exercise and IER enhance neuroplasticity and resistance of the brain to injury and disease. Some of the effects of exercise and IER on peripheral organs are mediated by the brain, including increased parasympathetic regulation of heart rate and increased insulin sensitivity of liver and muscle cells. In turn, peripheral tissues may respond to exercise and IER by producing factors that bolster neuronal bioenergetics and brain function. Examples include the following: mobilization of fatty acids in adipose cells and production of ketone bodies in the liver; production of muscle-derived neuroactive factors, such as irisin; and production of as yet unidentified neuroprotective “preconditioning factors.” Suppression of local inflammation in tissues throughout the body and the nervous system likely contributes to prevention and reversal of many different chronic disease processes.

Several articles on aging brains.

Talking about aging brains is sort of a downer, but it's something I feel like I want to do as I trek onward with open eyes from my current age of 72 years. So, pointers to three recent articles on brain changes in aging:

Douaud et al. characterize a common brain network linking development, aging, and vulnerability to disease. They show that the idea of brain decline mirroring brain development is correct. Analysis of structural brain images reveals that a network of mainly higher-order regions that develop relatively late during adolescence demonstrate accelerated degeneration in old age.

And, from Salami et al.:

Aging is accompanied by disruptive alterations in large-scale brain systems, such as the default mode network (DMN) and the associated hippocampus (HC) subsystem, which support higher cognitive functions. However, the exact form of DMN–HC alterations and concomitant memory deficits is largely unknown. We identified age-related decrements in resting-state functional connectivity of the cortical DMN, whereas elevated connectivity between the bilateral HC was found along with attenuated HC–cortical connectivity. Critically, elevated HC at rest restricts the degree to which HC interacts with other brain regions during memory tasks, and thus results in memory deficits. This study provides empirical evidence of how the relationship between the DMN and HC breaks down in aging and how such alterations underlie deficient mnemonic processing.

Finally, Yotsumoto et al. find white matter in the older brain is more plastic than in the younger brain. Its changes during learning a visual perceptual task are not observed when younger subjects learn the same task.

Exercise changes our muscle DNA

Following yesterday's post on changing gene expression with brain waves, I'll point to another bit of work on gene changing. Chemical changes to DNA, mainly methylation, can alter gene expression in response a number of environmental changes such as stress, diet, and pollutants. Reynolds points to work by Lindholm et al. now showing that exercise activates health enhancing genes by this epigenetic mechanism. They use the simple trick of measuring and comparing methylation of DNA in exercised and unexercised legs of single individuals (twentythree young subjects bicycled using only one leg, leaving the other unexercised, for three months. The pedaling was at a moderate pace for 45 min, four times per week for three months.) Not surprisingly, the exercised leg was more powerful, but in addition more than 5,000 sites on the genome of muscle cells from the exercised leg now featured new methylation patterns.

This work makes me wish I had a home kit for detecting methylation change in the DNA of my thumb muscles, which show dramatic changes in strength and size depending on how often and energetically I practice the piano.

A bit of science fiction...a brain implant that allows mind-controlled gene expression.

The experiments by Folcher et al. are done with optogenetic implants in mouse brains that are wirelessly controlled by human brain waves. This is the proof of concept step, preliminary to trying the implants in humans to control the expression of engineered light sensitive regulators of genes for therapeutic proteins. Here is their cartoon summary of the procedure:

The mind-controlled transgene expression device consisted of (a) an EEG headset that captured brain-wave activities (the encephalogram), identified mental state-specific electrical patterns (biofeedback, concentration, meditation) and processed discrete meditation-meter values (0–100; meditation-meter value plot), which were transmitted via Bluetooth to (b) the Arduino single-board microcontroller with a time-relay device and switching the (c) field generator ON and OFF. This BCI (a–c) controlled (d) the TC (c,d) of the field generator, which inductively coupled with the (d,e) receiver coil (RC) of the (e) wireless-powered optogenetic implant. (e) The NIR light LED illuminated the culture chamber of the wireless-powered optogenetic implant and programmed the designer cells to produce ​SEAP, which diffused through the semi-permeable membrane. The blood ​SEAP (human ​secreted alkaline phosphatase) levels of mice with subcutaneous wireless-powered optogenetic implants containing designer cells that were freely moving on the field generator could be modulated by the human subject’s mindset in a wireless, remote-controlled manner.

Impact of literacy on visual processing

From Pegado et al., a clear demonstration of how learning the act of reading enhances our visual processing:

How does learning to read affect visual processing? We addressed this issue by scanning adults who could not attend school during childhood and either remained illiterate or acquired partial literacy during adulthood (ex-illiterates). By recording event-related brain responses, we obtained a high-temporal resolution description of how illiterate and literate adults differ in terms of early visual responses. The results show that learning to read dramatically enhances the magnitude, precision, and invariance of early visual coding, within 200 ms of stimulus onset, and also enhances later neural activity. Literacy effects were found not only for the expected category of expertise (letter strings), but also extended to other visual stimuli, confirming the benefits of literacy on early visual processing.