Exercise helps your brain rewire.

Our brains are most capable of changing in response to experience when we are young, then this ability abruptly declines into adulthood. Lunghi and Sale do an interesting experiment showing how the plasticity that does remain can be enhanced by exercise. Covering one eye and watching a movie while relaxing in a chair boosts brain responses to the deprived eye. If study participants instead watched the movie while alternating 10 min. intervals of rest and cycling on a stationary bike, this enhancement of the deprived eye became much larger. A figure, followed by their abstract:

Brain plasticity, defined as the capability of cerebral neurons to change in response to experience, is fundamental for behavioral adaptability, learning, memory, functional development, and neural repair. The visual cortex is a widely used model for studying neuroplasticity and the underlying mechanisms. Plasticity is maximal in early development, within the so-called critical period, while its levels abruptly decline in adulthood. Recent studies, however, have revealed a significant residual plastic potential of the adult visual cortex by showing that, in adult humans, short-term monocular deprivation alters ocular dominance by homeostatically boosting responses to the deprived eye. In animal models, a reopening of critical period plasticity in the adult primary visual cortex has been obtained by a variety of environmental manipulations, such as dark exposure, or environmental enrichment, together with its critical component of enhanced physical exercise. Among these non-invasive procedures, physical exercise emerges as particularly interesting for its potential of application to clinics, though there has been a lack of experimental evidence available that physical exercise actually promotes visual plasticity in humans. Here we report that short-term homeostatic plasticity of the adult human visual cortex induced by transient monocular deprivation is potently boosted by moderate levels of voluntary physical activity. These findings could have a bearing in orienting future research in the field of physical activity application to clinical research.

Why doesn't economic growth lead to more happiness?

This is the Easterlin paradox, which I have mentioned in a previous post. Oishi and Kesebir now do an interesting analysis showing that economic growth is not associated with increases in happiness when it is accompanied by growing income inequality.:

One of the most puzzling social science findings in the past half century is the Easterlin paradox: Economic growth within a country does not always translate into an increase in happiness. We provide evidence that this paradox can be partly explained by income inequality. In two different data sets covering 34 countries, economic growth was not associated with increases in happiness when it was accompanied by growing income inequality. Earlier instances of the Easterlin paradox (i.e., economic growth not being associated with increasing happiness) can thus be explained by the frequent concurrence of economic growth and growing income inequality. These findings suggest that a more even distribution of growth in national wealth may be a precondition for raising nationwide happiness.

Modest exercise gives maximum health benefits.

Gretchen Reynolds points to a study in the Mayo Clinic Proceedings that reviews studies published in PubMed since 2000 that included at least 500 runners and 5-year follow-up to analyze the relationship between running, cardiovascular disease, and all-cause mortality. The optimal dose of running required for protection is surprisingly small. Running for 20-30 minutes twice per week appears to give maximum benefits. Three to four times the duration of walking is needed to achieve the same benefits.

Coffee consumption correlates with lower risk of dying.

From Nicholas Bakalar, who notes a study showing that people who drink more coffee have a reduced risk of death - a correlation (not necessarily a cause): 

Researchers followed more than 200,000 doctors and nurses for up to 30 years. The participants had periodic physical examinations and completed questionnaires on diet and behavior, including their coffee habits. The study is in Circulation.  

Compared with abstainers, nonsmokers who drank a cup of coffee a day had a 6 percent reduced risk of death, one to three cups an 8 percent reduced risk, three to five cups a 15 percent reduced risk, and more than five cups a 12 percent reduced risk. There was little difference whether they drank caffeinated or decaffeinated coffee. The association persisted after controlling for age, alcohol consumption, B.M.I. and other health and diet factors.  

Coffee drinking was linked to a reduced risk of death from heart disease, stroke, diabetes, neurological diseases and suicide, although not from cancer.

Exercise enhances frontal brain lateralization characteristic of younger brains.

As we age beyond 40 years or so, mental tasks that require attention, problem solving, decision-making and other types of high-level thinking become less localized to one of our frontal lobes and expand to engage both hemispheres of our prefrontal cortex. This represents a general reorganization and weakening of our brains' function with age. Hyodo et. al. show in a group of Japanese men with no signs of dementia, between between 64 and 75 years old, that increased aerobic fitness correlates with the increased lateralization during task performance characteristic of younger brains. Here are their summaries:

Highlights

• Association among fitness, brain activation, and cognitive function was examined. 

• Frontal laterality during Stroop task in older men was assessed by fNIRS. 

• We found the association between ventilatory threshold and Stroop performance. 

• The association was mediated by the lateralized prefrontal activation.

Abstract

Previous studies have shown that higher aerobic fitness is related to higher cognitive function and higher task-related prefrontal activation in older adults. However, a holistic picture of these factors has yet to be presented. As a typical age-related change of brain activation, less lateralized activity in the prefrontal cortex during cognitive tasks has been observed in various neuroimaging studies. Thus, this study aimed to reveal the relationship between aerobic fitness, cognitive function, and frontal lateralization. Sixty male older adults each performed a submaximal incremental exercise test to determine their oxygen intake at ventilatory threshold (VT) in order to index their aerobic fitness. They performed a color–word Stroop task while prefrontal activation was monitored using functional near infrared spectroscopy. As an index of cognitive function, Stroop interference time was analyzed. Partial correlation analyses revealed significant correlations among higher VT, shorter Stroop interference time and greater left-lateralized dorsolateral prefrontal cortex (DLPFC) activation when adjusting for education. Moreover, mediation analyses showed that left-lateralized DLPFC activation significantly mediated the association between VT and Stroop interference time. These results suggest that higher aerobic fitness is associated with cognitive function via lateralized frontal activation in older adults.

Mindfulness meditation and pain reduction.

An interesting analysis from Zeidan et al.:

SIGNIFICANCE

Recent findings have demonstrated that mindfulness meditation significantly reduces pain. Given that the “gold standard” for evaluating the efficacy of behavioral interventions is based on appropriate placebo comparisons, it is imperative that we establish whether there is an effect supporting meditation-related pain relief above and beyond the effects of placebo. Here, we provide novel evidence demonstrating that mindfulness meditation produces greater pain relief and employs distinct neural mechanisms than placebo cream and sham mindfulness meditation. Specifically, mindfulness meditation-induced pain relief activated higher-order brain regions, including the orbitofrontal and cingulate cortices. In contrast, placebo analgesia was associated with decreased pain-related brain activation. These findings demonstrate that mindfulness meditation reduces pain through unique mechanisms and may foster greater acceptance of meditation as an adjunct pain therapy.

ABSTRACT

Mindfulness meditation reduces pain in experimental and clinical settings. However, it remains unknown whether mindfulness meditation engages pain-relieving mechanisms other than those associated with the placebo effect (e.g., conditioning, psychosocial context, beliefs). To determine whether the analgesic mechanisms of mindfulness meditation are different from placebo, we randomly assigned 75 healthy, human volunteers to 4 d of the following: (1) mindfulness meditation, (2) placebo conditioning, (3) sham mindfulness meditation, or (4) book-listening control intervention. We assessed intervention efficacy using psychophysical evaluation of experimental pain and functional neuroimaging. Importantly, all cognitive manipulations (i.e., mindfulness meditation, placebo conditioning, sham mindfulness meditation) significantly attenuated pain intensity and unpleasantness ratings when compared to rest and the control condition (p less than 0.05). Mindfulness meditation reduced pain intensity (p = 0.032) and pain unpleasantness (p less than 0.001) ratings more than placebo analgesia. Mindfulness meditation also reduced pain intensity (p = 0.030) and pain unpleasantness (p = 0.043) ratings more than sham mindfulness meditation. Mindfulness-meditation-related pain relief was associated with greater activation in brain regions associated with the cognitive modulation of pain, including the orbitofrontal, subgenual anterior cingulate, and anterior insular cortex. In contrast, placebo analgesia was associated with activation of the dorsolateral prefrontal cortex and deactivation of sensory processing regions (secondary somatosensory cortex). Sham mindfulness meditation-induced analgesia was not correlated with significant neural activity, but rather by greater reductions in respiration rate. This study is the first to demonstrate that mindfulness-related pain relief is mechanistically distinct from placebo analgesia. The elucidation of this distinction confirms the existence of multiple, cognitively driven, supraspinal mechanisms for pain modulation.

Note: In the sham mindfulness training, conditions were identical to mindfulness training session, but subjects were told just to close their eyes and take a deep breath 'as we sit here in meditation' every 2-3 min. They were not given the specific mindfulness-based instructions to pay attention to the breath, acknowledge arising thoughts, feelings, and/or emotion without judgment or emotional reaction, and simply return attention back to the breath. In the placebo training/conditioning sessions, participants were told they were participating in the trial of a new topical local anesthetic (actually petrolatum jelly) being tested for reducing pain after multiple applications. In all of the conditions, pain was induced by local heating of the skin.

Gender bias in the attribution of creativity

Slightly edited abstract from Proudfoot et al., who provide further examples of gender discrimination:

We propose that the propensity to think creatively tends to be associated with independence and self-direction—qualities generally ascribed to men—so that men are often perceived to be more creative than women. In a first study, we found that “outside the box” creativity is more strongly associated with stereotypically masculine characteristics (e.g., daring and self-reliance) than with stereotypically feminine characteristics (e.g., cooperativeness and supportiveness.) A second study found that a man is ascribed more creativity than a woman when they produce identical output. A third study analyzed archival data, and found that men’s ideas are evaluated as more ingenious than women’s ideas. Study four found that female executives are stereotyped as less innovative than their male counterparts when evaluated by their supervisors. Finally, we observed that stereotypically masculine behavior enhances a man’s perceived creativity, whereas identical behavior does not enhance a woman’s perceived creativity. This boost in men’s perceived creativity is mediated by attributions of agency, not competence, and predicts perceptions of reward deservingness.

Lower leg power predicts cognitive aging.

Gretchen Reynolds points to a study of 162 healthy female twin pairs, some identical, and some not, who 10 years previously had completed extensive examinations of their thinking and memory abilities, as well as measurements of their leg-muscle power.

...those who had had the sturdiest legs a decade ago showed the least fall-off in thinking skills, even when the scientists controlled for such factors as fatty diets, high blood pressure and shaky blood-sugar control...a muscularly powerful twin now performed about 18 percent better on memory and other cognitive tests than her weaker sister...in the brain imaging of the identical twins, if one genetically identical twin had had sturdier legs than the other at the start of the study, she now displayed significantly more brain volume and fewer “empty spaces in the brain” than her weaker sister.

Keep in mind the 'this is only one study' caution. It involved only a single analysis of the brain health of middle-aged female twins. However, it is a plausible result, because it is known that exercise causes muscles to release brain growth factors, and sturdier muscles might be expected to release more.

Racial bias and time perception.

From Moskowitz et al.:

Arousal is known to shape time perception, and heightened arousal causes one to perceive that time has slowed (i.e., a given length of time feels longer than it actually is). The current experiments illustrate that among White people who experience arousal when contemplating race (specifically those for whom appearing biased is an ongoing concern), time perception slows when they observe faces of Black men. We asked participants to judge the duration of presentation for faces of White and Black men (shown for periods ranging from 300 to 1,200 ms) relative to a standard duration of 600 ms. Evidence of bias emerged when White participants concerned with bias saw faces of Black men (e.g., durations of less than 600 ms were perceived as being greater than 600 ms). The current findings have implications for intergroup interactions in which timing is essential—for example, length of job interviews, police officers’ perception of the length of an encounter and when force should be initiated, and doctors’ perception of the length of medical encounters. Racially biased time perception is a new form of implicit bias, one exerted at the perceptual level.

Cultural specificity of human fairness.

Blake et al. do an interesting experiment on how sensitive children are to inequality. They asked one child in a pair or to accept or reject an offer of Skittles on behalf of both of them. Between ages 4 and 15 offers that were equal for both children were accepted, but older children often refected offers that would provide more Skittles to their partner. The age at which children started rejecting such offers varied across the seven countries studied (Canada, India, Mexico, Peru, Senegal, Uganda, USA) suggesting different times for development of a sense of fairness. In three countries—the United States, Canada, and Uganda—some older children also rejected offers that were unfair to their partner.

A sense of fairness plays a critical role in supporting human cooperation. Adult norms of fair resource sharing vary widely across societies, suggesting that culture shapes the acquisition of fairness behaviour during childhood. Here we examine how fairness behaviour develops in children from seven diverse societies, testing children from 4 to 15 years of age (n = 866 pairs) in a standardized resource decision task. We measured two key aspects of fairness decisions: disadvantageous inequity aversion (peer receives more than self) and advantageous inequity aversion (self receives more than a peer). We show that disadvantageous inequity aversion emerged across all populations by middle childhood. By contrast, advantageous inequity aversion was more variable, emerging in three populations and only later in development. We discuss these findings in relation to questions about the universality and cultural specificity of human fairness.

The evolution of music from emotional signals

I want to pass on the slightly edited abstract of a recent article on the evolutionary origins of music, "Music evolution and neuroscience," in Progress in Brain Research, written by my Univ. of Wisconsin colleague Charles Snowdon.

There have been many attempts to discuss the evolutionary origins of music. We review theories of music origins and take the perspective that music is originally derived from emotional signals in both humans and animals. An evolutionary approach has two components: First, is music adaptive? How does it improve reproductive success? Second, what, if any, are the phylogenetic origins of music? Can we find evidence of music in other species? We show that music has adaptive value through emotional contagion, social cohesion, and improved well-being. We trace the roots of music through the emotional signals of other species suggesting that the emotional aspects of music have a long evolutionary history. We show how music and speech are closely interlinked with the musical aspects of speech conveying emotional information. We describe acoustic structures that communicate emotion in music and present evidence that these emotional features are widespread among humans and also function to induce emotions in animals. Similar acoustic structures are present in the emotional signals of nonhuman animals. We conclude with a discussion of music designed specifically to induce emotional states in animals, both cotton top tamarin monkeys and domestic cats.

Increased false-memory susceptibility after mindfulness meditation

From Wilson et al.:

The effect of mindfulness meditation on false-memory susceptibility was examined in three experiments. Because mindfulness meditation encourages judgment-free thoughts and feelings, we predicted that participants in the mindfulness condition would be especially likely to form false memories. In two experiments, participants were randomly assigned to either a mindfulness induction, in which they were instructed to focus attention on their breathing, or a mind-wandering induction, in which they were instructed to think about whatever came to mind. The overall number of words from the Deese-Roediger-McDermott paradigm that were correctly recalled did not differ between conditions. However, participants in the mindfulness condition were significantly more likely to report critical nonstudied items than participants in the control condition. In a third experiment, which tested recognition and used a reality-monitoring paradigm, participants had reduced reality-monitoring accuracy after completing the mindfulness induction. These results demonstrate a potential unintended consequence of mindfulness meditation in which memories become less reliable.

Religiousness decreases children’s altruistic behaviors.

Decety et al. challenge the view that religiosity facilitates prosocial behavior.:

Highlights

•Family religious identification decreases children’s altruistic behaviors
•Religiousness predicts parent-reported child sensitivity to injustices and empathy
•Children from religious households are harsher in their punitive tendencies 

Summary

Prosocial behaviors are ubiquitous across societies. They emerge early in ontogeny and are shaped by interactions between genes and culture. Over the course of middle childhood, sharing approaches equality in distribution. Since 5.8 billion humans, representing 84% of the worldwide population, identify as religious, religion is arguably one prevalent facet of culture that influences the development and expression of prosociality. While it is generally accepted that religion contours people’s moral judgments and prosocial behavior, the relation between religiosity and morality is a contentious one. Here, we assessed altruism and third-party evaluation of scenarios depicting interpersonal harm in 1,170 children aged between 5 and 12 years in six countries (Canada, China, Jordan, Turkey, USA, and South Africa), the religiousness of their household, and parent-reported child empathy and sensitivity to justice. Across all countries, parents in religious households reported that their children expressed more empathy and sensitivity for justice in everyday life than non-religious parents. However, religiousness was inversely predictive of children’s altruism and positively correlated with their punitive tendencies. Together these results reveal the similarity across countries in how religion negatively influences children’s altruism, challenging the view that religiosity facilitates prosocial behavior.

The effects of birth order on personality.

Rohrer et. al. issue a new installment on the perennial question of how our birth order influences us, with a study showing higher intelligence in firstborns,  but no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination.:

Significance

The question of whether a person’s position among siblings has a lasting impact on that person’s life course has fascinated both the scientific community and the general public for >100 years. By combining large datasets from three national panels, we confirmed the effect that firstborns score higher on objectively measured intelligence and additionally found a similar effect on self-reported intellect. However, we found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. This finding contradicts lay beliefs and prominent scientific theories alike and indicates that the development of personality is less determined by the role within the family of origin than previously thought. 

Abstract

This study examined the long-standing question of whether a person’s position among siblings has a lasting impact on that person’s life course. Empirical research on the relation between birth order and intelligence has convincingly documented that performances on psychometric intelligence tests decline slightly from firstborns to later-borns. By contrast, the search for birth-order effects on personality has not yet resulted in conclusive findings. We used data from three large national panels from the United States (n = 5,240), Great Britain (n = 4,489), and Germany (n = 10,457) to resolve this open research question. This database allowed us to identify even very small effects of birth order on personality with sufficiently high statistical power and to investigate whether effects emerge across different samples. We furthermore used two different analytical strategies by comparing siblings with different birth-order positions (i) within the same family (within-family design) and (ii) between different families (between-family design). In our analyses, we confirmed the expected birth-order effect on intelligence. We also observed a significant decline of a 10th of a SD in self-reported intellect with increasing birth-order position, and this effect persisted after controlling for objectively measured intelligence. Most important, however, we consistently found no birth-order effects on extraversion, emotional stability, agreeableness, conscientiousness, or imagination. On the basis of the high statistical power and the consistent results across samples and analytical designs, we must conclude that birth order does not have a lasting effect on broad personality traits outside of the intellectual domain.

A picture show; and, Alzheimer's and the innate immune system

Our nervous and immune systems interact with each other at the same time they both interact with our environment. Cell magazine has put together a picture show that illustrates the beauty and complexity of these interactions. It accompanies special issues of Trends in Neuroscience and Trends in Immunology that deal with neuroimmunology in disease and in normal aging. Of special interest is a description of how releasing an inhibition of the innate immune system can allow phagocytes to clear the Aβ/β-amyloid of Alzheimer's disease from the brain.

Online political communication: more than an echo chamber?

From Barbera et al.:

We estimated ideological preferences of 3.8 million Twitter users and, using a data set of nearly 150 million tweets concerning 12 political and nonpolitical issues, explored whether online communication resembles an “echo chamber” (as a result of selective exposure and ideological segregation) or a “national conversation.” We observed that information was exchanged primarily among individuals with similar ideological preferences in the case of political issues (e.g., 2012 presidential election, 2013 government shutdown) but not many other current events (e.g., 2013 Boston Marathon bombing, 2014 Super Bowl). Discussion of the Newtown shootings in 2012 reflected a dynamic process, beginning as a national conversation before transforming into a polarized exchange. With respect to both political and nonpolitical issues, liberals were more likely than conservatives to engage in cross-ideological dissemination; this is an important asymmetry with respect to the structure of communication that is consistent with psychological theory and research bearing on ideological differences in epistemic, existential, and relational motivation. Overall, we conclude that previous work may have overestimated the degree of ideological segregation in social-media usage.

Choosing to be grateful.

In a piece timed for Thanksgiving, Arthur Brooks does a nice job of fetching up and giving links to references to a number of interesting studies on the positive effects of gratitude on well-being. Arthur Brooks is a person who my knee-jerk liberal reflexes would dictate be discounted immediately, because he is head of the conservative American Enterprise Institute. However this former academic is one clever dude (Here is an Op-Ed piece on abundance. Other commentaries are found here.)

Musical expertise modulates the brain’s entrainment to music.

Yet another study, by Doelling and Poeppel, showing effects of musical training on the brain and supporting a role for cortical oscillatory activity in music perception and cognition.:

Significance

We demonstrate that cortical oscillatory activity in both low (less than 8 Hz) and high (15–30 Hz) frequencies is tightly coupled to behavioral performance in musical listening, in a bidirectional manner. In light of previous work on speech, we propose a framework in which the brain exploits the temporal regularities in music to accurately parse individual notes from the sound stream using lower frequencies (entrainment) and in higher frequencies to generate temporal and content-based predictions of subsequent note events associated with predictive models.

Abstract

Recent studies establish that cortical oscillations track naturalistic speech in a remarkably faithful way. Here, we test whether such neural activity, particularly low-frequency (less than 8 Hz; delta–theta) oscillations, similarly entrain to music and whether experience modifies such a cortical phenomenon. Music of varying tempi was used to test entrainment at different rates. In three magnetoencephalography experiments, we recorded from nonmusicians, as well as musicians with varying years of experience. Recordings from nonmusicians demonstrate cortical entrainment that tracks musical stimuli over a typical range of tempi, but not at tempi below 1 note per second. Importantly, the observed entrainment correlates with performance on a concurrent pitch-related behavioral task. In contrast, the data from musicians show that entrainment is enhanced by years of musical training, at all presented tempi. This suggests a bidirectional relationship between behavior and cortical entrainment, a phenomenon that has not previously been reported. Additional analyses focus on responses in the beta range (∼15–30 Hz)—often linked to delta activity in the context of temporal predictions. Our findings provide evidence that the role of beta in temporal predictions scales to the complex hierarchical rhythms in natural music and enhances processing of musical content. This study builds on important findings on brainstem plasticity and represents a compelling demonstration that cortical neural entrainment is tightly coupled to both musical training and task performance, further supporting a role for cortical oscillatory activity in music perception and cognition.

Our bodies can sabotage our healthy behaviors..

I pass on an interesting chunk from Reynolds' review of work by Mansoubi et al. showing that people who use sit-to-stand workstations in their office compensate by reducing activity and increasing sitting outside of working hours, thus canceling out the effects of their virtuous exercise at the office.

...the human body and brain are funny. They often, and rather insidiously, undermine some of our best efforts to be healthier, in an attempt to maintain our physiological status quo. The result can be that we do not benefit as much as we’d hoped from changes to our lifestyles. When we slash calories to lose weight, for instance, our bodies often lower our metabolic rate, and our weight doesn’t budge much.

Similarly, studies of people who begin or greatly intensify an exercise program have shown that these exercisers often start sitting more during the hours when they are not working out, so that their overall daily energy expenditure doesn’t increase substantially and the number of hours that they spend sitting grows.

Wielding power increases testosterone in women.

Anders et al. provide evidence for a gender→testosterone pathway:

Significance

Human biology is typically studied within the framework of sex (evolved, innate factors) rather than gender (sociocultural factors), despite some attention to nature/nurture interactions. Testosterone is an exemplar of biology studied as natural difference: men’s higher testosterone is typically seen as an innate “sex” difference. However, our experiment demonstrates that gender-related social factors also matter, even for biological measures. Gender socialization may affect testosterone by encouraging men but not women toward behaviors that increase testosterone. This shows that research on human sex biology needs to account for gender socialization and that nurture, as well as nature, is salient to hormone physiology. Our paper provides a demonstration of a novel gender→testosterone pathway, opening up new avenues for studying gender biology.

Abstract

Testosterone is typically understood to contribute to maleness and masculinity, although it also responds to behaviors such as competition. Competition is crucial to evolution and may increase testosterone but also is selectively discouraged for women and encouraged for men via gender norms. We conducted an experiment to test how gender norms might modulate testosterone as mediated by two possible gender→testosterone pathways. Using a novel experimental design, participants (trained actors) performed a specific type of competition (wielding power) in stereotypically masculine vs. feminine ways. We hypothesized in H1 (stereotyped behavior) that wielding power increases testosterone regardless of how it is performed, vs. H2 (stereotyped performance), that wielding power performed in masculine but not feminine ways increases testosterone. We found that wielding power increased testosterone in women compared with a control, regardless of whether it was performed in gender-stereotyped masculine or feminine ways. Results supported H1 over H2: stereotyped behavior but not performance modulated testosterone. These results also supported theory that competition modulates testosterone over masculinity. Our findings thus support a gender→testosterone pathway mediated by competitive behavior. Accordingly, cultural pushes for men to wield power and women to avoid doing so may partially explain, in addition to heritable factors, why testosterone levels tend to be higher in men than in women: A lifetime of gender socialization could contribute to “sex differences” in testosterone. Our experiment opens up new questions of gender→testosterone pathways, highlighting the potential of examining nature/nurture interactions and effects of socialization on human biology.