Why do we swear? For pain relief.

An interesting little nugget from Scientific American Mind.

Social contagion - Is happiness (or obesity) catching?

Clive Thompson does a nice article in this past Sunday's New York Times magazine on social contagion. It covers the Framingham study that I have mentioned in previous posts along with other studies that document how good as well as bad behaviors pass from friend to friend almost as if they were contagious viruses.

...behaviors may spread partly through the subconscious social signals that we pick up from those around us, which serve as cues to what is considered normal behavior. Scientists have been documenting this phenomenon; for example, experiments have shown that if a person is seated next to someone who’s eating more, he will eat more, too, unwittingly calibrating his sense of what constitutes a normal meal.

While emotional mirroring might be the most alluring idea about why behaviors spread, there are..

..two other possible explanations. One is “homophily,” the tendency of people to gravitate toward others who are like them. People who are gaining weight might well prefer to hang out with others who are also gaining weight, just as people who are happy might seek out others who are happy. The other possible explanation is that the shared environment — and not social contagion — might be causing the people of Framingham to change in groups. If a McDonald’s opens up in a Framingham neighborhood, it could cause a cluster of people living nearby to gain weight or become slightly happier (or sadder, depending on what they think about McDonald’s). The cluster of people would appear as though they are sharing a contagious form of behavior, but it would be an illusion.

How we change our decisions...

Resulaj et al develop a new model that accounts for how and when we change our mind after we make a decision. They do a series of experiments on subjects who were asked to move a handle to one of two positions dependent on a noisy visual stimulus. Analysis of the rare occasions where subjects changed their mind half way through selecting their answer shows that even after making a decision the brain continues to process the information it had gathered — information still in the processing pipeline— to either reverse or reaffirm its initial decision. Their new theory introduces the acts of vacillation and self correction into the decision-making process. The abstract outlines their basis idea:

A decision is a commitment to a proposition or plan of action based on evidence and the expected costs and benefits associated with the outcome. Progress in a variety of fields has led to a quantitative understanding of the mechanisms that evaluate evidence and reach a decision. Several formalisms propose that a representation of noisy evidence is evaluated against a criterion to produce a decision. Without additional evidence, however, these formalisms fail to explain why a decision-maker would change their mind. Here we extend a model, developed to account for both the timing and the accuracy of the initial decision, to explain subsequent changes of mind. Subjects made decisions about a noisy visual stimulus, which they indicated by moving a handle. Although they received no additional information after initiating their movement, their hand trajectories betrayed a change of mind in some trials. We propose that noisy evidence is accumulated over time until it reaches a criterion level, or bound, which determines the initial decision, and that the brain exploits information that is in the processing pipeline when the initial decision is made to subsequently either reverse or reaffirm the initial decision. The model explains both the frequency of changes of mind as well as their dependence on both task difficulty and whether the initial decision was accurate or erroneous. The theoretical and experimental findings advance the understanding of decision-making to the highly flexible and cognitive acts of vacillation and self-correction.

How chaos drives the brain.

I've been meaning to point out this excellent article in The New Scientist describing evidence that self-organised criticality is important brain function. It has links to a number of useful references.

Looming global disaster, anyone?

A panel of experts publishes a manifesto or guide in Science that is just the ticket for someone like myself who verges on clinical depression after every morning reading of the New York Times:

Energy, food, and water crises; climate disruption; declining fisheries; increasing ocean acidification; emerging diseases; and increasing antibiotic resistance are examples of serious, intertwined global-scale challenges spawned by the accelerating scale of human activity. They are outpacing the development of institutions to deal with them and their many interactive effects. The core of the problem is inducing cooperation in situations where individuals and nations will collectively gain if all cooperate, but each faces the temptation to take a free ride on the cooperation of others. The nation-state achieves cooperation by the exercise of sovereign power within its boundaries. The difficulty to date is that transnational institutions provide, at best, only partial solutions, and implementation of even these solutions can be undermined by internation competition and recalcitrance.


Figure - Interactive effects of global drivers on unwanted outcomes in the state of the world. Some outcomes also act as drivers of others (dashed arrows).

The major powers must be willing to enforce agreements, but legitimacy will depend on acceptance by numerous and diverse countries and by nongovernmental actors, such as civil society and business. This seems to be the basis for the greater success of the Montreal Protocol relative to the Kyoto Protocol. Strong backing by a majority for collective action, even though it may restrict individual freedoms, is necessary to institute and uphold an agreement. Formal sanctions are necessary to prevent cheating and are more likely to succeed where the backing is based on transparent, common norms. Agreements should not only be instruments of change but should establish processes for change, engaging a wide set of actors.

The institution of the nation-state has helped improve the well-being of many individuals, but at the cost of reduced global resilience. To address our common threats we need greater interaction among existing institutions, as well as new institutions, to help construct and maintain a global-scale social contract.

Our brain's fast response to morally objectionable statements.

Van Berkum et. al. make observations that go alongside the observations on moral conviction and religiosity mentioned in last friday's post.

How does the brain respond to statements that clash with a person's value system? We recorded event-related brain potentials while respondents from contrasting political-ethical backgrounds completed an attitude survey on drugs, medical ethics, social conduct, and other issues. Our results show that value-based disagreement is unlocked by language extremely rapidly, within 200 to 250 ms after the first word that indicates a clash with the reader's value system (e.g., "I think euthanasia is an acceptable/unacceptable…"). Furthermore, strong disagreement rapidly influences the ongoing analysis of meaning, which indicates that even very early processes in language comprehension are sensitive to a person's value system. Our results testify to rapid reciprocal links between neural systems for language and for valuation.

How much sleep do we need?

Recent work suggests a role for sleep in memory and/or synaptic plasticity. There is a large difference in how much sleep people need, ranging from less than 6 to more than 9 hours. Short sleepers are found in families, as are long sleepers, which suggests a genetic basis for sleep duration. He et al. now show that a mutation in a transcriptional factor, DEC2, is associated with short sleep in humans and mice. DEC2 is a transcription factor (protein that regulates gene function) involved in cell proliferation and differentiation, response to hypoxia, and circadian rhythms. Here is their abstract:

Sleep deprivation can impair human health and performance. Habitual total sleep time and homeostatic sleep response to sleep deprivation are quantitative traits in humans. Genetic loci for these traits have been identified in model organisms, but none of these potential animal models have a corresponding human genotype and phenotype. We have identified a mutation in a transcriptional repressor (hDEC2-P385R) that is associated with a human short sleep phenotype. Activity profiles and sleep recordings of transgenic mice carrying this mutation showed increased vigilance time and less sleep time than control mice in a zeitgeber time– and sleep deprivation–dependent manner. These mice represent a model of human sleep homeostasis that provides an opportunity to probe the effect of sleep on human physical and mental health.

Stimulate your waking memory with an electrical cap

A tiny oscillating electrical stimulation of which we are completely unaware (passed between electrodes on the forehead and jaw) can have the effect of enhancing memory consolidation during waking, an effect shown previously during sleep. The abstract of the open access PNAS article from Kirov et al.:

The application of transcranial slow oscillation stimulation (tSOS; 0.75 Hz) was previously shown to enhance widespread endogenous EEG slow oscillatory activity when applied during a sleep period characterized by emerging endogenous slow oscillatory activity. Processes of memory consolidation typically occurring during this state of sleep were also enhanced. Here, we show that the same tSOS applied in the waking brain also induced an increase in endogenous EEG slow oscillations (0.4–1.2 Hz), although in a topographically restricted fashion. Applied during wakefulness tSOS, additionally, resulted in a marked and widespread increase in EEG theta (4–8 Hz) activity. During wake, tSOS did not enhance consolidation of memories when applied after learning, but improved encoding of hippocampus-dependent memories when applied during learning. We conclude that the EEG frequency and related memory processes induced by tSOS critically depend on brain state. In response to tSOS during wakefulness the brain transposes stimulation by responding preferentially with theta oscillations and facilitated encoding.

Convergence of human and dog evolution, striving to please

Topál et al. perform some fascinating comparative studies that look in dogs for a curious error noted first by Piaget, who showed that 10-month-old humans infants will persist in looking for a toy in box A, where it has been placed several times, even after having been shown that it has been moved to box B, whereas 12-month-old infants do not. This phenomenon marks a developmental milestone in human infant cognition. Adult dogs, like human infants, will persevere in searching erroneously in box A because they regard the placement of the toy by a human experimenter as a social teaching event. By contrast, wolves rapidly learn correctly to search box B. They also observed that infants are able to generalize and thus still persevere when one experimenter places the toy in box A and a second then places the toy in box B. Dogs, however, display episodic learning, and a second experimenter reduces their searching choice to chance. Topál et al. suggest that sensitivity to human communicative signals stems from convergent social evolution of the Homo and the Canis genera.

MindBlog posts in the queue

I think I'll start passing along links to bits of work that I find interesting, but that are so far down my list of potential blog postings that they are unlikely to make it into a regular post. It seems a pity to let them disappear, because I'm aware that a few MindBlog readers with more specialized interests might be interested in some of them.

A study that suggests that increased gamma band (~40 Hz) event-related synchronization is related to, but not sufficient for, consciousness.

Clelland et al. show that synthesis of new nerve cells contributes to formation of spatial memories.

I Heard That Coming: Bendixen et al. show that event related potentials can signal the predictability of pattern in an upcoming a tone sequence.

Watching whales watching us. The evidence suggesting association between sonar and whale deaths is very convincing.

Scientists have now documented behaviors like tool use and cooperative hunting strategies among whales. Orcas, or killer whales, have been found to mourn their own dead. Just three years ago, researchers at Mount Sinai School of Medicine in New York discovered, in the brains of a number of whale species, highly specialized neurons that are linked to, among other things, the use of language and were once thought to be the exclusive property of humans and a few other primates. Indeed, marine biologists are now revealing not only the dizzying variety of vocalizations among a number of whale species but also complex societal structures and cultures.

Vorauer et al. on multiculturalism versus avoidance in influencing the tone of dominant/minority group interactions.

David Sloane Wilson and collaborators on how nice guys can finish last. From the summary in Nature:

Selfish individuals can profit from the altruism of others in their group, and can even exploit a group's resources so much that the resources become exhausted — an event known as the tragedy of the commons...Omar Eldakar, of the University of Arizona in Tucson, and his colleagues have now shown experimentally that aggressive mating in water striders (Aquarius remigis) can result in one such tragedy. Harassment of female water striders by males has previously been shown to drive away females, diminishing the mating success of all males in a group...The team built pools and manipulated the number of aggressive and nonaggressive males in each. They found that hyperaggressive males had greater mating success than those which were not aggressive within mixed pools. But as the number of hyperaggressive insects increased, the mating success of both types decreased.

Testosterone levels and long term career choices

From Sapienzaore et al., more on testosterone, gender, and risk aversion:

Women are generally more risk averse than men. We investigated whether between- and within-gender variation in financial risk aversion was accounted for by variation in salivary concentrations of testosterone and in markers of prenatal testosterone exposure in a sample of >500 MBA students. Higher levels of circulating testosterone were associated with lower risk aversion among women, but not among men. At comparably low concentrations of salivary testosterone, however, the gender difference in risk aversion disappeared, suggesting that testosterone has nonlinear effects on risk aversion regardless of gender. A similar relationship between risk aversion and testosterone was also found using markers of prenatal testosterone exposure. Finally, both testosterone levels and risk aversion predicted career choices after graduation: Individuals high in testosterone and low in risk aversion were more likely to choose risky careers in finance. These results suggest that testosterone has both organizational and activational effects on risk-sensitive financial decisions and long-term career choices.

Moral conviction and religiosity - different in the viscera

An interesting bit from Wisneski et al. :

Theory and research point to different ways moral conviction and religiosity connect to trust in political authorities to decide controversial issues of the day. Specifically, we predicted that stronger moral convictions would be associated with greater distrust in authorities such as the U.S. Supreme Court making the "right" decisions regarding controversial issues. Conversely, we predicted that stronger religiosity would be associated with greater trust in authorities. We tested these hypotheses using a survey of a nationally representative sample of Americans (N = 727) that assessed the degree to which people trusted the U.S. Supreme Court to rule on the legal status of physician-assisted suicide. Results indicated that greater religiosity was associated with greater trust in the U.S. Supreme Court to decide this issue, and that stronger moral convictions about physician-assisted suicide were associated with greater distrust in the U.S. Supreme Court to decide this issue. Also, the processes underlying religious trust and distrust based on moral convictions were more quick and visceral than slow and carefully considered.

The amygdala contributes to both aversive and appetitive arousal

Apparently the "scram!" and "go for it" emotions share some brain wiring. Shabel and Janak note that a large part of the amygdala, whose activation is usually associated with aversive emotions, is also activated during appetitive emotions. Thus there do not appear to be different circuits for the amygdala and autonomic nervous system arousal caused by positive versus aversive stimuli.

The amygdala is important for determining the emotional significance of environmental stimuli. However, the degree to which appetitive and aversive stimuli are processed by the same or different neuronal circuits within the amygdala remains unclear. Here we show that neuronal activity during the expression of classically conditioned appetitive and aversive emotional responses is more similar than expected by chance, despite the different sensory modalities of the eliciting stimuli. We also found that the activity of a large number of cells (> 43%) was correlated with blood pressure, a measure of emotional arousal. Together, our results suggest that a substantial proportion of neuronal circuits within the amygdala can contribute to both appetitive and aversive emotional arousal.

Another reason I live in Wisconsin

I can certify that medical care in Florida (where I now spend the winter) and Texas (where I grew up) is medieval in comparison with Wisconsin. My experience is consonant with a great graphic from a New York Times article on health care costs and quality (click on graphic to enlarge it):

Why fear memories are hard to erase.

Gogolla et al. present evidence that fear memories are protected from erasure (extinction) by an matrix of compounds (chondroitin sulfate proteoglycans) outside of nerve cells in the amygdala, ie. in the extra-cellular matrix:

In adult animals, fear conditioning induces a permanent memory that is resilient to erasure by extinction. In contrast, during early postnatal development, extinction of conditioned fear leads to memory erasure, suggesting that fear memories are actively protected in adults. We show here that this protection is conferred by extracellular matrix chondroitin sulfate proteoglycans (CSPGs) in the amygdala. The organization of CSPGs into perineuronal nets (PNNs) coincided with the developmental switch in fear memory resilience. In adults, degradation of PNNs by chondroitinase ABC specifically rendered subsequently acquired fear memories susceptible to erasure. This result indicates that intact PNNs mediate the formation of erasure-resistant fear memories and identifies a molecular mechanism closing a postnatal critical period during which traumatic memories can be erased by extinction.

These results, together with previous experiments in the visual cortex on visual plasticity, suggest that maturation of the extracellular matrix could be a mechanism used by different brain circuits to change from a malleable to a more crystallized state during development. The presence of a high concentration of CSPGs in the perineuronal nets surrounding inhibitory neurons suggests that inhibitory circuits could play an important role in the developmental control of plasticity.

Lessons from Hell

In the New York Times Book Review Tom Vanderbilt discusses the new book by Rebecca Solnit on the communities (frequently amazingly altruistic) that arise in times of disaster, during which one might have expected the social fabric to rend.

Disasters, for Solnit, do not merely put us in view of apocalypse, but provide glimpses of utopia. They do not merely destroy, but create. “Disasters are extraordinarily generative,” she writes. As the prevailing order — which she elliptically characterizes as advanced global capitalism, full of anomie and isolation — collapses, another order takes shape: “In its place appears a reversion to improvised, collaborative, cooperative and local society.” These “disaster communities” represent something akin to the role William James claimed for “the utopian dreams” of social justice: “They help to break the general reign of hardness, and are slow leavens of a better order.”

A meta-narrative governing official response to the various disasters Solnit examines, from the industrial explosion that devastated Halifax in 1917 to the Mexico City earthquake of 1985 to New York on 9/11, is that cities wracked by disaster need to be protected from rampaging mobs, that government needs to suppress the panicked masses and save the day. But as Solnit illustrates, through an absorbing study of the academic subfield of “disaster sociology,” these Hobbesian (and Holly­wood) beliefs are seldom true.

First, official emergency responders are rarely the first people to respond to an emergency. Second, the central command-and-control model often misinterprets the reality on the ground. Third, the hero motif neglects the role of social capital, a soft-power variable that is played down in disaster management but which might help answer such interesting questions as why Cuba, in contrast to its neighbors (including the United States), responds so well to hurricanes, or why the 2003 New York City blackout was calm while its 1977 equivalent was not...Lastly, there’s the panic myth. A sociologist who set out to research panic in disasters found it was a “vanishingly rare phenomenon,” with cooperation and rational behavior the norm. More typically, panic comes from the top

Walter Kirn on performance enhancing drugs

Check out his account of his own experience.

The ability to stay on task, even the dullest, most numbing task, was Adderall’s first gift to me. It was also its first curse, because it encouraged me to take on work of an increasingly stupefying nature and do it well enough that I got more of it, until I was doing almost no other kind. I can see, though, how harried students might covet this power and why, according to some estimates, a quarter of undergraduates at certain colleges are availing themselves of such stimulants. They’re well aware of the dire economic news — big law firms instituting hiring freezes; whole industries, like publishing, imploding — and it’s natural that they would welcome any advantage in their quests to get the grades that will get them the jobs that will get them the insurance that will get them the medications to do the jobs.

I reached a point with Adderall that reminded me of a warning the United States Marine Corps is said to give its enemies: You can run, but you’ll only die tired...Or graduate tired, in the case of college students. And what’s so wrong with that? The course of a formal education is short but its consequences vast, so why not give it your spirit-crushing all, especially during a fiercely competitive age? “Simply because,” the parent in me says. He’s been there, this man. He’s weary, he’s spent and he just knows.

A cartoon...

Cartoon from the Sept. 7 New Yorker that really struck home for Deric (given that such a tiny fraction of what I am actually thinking ever makes it into this blog):

Some comic relief - talk about costume changes!

The amygdala as the neural source of personal space.

It turns out the amygdala, known to be important in our social interactions, may also be the core of regulating our personal space. (Americans and northern Europeans prefer a larger personal space than southern Europeans, while people with autism tend to unknowingly invade others' personal space.) Here is a a clip from a ScienceNow account of studies on a 42-year-old woman with a rare genetic disorder that destroyed both sides of her amygdala.

In early experiments, the scientists discovered that the woman, referred to as SM, couldn't spot fear in other people's faces; she also rated people as more trustworthy than an average person did. And she was extremely outgoing, "almost to the point where it isn't normal," says team member Daniel Kennedy. Even if she's only just met someone, he says, SM will invade their personal space--touching their arm as she talks or poking their stomach...In the new study, Kennedy and his colleagues more rigorously tested SM's sense of personal space. They compared her with 20 healthy subjects in a series of experiments. In one test, an experimenter slowly walked toward a subject until the subject felt uncomfortable and told the experimenter to stop. SM let experimenters get about twice as close as other subjects did, 0.34 meters versus 0.64 meters, the team reports online this week in Nature Neuroscience. She even felt fine standing nose to nose with an experimenter.

The findings in general support the idea that the amygdala functions as the brakes in social interactions. Here is a figure from the Nature Neuroscience report:

(a) Preference of S.M. (red) was the closest distance to the experimenter (black), among age-, gender-, race- and education-matched controls (purple, n = 5), as well as general comparison subjects (blue, n = 15). (b) S.M.'s mean preferred distance from the experimenter (image drawn to scale). (c) Control participants' mean preferred distance from the experimenter, excluding the three largest outliers (image drawn to scale).