Chronic stress dials the brain from adaptive to habitual behaviors.

Sousa's group makes interesting observations on brain changes caused by chronic stress. There is a distinctive shift away from adaptive goal directed decision making towards habitual routines that can persist in spite of being inappropriate. Chronic stress actually causes opposing structural changes in the associative and sensorimotor corticostriatal circuits underlying these different behavioral strategies, with atrophy of medial prefrontal cortex and the associative striatum and hypertrophy of the sensorimotor striatum. The change is reversible: rats given a four week vacation from the bullying and tasers used for the stress-out reverted to normal behaviors. Angier's review points out the obvious relevance of such observation to our human behavior:

If after a few months’ exposure to our David Lynch economy, in which housing markets spontaneously combust, coworkers mysteriously disappear and the stifled moans of dying 401(k) plans can be heard through the floorboards, you have the awful sensation that your body’s stress response has taken on a self-replicating and ultimately self-defeating life of its own, congratulations. You are very perceptive. It has....Robert Sapolsky, a neurobiologist who studies stress at Stanford University School of Medicine, said, “This is a great model for understanding why we end up in a rut, and then dig ourselves deeper and deeper into that rut.”...The truth is, Dr. Sapolsky said, “we’re lousy at recognizing when our normal coping mechanisms aren’t working. Our response is usually to do it five times more, instead of thinking, maybe it’s time to try something new.”

With regard to the reversibility of the behavior:

According to Bruce S. McEwen, head of the neuroendocrinology laboratory at Rockefeller University, the new findings offer a particularly elegant demonstration of a principle that researchers have just begun to grasp. “The brain is a very resilient and plastic organ,” he said. “Dendrites and synapses retract and reform, and reversible remodeling can occur throughout life.”

The stress response is essential for maneuvering through a dynamic world — for dodging a predator or chasing down prey, swinging through the trees or fighting off disease — and it is itself dynamic. As we go about our days, Dr. McEwen said, the biochemical mediators of the stress response rise and fall, flutter and flare. “Cortisol and adrenaline go up and down,” he said. “Our inflammatory cytokines go up and down.”...The target organs of stress hormones likewise dance to the beat: blood pressure climbs and drops, the heart races and slows, the intestines constrict and relax. This system of so-called allostasis, of maintaining control through constant change, stands in contrast to the mechanisms of homeostasis that keep the pH level and oxygen concentration in the blood within a narrow and invariant range.

Unfortunately, the dynamism of our stress response makes it vulnerable to disruption, especially when the system is treated too roughly and not according to instructions. In most animals, a serious threat provokes a serious activation of the stimulatory, sympathetic, “fight or flight” side of the stress response. But when the danger has passed, the calming parasympathetic circuitry tamps everything back down to baseline flickering...In humans, though, the brain can think too much, extracting phantom threats from every staff meeting or high school dance, and over time the constant hyperactivation of the stress response can unbalance the entire feedback loop. Reactions that are desirable in limited, targeted quantities become hazardous in promiscuous excess. You need a spike in blood pressure if you’re going to run, to speedily deliver oxygen to your muscles. But chronically elevated blood pressure is a source of multiple medical miseries.

Why should the stressed brain be prone to habit formation? Perhaps to help shunt as many behaviors as possible over to automatic pilot, the better to focus on the crisis at hand. Yet habits can become ruts, and as the novelist Ellen Glasgow observed, “The only difference between a rut and a grave are the dimensions.”

The smell of stress activates our amygdala.

To continue the topic of an earlier post on the smell of emotion, I would like to point out work from Mujica-Parodi et al. Their abstract:

Alarm substances are airborne chemical signals, released by an individual into the environment, which communicate emotional stress between conspecifics. Here we tested whether humans, like other mammals, are able to detect emotional stress in others by chemosensory cues. Sweat samples collected from individuals undergoing an acute emotional stressor, with exercise as a control, were pooled and presented to a separate group of participants (blind to condition) during four experiments. In an fMRI experiment and its replication, we showed that scanned participants showed amygdala activation in response to samples obtained from donors undergoing an emotional, but not physical, stressor. An odor-discrimination experiment suggested the effect was primarily due to emotional, and not odor, differences between the two stimuli. A fourth experiment investigated behavioral effects, demonstrating that stress samples sharpened emotion-perception of ambiguous facial stimuli. Together, our findings suggest human chemosensory signaling of emotional stress, with neurobiological and behavioral effects.

Independence of our logical inference and natural language

Monti et al. examine the proposition that logic inference recruits neural structures traditionally engaged by linguistic processing, and make some very interesting points. Their abstract:

Is human thought fully embedded in language, or do some forms of thought operate independently? To directly address this issue, we focus on inference-making, a central feature of human cognition. In a 3T fMRI study we compare logical inferences relying on sentential connectives (e.g., not, or, if … then) to linguistic inferences based on syntactic transformation of sentences involving ditransitive verbs (e.g., give, say, take). When contrasted with matched grammaticality judgments, logic inference alone recruited “core” regions of deduction [Brodmann area (BA) 10p and 8m], whereas linguistic inference alone recruited perisylvian regions of linguistic competence, among others (BA 21, 22, 37, 39, 44, and 45 and caudate). In addition, the two inferences commonly recruited a set of general “support” areas in frontoparietal cortex (BA 6, 7, 8, 40, and 47). The results indicate that logical inference is not embedded in natural language and confirm the relative modularity of linguistic processes.

A sane article on life-extending drugs.

Nicholas Wade offers one of the best reviews I have seen of work with drugs like resveratrol, which mimic the effect or caloric restriction in animal tests. A companion article by Arnquist notes the proliferation of web sites making unproven health claims and using false celebrity product endorsements for anti-aging and weight-loss pills made from resveratrol. (previous MindBlog postings in this areas can be found by clicking on aging in the topics list in the left column of this web page.) Here are clips from the Wade article which point out reservations about the existing studies:

...the whole phenomenon of caloric restriction may be a misleading result unwittingly produced in laboratory mice. The mice are selected for quick breeding and fed on rich diets. A low-calorie diet could be much closer to the diet that mice are adapted to in the wild, and therefore it could extend life simply because it is much healthier for them...To decide whether life extension by caloric restriction is an artifact of mice in captivity, why not try it on wild mice? Just such an experiment has been done by Steven N. Austad of the University of Texas Health Science Center. Dr. Austad reported that caloric restriction did not extend the average life span of wild mice, suggesting the diet’s benefits are indeed an artifact of mice in captivity. But others interpret his results differently. Richard A. Miller of the University of Michigan, says the maximum life span of the wild mice was extended, and so the experiment was a success for caloric restriction.

With reference to the study at Wisconsin on caloric restriction in monkeys:

The monkeys who had spent 20 years on caloric restriction were in better health than their normally fed counterparts, and suffered less diabetes, cancer and heart disease, apparently confirming that caloric restriction holds off the degenerative diseases of aging in primates as well as rodents...But as for life span, the diet extended life significantly only if the researchers excluded deaths that were apparently unrelated to aging, such as under the anesthesia necessary to take blood samples. When all deaths were counted, life span was not significantly extended...Some researchers think it is perfectly valid to ignore such deaths. Others note that in mouse studies one just counts the numbers of dead mice without asking what they died of, and the same procedure should be followed with monkeys, since one cannot be sure if a death under anesthesia might have been age related.

Another point:

...last month the results with another substance, the antifungal drug rapamycin, were published (see my July 22 post) Rapamycin was found to extend mice’s lives significantly even though by accident the mice were already the equivalent of 60 years old when the experiment started...Rapamycin has nothing to do with caloric restriction, so far as is known, but the study provided striking proof that a chemical can extend life span.

A nation's mood from its songs and blogs?

As a followup on monday's post on happiness and the blogosphere, Benedict Carey points to researchers who suggest that linguistic analysis — of song lyrics, blogs and speeches — could add a new and valuable dimension to a growing area of mass psychology: the determination of national well-being.

Bilingual infants are more flexible learners.

From Kovács and Mehler:

Children acquire their native language according to a well-defined time frame. Surprisingly, although children raised in bilingual environments have to learn roughly twice as much about language as their monolingual peers, the speed of acquisition is comparable in monolinguals and bilinguals. Here, we show that preverbal 12-month-old bilingual infants have become more flexible at learning speech structures than monolinguals. When given the opportunity to simultaneously learn two different regularities, bilingual infants learned both, whereas monolinguals learned only one of them. Hence, bilinguals may acquire two languages in the time in which monolinguals acquire one because they quickly become more flexible learners.

Even cockroaches get lonely.

The research highlights section of the July 29 Nature points out an interesting study from Lihoreau et al. suggesting why, when you find cockroaches in your home, "there's never just one."

Even cockroaches develop psychological problems if they are denied a normal social life. Animals reared in solitude are less likely to explore new environments or search for food, are more timid when approaching other cockroaches and are less able to spot the signs of a good mate. The effects of solitary confinement parallel those of 'isolation syndrome' described in a variety of vertebrates, and the suggestion is that it may develop when any group-living species is denied company.

Here is the abstract from the Lihoreau et al study:

Social isolation has dramatic consequences on the development of individuals of many vertebrate species, and it induces a set of behavioural disturbances rending them unable to process environmental as well as social stimuli appropriately. We hypothesized that isolation syndrome is a ubiquitous trait of social life that can be observed in a wide array of species, including invertebrates. Here we report that gregarious cockroaches (Blattella germanica) reared in isolation showed (i) stronger exploration-avoidance, (ii) reduced foraging activity, (iii) reduced willingness to interact socially, and (iv) reduced ability to assess mating partner quality than conspecifics reared in groups. We demonstrate the occurrence of a behavioural syndrome induced by social isolation, similar to syndromes described in vertebrates, revealing the importance of social interactions and group-living in this non-eusocial insect species. We suggest that investigating social isolation effects on individual development should provide interesting results to assess social cohesion of species and thus constitute an additional tool for comparative studies focusing on the evolution of social life.

Brain activity accociated with honest and dishonest decisions.

Greene and Paxton make some interesting observations:

What makes people behave honestly when confronted with opportunities for dishonest gain? Research on the interplay between controlled and automatic processes in decision making suggests 2 hypotheses: According to the “Will” hypothesis, honesty results from the active resistance of temptation, comparable to the controlled cognitive processes that enable the delay of reward. According to the “Grace” hypothesis, honesty results from the absence of temptation, consistent with research emphasizing the determination of behavior by the presence or absence of automatic processes. To test these hypotheses, we examined neural activity in individuals confronted with opportunities for dishonest gain. Subjects undergoing functional magnetic resonance imaging (fMRI) gained money by accurately predicting the outcomes of computerized coin-flips. In some trials, subjects recorded their predictions in advance. In other trials, subjects were rewarded based on self-reported accuracy, allowing them to gain money dishonestly by lying about the accuracy of their predictions. Many subjects behaved dishonestly, as indicated by improbable levels of “accuracy.” Our findings support the Grace hypothesis. Individuals who behaved honestly exhibited no additional control-related activity (or other kind of activity) when choosing to behave honestly, as compared with a control condition in which there was no opportunity for dishonest gain. In contrast, individuals who behaved dishonestly exhibited increased activity in control-related regions of prefrontal cortex, both when choosing to behave dishonestly and on occasions when they refrained from dishonesty. Levels of activity in these regions correlated with the frequency of dishonesty in individuals.

Our bias blind spot.

Pronin et al carry out three studies that suggest that knowledge of particular biases in our judgment and inference, and the ability to recognize the impact of those biases on others, neither prevents us from succumbing nor makes us aware of having done so. Indeed, participants in their research denied that their assessments of their personal qualities and their attributions for a particular success or failure had been biased even after having displayed the relevant biases and reading descriptions of them.

Mindblog is back...

Still jet-lagged, I'll be taking some time to cobble myself back together again. Here are a few vacation photos of Deric in London, and Len and Deric in Hagley (Hagley is a far western surburb of Birmingham where we used a colleague's house as a base to explore some spots in the Cotswolds). If I ever needed more personal objective data on the decay of one's brain plasticity on aging, I sure got it when I started to drive on the left after a 14 year absence from the UK! What I recalled as being rather fun and effortless (negotiating complex roundabouts, etc.) now went with much more energy, concentration, focus, and stress. This, I presume, reflects the difference between the 67 year old and the 53 year old versions of Deric's brain.

Why health care reform is paralyzed...

In the Aug. 3 issue of the New Yorker, Hertzberg writes a concise and lucid description of why we are the only wealthy democracy on this planet that has failed to get either universal health care or some form of guaranteed health insurance. Other democracies can actually make democratic decisions, we appear to be unable to:

A president may fancy that he has a mandate (and, morally, he may well have one), but the two separately elected, differently constituted, independent legilatures whose acquiescence he needs are under no compulsion to agree. Within those legilatures, a system of overlapping committees dominated by powerful chairmen creates a plethora of veto points where well-organized special interest can smother or distort a bill meant to benefit a large but amorphous public. In the smaller of the two legislatures - which is even more heavily weighted toward conservative rural interests than is the larger one, and where one member may represent as little as one-seventieth as many people as the member in the next seat - an arcane and patently unconstitutional rule, the filibuster, allows a minority of members to block almost any action. The process that results is less like the Roman Senate than like the Roman Games: a sanguinary legislative Colosseum where at any moment some two-bit emperor is apt to signal the thumbs-down.

Happiness increasing in the blogosphere...

The following is from the "Random Samples" section of the Aug. 7 issue of Science. This may be just a tad simplistic??

Day in, day out, bloggers pour their feelings onto the Web. Now researchers are mining those outpourings to track society's mood swings.

Peter Dodds and Christopher Danforth, applied mathematicians at the University of Vermont, Burlington, automatically searched 2.4 million blogs, via the Web site www.wefeelfine.org, for phrases containing the words "I feel." Their computers then scanned those phrases for 1034 emotionally charged words that a 1999 psychology study had ranked on a happiness scale from 1 (miserable) to 9 (ecstatic). From the words' frequency and scores, an algorithm calculated a net feel-good factor for each day and month.

For the past 4 years, happiness has steadily increased in the blogosphere, Dodds and Danforth reported online recently in the Journal of Happiness Studies. Spirits spike on Christmas and Valentine's Day but dip on 11 September. The happiest day since 2005 was 4 November 2008, the day of the U.S. presidential election. In contrast, Michael Jackson's death in June triggered a 3-day trough.

The Vermont scientists are now studying Twitter feeds. James Fowler, a social scientist at the University of California, San Diego, says the new method will enable scientists "to take the pulse of the whole world, assessing the mood of human society."

Deric's MindBlog on vacation in the UK.

I've just arrived in London on my second trip of the summer: 16 days in the UK, first staying at a friend's flat near the Baker St. station, then with my partner in a Univ. of Wisconsin colleague's house in Hagley, just west of Birmingham. Deric Bownds' MindBlog will be taking a break unless I find myself in the mood to do some posts during the trip.

Taking turns in conversations - universals and cultural variation

Stivers et al. examine the frequent claims in anthropological literature that cultures differ radically in the timing of conversational turn-taking (e.g. Nordic cultures as slow, New York Jewish culture as fast):

Informal verbal interaction is the core matrix for human social life. A mechanism for coordinating this basic mode of interaction is a system of turn-taking that regulates who is to speak and when. Yet relatively little is known about how this system varies across cultures. The anthropological literature reports significant cultural differences in the timing of turn-taking in ordinary conversation. We test these claims and show that in fact there are striking universals in the underlying pattern of response latency in conversation. Using a worldwide sample of 10 languages drawn from traditional indigenous communities to major world languages, we show that all of the languages tested provide clear evidence for a general avoidance of overlapping talk and a minimization of silence between conversational turns. In addition, all of the languages show the same factors explaining within-language variation in speed of response. We do, however, find differences across the languages in the average gap between turns, within a range of 250 ms from the cross-language mean. We believe that a natural sensitivity to these tempo differences leads to a subjective perception of dramatic or even fundamental differences as offered in ethnographic reports of conversational style. Our empirical evidence suggests robust human universals in this domain, where local variations are quantitative only, pointing to a single shared infrastructure for language use with likely ethological foundations.

The "Neuro Revolution"

German cognitive scientist and writer Stephan Schleim writes a review (download here) that is appropriately critical of Zack Lynch's new spiel "The Neuro Revolution: How Brain Science Is Changing Our World."

Some midweek Chopin - a Polonaise

Mapping the human brain "connectome"

It seems that almost everything can come now with an "-ome" suffix (referring to a totality of some sort. Beyond the original "genome" we now have a long list, including the proteome, speechome, mechanome, etc.). A massive project to establish a human brain connectome, or map of all brain connections, has just received a 30 million dollar cash infusion from the N.I.H. This is an unbelievably daunting task, Over the past century, neuroscientists have used three main sets of anatomical approaches to study neural connectivity: single-cell impregnation, optically based tract-tracing and electron microscopy. More recent techniques involve attaching color markers to intrinsic neuronal labels (shown in figure). Resolution at the electron microscope level, so far done only for the small nervous system of the nematode roundworm, is still technically inaccessible, so that the work will actually be on lower resolution of nerve tracts. But... I wonder then about the minor detail that no two human brains are the same. Even the brains of identical twins have been shown to differ significantly in their activation patterns and connectivity. (The same variability also confounds comparative genome studies.) While it will indeed be exciting, as it was for the human genome, to be told "We now have the first human brain connectome," an awesome amount of work then must follow.

Science Tattoos

An amazing gallery of what people will do to themselves (in the name of science?).

The cognitive neuroscience of dyslexia and its repair

John Gabrieli offers a review article in the July 17 issue of Science. Several clips:

Reading is essential in modern societies, but many children have dyslexia, a difficulty in learning to read. Dyslexia often arises from impaired phonological awareness, the auditory analysis of spoken language that relates the sounds of language to print. Behavioral remediation, especially at a young age, is effective for many, but not all, children. Neuroimaging in children with dyslexia has revealed reduced engagement of the left temporo-parietal cortex for phonological processing of print, altered white-matter connectivity, and functional plasticity associated with effective intervention. Behavioral and brain measures identify infants and young children at risk for dyslexia, and preventive intervention is often effective. A combination of evidence-based teaching practices and cognitive neuroscience measures could prevent dyslexia from occurring in the majority of children who would otherwise develop dyslexia.


Brain activation differences in dyslexia and its treatment. Functional magnetic resonance imaging activations shown on the left hemisphere for phonological processing in typically developing readers (left), age-matched dyslexic readers (middle), and the difference before and after remediation in the same dyslexic readers (right). Red circles identify the frontal region, and blue circles identify the temporo-parietal region of the brain. Both regions are hypoactivated in dyslexia and become more activated after remediation.

Brain changes from childhood to young adulthood

Supekar et al. compare large scale brain functional networks in 7-9 and 19-22 year olds and find that they differ significantly in hierarchical organization and interregional connectivity. Subcortical areas are more strongly connected with primary sensory, association, and paralimbic areas in children, whereas young-adults show stronger cortico-cortical connectivity between paralimbic, limbic, and association areas.