Delayed brain development in humans compared with other primates

A prevailing view is that the appearance of many human-specific features during development has been made possible by a slowing down of the process, particularly in the brain (developmental retardation, or neoteny). Somel et al. prove the point by looking at gene expression in humans and other primates during development:

In development, timing is of the utmost importance, and the timing of developmental processes often changes as organisms evolve. In human evolution, developmental retardation, or neoteny, has been proposed as a possible mechanism that contributed to the rise of many human-specific features, including an increase in brain size and the emergence of human-specific cognitive traits. We analyzed mRNA expression in the prefrontal cortex of humans, chimpanzees, and rhesus macaques to determine whether human-specific neotenic changes are present at the gene expression level. We show that the brain transcriptome is dramatically remodeled during postnatal development and that developmental changes in the human brain are indeed delayed relative to other primates. This delay is not uniform across the human transcriptome but affects a specific subset of genes that play a potential role in neural development.

MindBlog is on the road again.

This is the time of year when I leave Fort Lauderdale with my new one year old children, shown in the photographs, to drive first to Austin Texas for a visit with my son and his wife, and then on to my home in Madison Wisconsin. (The photos show Marvin and Melvin checking out their carrier, then in the carrier on top of the car, but in fact they are given free range while in the car ). The posts in the queue this week for Tuesday through Friday are mainly passing on abstracts that I have found interesting, with an occasional figure.

The surprising power of neighborly advice.

I did a series of posts in June, 2006 abstracting Dan Gilberts book "Stumbling on Happiness." (You can use the blog search box to find them by entering the word "stumbling.") His main suggestion for knowing how you might actually feel emotionally about a desired future situation was simply to ask someone who has been there (become a successful doctor, actor, writer, etc.) Following in this vein, his group has recently obtained a very simple result concerning how people predict their future emotional reactions. Their abstract, following by some text:

Two experiments revealed that (i) people can more accurately predict their affective reactions to a future event when they know how a neighbor in their social network reacted to the event than when they know about the event itself and (ii) people do not believe this. Undergraduates made more accurate predictions about their affective reactions to a 5-minute speed date (n = 25) and to a peer evaluation (n = 88) when they knew only how another undergraduate had reacted to these events than when they had information about the events themselves. Both participants and independent judges mistakenly believed that predictions based on information about the event would be more accurate than predictions based on information about how another person had reacted to it.

Some context from the text of the article:

People make systematic errors when attempting to predict their affective reactions to future events...to overestimate how unhappy they will be after receiving bad test results, becoming disabled, or being denied a promotion, and to overestimate how happy they will be after winning a prize, initiating a romantic relationship, or taking revenge against those who have harmed them. Research suggests that the main reason people mispredict their affective reactions to future events is that they imagine those events inaccurately.

The 17th century writer François de La Rochefoucauld suggested that rather than mentally simulating a future event, people should consult those who have experienced it. "Before we set our hearts too much upon anything," he wrote, "let us first examine how happy those are who already possess it" . La Rochefoucauld was essentially suggesting that forecasters should use other people as surrogates for themselves, and the advantages of his "surrogation strategy" are clear: Because surrogation does not rely on mental simulation, it is immune to the many errors that inaccurate simulations produce.

The disadvantages of surrogation are also clear: Individuals differ, and thus, one person's affective reaction is almost certainly an imperfect predictor of another's. But there are at least two reasons to suspect that affective reactions are not as different as people may believe. First, affective reactions are produced in large part by physiological mechanisms that are evolutionarily ancient, which is why people the world over have very different beliefs and opinions but very similar affective reactions to a wide range of stimuli, preferring warm to cold, satiety to hunger, friends to enemies, winning to losing, and so on.

Their summary and conclusions:

In two experiments, participants more accurately predicted their affective reactions to a future event when they knew how a neighbor in their social network had reacted to it than when they knew about the event itself. Women made more accurate predictions about how much they would enjoy a date with a man when they knew how much another woman in their social network enjoyed dating the man than when they read the man's personal profile and saw his photograph. Men and women made more accurate predictions about how they would feel after being evaluated by a peer when they knew how another person in their social network had felt after being evaluated than when they previewed the evaluation itself. Although surrogation trumped simulation, both participants and independent judges had precisely the opposite intuition. By a wide margin, they believed that simulation was more likely than surrogation to produce accurate affective forecasts.

Two points are worthy of note. First, surrogation is by definition superior to simulation when individual differences are relatively small and simulations errors are relatively large, and it is inferior to simulation when the opposite is true. Although there is no way to know which of these is more typical in everyday life, the situations we studied—dating and peer-evaluation—are by no means exotic.

Second, although our experiments demonstrate the power of surrogation, they also suggest that people may not normally take advantage of this power. Our participants mistakenly believed that simulation was the superior strategy even after it had failed them, which suggests that people may be reluctant to engage in surrogation if they have the opportunity to do otherwise...it seems likely that in everyday life, La Rochefoucauld's advice—like the advice of good neighbors—is more often than not ignored. When we want to know our emotional futures, it is difficult to believe that a neighbor's experience can provide greater insight than our own best guess.

Language shapes fundamental unconscious visual perception.

From Thierry et al:

It is now established that native language affects one's perception of the world. However, it is unknown whether this effect is merely driven by conscious, language-based evaluation of the environment or whether it reflects fundamental differences in perceptual processing between individuals speaking different languages. Using brain potentials, we demonstrate that the existence in Greek of 2 color terms—ghalazio and ble—distinguishing light and dark blue leads to greater and faster perceptual discrimination of these colors in native speakers of Greek than in native speakers of English. The visual mismatch negativity, an index of automatic and preattentive change detection, was similar for blue and green deviant stimuli during a color oddball detection task in English participants, but it was significantly larger for blue than green deviant stimuli in native speakers of Greek. These findings establish an implicit effect of language-specific terminology on human color perception.

Previous choice shapes MRI signals reflecting future expectation and choice

An interesting piece from Dolan's group (open access) on correlates of future expected hedonic outcome:

Humans tend to modify their attitudes to align with past action. For example, after choosing between similarly valued alternatives, people rate the selected option as better than they originally did, and the rejected option as worse. However, it is unknown whether these modifications in evaluation reflect an underlying change in the physiological representation of a stimulus' expected hedonic value and our emotional response to it. Here, we addressed this question by combining participants' estimations of the pleasure they will derive from future events, with brain imaging data recorded while they imagined those events, both before, and after, choosing between them. Participants rated the selected alternatives as better after the decision stage relative to before, whereas discarded alternatives were valued less. Our functional magnetic resonance imaging findings reveal that postchoice changes in preference are tracked in caudate nucleus activity. Specifically, the difference in blood oxygenation level-dependent (BOLD) signal associated with the selected and rejected stimuli was enhanced after a decision was taken, reflecting the choice that had just been made. This finding suggests that the physiological representation of a stimulus' expected hedonic value is altered by a commitment to it. Furthermore, before any revaluation induced by the decision process, our data show that BOLD signal in this same region reflects the choices we are likely to make at a later time.

Brain activity related to estimated hedonic experience. Regions in which BOLD response was positively correlated with participants' ratings of estimated hedonic experience included the right and left caudate nucleus, previously associated with reward expectancy (a), as well as the left amygdala (b), and left pregenual anterior cingulate cortex (c), both previously shown to be engaged when imagining positive future autobiographical events.

The decline of science journalism.

Brumfield writes an essay on the rise of science blogging alongside the decay of science journalism:
because of a generalized downturn, especially in newspaper revenues, the traditional media are shedding full-time science journalists...At the same time, researcher-run blogs and websites are growing apace in both number and readership.

An online 'science of happiness' course.

Foundations of Positive Psychology, from the University of Pennsylvania College of Liberal and Professional Studies.

Facebook, Twitter...can evolution keep up with us? A coming crash?

This post continues the thread started in last Monday's post on future shock and yesterday's iParticipate post. I try to stay informed about (and even join, to check out) the emerging connectivity contexts such as Facebook and Twitter (these links are to NY Times articles on these services, some graphics are shown below). All of these can bind us into increasingly complex and numerous interactions at an ever accelerating pace (see also Rapid Publishing). This may be congenial to the 18-30 demographic, but it leaves me with a sense of vertigo and overload. We know that human evolution occurs much more rapidly than previously thought, and that the plasticity of developing brains allows young people to acquire more complex mental abilities. But, how long will it be until our physiological and emotional repertoires, still largely those of our paleolithic ancestors, are sufficiently overwhelmed that the resulting stress and immune dysfunction increases from being a 'problem' to really shutting us down? I find myself wishing there was a STOP! function, with a RESET button, that could start us all over again with the rate knob dialed down ten-fold, in the spirit of slow food.

Facebook just passed the 200 million mark in membership. It started with 17-24 year olds, but the fastest growing member group of members is now over 35. What a 'friend' is on Facebook depends on how you define friend (click to enlarge):


Here is a small subset of the Twitter-verse, a subsection of a larger graphic that focuses on celebrities (click to enlarge):

MindBlog on Twitter

In spite of today's companion post on potential toxic effects of new social phenomena such as Twitter and Facebook, I can't give it a rest, and so have decided to jump in and see what happens. My twitter name is DericBownds. I've put a link to my "tweets" in the left column of the blog under the links to the podcasts. I'm thinking this might be useful not to tell you things like 'now I'm brushing my teeth', but rather to pass on ideas and URLs that I think are interesting, but that are unlikely to make it into a regular post. And to continue my (headache-inducing) entry into the Twitter/Facebook world I've linked the two. I hope I can back track and delete all this if I panic at some point.

Check out this humorous video on the follies:

Want some diet soda?

iParticipate - social participation networks

I guess I am a hard wired old curmudgeon. I wonder how many of you also get an overload headache when confronting this brave new social networking environment on the internet (Facebook, Twitter, etc)? I pass on a few points from an enthusiastic bubbly letter to Science Magazine titled "A National Initiative for Social Participation" which proposes an organized research program to study social action networks:

This program would systematically study the emerging phenomena, determine the sources of success or failure, and disseminate best practices. The payoffs are large enough to warrant an intense national effort akin to NASA's space program or the National Institutes of Health.

Some clips from the letter:

Health discussion groups have long been one of the Internet's success stories. Now, clever entrepreneurs are exploring new social participation ideas with projects such as the www.PatientsLikeMe.com Web site, where users offer their medical experiences in the hope of learning about treatment outcomes from one another. At the same time, these users are building a remarkable resource for medical research and discovery. Physicians have already discussed 30,000 cases at www.sermo.com, where they can offer insights about innovative treatments as well as detect unusual disease patterns. Large corporations also recognize the opportunities and are inviting users to store their medical histories in the Microsoft Health Vault or at Google Health.

Although social networking plays only a small role in national security, community safety could be enormously improved by expanding resident reporting systems, such as www.WatchJeffersonCounty.net, which collects reports of unusual behaviors. These reports provide important clues for civic officials to prevent crimes, control teenage gangs, or simply fix potholes.

The micro-blogging tool Twitter is now rapidly spreading, as users from Orange County fire-fighters to Mumbai police post their 140-character messages about where they are and what they are doing.

The benefits of social media participation are well understood by Obama's staff--during the campaign, they engaged 4 million donors and volunteers. To replicate their success, a National Initiative for Social Participation could stimulate effective collaborations in many professions, restore community social capital, and coordinate national service projects. The challenge is to understand what motivates participants, such as altruism, reputation, or community service. Researchers would have to develop fresh strategies that increased the conversion rates from readers to contributors from the currently typical 100 to 1 to much higher rates. Getting contributors to collaborate for ambitious efforts and to become leaders or mentors are further challenges. Coping with legitimate dangers such as privacy violations, misguided rumors, malicious vandalism, and infrastructure destruction or overload all demand careful planning and testing of potential solutions.

The huge research effort required for a National Initiative for Social Participation would tap the skills of computer scientists to build scalable and reliable systems, interface designers to accommodate diverse user needs, and social scientists to study successes and failures. The risks are substantial, but the payoffs could be enormous.

Markers of conscious access.

An interesting study from Gaillard et. al. :

What is the neural signature of the conscious perception of a visual stimulus? To address this question, we recorded neural activity directly from the brains of human subjects (who were undergoing neural surgery for medical reasons). This rare opportunity afforded greater spatial and temporal resolution than noninvasive methods used previously to probe the neural basis of consciousness. We compared neural activity concomitant with conscious and nonconscious processing of words by using a visual masking procedure that allowed us to manipulate the conscious visibility of briefly masked words. Nonconscious processing of words elicited short-lasting activity across multiple cortical areas, including parietal and visual areas. In sharp contrast, only consciously perceived words were accompanied by long-lasting effects (>200 ms) across a great variety of cortical sites, with a special involvement of the prefrontal lobes. This sustained pattern of neural activity was characterized by a specific increase of coherence between distant areas, suggesting conscious perception is broadcasted widely across the cortex.

The enlightenment returns.

I have been almost reduced to tears of gratitude by Obama's statements on restoring an American government that is guided by rationality and scientific integrity rather than a conservative religious faith that distorts both. Kurt Gottfried and Harold Varmus (see below) write an editorial in Science Magazine that salutes this (Here is the President's memorandum):

The authors of the Declaration of Independence and the Constitution of the United States were children of the Enlightenment. They understood the power that flows from combining human reason with empirical knowledge, and they assumed that the political system they were creating would thrive only in a culture that upheld the values of the Enlightenment. And thrive it did, in large part because our people and government upheld those values throughout most of U.S. history. Recently, however, the precepts of the Enlightenment were ignored and even disdained with respect to the manner in which science was used in the nation's governance. Dogma took precedence over evidence, and opinion over facts. Happily, as was made clear by two policy announcements by President Barack Obama on 9 March 2009, the break in the traditionally harmonious relationship between science and government is now ending

As the president put it, "promoting science isn't just about providing resources--it is also about protecting free and open inquiry … free from manipulation or coercion, and listening to what [scientists] tell us, even when it's inconvenient--especially when it's inconvenient." In using the words "manipulation" and "coercion," the president was not speaking purely in the abstract; he was alluding to recent breaches of a code to which government must adhere if science is to play its proper role in advising the government on such complex issues as public health, climate change, or environmental protection. When the government systematically disregards this code, it undermines the historic role of science as a bulwark of an enlightened democracy.

In the president's Memorandum on Scientific Integrity last week, addressed to the heads of all executive departments and agencies, he directed those officials to neither suppress nor alter scientific and technological findings solicited in the process of policy formulation. He also asked that scientific information developed or used by the government be made readily available to the public. To put these directives in place, the president requested the director of the Office of Science and Technology Policy to develop, within 120 days, recommendations "designed to guarantee scientific integrity throughout the executive branch" and to ensure "that scientific data is never distorted or concealed to serve a political agenda."

(Kurt Gottfried is a cofounder of the Union of Concerned Scientists and chair of its board of directors. He is professor of physics emeritus at Cornell University. Harold Varmus is president of the Memorial Sloan-Kettering Cancer Center, a cochair of the President's Council of Advisors on Science and Technology, and a former director of the National Institutes of Health.)

Brain structures that correlate with impulse control in boys.

From Boes et al.:

Emerging data on the neural mechanisms of impulse control highlight brain regions involved in emotion and decision making, including the ventromedial prefrontal cortex (vmPFC), anterior cingulate cortex (ACC) and amygdala. Variation in the development of these regions may influence one's propensity for impulsivity and, by extension, one's vulnerability to disorders involving low impulse control (e.g. substance abuse). Here we test the hypothesis that lower impulse control is associated with structural differences in these regions, particularly on the right side, in 61 normal healthy boys aged 7–17. We assessed parent- and teacher-reported behavioral ratings of impulse control (motor impulsivity and non-planning behavior) in relation to vmPFC, ACC and amygdala volume, measured using structural magnetic resonance imaging and FreeSurfer. A regression analysis showed that the right vmPFC was a significant predictor of impulse control ratings. Follow-up tests showed (i) a significant correlation between low impulse control and decreased right vmPFC volume, especially the medial sector of the vmPFC and (ii) significantly lower right vmPFC volume in a subgroup of 20 impulsive boys relative to 20 non-impulsive boys. These results are consistent with the notion that right vmPFC provides a neuroanatomical correlate of the normal variance in impulse control observed in boys.

Future shock...

I found this video about the growth of information interesting and overwhelming...you will want to turn down the volume a bit. Again, a tip of the hat to my son Jon for finding it.

Restore damaged brain circuits with light...

I generally don't delve into cellular and molecular stuff in this blog (even though my previous lab research was at this level), but sometimes a trick comes along that is so neat that I want to mention it. Alilain et al. manage to restore breathing in rodents with acute spinal cord injury by infecting neurons that constitute the phrenic motor nucleus with a sindbis virus that expresses an algal light-gated ion channel that activates nerve cells by driving cation influx when illuminated with blue light, and also expresses green fluorescent protein (to visualize the nerve cells that have taken up the virus). The authors were able to both visualize and photostimulate the target cells that directly innervate the diaphragm muscles. Here is their abstract, following by a summary graphic from the review by Arenkiel and Peca.

Paralysis is a major consequence of spinal cord injury (SCI). After cervical SCI, respiratory deficits can result through interruption of descending presynaptic inputs to respiratory motor neurons in the spinal cord. Expression of channelrhodopsin-2 (ChR2) and photostimulation in neurons affects neuronal excitability and produces action potentials without any kind of presynaptic inputs. We hypothesized that after transducing spinal neurons in and around the phrenic motor pool to express ChR2, photostimulation would restore respiratory motor function in cervical SCI adult animals. Here we show that light activation of ChR2-expressing animals was sufficient to bring about recovery of respiratory diaphragmatic motor activity. Furthermore, robust rhythmic activity persisted long after photostimulation had ceased. This recovery was accomplished through a form of respiratory plasticity and spinal adaptation which is NMDA receptor dependent. These data suggest a novel, minimally invasive therapeutic avenue to exercise denervated circuitry and/or restore motor function after SCI.


Figure: (click to enlarge) Phrenic motor neurons in the respiratory circuit show light-induced plasticity. A: anatomical diagram of the respiratory circuit. Dashed blue and red lines represent known ipsilateral and contralateral connections between the ventral respiratory group neurons, whereas the solid gray line represents potential cross talk between the phrenic motor neurons. Lesion region is highlighted in addition to the neurons targeted for Channelrhodopsin-2 (ChR2) expression (green circles). B: cellular model of how light-gated ion influx leads to classic potentiation. Photostimulation of ChR2 drives rapid cation influx, which in turn removes N-methyl-D-aspartate receptor (NMDAR) block and allows sparse glutamate signaling to activate NMDARs. NMDAR activation might then mediate classic potentiation mechanisms by promoting AMPA receptor insertion.

Digit ratios and high frequency trading

As a followup to my Jan 16 posting on this topic, I pass on a 'letters to the editor' exchange.
From Kobe Miller:

The article by Coates et al. adds interesting evidence that a low 2D:4D ratio in men predicts success, not only in sports or music, but also in job performance. According to the authors, low-2D:4D traders perform better (i.e., they earn more) because of basic characteristics: rapid visuomotor scanning and physical reflexes. However, they overlook another frugal explanation for their findings. Recently, it has been shown that low-2D:4D men react much more strongly on performance feedback than high-2D:4D men, irrespective of the performance itself. When men with a low 2D:4D ratio find themselves in a subordinate status position (e.g., when they lose a game), they might react strongly, e.g., by acting impulsively, or perhaps even abandoning the activity if possible. Following this rationale, my hypothesis is that low-2D:4D men want to excel and therefore will look for a specific domain (in both hobbies and jobs) where they have the abilities to excel. This idea might help to explain why a low 2D:4D ratio in men is related to better performance in completely different domains such as sports and music.The same mechanism might also lead to a better performance in trading in the financial world but needs not be limited to this type of job. I expect low-2D:4D people to outperform high-2D:4D people in all kind of competitive jobs, sports, and other activities, not because of specific physical characteristics, but because of one specific psychological characteristic: a higher need for achievement.

From the original author, Coates:

Kobe Millet, in a letter commenting on the correlations we found between digit ratios and success in high-frequency trading, suggests that digit ratios gauge the psychological need to excel rather than a physiological characteristic. However, if this were true, then we would find low 2D:4D among successful people of most occupations, but I do not believe we do. One study, for example, found that faculty in the math and science departments of universities had higher more-feminine digit ratios. Furthermore, several digit-ratio studies have controlled for effort and found that relative performance in many sports is predicted by 2D:4D independently of training intensity. Lastly, our own findings show that a lower 2D:4D predicts greater trading profit and loss when the volatility of the market increases, higher volatility demanding faster reaction times. This result, together with the sporting studies mentioned above, suggests that a physiological trait rather than a psychological one is at least partly responsible for success in these fields.

We should, however, point out that our study could not fully test for the mechanism underlying the correlations between trading success and digit ratio. Only laboratory work can establish this mechanism. Our study rather was a piece of field work, a type of study we feel is sadly lacking in the new subject of neuroscience and economics. In field work, you forgo the ability to establish mechanism, but what you lose in rigor you pick up in relevance.

We are all wired differently - first analysis of a mammalian "connectome"

In a striking demonstration, Lu et al have shown that even for one of the smallest muscles in a mouse, the wiring diagram differs between two individuals, and even between the left and right sides of the same mouse. Almost every axon was longer than optimal, breaking a long-held assumption that the total wiring length in a branched axon should be minimized, since the energy costs for conduction increase with length. From Richard Robinson's review:

A complete wiring diagram—where axons go, how they branch, and where they link to muscle—has been developed for roundworms, but never before for a mammal. Performing the same feat in the mouse has presented an enormous technical challenge because of the larger size and complexity of the nervous system. The authors chose to study the interscutularis muscle, which connects the base of the ear to the middle of the skull, because it was small, accessible, and innervated by relatively few neurons...Using mice whose cells all bore a fluorescent tag, and a confocal microscope with a computer-controlled, motorized stage, the authors took thousands of individual photographs and reconstructed them to trace individual axons as they stretched across the skull, entered the muscle, branched repeatedly, and ultimately formed synapses with individual muscle fibers.

In the worm, the routes taken and connections made by axons are highly stereotyped, indicating a high degree of genetic control. But in the mouse, the actual number of axons innervating a single muscle ranged from 13 to 16, differing between mice and even between the left and right sides of the same mouse. Axonal length, including all the branches, varied much more widely, from 1.5 millimeters to 13.3 millimeters, and the number of synapses formed by a single axon ranged from a low of one (for an axon that didn't branch at all) to a high of 37. The branching pattern of axons that innervate a similar number of muscle fibers from different muscles also differed significantly, suggesting that unlike in the worm, branching in the mammal is not a deterministic process; instead it is governed by some general developmental rules, while the details of final connection are shaped by contingencies, as excess synapses are pruned.

Observing a brain rewiring itself

Our motor cortex has a topographic representation of our bodies (a homunculus), as shown in the figure. It has generally been assumed that this organization is "hard wired" by genetic instructions. Stoeckel et al. have now made the fascinating observation that in subjects with congenitally compromised hand function and compensatory skillful foot use, a representation of the foot appears in the vicinity of the normal hand area. Their results imply that during early motor development experience may play a more critical role in the shaping of genetically determined neural networks than previously assumed.

I feel what you feel if we are similar

From Serino et al.:

Social interactions are influenced by the perception of others as similar or dissimilar to the self. Such judgements could depend on physical and semantic characteristics, such as membership in an ethnic or political group. In the present study we tested whether social representations of the self and of others could affect the perception of touch. To this aim, we assessed tactile perception on the face when subjects observed a face being touched by fingers. In different conditions we manipulated the identity of the shown face. In a first experiment, Caucasian and Maghrebian (Northern African) participants viewed a face belonging either to their own or to a different ethnic group; in a second experiment, Liberal and Conservative politically active participants viewed faces of politicians belonging to their own or to the opposite political party. The results showed that viewing a touched face most strongly enhanced the perception of touch on the observer's face when the observed face belonged to his/her own ethnic or political group.