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birth_cover_500 Gary Marcus’ The Birth of the Mind keyed me in to the fact that claims of neural plasticity often also suggest that the brain can not completely compensate for alterations structure. This was relevant in his discussion of mental modularity, but it is something to keep in mind whenever you encounter “amazing” instances of people who survive damage to their brain. A case in point, Woman of 24 found to have no cerebellum in her brain:

… woman has reached the age of 24 without anyone realising she was missing a large part of her brain. The case highlights just how adaptable the organ is.

The discovery was made when the woman was admitted to the Chinese PLA General Hospital of Jinan Military Area Command in Shandong Province complaining of dizziness and nausea. She told doctors she’d had problems walking steadily for most of her life, and her mother reported that she hadn’t walked until she was 7 and that her speech only became intelligible at the age of 6.

Yes, a case of the adaptability of the brain. But she still has problems walking steadily, and that’s not a trivial matter for an “upright ape.” The structures of our brains are not coincidence, which can be discarded without consequence.

 
• Category: Science • Tags: Neuroscience 
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I remember the specific moment when I was 13 that I became aware of the 1950s hit “Why Do Fools Fall in Love” by Frankie Lymon & The Teenagers. I’m rather sure I heard it before, but it didn’t penetrate my consciousness. But as we all know puberty changes things, and the idea of love becomes more comprehensible. As I’ve grown older I’ve also started to ponder the lyrics a bit more. Not out of any sense of sensitivity toward music criticism, but because of the evolutionary implications. Here are some relevant sections:

Why do fools fall in love?
Why do birds sing so gay?
And lovers await the break of day
Why do they fall in love?

Love is a losing game
Love can a be shame
I know of a fool

And lovers await the break of day?

Why does my heart skip a crazy beat?
Before I know it will reach defeat!

 

A few quick points about these selections of the lyrics. They allude to the possibility of love among birds. This is appropriate because birds are notionally monogamous. Though the anthropomorphizing is probably not for the best, there is a real analogy with the pair bond; the behavior of lovers has analogs in the wider world. It’s not just a human creation. Second, the reference to the skipping of one’s heart beat points to the physiological reality of how love manifests itself. Love and infatuation aren’t abstract concepts, they’re made real by the fact that they change your own internal equilibrium. Third, love is often unrequited. The physiological responses in this case are not very appealing, and likely they put one in a vulnerable situation, increasing stress and reducing fitness.

So the question then comes back to why? And this is an evolutionary question. In some domains of biology one focuses on proximate function and mechanism, but in evolutionary biology it is important to consider the contextual whole, and evaluate the trait’s function and utility over time. If romantic love is so often miserable, then it must pay in some fashion, no?

One possibility is that it is a necessary side effect of other important traits and functions. For example, romantic love could be modeled as a secondary derivative of the love that mammals feel toward their offspring. Or more precisely, the capacity for love that one exhibits toward the offspring one is born with becomes co-opted by other relationships. And then there is the idea of love as an invention of a particular culture. This seems ridiculous, but I have read before that romantic love was invented by the Arab or Provencal poets of the High Middle Ages! In a straightforward sense this seems false on the face of it. The tensions which arise due to romantic love seem to figure in the myths of all people. Love is primal, a genuine human universal, and the constraint of love is a cultural invention, not love itself. In cultures where marital bonds are controlled by the family love is bad only insofar as it conflicts and interferes with other socially valued interests. The banishment of love is a necessary evil (contrast this with homosexuality, which is labeled ‘unnatural,’ not just inconvenient).

The evolutionary biology and neuroscience of love has been addressed in several books. Geoffrey Miller’s The Mating Mind, and Helen Fisher’s Why We Love: The Nature and Chemistry of Romantic Love. My mild frustration is that more scholars haven’t taken up the project of constructing a scientific study of the question of love. Though I am generally skeptical of most strict genetically determinist “hard-wired” arguments, in the case of love I believe that this capacity is lacking only in those with pathology (I hope as whole genome sequencing to high coverage comes online we’ll see that sociopathic tendencies aren’t low frequency morphs, but the tail of the mutational load distribution).

When reading Nature’s Oracle I was struck by the author’s descriptions of W. D. Hamilton’s darker conclusions derived from evolutionary biology, in particular the tendency toward faction and inter-group conflict. And yet though I’m no acolyte of Rousseau there is hope, because the germ of human goodness is also in our natures. It’s cliche (and correct) to say that it’s not about nature vs. nurture, but nature and nature. But it’s also true that nurture can cultivate aspects of our nature. With eyes wide open perhaps we can allow for the flourishing of what is right, good, and true in the world.

(Republished from Discover/GNXP by permission of author or representative)
 
• Category: Science • Tags: Anthropology, Neuroscience 
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Gawker published a piece on the neurological problems which might result in pedophilia, and naturally a lot of shock and disgust was triggered. The piece is titled Born This Way: Sympathy and Science for Those Who Want to Have Sex with Children. This isn’t something you want to click through to lightly. So fair warning. The neurobiological material did pique my interest:

“There was nothing significant in the frontal lobes or temporal lobes,” says Cantor. “It turned out the differences weren’t in the grey matter. The differences were in the white matter.”

“The white matter” is the shorthand term for groupings of myelinated axons and glial cells that transmit signals throughout the gray matter that composes the cerebrum. Think of the gray matter like the houses on a specific electricity grid and the white matter like the cabling connecting those houses to the grid.

“There doesn’t seem to be a pedophilia center in the brain,” says Cantor. “Instead, there’s either not enough of this cabling, not the correct kind of cabling, or it’s wiring the wrong areas together, so instead of the brain evoking protective or parental instincts when these people see children, it’s instead evoking sexual instincts. There’s almost literally a crossed wiring.”

The good news, according to Cantor, is that it if they can figure out how the wiring gets crossed, they might be able to suggest ways pregnant mothers can help ensure their baby is unlikely to be born a pedophile. “It is quite possible that one or more components of the process are related to prenatal stresses like poor maternal nutrition, toxin exposure, ill health, or poor health care,” he says. “If so, then improving health and health care in general may reduce the numbers of people vulnerable to developing pedophilia, as well as other problems.”


Fair enough as far as that goes. I think it is important to look at controversial and explosive topics objectively. You don’t always need to be objective about the issue at hand, or lack opinions, but you need to step back and analyze in a value-free manner on occasion. For me the confusing thing is that to my knowledge Gawker today takes conventionally Leftish stances on “nature vs. nurture” type issues. Would they post something by Steven Pinker defending the concept of robust behavioral differences between the sexes? So why are they sticking their necks out here?

In any case, I think the problem with the Gawker piece is that it doesn’t really come off as a cold and rational assessment. Rather, there is genuine sympathy for people who are afflicted with the mental disease of pedophilia. The author finishes:

The old adage is that the true mark of a society is how it treats the weakest in its ranks. Blacks, women, Latinos, gays and lesbians, and others are still in no way on wholly equal footing in America. But they’re also not nearly as lowly and cursed as men attracted to children. One imagines that if Jesus ever came to Earth, he’d embrace the poor, the blind, the lepers, and, yes, the pedophiles. As a self-professed “progressive,” when I think of the world I’d like to live in, I like to imagine that one day I’d be OK with a man like Terry moving next door to me and my children. I like to think that I could welcome him in for dinner, break bread with him, and offer him the same blessings he’s offered me time and again. And what hurts to admit, even knowing all I know now, is that I’m not positive I could do that.

I’m not a professed “progressive.” I can see where the author is coming from probably (and so can Jonathan Haidt)…but can my progressive readers get into his mind here? Does being progressive mean you can not take into account probability to any extent? That you need to treat people as singular individuals in even the most extreme cases? For example, in the case of a pedophile who has never acted upon their instincts one presumes that they could find social acquaintances who were childless. Many biological dispositions aren’t deterministic, they’re probabilistic. That means controlling or channeling them in non-destructive ways entails changing the situations and contexts one is placed it. That’s not unjust, that’s just common sense. You aren’t a bad person to think it is prudent that someone with pedophile urges should avoid developing close friendships with people with young children.

Many of my liberal readers and friends have expressed the position that if a hereditarian position was true for a range of issue that that would result in a lot of unpleasant normative and political downstream consequences. I’m generally skeptical of this position. I have plenty of hereditarian ideas, and believe it or not I’m not a hateful Nazi. But the response above to the possibility that pedophilia has a biological basis does make me reconsider. I’m not a neo-Freudian, so I had always assumed that this behavior and tendency had neurobiological roots. That didn’t make me any more sympathetic to individuals who committed unmentionable acts. The world isn’t fair, unfortunately.

(Republished from Discover/GNXP by permission of author or representative)
 
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I approached Sheril Kirshenbaum’s The Science of Kissing: What Our Lips Are Telling Us with some trepidation and excitement. The former is a consequence of my hypochondria and its associated germophobia. I have no aversion to kissing in my own life (apologies for divulging personal information), but I did have some worries about having to read about other humans engaged in such an act of hygienic daring. And yet I was excited because I am interested in multidisciplinary explorations of human behavior. And of course I was familiar with the author’s oeuvre, and was expecting an engaging and wide-ranging exploration of the topic at hand.

I was not disappointed. The Science of Kissing is an intellectual full-court press; every conceivable discipline of relevance is brought into the mix. History, ethnography, ethology, neuroscience, evolutionary biology, physiology, and epidemiology, all receive attention, to name just a few of the more prominent lenses which the author fits over the course of the narrative. In other words you’re presented with an intellectual buffet. A well rounded meal will require you to sample widely, but if the lack of punctiliousness of Romans in matters of hygiene is not to your taste, you may find a discussion of the latest neuroimaging techniques and their application to matters of behavioral response more to your liking.


After the first chapter one immediately perceives that The Science of Kissing is not a tight and narrowly argued case for a positive hypothesis. Rather, it is more synoptic. Of broad scope, and yet rather tentative in its conclusions. The author makes clear in The Science of Kissing that this stance of humility of what we know is the position which is warranted by the science as it is now: the science of kissing is immature at best. In fact, this reality seems to have been one of the prods for the author’s project. Her own curiosity as to the lack of a general and accessible entry into the literature, provisional as it is, turned into the opportunity to transform her own journey of discovery into a book-length exposition.

Each chapter in The Science of Kissing is rather concise, but they are bracketed into three thematic portions. First, there is an exploration of the ultimate roots of kissing. That is, why? Naturally this entails a historical perspective, both human and natural. This is where the author immediately abdicates any pretense at making a forceful and tight argument which brooks no ambiguity or uncertainty. A book about the science of kissing might plausibly begin by asserting that the phenomenon is a human universal. No, not exactly. The author reviews a diverse range of contemporary and ancient ethnographic reports which indicate a wide variety of cultural attitudes toward kissing and its substitutes.They are often amusing, and it must be said, occasionally kinky. I have admit that the idea of foreplay not including kissing struck me as profoundly alien, but it was a reality check on the presuppositions that we bring to expectations of the plausible range of human behaviors. On the other hand, the deviations from kissing do seem to share general features with the behavior, whether it be an attention to the face or violation of norms of personal space. For example many substitutes for kissing seem to involve a sort of sniffing of the other, and it could be argued that kissing is one particular route to this general behavior of olfactory exchange. It is also notable that kissing can be found among other animals, for example the Bonobo chimpanzee.

As a social species there are a clear range of ultimate rationales for why kissing may emerge. A form of grooming, interpersonal communication, as well as ascertainment of genetic fitness. But as a complex behavior which is culturally modified and channelled the sum of human and natural historical evidence point to kissing as being a specific instantiation of a general phenomenon. Kissing seems to be on the way to becoming a human universal, but that may be a contingent fact of human history. In particular, the rise of European hegemony, and the acceptability of kissing in companionate relationships within this culture (though not exclusively within this culture, as evidenced by records of kissing in the Hebrew Bible and Hindu epics). But the contingency of the phenomenon of kissing does not entail that its emergence was arbitrary. Rather, the balance of evidence seems to suggest that kissing is a phenomenon which we humans are mildly disposed toward. Kissing exists in related taxa and has been independently practiced across disparate human societies. Ultimately kissing as a universal human phenomenon may not have been inevitable, but it was at least not improbable.

Next The Science of Kissing moves to the proximate: how the phenomenon expresses in a concrete sense. Here’s a chestnut of wisdom: men like sloppy kisses, while women do not. Another: men are much more likely to be willing to have sex with someone without kissing. The author was skeptical about the robustness of such results indicating strong sex differences, and so she decided to do a personal survey. To her surprise these sorts of sex differences were perfectly replicated in her own sample. This is where ultimate causes loom large: males and females have somewhat different sample spaces of possible reproductive strategies as a function of the number of offspring they may have. Women have about ~30 gestations available in their lives. Men on the other hand have a much higher upper bound on the number of offspring they can have via polygyny thanks to the surfeit of sperm. This tension is at the heart of much of evolutionary psychology, so the leveraging of this framework to explain sex differences in kissing seems to be on relatively solid ground.

But the differences between men and women are explored in more than just ultimate abstract causes. The Science of Kissing also delves into behavioral and cognitive neuroscience and genetics, exploring the possible links between chemistry and kissing. Earlier I noted that kissing may serve as a predictor of genetic fitness or compatibility. How? It may be an avenue by which potential mates can assess their long term compatibility, whether through pheromones, or modulation of hormones such as testosterone, oxytocin or epinephrine. Kissing in this telling may be one of the roads which leads to the Rome of pair bonding. This dovetails well with the model where kissing is one of a set of probable behavioral phenomena to facilitate necessary relations for reproductive fitness. The author is admittedly on tendentious ground in this section, but though many of the hypotheses may be falsified, it seems unlikely that all will be.

And then we move to “cooties.” Needless to say this was the chapter which discomfited me the most. And yet the lessons here are rather plain and straightforward. Follow your dentist’s advice. Those of you engaged in promiscuous polyamory may have to worry a bit more than those of us who are not so engaged. And that vampire fad? Don’t get too into biting fetishes unless you want to risk your mortality. Don’t French kiss wild animals. Seriously.

The final in depth section is perhaps one of the more peculiar, and praiseworthy, aspects of The Science of Kissing. Quite often popular science books are written by scientists who focus on their own research, scaffolded with extraneous “hooks” when necessary. If not, they are written by journalists who serve as tour guides to the world of science. Intellectual voyeurs. The author was not reviewing her own research, but she also deviated from the “outsider” viewer as well. She managed to obtain the collaboration of David Poeppel at NYU to perform a set of experiments utilizing magnetoencephalography (MEG). I won’t detail the experiments and their results, except to relay that the author had some “interesting” adventures with finding images of same sex kissing on Google Images. The Science of Kissing begins as a readable but rather conventional popular science book, if a touch on the cautious side. But through this survey of a real set of experiments inspired by the author’s curiosity in researching The Science of Kissing you get a taste of the excitement and possibilities of science as an enterprise and method, rather than a set of results and “facts.” To me this portion seems almost a challenge to the complacent preconceptions of the public as to what science is, as opposed to how science operates. Instead of an answer one is left with a series of questions.

The Science of Kissing tells its story with economy. The chapters are short and to the point. But quite often there is a density of fact which will satisfy. The qualified and nuanced take on many of the issues will appeal to the nerd, who yearns to dig between the layers of the scholarly strata. Quite often I found myself putting the book down to do further research on Wikipedia or Google Scholar. This is not a book which punches you in the face with a bold and explosive thesis. When it comes to human behavior and biology robust bold explosions are hard to come by, so I believe that this tack was the honest one. The author navigates deftly between the shoals of the “blank slate” model dominated by nearly arbitrary historical contingency and a naive genetic determinism which is hard to justify based on the empirical data.

In some ways kissing is something which has two faces. On the one hand most people would not deny its central integrity to our most personal relationships. It seems far more substantive a matter than whether you shake someone’s hand. And yet kissing may also seem a sliver of a window upon the broad expanse which is human nature. The Science of Kissing illustrates that this is not so; an exploration of the phenomenon of kissing allowed the author to shine a bright light on the gamut of the human sciences, from those which focus on the ultimate biological bases of behavior, to those which characterize its proximate manifestations. Perhaps it is the omnipresent and most personal of behaviors which may serve as the most representative windows upon how our biological inheritance interfaces with the environment in which we express our predispositions and needs. How about the science of laughing? Crying? Blinking? The possibilities are endless. But this was an excellent start.

Note: Also follow the author’s posts on the book.

(Republished from Discover/GNXP by permission of author or representative)
 
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Real vs Placebo Coffee. There’s a real effect. Though interestingly those who secretly were given decaf didn’t notice it in their self-reports.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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ScienceDaily, Genetic Variations Linked To Brain Size. The write-up seems a bit garbled to me, so probably best to read the paper, A common MECP2 haplotype associates with reduced cortical surface area in humans in two independent populations, when it is live on the PNAS site.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Genetics, Neuroscience 
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A new neuroscience take on moral psychology, Right or Wrong? The brain’s fast response to morally objectionable statements:

How does the brain respond to statements that clash with a person’s value system? We recorded EEG 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 200-250 milliseconds after the first word at which a statement begins to 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, indicating 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.

You can read a preprint at the link, or, ScienceDaily‘s summary. The authors reference Jonathan Haidt’s findings, which suggest that moral values have less to do with reason than emotionally colored intuition. Anyone familiar with the importance of emotion in decision making and judgement, or the heuristics & biases literature, won’t be surprised by these results. The main obvious implication is that yes, psychology does manifest biophysically in the brain.

My interest is not in general average propensities, but individual differences. Bryan Caplan has shown for example that intelligence is correlated with economic rationality. To some extent one might view this as another fruit of high g, but another unrelated component might be the way in which emotions express themselves when faced with assertions counter to one’s intuition or moral outlook. One problem that I face with many extremely intelligent individuals is a reflexive aversion to entertaining possibilities or thought experiments which are abhorrent to their moral or political orientation. One the one hand these emotional responses probably have an important role in sorting and ranking the order in which one performs cognitive tasks. Many thought experiments are after all useless. But when feeling has reason too tightly on the leash there is unfortunately a tendency for it to constrain the search space of intellectual possibilities.

It would be interested to see if there is an aspect of rationality which is related to the ability of individuals to suppress or shunt aside the power of emotional response, a dynamic which I presume could be ferreted out by various imaging techniques. As an analogy, those with higher g may have more powerful tools, but to some extent there is something to be said for willingness to use the tools one has on hand as well.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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Asymmetric fMRI adaptation reveals no evidence for mirror neurons in humans:

Neurons in macaque ventral premotor cortex and inferior parietal lobe discharge during both the observation and the execution of motor acts. It has been claimed that these so-called mirror neurons form the basis of action understanding by matching the visual input with the corresponding motor program (direct matching). Functional magnetic resonance imaging (fMRI) adaptation can be used to test the direct matching account of action recognition by determining whether putative mirror neurons show adaptation for repeated motor acts independently of whether they are observed or executed. An unambiguous test of the hypothesis requires that the motor acts be meaningless to ensure that any adaptation effect is directly because of movement recognition/motor execution and not contextually determined inferences. We found adaptation for motor acts that were repeatedly observed or repeatedly executed. We also found adaptation for motor acts that were first observed and then executed, as would be expected if a previously seen act primed the subsequent execution of that act. Crucially, we found no signs of adaptation for motor acts that were first executed and then observed. Failure to find cross-modal adaptation for executed and observed motor acts is not compatible with the core assumption of mirror neuron theory, which holds that action recognition and understanding are based on motor simulation.

Many great claims have been made for mirror neurons. V.S. Ramachandran said on Edge MIRROR NEURONS and imitation learning as the driving force behind “the great leap forward” in human evolution.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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A Genetically Mediated Bias in Decision Making Driven by Failure of Amygdala Control:

Genetic variation at the serotonin transporter-linked polymorphic region (5-HTTLPR) is associated with altered amygdala reactivity and lack of prefrontal regulatory control. Similar regions mediate decision-making biases driven by contextual cues and ambiguity, for example the “framing effect.” We hypothesized that individuals hemozygous for the short (s) allele at the 5-HTTLPR would be more susceptible to framing. Participants, selected as homozygous for either the long (la) or s allele, performed a decision-making task where they made choices between receiving an amount of money for certain and taking a gamble. A strong bias was evident toward choosing the certain option when the option was phrased in terms of gains and toward gambling when the decision was phrased in terms of losses (the frame effect). Critically, this bias was significantly greater in the ss group compared with the lala group. In simultaneously acquired functional magnetic resonance imaging data, the ss group showed greater amygdala during choices made in accord, compared with those made counter to the frame, an effect not seen in the lala group. These differences were also mirrored by differences in anterior cingulate-amygdala coupling between the genotype groups during decision making. Specifically, lala participants showed increased coupling during choices made counter to, relative to those made in accord with, the frame, with no such effect evident in ss participants. These data suggest that genetically mediated differences in prefrontal–amygdala interactions underpin interindividual differences in economic decision making.

Check out the Wikipedia entry on 5-HTTLPR; lots of behavioral phenotypes associated with this variant. ScienceDaily:

The researchers also measured the degree of interaction, or connectivity, between the amygdala and the prefrontal cortex, the brain region most implicated in human intelligence, personality and decision making. When resisting the frame effect, the participants with two copies of the long variant had stronger connectivity between the prefrontal cortex and amygdala, while those with a pair of short variants did not.

“This difference in connectivity is really interesting,” says Dr Roiser. “It suggests that the volunteers carrying the long variant might regulate automatic emotional responses, which are driven by the amygdala, more efficiently, lessening their vulnerability to the framing effect.

“This one gene cannot tell the whole story, however, as it only explains about ten per cent of the variability in susceptibility to the framing effect. What determines the other ninety per cent of variability is unclear. It is probably a mixture of people’s life experience and other genetic influences.

“An interesting question would be whether the gene might affect real-life decision-making. For example, traders in banks need to make quick and accurate estimations of risk and consistent decisions, no matter how the information is presented to them. So you might hypothesise that traders with the long genetic variant would make more consistent decisions, though this needs to be tested in future research.”

So this genetic variation only explains 10% of the variation within the population when it comes to frame effect in behavioral economics. Fair enough. But, I do wonder if in the current political environment fewer would oppose genetically black-balling individuals with the short variants of 5-HTTLPR from becoming traders! (I’m not proposing this seriously myself, but I think there might be some amygdala-driven acceptance of this sort of genetic profiling right now even if the returns are small)

(Republished from GNXP.com by permission of author or representative)
 
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Follow up to the post below, Jake Young at Pure Pedantry has a thorough review.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: IQ, Neuroscience 
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Transcriptional neoteny in the human brain:

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.

Here are the 4 classes of gene expression trajectories they’re focusing on:

They found that there was a relative enrichment of genes which exhibited human neoteny, with delayed expression:

Finally:

We analyzed the genes affected by the neotenic shift in the human prefrontal cortex with respect to their histological location, function, regulation, and expression timing. First, with respect to their histological location, we used published gene expression data from human gray and white matter…and found that, in both brain regions, human neotenic genes are significantly overrepresented among genes expressed specifically in gray matter…but not among genes expressed in white matter….

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Cognitive Science, Neuroscience 
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Readers of this weblog from back in 2002 know that we used to point to Paul Thompson’s research. So see this, Genetics of Brain Fiber Architecture and Intellectual Performance:

The study is the first to analyze genetic and environmental factors that affect brain fiber architecture and its genetic linkage with cognitive function. We assessed white matter integrity voxelwise using diffusion tensor imaging at high magnetic field (4 Tesla), in 92 identical and fraternal twins. White matter integrity, quantified using fractional anisotropy (FA), was used to fit structural equation models (SEM) at each point in the brain, generating three-dimensional maps of heritability. We visualized the anatomical profile of correlations between white matter integrity and full-scale, verbal, and performance intelligence quotients (FIQ, VIQ, and PIQ). White matter integrity (FA) was under strong genetic control and was highly heritable in bilateral frontal….bilateral parietal…and left occipital…lobes, and was correlated with FIQ and PIQ in the cingulum, optic radiations, superior fronto-occipital fasciculus, internal capsule, callosal isthmus, and the corona radiata…for PIQ, corrected for multiple comparisons). In a cross-trait mapping approach, common genetic factors mediated the correlation between IQ and white matter integrity, suggesting a common physiological mechanism for both, and common genetic determination. These genetic brain maps reveal heritable aspects of white matter integrity and should expedite the discovery of single-nucleotide polymorphisms affecting fiber connectivity and cognition.

Here’s the summary at ScienceDaily.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: IQ, Neuroscience 
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If you read The Corner you know that John has been in Tucson for the Toward a Science of Consciousness conference the past week. He’s now assembled his reflections.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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A comparison of resting-state brain activity in humans and chimpanzees:

In humans, the wakeful resting condition is characterized by a default mode of brain function involving high levels of activity within a functionally connected network of brain regions…We find that, like humans, chimpanzees show high levels of activity within default mode areas, including medial prefrontal and medial parietal cortex. Chimpanzees differ from our human sample in showing higher levels of activity in ventromedial prefrontal cortex and lower levels of activity in left-sided cortical areas involved in language and conceptual processing in humans. Our results raise the possibility that the resting state of chimpanzees involves emotionally laden episodic memory retrieval and some level of mental self-projection, albeit in the absence of language and conceptual processing.

Any cognitive neuroscience people want to chip in?

Addendum: Readers might be interested in this post by Chris Chatham on primate evolution & handedness & neuroscience.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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Be Good Now, Or Else:

Neuroscientists have taken a step closer to a physiological explanation of why some people work and play well with others. Two areas in the brain appear to have key roles in how people conform with social norms. These parts of the brain mature slowly, which may help explain why adolescents are less easily cowed by the threat of punishment than are adults.

Chris likes to joke that cognitive neuroscience basically tells us that “stuff happens in the brain.” There’s some truth in that, but I still think that methods like fMRI are going to be an important piece of the bigger jigsaw puzzle that is human nature. For example, variation in fMRI combined with behavior genetic expectation that said variation should have a biological (genetic) underpinning seems a lot more compelling than either datum alone.

Also, ever notice how some people who were assholes when they were kids turn out normal? The conventional assumption is that people grow up and learn, but perhaps they couldn’t learn for neurological reasons until they grew up!

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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Chris reviews a study on the cognitive neuroscience of liberalism & conservatism (The LA Times has an article on the study). He’s skeptical of the relevance and coherency of the findings. I would add that the heritability of political orientation is about 0.5, so I don’t doubt that there’s some innate predispositions which predispose individuals toward particular world views. Rather, I think this is analogous to genome surveys which can detect natural selection, but can’t necessarily offer a plausible rationale for why selection occurred on a particular locus. Finally, I would add that my own hunch is that libertarians would probably be with the liberals here; because fundamentally there are some core axioms (individual self-actualization) and ends (a materialistic utilitarianism) which the Left and libertarians share despite the latter’s traditional location on the Right.

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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There’s a new paper which uses fMRI to localize an area of the brain which seems to be involved in preventing impulsive actions. I can’t but help think that something like this, which might vary from person to person, could be one of the upstream factors which shapes individual time preference. This is on my mind because I just finished Farewell to Alms by Greg Clark, and change in mean time preference is at the root of a shift in behavior which he believes primed the English (among others) for their breakout from the Malthusian trap. But it is one thing to posit a behavior whose distribution is governed by selective forces of a quantitative genetic nature, the case for any such arguments gains a boost if one could tunnel down to the level of biophysical specificity so as to assess variation across individuals and populations.

In other news, watch this space. Our own Herrick has a “10 questions” with Clark pending, so keep an eye out (that means you Ambrosini Critique).

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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I’m assuming that readers who know some neuroscience can make more sense of this paper, Monotonic Coding of Numerosity in Macaque Lateral Intraparietal Area (Neurons for Numerosity: As Quantities Increase, So Does the Neuronal Response, a summary for the general public). But this part of the abstract is what caught my eye:

The responses of these neurons resemble the outputs of “accumulator neurons” postulated in computational models of number processing. Numerical accumulator neurons may provide inputs to neurons encoding specific cardinal values, such as “4,” that have been described in previous work. Our findings may explain the frequent association of visuospatial and numerical deficits following damage to parietal cortex in humans.

I’m sure most of you know know in psychometrics there is a correlation between visuospatial & mathematical aptitude. There is one group though which decouples these two traits: Ashkenazi Jews (who are weak on visuospatial tests in relation to their mathematical aptitude).

(Republished from GNXP.com by permission of author or representative)
 
• Category: Science • Tags: Neuroscience 
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Razib Khan
About Razib Khan

"I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. If you want to know more, see the links at http://www.razib.com"