neurodudes

http://www.nytimes.com/2007/07/08/magazine/08sociability-t.html

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This article (from last December) has identified what it thinks are 244 new human microRNAs from human fetal brain tissue, of which 20 seem to be species-specific (see figure 1d). They also mention 2 previously-known human-specific microRNAs.

Eugene Berezikov, Fritz Thuemmler, Linda W van Laake1, Ivanela Kondova, Ronald Bontrop, Edwin Cuppen and Ronald H A Plasterk Diversity of microRNAs in human and chimpanzee brain. Nature Genetics – 38, 1375 – 1377 (2006)

Science has a special online feature this week on behavioral science. One of the articles is a review by Paul Bloom and Deena Skolnick Weisberg (a fellow SymSys alum!) presents some interesting evidence about how dualistic ideas about mind/brain are present from an early age. They state:

Another consequence of people’s common-sense psychology is dualism, the belief that the mind is fundamentally different from the brain (5). This belief comes naturally to children. Preschool children will claim that the brain is responsible for some aspects of mental life, typically those involving deliberative mental work, such as solving math problems. But preschoolers will also claim that the brain is not involved in a host of other activities, such as pretending to be a kangaroo, loving one’s brother, or brushing one’s teeth (5, 17). Similarly, when told about a brain transplant from a boy to a pig, they believed that you would get a very smart pig, but one with pig beliefs and pig desires (18). For young children, then, much of mental life is not linked to the brain.

And,

For one thing, debates about the moral status of embryos, fetuses, stem cells, and nonhuman animals are sometimes framed in terms of whether or not these entities possess immaterial souls (20, 21). What’s more, certain proposals about the role of evidence from functional magnetic resonance imaging in criminal trials assume a strong form of dualism (22). It has been argued, for instance, that if one could show that a person’s brain is involved in an act, then the person himself or herself is not responsible, an excuse dubbed “my brain made me do it” (23).

The authors conclude that adult resistance to science is strongest in fields where scientific claims are contested by the society (that is, contested by non-science alternatives rather than by scientific uncertainty). They claim that this accounts for the difference in the United States (versus other countries with less vociferous advocacy of non-science) in the resistance to the central tenets of evolutionary biology and neuroscience.

I think this says something important about science education, namely that it should start earlier in life. And there’s no reason that neuroscience should be left as a “college-level” subject. I think modern neuroscience has progressed to the point where we can confidently teach some basics at a high-school or earlier stage. Judging from my own experiences, I think the desire to learn about neuroscience is certainly there in younger children.

Comment on “Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens” — Yu et al. 316 (5823): 370b — Science

Some new evidence contradicting previous claims that a particular haplotype of the ASPM gene was selected. We posted about some related work in 2005.

An excerpt:

We also assessed evidence for selection at ASPM by carrying out the long-range haplotype (LRH) test (9). This test assesses whether a haplotype is too young to have risen to its frequency without selection. The LRH test is not affected by uncertainty in recombination rate estimates. We compared LRH results for the A44871G polymorphism to SNPs of matched frequency in HapMap CEU (3, 10) (Fig. 1C). We observed at least as strong a signal for selection at 90% of the regions examined (3, 11). Several genome-wide surveys using similar methods also failed to find evidence for selection at ASPM in European-derived populations (4, 12, 13). The one survey that did find a signal near ASPM did so only in individuals of Chinese ancestry (13), failing to support the contention of (1) of recent selection in European history. Based on linkage disequilibrium (LD) breaking down within ~100 kb on either side (Fig. 1B), we estimate that the G allele arose in European history at least tens of thousands of years ago and possibly more than 100,000 years ago (14) (table S3 and SOM Text). These dates are difficult to reconcile with selection ~6000 years ago, as suggested in (1).

Saw this book on the Daily Show a few nights ago and it looked interesting: Survival of the Sickest by Sharon Moalem

The author mentioned a theory of schizophrenia as due to toxoplasma infected cats, who are themselves infected by rats carrying the disease. Apparently, when the rat is infected, the toxoplasma alters the behavior of the rat such that it doesn’t run away from a cat. So, the parasite ensures its survival.

Although I’m not a big fan of just-so evolutionary explanations in general, this book sounds like it might be a fun read.

In the provocative-hypothesis-of-the-week department:

Kevin Lafferty, a parasitologist, has put forth the idea that a fairly ubiquitous parasite (infecting O(10%) of Americans, and up to 2/3 of people in places like Brazil) is responsible for some of the diversity of human culures (1). The parasite uses common housecats to increase its transmission to the next host in the life cycle, and has a subtle effect on human personality, with some studies claiming that it even causes neuroticism, and even schizophrenia. (One clinical report (2) claims that “subjects with latent toxoplasmosis had higher intelligence [and] lower guilt proneness.” Hmm!)

Anyway, Lafferty noted that toxoplasmosis varies in prevalence from world region to world region, and then tries to draw correlates between these prevalences and local cultures:

“Drivers of the geographical variation in the prevalence of this parasite include the effects of climate on the persistence of infectious stages in soil, the cultural practices of food preparation and cats as pets. Some variation in culture, therefore, may ultimately be related to how climate affects the distribution of T. gondii, though the results only explain a fraction of the variation in two of the four cultural dimensions, suggesting that if T. gondii does influence human culture, it is only one among many factors.”

I wonder how one could test this hypothesis? Look for recent immigrants from one culture to another, who have lower Toxoplasmosis incidence? (Preferably finding populations that go in opposite directions, as a control.) Track culture change vs. migration vs. climate change?

Unlikely, perhaps. But nice that people are still thinking big

– Ed

(1) Lafferty, K
Can the common brain parasite, Toxoplasma gondii, influence human culture?
Proceedings of the Royal Society B: Biological Sciences
doi:10.1098/rspb.2006.3641

Picked up by the popular press here

(2) Flegr J, Havlicek J.
Changes in the personality profile of young women with latent toxoplasmosis.
Folia Parasitol (Praha). 1999;46(1):22-8.

A Resilient, Low-Frequency, Small-World Human Brain Functional Network with Highly Connected Association Cortical Hubs (Achard et al., 2006)

A study on network properties of the whole brain (functional connectivity data from fMRI)… interesting to see this type of work published in J. Neurosci. Building on previous fMRI/whole brain connectivity studies, the authors use a set of wavelet basis functions to estimate the correlations between different anatomical regions.

Also includes some analyses on resiliency of the system (via a metric like “largest connected cluster”) to random and targeted attack (ie. node deletion). It would be neat if they also did some analysis of common stroke damage. I would think that a stroke probably doesn’t qualify as a “targeted attack”, in the traditional sense, but, due to the predefined structure of the major circulatory structures (eg. circle of Willis), there are likely regions that are near the most commonly blocked arteries, etc. Perhaps someone with some medical qualifications could weigh in here?

There is also a nice discussion of why the human brain does not appear to be a scale-free network: That nodes do not seem to follow the “rich-get-richer” rule of preferential attachment. Evolutionarily recent structures like prefrontal seem to be among the hubs of the system and older structures like limbic regions do not dominate. Here’s a picture of the connectivity map from the paper:

Full abstract after the jump.
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So, Edge has a new question for 2006 for its All-Stars of Academia to answer: What is your dangerous idea? (Suggested to Edge by Steven Pinker, who perhaps got the idea from a colloquium series at his old haunting grounds.)

Offhand, one might expect a broad range of perceived dangerous ideas, varying by research interests and such. What’s surprising is that many of the luminaries think that the “most dangerous idea” is this particular, same idea: As neuroscience progresses, popular realization that the “astonishing hypothesis” — that mind is brain — will create a potentially cataclysmic upheaval of society as we know and have profound (negative) moral implications as people claim less responsibility for their actions.

Of course, this just isn’t true. But, would you believe that
Paul Bloom,
VS Ramachandran,
John Horgan,
Andy Clark,
Marc Hauser,
Clay Shirky,
Eric Kandel,
John Allen Paulos,
and, in a more genetic context, Jerry Coyne and Craig Venter
are all very worried about this issue? (And I didn’t even read 50% of the Edge dangerous ideas… there might be even more… ) Is this really the most dangerous idea out there to all of these talented thinkers?

I feel strongly that science and morality have always been separate domains and that any worry that, by “debunking” the mind, we automatically become immoral machines is just ridiculous. Through this scientific knowledge, we might gain some humility, maybe better see our close relatedness to nonhuman primates and place in nature, etc., but we’re not going to flip out and become crazed zombies. This just isn’t going to happen.

Does anybody else think that this just isn’t a truly dangerous idea (although certainly an “astonishing” one, in the Crick sense)? Or am I wrong here?

Samples of academic worrying after the jump.
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The nice NYT article on the function of sleep follows on a recent NIH-funded Nature insight series.

Some interesting facts from the NYT article:

• Sleep patterns vary greatly. Some bats sleep 20 hours, giraffes get 2 hours. (hmmm… grad students might be evolving toward giraffes…)
• Sleep has recently been found to occur in invertebrates too. Alternatively stated: Sleep is evolutionarily very old.
• Slow wave sleep is also found in fruit flies. (Divergence from fruit flies for us was 600 million years ago.)
• Some people don’t have any REM sleep. Behaviorally, these people are entirely normal, implying that it’s purpose might not be as obvious as one had thought (ie. required for the preservation of new memories, etc.)
• If you put a bunch of ducks in a row, the ones on the inside will sleep more often with both eyes closed. The ones on the outside will sleep with one eye open and it is (always?) the eye facing outward from the huddle. They are able to “sleep” one half of the brain at a time and, apparently, this sleeping with one eye open was lost in higher mammalian evolution. Fascinating.

The Guardian has posted a very well written and entertaining profile of Robert Trivers, an evolutionary biologist who proposed controversial but influential ideas concerning the emergence of concepts such as altruism and justice as a natural consequence of Darwinian evolution. As with all evolutionary {biology, psychology, computation}, you may readily disagree with the strength of the theories, but it is fun to consider their logical structure. Not to mention Trivers is a guy with an amusing biography and quotes.