neurodudes

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.

Postdoctoral/research scientist positions are available in the inter-disciplinary group of Dmitri Chklovskii at the new Janelia Farm Research Campus of the Howard Hughes Medical Institute located in the suburbs of Washington, D.C. Candidates are expected to have a PhD in neuroscience, physics, computer science or electrical engineering. Most of the work is theoretical or computational and is done in collaboration with several experimental laboratories. Successful applicants will work on projects centered on neuronal circuits such as high-throughput reconstruction of wiring diagrams as well as combining structural and physiological data to infer circuit function. Salary will be commensurate with qualifications. For more information about research directions in the group please see: http://www.hhmi.org/research/groupleaders/chklovskii.html
Interested applicants should send their CV and a statement of research interests to mitya (at) janelia.hhmi.org, and arrange for three recommendation letters to be emailed to me.

Spindle cells, a type of cell previously thought to be found only in great apes, have been found in large whales. Spindle cells are also called Von Economo neurons.

(more…)

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 very nice neuroecon expt. in the newest Nature:

Daw et al. find that humans choose between multiple slot machines (with different payoff probabilities) based on expected value (versus just going with the highest probability one most of the time and then randomly choosing another one every so often). Then, with fMRI, they find brain areas correlated with different value predictions.

News & Views (Daeyol Lee)

Cortical substrates for exploratory decisions in humans (Daw, Dayan)

Abstract:

Decision making in an uncertain environment poses a conflict between the opposing demands of gathering and exploiting information. In a classic illustration of this ‘exploration-exploitation’ dilemma, a gambler choosing between multiple slot machines balances the desire to select what seems, on the basis of accumulated experience, the richest option, against the desire to choose a less familiar option that might turn out more advantageous (and thereby provide information for improving future decisions). Far from representing idle curiosity, such exploration is often critical for organisms to discover how best to harvest resources such as food and water. In appetitive choice, substantial experimental evidence, underpinned by computational reinforcement learning (RL) theory, indicates that a dopaminergic, striatal and medial prefrontal network mediates learning to exploit. In contrast, although exploration has been well studied from both theoretical and ethological perspectives, its neural substrates are much less clear. Here we show, in a gambling task, that human subjects’ choices can be characterized by a computationally well-regarded strategy for addressing the explore/exploit dilemma. Furthermore, using this characterization to classify decisions as exploratory or exploitative, we employ functional magnetic resonance imaging to show that the frontopolar cortex and intraparietal sulcus are preferentially active during exploratory decisions. In contrast, regions of striatum and ventromedial prefrontal cortex exhibit activity characteristic of an involvement in value-based exploitative decision making. The results suggest a model of action selection under uncertainty that involves switching between exploratory and exploitative behavioural modes, and provide a computationally precise characterization of the contribution of key decision-related brain systems to each of these functions.

PLoS Biology: Economy of the Mind

A very nice, in-depth neuroecon review from PLoS Biology, includes Camerer, Glimcher, Schultz, DeWaal, Montague, and McCabe.

Enter the Neuro-Economists: Why Do Investors Do What They Do? - New York Times

A brief overview of the major researchers and research in neuroecon today.

I liked this part:

Are phrases like “nucleus accumbens” — referring to a subcortical nucleus of the brain associated with reward — welcome in a profession caught up in interest rates and money supply? Skeptics question whether neuro-economics explains real-world phenomena.

On Making the Right Choice: The Deliberation-Without-Attention Effect — Dijksterhuis et al. 311 (5763): 1005 — Science

I don’t know quite what to make of this. In fact, I just don’t understand what is going on. But I can definitely think of examples from my own life where this is true. Sometimes not thinking about a problem really does lead to its solution and it’s fascinating to think about why this may be.

Also, the authors draw a connection between what they call unconscious thought (as performed in their experiments) and insights that can come “after sleeping on it”; I’m not sure these phenomena are the same. I think sleep taps into deeper organization processes that are not available on the timescale of unconscious thought, as given in the experiment.

Abstract:

Contrary to conventional wisdom, it is not always advantageous to engage in thorough conscious deliberation before choosing. On the basis of recent insights into the characteristics of conscious and unconscious thought, we tested the hypothesis that simple choices (such as between different towels or different sets of oven mitts) indeed produce better results after conscious thought, but that choices in complex matters (such as between different houses or different cars) should be left to unconscious thought. Named the “deliberation-without-attention” hypothesis, it was confirmed in four studies on consumer choice, both in the laboratory as well as among actual shoppers, that purchases of complex products were viewed more favorably when decisions had been made in the absence of attentive deliberation.