neurodudes

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.

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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.

Stanford Neuroscientist Bill Newsome wants to implant an electrode in his own brain to study consciousness in ways that would be difficult with volunteer human subjects.

When considered alongside the story of Kevin Warwick who had a 100-electrode array implanted in his arm in 2002 in order to study electrical signals from his hand, one must wonder: is this a starting trend?

From the article:

TR: Do you really want to do this?

BN: Well, I’ve thought about it very carefully. I’ve talked to neurosurgeons, both in the United States and outside the country where the regulatory environment is less strict, about how practical and risky it is. If the risk of serious postsurgical complications was one in one hundred, I wouldn’t do it. If it was one in one thousand, I would seriously consider doing it. To my chagrin, most surgeons estimate the risk to be somewhere in between my benchmarks.

–Stephen

The Animal Self – New York Times

Interesting read on the return of personality psych (and the use of the term “personality”) to ethology.

Some tidbits:

It was back in 1991 that Anderson and Jennifer Mather, a psychologist from the University of Lethbridge in Alberta, Canada, first decided to undertake a joint personality study of 44 smaller red octopuses at the aquarium as a way to begin to codify and systematize what they thought they had been observing. Using three categorizations from a standard human-personality-assessment test – shy, aggressive and passive – their data would ultimately show that the animals did consistently clump together under these different categories in response to various stimuli, like touching them with a bristly test-tube brush or dropping a crab into the tank.

“The aggressive ones would pounce on the crab,” Anderson told me. “The passive ones would wait for the crab to come past and then grab it. The shy animal would wait till overnight when no one was looking, and we’d find this little pile of crab shell in the morning.”

Anderson and Mather’s resulting 1993 paper in the Journal of Comparative Psychology, entitled “Personalities of Octopuses,” was not only the first-ever documentation of personality in invertebrates. It was the first time in anyone’s memory that the term “personality” had been applied to a nonhuman in a major psychology journal.

And,

Alison Bell has done related experiments with sticklebacks. It has long been clear to researchers that fish that have lived for many generations in the proximity of dangerous predators are less bold and less aggressive than animals that have lived relatively risk-free. What Bell discovered is that those cautious tendencies outlast the presence of risk, even by a generation. When she moved sticklebacks who had always lived in a high-risk environment into a low-risk environment, she found that not only did they retain their cautious tendencies, but so did their offspring. Even fish raised from birth in a low-risk environment behave more fearfully if raised by a particularly vigilant father from a high-risk background.

“There’s definitely the effect of genetic difference,” Bell explained, “but there’s also the effect of what is experienced as they grow up. Genotype and environment interactions make it difficult to detect the effects of genes, because you have to take the environment into account. This is annoying to geneticists.” To scientists like Bell who are studying the interplay of genes and environment, however, it is of profound interest.

When Bad People Are Punished, Men Smile (but Women Don’t) – New York Times

I think there has been studies similar to this before… here’s the relevant details:

Furthermore, researchers found that the brain’s pleasure centers lit up in males when just punishment was meted out.

The researchers cautioned that it was not clear if men and women are born with divergent responses to revenge or if their social experiences generate the responses.

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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