Friday, February 29, 2008

A primer on executive function in the prefrontal cortex

Gilbert and Burgess offer a brief review of our prefrontal brain cortex structures that enable our flexible responses to situations with alternative choices. I think it provides a good look-up reference, and so I want to excerpt a few of the summary figures and text here:

At the heart of most (but not all) theories of executive function is a distinction, or gradation, between routine (or ‘automatic’) and non-routine (or ‘controlled’) processing. Routine processing refers to mental operations that are well rehearsed or overlearned, for example reading out a word. By contrast, non-routine processing most commonly refers to mental operations that are used in situations when there is not a well-established stimulus-response association, or where a behavioural impasse has occurred (for example one notices an error, or realises that one is behaving in a sub-optimal fashion). The term ‘executive functions’ has become synonymous with those behaviours and abilities.

Determining the relative contributions of different frontal subregions to different executive functions is a highly complex matter, both theoretically and methodologically. On current evidence, however, one can make some preliminary suggestions. The figure illustrates some of the major subdivisions of the human PFC, which may be divided into lateral and medial surfaces. On the lateral surface, the PFC may be further subdivided into ventrolateral, dorsolateral, and rostral regions. Although the medial PFC is depicted as a single area in the figure, there is now strong evidence that this part of PFC can also be subdivided both on cytoarchitectonic and functional grounds. The figure shows the lateral surface split into a ventrolateral region (VLPFC), dorsolateral region (DLPFC) and rostral region (RPFC). The medial surface (MPFC) is illustrated as a single region, but recent studies indicate considerable anatomical and functional variation within this region as well. (Click to enlarge)


Ventrolateral PFC (VLPFC) is thought to be involved in comparatively simple tasks, such as short-term maintenance of information that cannot currently be perceived in ‘working memory’ (for example, memorising a phone number you have just been told, before keying the numbers into a telephone). It has also been proposed — although this is controversial — that different parts of the VLPFC are used to store different types of information (for example, the sound of a word versus its meaning). By contrast, dorsolateral PFC (DLPFC) has been most commonly implicated not so much in maintaining information that is no longer available in our environment, but in manipulating that information. For example, although DLPFC is probably not involved in processes such as remembering a telephone number, it does seem to play a role in more difficult tasks, such as dialling the number in reverse order (rearranging the digits that we have just been told). DLPFC has also been suggested to be involved in complex functions such as making plans for the future.

A brain region with strong projections to and from the DLPFC is the anterior cingulate cortex (ACC), part of the medial PFC. One influential theory proposes that this brain region detects the need for control, for example where there is competition between two or more ways of behaving in a certain situation, both of which may be triggered by events in our environment, requiring top-down input to resolve the conflict. It is suggested that the ACC does not itself provide higher-level modulation of lower-level processes, but instead signals to DLPFC when such higher-level modulation is required.

The largest, but most mysterious, sub-region of prefrontal cortex is the rostral PFC (RPFC). As a proportion of whole-brain volume, some have estimated the human RPFC to be twice as large as the corresponding region in the chimpanzee brain. Yet curiously, patients with damage restricted to the RPFC often perform well on standard neuropsychological tests, including ‘classical’ tests of executive function such as the Wisconsin card sorting test. Instead, patients with damage to this region seem to have particular difficulty in real-world ‘multitasking’ situations, such as organising a shopping trip when there are few strict constraints — participants are relatively free to organise their behaviour however they like — but there are also multiple instructions to be remembered, rules to be followed, and potential distractions in the environment. Recent accounts have focused on the role of RPFC in the most high-level human abilities, such as combining two distinct cognitive operations in order to perform a single task, trying to work out what other people are thinking (‘mentalising’), and reflecting on information we retrieve from long-term memory (‘source memory’, for example trying to work out when we last saw a person familiar to us). We recently put forward the unifying hypothesis that this brain region serves as a ‘gateway’ between cognitive processes directed towards current incoming perceptual information, versus information that we generate ourselves. We have also shown (see following figure) by a meta-analysis of functional neuroimaging results that there are distinct functions associated with different parts of the RPFC, with segregation especially between lateral versus medial regions, and between rostral versus caudal regions. (Click to enlarge)





Thursday, February 28, 2008

Kahneman on happiness.

An interesting shift in opinion on what we thought we knew about measuring happiness from Nobel laureate Daniel Kahneman:

Ten years ago the generally accepted position was that there is considerable hedonic adaptation to life conditions. The effects of circumstances on life satisfaction appeared surprisingly small: the rich were only slightly more satisfied with their lives than the poor, the married were happier than the unmarried but not by much, and neither age nor moderately poor health diminished life satisfaction. Evidence that people adapt — though not completely — to becoming paraplegic or winning the lottery supported the idea of a "hedonic treadmill": we move but we remain in place. The famous "Easterlin paradox" seemed to nail it down: Self-reported life satisfaction has changed very little in prosperous countries over the last fifty years, in spite of large increases in the standard of living.

Hedonic adaptation is a troubling concept, regardless of where you stand on the political spectrum. If you believe that economic growth is the key to increased well-being, the Easterlin paradox is bad news. If you are a compassionate liberal, the finding that the sick and the poor are not very miserable takes wind from your sails. And if you hope to use a measure of well-being to guide social policy you need an index that will pick up permanent effects of good policies on the happiness of the population.

...an idea that seemed to solve these difficulties: perhaps people's satisfaction with their life is not the right measure of well-being. ..happy people have high aspirations. The aspiration treadmill offered an appealing solution to the puzzles of adaptation: it suggested that measure of life satisfaction underestimate the well-being benefits of life circumstances such as income, marital status or living in California. The hope was that measures of experienced happiness would be more sensitive.
Then after a series of experiments thoroughly refuted this hypothesis, further problems with the original issue:
...recent findings from the Gallup World Poll raise doubts about the puzzle itself. The most dramatic result is that when the entire range of human living standards is considered, the effects of income on a measure of life satisfaction (the "ladder of life") are not small at all. We had thought income effects are small because we were looking within countries. The GDP differences between countries are enormous, and highly predictive of differences in life satisfaction. In a sample of over 130,000 people from 126 countries, the correlation between the life satisfaction of individuals and the GDP of the country in which they live was over .40 – an exceptionally high value in social science. Humans everywhere, from Norway to Sierra Leone, apparently evaluate their life by a common standard of material prosperity, which changes as GDP increases. The implied conclusion, that citizens of different countries do not adapt to their level of prosperity, flies against everything we thought we knew ten years ago. We have been wrong and now we know it. I suppose this means that there is a science of well-being, even if we are not doing it very well.


Wednesday, February 27, 2008

Your pupils reveal shifts in your perception



Here is an interesting nugget from Christof Koch's laboratory at Cal Tech. When we look at an ambiguous image such as the Necker Cube or the duck/rabbit shown here, our perception switches back and forth between the alternatives.


It turns out that our pupil diameter increases just before the perceptual switch, and predicts its duration. Here is their abstract:

During sustained viewing of an ambiguous stimulus, an individual's perceptual experience will generally switch between the different possible alternatives rather than stay fixed on one interpretation (perceptual rivalry). Here, we measured pupil diameter while subjects viewed different ambiguous visual and auditory stimuli. For all stimuli tested, pupil diameter increased just before the reported perceptual switch and the relative amount of dilation before this switch was a significant predictor of the subsequent duration of perceptual stability. These results could not be explained by blink or eye-movement effects, the motor response or stimulus driven changes in retinal input. Because pupil dilation reflects levels of norepinephrine (NE) released from the locus coeruleus (LC), we interpret these results as suggestive that the LC–NE complex may play the same role in perceptual selection as in behavioral decision making.

Study increases learning less than testing...

Karpicke and Roediger question the common assumption that learning increases as people study and encode material, while measuring that learning by testing does not by itself produce learning. They examined undergraduates tasked with learning the meanings of 40 words in Swahili. Repeated testing of already learned words enhanced long-term recall when assessed 1 week later, whereas repeated studying had no beneficial effects. Testing required the students to retrieve the English-Swahili word associations, which suggests that encoding, although critical for the formation of a memory, may not be sufficient for its retention or consolidation. Their abstract:

Learning is often considered complete when a student can produce the correct answer to a question. In our research, students in one condition learned foreign language vocabulary words in the standard paradigm of repeated study-test trials. In three other conditions, once a student had correctly produced the vocabulary item, it was repeatedly studied but dropped from further testing, repeatedly tested but dropped from further study, or dropped from both study and test. Repeated studying after learning had no effect on delayed recall, but repeated testing produced a large positive effect. In addition, students' predictions of their performance were uncorrelated with actual performance. The results demonstrate the critical role of retrieval practice in consolidating learning and show that even university students seem unaware of this fact.


Tuesday, February 26, 2008

Bright light and good moods...

We are more agreeable when the light is brighter: here is the abstract, and one figure, from "Exposure to bright light is associated with positive social interaction and good mood over short time periods: A naturalistic study in mildly seasonal people" published in the Journal of Psychology:

Bright light is used to treat winter depression and might also have positive effects on mood in some healthy individuals. We examined possible links between bright light exposure and social interaction using naturalistic data. For 20 days in winter and/or summer, 48 mildly seasonal healthy individuals wore a light meter at the wrist and recorded in real-time their behaviours, mood, and perceptions of others during social interactions. Possible short-term effects of bright light were examined using the number of minutes, within any given morning, afternoon or evening, that people were exposed to light exceeding 1000 lux (average: 19.6 min). Social interactions were labelled as having occurred under conditions of no, low or high bright light exposure. Independent of season, day, time, and location, participants reported less quarrelsome behaviours, more agreeable behaviours and better mood when exposed to high but not low levels of bright light. Given that the effects were seen only when exposure levels were above average, a minimum level of bright light may be necessary for its positive effects to occur. Daily exposure levels were generally low in both winter and summer. Spending more time outdoors and improving indoor lighting may help optimize everyday social behaviour and mood across seasons in people with mild seasonality.

Figure - Quarrelsome behaviours (a) and agreeable behaviours (b) during time periods of no, low, or high levels of bright light exposure. Values are expressed as estimated least squares means of ipsatized frequencies, multiplied by a factor 100. Error bars represent standard errors of the mean. (* Significantly different from social interactions with low bright light exposure.)

Life expectancy increases

Taken from an article by Kirkwood on a systems biology approach to longevity...


The graph shows the life expectancy in the then longest-living country. During the nineteenth and early twentieth centuries, the increase was driven mainly by improvements in sanitation, housing and education, causing a steady decline in early and mid-life mortality, which was chiefly due to infections. This trend continued with the development of vaccines and then antibiotics. By the latter half of the twentieth century, there was little room for further reduction in early and mid-life mortality. The continuing increase is due almost entirely to a new phenomenon: the decline in late-life mortality.

Monday, February 25, 2008

Love speed dating

You may do better in relying on your impression after only 4 minutes of interaction with a potential partner than if you think about it a lot. Here is an engaging essay by Matt Kaplan.

Watching an anesthetic block emotional memory

Here is an intriguing observation by Alkiri et al. We usually recall emotional pictures or events better than neutral ones. They found that low levels of the inhalation anesthetic sevoflurane could block this effect, and with PET imaging found a corresponding suppression of amygdala to hippocampal effective connectivity. Here is their abstract and one summary figure:

It is hypothesized that emotional arousal modulates long-term memory consolidation through the amygdala. Gaseous anesthetic agents are among the most potent drugs that cause temporary amnesia, yet the effects of inhalational anesthesia on human emotional memory processing remain unknown. To study this, two experiments were performed with the commonly used inhalational anesthetic sevoflurane. In experiment 1, volunteers responded to a series of emotional and neutral slides while under various subanesthetic doses of sevoflurane or placebo (no anesthesia). One week later, a mnemonic boost for emotionally arousing stimuli was evident in the placebo, 0.1%, and 0.2% sevoflurane groups, as measured with a recognition test. However, the mnemonic boost was absent in subjects who received 0.25% sevoflurane. Subsequently, in experiment 2, glucose PET assessed brain-state-related activity of subjects exposed to 0.25% sevoflurane. Structural equation modeling of the PET data revealed that 0.25% sevoflurane suppressed amygdala to hippocampal effective connectivity. The behavioral results show that 0.25% sevoflurane blocks emotional memory, and connectivity results demonstrate that this dose of sevoflurane suppresses the effective influence of the amygdala. Collectively, the findings support the hypothesis that the amygdala mediates memory modulation by demonstrating that suppressed amygdala effectiveness equates with a loss of emotional memory.

Figure - The cerebral metabolic effects of 0.25% sevoflurane are shown. (A) Representative high-resolution PET scans. (B) Absolute (mean ± SD) regional metabolic changes (white bars, placebo, no anesthesia; dark bars, 0.25% sevoflurane; marked with * for P less than 0.05). (C) Relative percent decreases of regional metabolism. (D) Regional SPM results of sevoflurane induced metabolic suppression (Upper, sagittal; Lower, axial). E shows the regional thalamic finding (brain center) on a colorized MRI. The SPM effects are significant at P less than 0.001, uncorrected; displayed at P less than 0.005, with a 500-voxel extent.

Friday, February 22, 2008

Languages shape the nuts and bolts of our perception.

The debate over whether language nudges the way we actually see the world is being resolved, and what has been the prevailing dogma - that basic parts of perception are too low-level, too hard-wired, too constrained by the constants of physics and physiology to be affected by language - is breaking down. Lera Boroditsky at Standford comments on this.

I used to think that languages and cultures shape the ways we think. I suspected they shaped they ways we reason and interpret information. But I didn't think languages could shape the nuts and bolts of perception, the way we actually see the world. That part of cognition seemed too low-level, too hard-wired, too constrained by the constants of physics and physiology to be affected by language.

Then studies started coming out claiming to find cross-linguistic differences in color memory. For example, it was shown that if your language makes a distinction between blue and green (as in English), then you're less likely to confuse a blue color chip for a green one in memory. In a study like this you would see a color chip, it would then be taken away, and then after a delay you would have to decide whether another color chip was identical to the one you saw or not.

Of course, showing that language plays a role in memory is different than showing that it plays a role in perception. Things often get confused in memory and it's not surprising that people may rely on information available in language as a second resort. But it doesn't mean that speakers of different languages actually see the colors differently as they are looking at them. I thought that if you made a task where people could see all the colors as they were making their decisions, then there wouldn't be any cross-linguistic differences.

I was so sure of the fact that language couldn't shape perception that I went ahead and designed a set of experiments to demonstrate this. In my lab we jokingly referred to this line of work as "Operation Perceptual Freedom." Our mission: to free perception from the corrupting influences of language.

We did one experiment after another, and each time to my surprise and annoyance, we found consistent cross-linguistic differences. They were there even when people could see all the colors at the same time when making their decisions. They were there even when people had to make objective perceptual judgments. They were there when no language was involved or necessary in the task at all. They were there when people had to reply very quickly. We just kept seeing them over and over again, and the only way to get the cross-linguistic differences to go away was to disrupt the language system. If we stopped people from being able to fluently access their language, then the cross-linguistic differences in perception went away.

I set out to show that language didn't affect perception, but I found exactly the opposite. It turns out that languages meddle in very low-level aspects of perception, and without our knowledge or consent shape the very nuts and bolts of how we see the world.

Thursday, February 21, 2008

Watching waves of activity sweep across the brain

This is sensory physiology in the age of YouTube. Peterson and colleagues have used a voltage sensitive dye technique to watch the wave of first sensory area and then motor area excitation that is caused by a tiny deflection of a face whisker of a mouse:

Single brief whisker deflections evoked highly distributed depolarizing cortical sensory responses, which began in the primary somatosensory barrel cortex and subsequently excited the whisker motor cortex. The spread of sensory information to motor cortex was dynamically regulated by behavior and correlated with the generation of sensory-evoked whisker movement. Sensory processing in motor cortex may therefore contribute significantly to active tactile sensory perception.

The video shows the response when a mouses whisker touches an edge:


The movement of the C2 whisker was filmed with a high-speed camera at 500 Hz in an awake behaving mouse during an active touch sequence. Sensorimotor cortex was simultaneously imaged with VSD. At the time indicated by the vertical dotted line, the whisker contacts the object evoking a spreading sensorimotor response, first in S1 and subsequently in M1. The single trial imaging of cortical activity and the behavioral filming are matched frame-by-frame, synchronized through TTL pulses.

Consciousness papers for January

Most downloaded in January 2008 from the ASSC archives:

1. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge handbook
of consciousness. Cambridge University Press, New York, USA. 1359 downloads
from 27 countries. http://eprints.assc.caltech.edu/175/
2. Sagiv, Noam and Ward, Jamie (2006) Crossmodal interactions: lessons from
synesthesia. In: Visual Perception, Part 2. Progress in Brain Research,
Volume 155. 925 downloads from 19 countries.
http://eprints.assc.caltech.edu/224/
3. Robbins, Stephen E (2007) Time, Form and the Limits of Qualia. Journal of
Mind and Behavior, 28 (1). pp. 19-43. 760 downloads from 14 countries.
http://eprints.assc.caltech.edu/333/
4. Gomes, Gilberto (2005) Is consciousness epiphenomenal? Comment on Susan
Pockett. Journal of Consciousness Studies, 12 (12). pp. 77-79. 739 downloads
from 12 countries. http://eprints.assc.caltech.edu/160/
5. Seth, A.K. and Baars, B.J. (2005) Neural Darwinism and Consciousness.
Consciousness and Cognition, 14. pp. 140-168. 644 downloads from 18
countries. http://eprints.assc.caltech.edu/163/

Wednesday, February 20, 2008

Your amygdala and your blood pressure

I was intrigued by this article, because it shows what I suppose must be going on in my brain as I notice my blood pressure increasing when my stress system ramps up. (Being an introspective retired professor with sufficient time, I am increasingly noticing small changes in my breathing, heart rate, blood pressure, and relative sympathetic versus parasympathetic activation that accompany changes in context.)

In the article Gianaros et al. use the well-know Stroop color-word interference task to generate stress responses in a group of defined college students. They connect stressor processing with the brainstem cardiovascular control mechanisms regulating blood pressure. People with higher stressor-evoked blood pressure reactivity displayed more activation of the amygdala, especially in the dorsal part that contains the central nucleus. Individuals showing greater blood pressure reactivity also had a lower amygdala gray matter volume, which itself predicted greater amygdala activation. In addition, greater stressor- evoked blood pressure reactivity was correlated with stronger functional connectivity between the amygdala and the pons areas in the brainstem, which is critical for blood pressure control, as well the perigenual anterior cingulate cortex.

The data suggest that the amygdala and some of its projection areas play a role in mediating individual differences in autonomic stress responses and hence vulnerability to psychological stressors.

Figure - A. Greater mean arterial blood pressure (MAP) reactivity varied with greater amygdala activation to the incongruent condition. A, Clusters of the left and right amygdala where MAP reactivity varied with activation after covariate control for sex. Parametric maps are projected onto coronal (top) and axial (bottom) sections of a template derived from study participants. B, MAP reactivity (change from a resting baseline) is shown as a function of mean-centered and standardized amygdala BOLD activation values extracted from the peak voxels of the left (L; open circles, dashed line) and right (R; closed circles, solid line) amygdala clusters profiled in A.

Figure - Greater MAP reactivity varied with stronger positive amygdala-pons functional connectivity. A, Statistical parametric maps derived from an ROI regression analysis identifying pons areas where MAP reactivity varied as a function of connectivity with left (top) and right (bottom) amygdala seed regions. B, MAP reactivity is plotted as a function of amygdala-pons connectivity coefficients for the left (L; open circles, dashed line) and right (R; closed circles, solid line) amygdala.

Oliver Sachs on Migraines

An interesting article on Migraines by Oliver Sachs in the Op-Extra section of The New York Times, focusing on the geometric hallucinations they so often evoke.

...when I first saw photographs of the Alhambra, with its intricate geometric mosaics, I started to wonder whether what I had taken to be a personal experience and resonance might in fact be part of a larger whole, whether certain basic forms of geometric art, going back for tens of thousands of years, might also reflect the external expression of universal experiences. Migraine-like patterns, so to speak, are seen not only in Islamic art, but in classical and medieval motifs, in Zapotec architecture, in the bark paintings of Aboriginal artists in Australia, in Acoma pottery, in Swazi basketry — in virtually every culture. There seems to have been, throughout human history, a need to externalize, to make art from, these internal experiences, from the decorative motifs of prehistoric cave paintings to the psychedelic art of the 1960s. Do the arabesques in our own minds, built into our own brain organization, provide us with our first intimations of geometry, of formal beauty?

Whether or not this is the case, there is an increasing feeling among neuroscientists that self-organizing activity in vast populations of visual neurons is a prerequisite of visual perception — that this is how seeing begins. Spontaneous self-organization is not restricted to living systems — one may see it equally in the formation of snow crystals, in the roilings and eddies of turbulent water, in certain oscillating chemical reactions. Here, too, self-organization can produce geometries and patterns in space and time, very similar to what one may see in a migraine aura. In this sense, the geometrical hallucinations of migraine allow us to experience in ourselves not only a universal of neural functioning, but a universal of nature itself.

Tuesday, February 19, 2008

Video game addiction, and taking play seriously.

Video games trigger reward and addiction centers of the brain, just like cocaine. Hoeft et. al. at Stanford have compared the activation of these centers in men's and women's brains as they played video games and found them to be more active in male than in female participants. Males showed greater activation and functional connectivity compared to females in the mesocorticolimbic system. The more the men won, the stronger their brain activity. Women's responses were less intense and didn't correlate with winning. This may have something to do with why men seem to become addicted to video games much more easily than women.

There is an interesting and more general article by Robin Henig on play in animals and humans in the New York Times Magazine. The general consensus is that play activity is very important in the development of social intelligence and the ability to respond to rapidly changing situations. It turns out that the rise and decay of play activity in animals corresponds closely to the development curve of the cerebellum, which is important in skilled movements. In one interesting study, experimenters:

...raised 12 female rats from the time they were weaned until puberty under one of two conditions. In the control group, each rat was caged with three other female juveniles. In the experimental group, each rat was caged with three female adults. Pellis knew from previous studies that the rats caged with adults would not play, since adult rats rarely play with juveniles, even their own offspring. They would get all the other normal social experiences the control rats had — grooming, nuzzling, touching, sniffing — but they would not get play... (in) the rats raised in a play-deprived environment, they found a more immature pattern of neuronal connections in the medial prefrontal cortex... less selective pruning of cells and a more tangled, immature medial prefrontal cortex in play-deprived rats might mean that the rat will be less able to make subtle adjustments to the social world.
There are numerous theories about the function of play. It doesn't seem unreasonable that that the fragmentary, disorderly, unpredictable, exaggerated, improvised, vertiginous, and nonsensical nature of play trains the brain allows for a wider behavioral repertory and perhaps more competence in responding to novel or unforeseen situations.

Killer Instincts.

Dan Jones writes a news feature in Nature on neuroscientific and evolutionary perspectives on homicide, mainly carried out by men. Here are some selected chunks:

Men are not just more likely to kill other people than women are, they are also more likely to do so in groups ...Humans are not the only primates to form coalitions that kill members of neighbouring communities. ...five long-term study sites dotted around Africa have seen murderous 'gang violence' in chimpanzees...Wilson and Muller have compared death rates from conflict between groups of chimps in the five long-term study sites with data for inter-group human conflicts in numerous subsistence-farmer and hunter–gatherer societies...Overall, humans and chimpanzees showed comparable levels of violent death from aggression between groups...however, chimps display within group aggression and killing behaviour 200 times more frequently that aboriginal human groups...this prosocial lack of violence looks like a fundamental aspect of human nature — the human ability to generate in-group amity often goes hand in hand with out-group enmity...Choi and Bowles have produced models in which altruism and war co-evolve, promoting conflict between groups and greater harmony within them.

A decline in inter-personal violence (as opposed to inter-group war) can be seen over the shorter timescale and narrower field of modern European history. Eisner has documented a trend of declining homicide rates estimated from historical records left by coroners, royal courts and other official sources spanning Europe from the twelfth century to the modern day. After rising from an average of 32 homicides per 100,000 people per year in the thirteenth and fourteenth centuries to 41 in the fifteenth, the murder rate has steadily dropped in every subsequent century, to 19, 11, 3.2, 2.6 and finally 1.4 in the twentieth century...a few centuries is too short a time for evolution to have shaped human nature much... A part of the answer that is consistent with an evolutionary approach is a long-term reduction in inequalities of life circumstances and prospects.

Human and Animal Math

Michael Beran writes a brief review of the evolutionary and developmental foundations of mathematics. Humans and other higher animals are born with a dedicated systems for numerical processing.

Monday, February 18, 2008

The view from my window....

The title line for this posting is stolen from Andrew Sullivan's blog -

This is the view looking out of the window by the piano in my Wisconsin home yesterday (the reason I am in Ft. Lauderdale right now), and below is the outside view of that window this past spring.

T

Persuasion, bonding, and social mimicry

Benedict Cary mentions some interesting studies on social mimicry, persuasion, and affiliative behavior in an article from the NY Times science section. (Chapter 5 of my book has some stuff on this topic.) In one experiment he cites, the experimenter:

...had student participants go to a lab and give their opinions about a series of advertisements. A member of his research team mimicked half the participants while they spoke, roughly mirroring the posture and the position of their arms and legs, taking care not to be too obvious. Minutes later, the experimenter dropped six pens on the floor, making it look like an accident. In several versions of this simple sequence, participants who had been mimicked were two to three times as likely to pick up the pens as those who had not. The mimicry had not only increased good will toward the researcher within minutes, the study concluded, but it also prompted “an increased pro-social orientation in general.”
Another experiment tested how being mimicked might affect the behavior of a potential client or investor:
The team had 37 Duke students try out what was described as a new sports drink, Vigor, and answer a few questions about it. The interviewer mimicked about half the participants using a technique of mirroring a person’s posture and movements, with a one- to two-second delay. The idea is to be a mirror but a slow, imperfect one. Follow too closely, and most people catch it — and the game is over. None of the copied participants picked up on the mimicry. But by the end of the short interview, they were significantly more likely than the others to consume the new drink, to say they would buy it and to predict its success in the market. In a similar experiment, the psychologists found that this was especially true if the participants knew that the interviewer, the mimic, had a stake in the product’s success.
The article gives several other example of the subconscious social waltz, or kinesic communication, that underlies smooth human communication.

Need something to worry about? Climate tipping points...

This graphic is from an open access article in PNAS by Lenton et al. on tipping elements in the earth's climate system. You probably need to click on the graphic to make it larger; the color indicating the population densities is hard to see. In the same issue of PNAS, there is an article on how when it get warm (as in the Paleocene – Eocene Thermal Maximum caused by a carbon dioxide increase about 55 million years ago), the insects chow down on the plants.

Legend for graphic - Map of potential policy-relevant tipping elements in the climate system, overlain on global population density. Subsystems indicated could exhibit threshold-type behavior in response to anthropogenic climate forcing, where a small perturbation at a critical point qualitatively alters the future fate of the system. They could be triggered this century and would undergo a qualitative change within this millennium. We exclude from the map systems in which any threshold appears inaccessible this century (e.g., East Antarctic Ice Sheet) or the qualitative change would appear beyond this millennium (e.g., marine methane hydrates). Question marks indicate systems whose status as tipping elements is particularly uncertain.

Friday, February 15, 2008

High-Functioning Autism: a neural phenotype in the cingulate cortex

A review by Chris and Uta Frith discusses and important paper in Neuron from Montague's group in Houston, who:

...have measured brain activity (using fMRI) while volunteers, who are classified as being at the high-functioning end of the autistic spectrum, were engaged in a simple social interaction. The task was an iterated trust game in which two subjects take turns as investor or trustee. The investor chooses how much to money to invest. This chosen amount is tripled on its way to the trustee, and the trustee then chooses how much to repay to the investor. Read Montague and his colleagues have studied this game extensively in large groups of volunteers and have observed a characteristic pattern of brain activity in the anterior cingulate cortex. When making an investment (self phase), transient increases in activity are seen in an area of mid cingulate cortex (−7 <>A graphic from the Chiu et al paper showing the diminished "self" response in autism spectrum patients:


...the results suggest that the abnormality associated with autism is restricted to only one phase of the interactive game: the point where the autistic volunteer makes an investment, not the point where the autistic volunteer is told about the repayment made by their partner. Additional results from Read Montague's group give further clues as to the implications of this result. First, the same pattern of activity in cingulate cortex is observed when volunteers are shown pictures of people engaged in athletic activities and asked to imagine themselves taking part. This is further evidence as to the nature of the cognitive process associated with this pattern of activity: it involves thinking about the self acting in a social context. Second, the characteristic patterns of activity in the cingulate cortex are only observed when the trust game is played with a human partner. No such distinct patterns emerge when the game is played in the absence of a responsive social partner...At least part of the imagining must involve thinking about how one would fit in with the group, and how other group members would evaluate one's performance. Actually, this is a question about the kind of reputation one might gain in the eyes of the others. Likewise, in the self phase of the trust game, the amount one invests can be seen as a measure of how much one trusts one's partner. It is not just giving an amount of money; it is giving a signal to the other person: “trust me” and “I trust you.”
In other words, at the point of investment we are predicting what the effect of our investments is going to be on the behavior of our partners. In the other phase of the game, we are also evaluating a signal. But there is a difference. The evaluation is after the fact. We know what the investment is. We are not at this point trying to build our reputation in the other player's eyes.

A non-invasive brain-machine interface?

Waldert et al. show that hand movement direction can be decoded from magneto- (MEG) and electro-(EEG) encephalography recordings. They suggest that this might make it possible to design a non-invasive brain machine interface. Here is their abstract:

Brain activity can be used as a control signal for brain–machine interfaces (BMIs). A powerful and widely acknowledged BMI approach, so far only applied in invasive recording techniques, uses neuronal signals related to limb movements for equivalent, multidimensional control of an external effector. Here, we investigated whether this approach is also applicable for noninvasive recording techniques. To this end, we recorded whole-head MEG during center-out movements with the hand and found significant power modulation of MEG activity between rest and movement in three frequency bands: an increase for ≤7 Hz (low-frequency band) and 62–87 Hz (high-{gamma} band) and a decrease for 10–30 Hz (β band) during movement. Movement directions could be inferred on a single-trial basis from the low-pass filtered MEG activity as well as from power modulations in the low-frequency band, but not from the β and high-{gamma} bands. Using sensors above the motor area, we obtained a surprisingly high decoding accuracy of 67% on average across subjects. Decoding accuracy started to rise significantly above chance level before movement onset. Based on simultaneous MEG and EEG recordings, we show that the inference of movement direction works equally well for both recording techniques. In summary, our results show that neuronal activity associated with different movements of the same effector can be distinguished by means of noninvasive recordings and might, thus, be used to drive a noninvasive BMI.

Thursday, February 14, 2008

Creating new worlds - science and fiction as the same thing

Alison Gopnik has an interesting take on why children pretend much of the time and spend time in imaginary worlds:

Recently, I've had to change my mind about the very nature of knowledge because of an obvious, but extremely weird fact about children - they pretend all the time. Walk into any preschool and you'll be surrounded by small princesses and superheroes in overalls - three-year-olds literally spend more waking hours in imaginary worlds than in the real one. Why? Learning about the real world has obvious evolutionary advantages and kids do it better than anyone else. But why spend so much time thinking about wildly, flagrantly unreal worlds? The mystery about pretend play is connected to a mystery about adult humans - especially vivid for an English professor's daughter like me. Why do we love obviously false plays and novels and movies?

The greatest success of cognitive science has been our account of the visual system. There's a world out there sending information to our eyes, and our brains are beautifully designed to recover the nature of that world from that information. I've always thought that science, and children's learning, worked the same way. Fundamental capacities for causal inference and learning let scientists, and children, get an accurate picture of the world around them - a theory. Cognition was the way we got the world into our minds.

But fiction doesn't fit that picture - its easy to see why we want the truth but why do we work so hard telling lies? I thought that kids' pretend play, and grown-up fiction, must be a sort of spandrel, a side-effect of some other more functional ability. I said as much in a review in Science and got floods of e-mail back from distinguished novel-reading scientists. They were all sure fiction was a Good Thing - me too, of course, - but didn't seem any closer than I was to figuring out why.

So the anomaly of pretend play has been bugging me all this time. But finally, trying to figure it out has made me change my mind about the very nature of cognition itself.

I still think that we're designed to find out about the world, but that's not our most important gift. For human beings the really important evolutionary advantage is our ability to create new worlds. Look around the room you're sitting in. Every object in that room - the right angle table, the book, the paper, the computer screen, the ceramic cup was once imaginary. Not a thing in the room existed in the pleistocene. Every one of them started out as an imaginary fantasy in someone's mind. And that's even more true of people - all the things I am, a scientist, a philosopher, an atheist, a feminist, all those kinds of people started out as imaginary ideas too. I'm not making some relativist post-modern point here, right now the computer and the cup and the scientist and the feminist are as real as anything can be. But that's just what our human minds do best - take the imaginary and make it real. I think now that cognition is also a way we impose our minds on the world.

In fact, I think now that the two abilities - finding the truth about the world and creating new worlds-are two sides of the same coins. Theories, in science or childhood, don't just tell us what's true - they tell us what's possible, and they tell us how to get to those possibilities from where we are now. When children learn and when they pretend they use their knowledge of the world to create new possibilities. So do we whether we are doing science or writing novels. I don't think anymore that Science and Fiction are just both Good Things that complement each other. I think they are, quite literally, the same thing.

The Best Men Are (Not Always) Already Taken

Bressan1 and Stranieri take a (dubious) evolutionary psychological approach to the question of female preference for single versus attached males. The outcome is interesting. Here is their abstract:

Because men of higher genetic quality tend to be poorer partners and parents than men of lower genetic quality, women may profit from securing a stable investment from the latter, while obtaining good genes via extrapair mating with the former. Only if conception occurs, however, do the evolutionary benefits of such a strategy overcome its costs. Accordingly, we predicted that (a) partnered women should prefer attached men, because such men are more likely than single men to have pair-bonding qualities, and hence to be good replacement partners, and (b) this inclination should reverse when fertility rises, because attached men are less available for impromptu sex than single men. In this study, 208 women rated the attractiveness of men described as single or attached. As predicted, partnered women favored attached men at the low-fertility phases of the menstrual cycle, but preferred single men (if masculine, i.e., advertising good genetic quality) when conception risk was high.

Wednesday, February 13, 2008

Painful or disgusting? - ask parietal and cingulate cortex

Benuzzi et al. find brain activity specific for disgusting scenes in the posterior cingulate cortex. Signal changes in perigenual cingulate and left anterior insula are linearly related to the perceived unpleasantness. Painful scenes selectively induce activation of left parietal foci including the parietal operculum, the postcentral gyrus, and adjacent portions of the posterior parietal cortex. Their abstract is here, and here is one figure from the paper:

Top, Cortical foci active during the observation of painful video clips. Bottom, Cortical foci active during the observation of disgusting video clips.

Are today's young people really more narcissistic?

A comment by Trzesniewski et al. on the idea that today's young people have inflated impressions of themselves compared with previous generations. They:

..investigated secular trends in narcissism and self-enhancement over the past three decades. Despite recent claims about the impact of the "self-esteem movement" on the current generation of young people, we found no evidence that college students' scores on the Narcissistic Personality Inventory increased from the 1980s through 2007 (N = 26,867), although we did find small changes in specific facets of narcissism. Similarly, we found no evidence that high school students' level of self-enhancement, defined by the discrepancy between their perceived intelligence and their actual academic achievements, increased from 1976 to 2006 (N = 410,527). These results cast doubt on the belief that today's young people have increasingly inflated impressions of themselves compared with previous generations.

Tuesday, February 12, 2008

100% accuracy in automatic face detection.

A problem with the automatic face recognition systems being tested in some airport security screening systems is that none can cope with the kind of image variability encountered in the real world. Jenkins and Burton have used a simple averaging technique to increase the accuracy of an industry standard face-recognition algorithm from 54% to 100%. They averaged the images from 20 different photographs for each of 25 male celebrities who were also in a large public online database of 31,077 photographs of famous faces, comprising an average of nine different photos for each of 3628 celebrities - these images were highly variable in their quality and covered a wide range of lighting conditions, facial expressions, poses, and age. Using the FaceVACS (Cognitec Systems GmbH, Dresden, Germany)industry standard face-recognition system that has been widely adopted, they fed this database their averaged images for each of 25 male celebrities who were also in the online database (excluding photos that were both in their sample and in the database). With the averaged images, the database returned the correct identification 100% of the time. When individual photographs were presented to the database the correct identification was returned only ~50% of the time. From their text:

We demonstrated this improvement with a commercially available algorithm and an online face database over which we had no control. We suggest that image averaging enhances performance by stabilizing the face image. With standard photographs, the match tends to be dominated by aspects of the image that are not diagnostic of identity (e.g., lighting and pose). Averaging together multiple photographs of the same person dilutes these transients while preserving aspects of the image that are consistent across photos. The resulting images capture the visual essence of an individual's face and elevate machine performance to the standard of familiar face recognition in humans. It would be technically straightforward to incorporate an average image into identification documents. Doing so would greatly reduce the incidence of face-recognition errors and raise the prospect of a viable automatic face-recognition infrastructure.


Example photographs of Bill Clinton and their average (right). [Image 1, photo by Marc Nozell (www.flickr.com/photos/marcn/534512066); image 2, photo by Roger Goun (www.flickr.com/photos/sskennel/829574139); image 20, photo by Nelson Pavlosky (www.flickr.com/photos/skyfaller/26752190). All photos were used under a Creative Commons license.] Different pictures of a single face can vary enormously, making automatic recognition difficult. Averaging together multiple photos of the same face stabilizes the image, improving performance dramatically.

Need an antidepressant?

Could a presidential debate on science backfire?

An interesting essay by David Goldston argues that a debate on science by presidential candidates might do more harm than good.

Monday, February 11, 2008

Sharing posts, bookmarking, related content, etc.

My friend Kelly Doering who does internet consulting and website design, has just helped me dink around a bit with the mechanics of MindBlog. You will now notice a single icon after each post that lets you bookmark or share a post using more than 30 of the major services like StumbleUpon, Reddit, Del.icio.us, Reddit, etc. If you haven't already, you should try the sphere:related content link that may appear just below the bookmark icon with a post that interests you. It sometimes does a very nice job of bringing up related material on other websites.

Your brain is shrinking sooner than you thought...

Here is a chilling little item from Pieperhoff et al., who examined MRI images of the brains of 51 healthy male subjects from 18 to 51 years old. They found age-related volume declines in circumscribed brain regions: the sensorimotor system, encompassing the cerebellum, thalamus, somatosensory and motor cortices, and the prefrontal system, encompassing the anterior cingulate as well as the lateral and basomedial frontal cortices. Regions belonging to other functional systems, such as the auditory system or the visual system, did not show such age–volume relationships.

Horizontal sections of the reference brain with statistical maps, showing the t values of age-related volume decline and increase. t values were calculated by a two-sided t test for a linear regression in the voxels of the LVR maps, depending on age.

The incubator of suicide attacks - Fictive Kinship

Anthropologist Scott Atran (Author of "In Gods We Trust") writes an essay laying out his change of mind about why people are willing to die for a cause. He has moved from thinking that individual cognition and personality, influences from broad socio-economic factors, and degree of devotion to religious or political ideology were determinant, to seeing friendship and others aspects of small group dynamics, especially acting together, trumping most everything else.

...people don't kill and die simply for a cause. They do it for friends — campmates, schoolmates, workmates, soccer buddies, body-building buddies, pin-ball buddies — who share a cause. Some die for dreams of jihad — of justice and glory — but nearly all in devotion to a family-like group of friends and mentors, of "fictive kin." (Atran gives a number of explicit examples of such groups)

... it is no accident that nearly all religious and political movements express allegiance through the idiom of the family — Brothers and Sisters, Children of God, Fatherland, Motherland, Homeland, and the like. Nearly all such movements require subordination, or at least assimilation, of any real family (genetic kinship) to the larger imagined community of "Brothers and Sisters." Indeed, the complete subordination of biological loyalty to ideological loyalty for the Ikhwan, the "Brotherhood" of the Prophet, is Islam's original meaning, "Submission."
...Social psychology tends to support the finding that "groupthink" often trumps individual volition and knowledge, whether in our society or any other. But for Americans bred on a constant diet of individualism the group is not where one generally looks for explanation.

Sunday, February 10, 2008

Back in Wisconsin....

I am SO grateful that I am able to be a snowbird, now in Ft. Lauderdale. Here is a picture of my home in Wisconsin, where more snow has fallen this winter than in any year since recordings of snowfall began in the 19th century.

Friday, February 08, 2008

MindBlog's second anniversary

I just realized that today is MindBlog's second anniversary. It is hard for me to believe that there have been 902 postings since Feb. 8, 2006. Back then I had just read an article in the New York Times on the rising blogging fad and thought to myself, "Since I am reading and thinking about all this stuff anyway, I might as well take the small extra effort to clean it up a bit and present it." The extra effort turns out to be not so small. The number of subscribers to the MindBlog feed has risen to over 400, and on a given day there are 300-1,500 views of individual postings. Being a borderline (or maybe not even borderline) obsessive-compulsive, I've become yoked to the lockstep production of at least two blog postings a day. The retired professor isn't feeling all that retired..... Anyway, I am grateful for the kind emails I have received, and I've enjoyed responding to requests for further analysis or information.

Middle Age Misery

Blanceflower and Oswald have done a fascinating study (PDF here) showing that across cultures, from Azerbaijan to Zimbabwe, we are happiest towards the beginning and end of our lives, leaving us most miserable in middle years between 40 and 50. For both men and women in the UK, the probability of depression peaked at around the age of 44. In the US, men were most likely to be unhappiest at 50, while for women the age was 40. The cause of the apparent U-shaped curve is not known. Quoting Oswald (the graphic is from his website):

...one possibility is that individuals learn to adapt to their strengths and weaknesses, and in mid-life quell their infeasible aspirations. Another possibility is that cheerful people live systematically longer...A third possibility is that older people might compare their lives with their peers'. Seeing their friends die could mean people value their remaining years more highly...It looks from the data like something happens deep inside humans. For the average person in the modern world, the dip in mental health and happiness comes on slowly, not suddenly in a single year...Only in their 50s do most people emerge from the low period. But encouragingly, by the time you are 70, if you are still physically fit then on average you are as happy and mentally healthy as a 20-year-old. Perhaps realising that such feelings are completely normal in mid-life might even help individuals survive this phase better.

The World in the Brain

Here are a few excerpts from a brief essay by Steve Kosslyn in the Edge.org series "What have you changed your mind about?

There is a really elegant solution to the problem that the genes can't know in advance how far apart the eyes will be. To cope with this problem, the genes overpopulate the brain, giving us options for different environments (where the distance between eyes and length of the arms are part of the brain's "environment," in this sense), and then the environment selects which connections are appropriate, and the useless connections are pruned away. In other words, the genes take advantage of the environment to configure the brain.

This overpopulate-and-select mechanism is not limited to stereovision. In general, the environment sets up the brain (above and beyond any role it may have had in the evolution of the species), configuring it to work well in the world a person inhabits. And by environment I'm including everything outside the brain — including the social environment. For example, it's well known that children can learn multiple languages without an accent and with good grammar, if they are exposed to the language before puberty. But after puberty, it's very difficult to learn a second language so well.

This perspective leads me to wonder whether we can assume that the brains of people living in different cultures process information in precisely the same ways. Yes, people the world over have much in common (we are members of the same species, after all), but even small changes in the wiring may lead us to use the common machinery in different ways. If so, then people from different cultures may have unique perspectives on common problems, and be poised to make unique contributions toward solving such problems... to understand how any specific brain functions, we need to understand how that person was raised, and currently functions, in the surrounding culture.
A similar, more brief, response to the edge.org question was offered by Jeffrey Epstein, A science Philanthropist:
The question presupposes a well defined "you", and an implied ability that is under "your" control to change your "mind". The "you" I now believe is distributed amongst others (family friends , in hierarchal structures,) i.e. suicide bombers, believe their sacrifice is for the other parts of their "you". The question carries with it an intention that I believe is out of one's control. My mind changed as a result of its interaction with its environment. Why? because it is a part of it.

Thursday, February 07, 2008

Nicholas Humphrey on consciousness...

I have always admired Nicholas Humphrey's perspectives on sensing and consciousness, and referenced his ideas on evolution of the nervous system in my Biology of Mind book. He has now written a nice essay in Seed Magazine, and I strongly recommend that you read it. He argues against the idea:

...that consciousness must be helping us do something that we can do only by virtue of being conscious, in the way that, say, a bird can fly only because it has wings, or you can understand this sentence only because you know English.
Rather,
...I want to suggest the role of phenomenal consciousness may not be like this at all. Its role may not be to enable us to do something we could not do otherwise, but rather to encourage us to do something we would not do otherwise: to make us take an interest in things that otherwise would not interest us, or to mind things we otherwise would not mind, or to set ourselves goals we otherwise would not set.

I will not hold back from telling you my own main conclusion from a lifetime's interest in what consciousness does. I may shock you by what may seem the naivety of my conclusion (I've shocked myself): I think the plain and simple fact is that consciousness—on various levels—makes life more worth living.

We like being phenomenally conscious. We like the world in which we're phenomenally conscious. We like ourselves for being phenomenally conscious. And the resulting joie de vivre, the enchantment with the world we live in, and the enhanced sense of our own metaphysical importance have, in the course of evolutionary history, turned our lives around.

Added note 11/16/08: I just found a later published version of this article. PDF here.

Evolutionary psychology on steroids...

Here are Steven Pinker's comments on recent data showing that the human genome has undergone strong recent selection, rendering invalid evolutionary psychology's initial assumption that human evolution halted 10,000 - 50,000 years ago.

New results from the labs of Jonathan Pritchard, Robert Moyzis, Pardis Sabeti, and others have suggested that thousands of genes, perhaps as much as ten percent of the human genome, have been under strong recent selection, and the selection may even have accelerated during the past several thousand years. The numbers are comparable to those for maize, which has been artificially selected beyond recognition during the past few millennia.

If these results hold up, and apply to psychologically relevant brain function (as opposed to disease resistance, skin color, and digestion, which we already know have evolved in recent millennia), then the field of evolutionary psychology might have to reconsider the simplifying assumption that biological evolution was pretty much over and done with 10-000 — 50,000 years ago.

And if so, the result could be evolutionary psychology on steroids. Humans might have evolutionary adaptations not just to the conditions that prevailed for hundreds of thousands of years, but also to some of the conditions that have prevailed only for millennia or even centuries. Currently, evolutionary psychology assumes that any adaptation to post-agricultural ways of life are 100% cultural.

Though I suspect some revisions will be called for, I doubt they will be radical, for two reasons. One is that many aspects of the human (and ape) environments have been constant for a much longer time than the period in which selection has recently been claimed to operate. Examples include dangerous animals and insects, toxins and pathogens in spoiled food and other animal products, dependent children, sexual dimorphism, risks of cuckoldry and desertion, parent-offspring conflict, risk of cheaters in cooperation, fitness variation among potential mates, causal laws governing solid bodies, presence of conspecifics with minds, and many others. Recent adaptations would have to be an icing on this cake -- quantitative variations within complex emotional and cognitive systems.

The other is the empirical fact that human races and ethnic groups are psychologically highly similar, if not identical. People everywhere use language, get jealous, are selective in choosing mates, find their children cute, are afraid of heights and the dark, experience anger and disgust, learn names for local species, and so on. If you adopt children from a technologically undeveloped part of the world, they will fit in to modern society just fine. To the extent that this is true, there can't have been a whole lot of uneven psychological evolution postdating the split among the races 50-100,000 years ago (though there could have been parallel evolution in all the branches).

Wednesday, February 06, 2008

Staying a Step Ahead of Aging

Being a person who exercises daily at moderate levels, the New York Times article with the title of this post was not a welcome read. It argues that blowing yourself away every few days is a better deal - i.e., that exercising intensely is more important than exercising often. I've always been suspicious of the 'no pain, no gain' school of exercise, thinking that while it might work for younger folks, it might not be taking enough account of potential long term inflammatory responses in people over 50.

Accurate visual movement without visual perception in normal subjects

An interesting article by Christensen et al. demonstrates blindsight in normal subjects:

Clinical cases of blindsight have shown that visually guided movements can be accomplished without conscious visual perception. Here, we show that blindsight can be induced in healthy subjects by using transcranial magnetic stimulation over the visual cortex. Transcranial magnetic stimulation blocked the conscious perception of a visual stimulus, but subjects still corrected an ongoing reaching movement in response to the stimulus. The data show that correction of reaching movements does not require conscious perception of a visual target stimulus, even in healthy people.
Here is part of their analysis:
It has been suggested that an important mechanism for the ability to perform fast corrections of goal-directed movement is an efference copy (i.e. a parallel signal indicating the expected sensory consequence of a motor command)... The argument is that the initial motor reaction time, when the subject reaches toward the first target, requires that the visual signal is processed via the visual cortex to motor regions of the brain. The advantage of an efference copy is that already at a very early point in the movement process any deviation in the performed movement from the intended movement can be adjusted. Hence, lower reaction time during the correction can be accomplished compared with the initial motor reaction time.

Furthermore, our results suggest that the mechanism responsible for fast visually guided corrective movements lies outside visual cortex and that the visual signals used for correction of movements bypass visual cortex. There may be subcortical routes for visually guided reaching that bypass the cortical regions affected by TMS.

Tuesday, February 05, 2008

Our left hemisphere is superior at perceiving global topology.

Most theories on how we extract visual information from our environment start with the sensible hierarchy of detecting features first and then integrating them to build objects. Li Chen and colleagues have also argued for the importance of extracting global topological properties as primitives in object perception, and they now have reported the intriguing discovery that the human visual system's sensitivity to topological properties is superior in the left hemisphere, at least for right-handers. Here is a graphic showing the basic conclusion of their work, from the commentary by He:

Figure - Schematic depiction of the left hemisphere's superiority in topological discrimination. A pair of shapes was briefly presented in either the right or the left visual field, projecting initially to the left or right hemispheres (LH or RH), respectively. Observers were asked to respond to whether the two shapes were the same or different. Although the triangle may appear more different from the disk than the ring does, human observers are more sensitive to the difference between the disk and the ring, which are topologically different, but are less sensitive to the difference between the triangle and the disk, which are topologically equivalent. Now, the authors show that the ability to discriminate topological differences is more superior in the left hemisphere than in the right hemisphere, as indicated by the bar plots showing the percent correct discrimination

Poetry in your genome?

Now that we are able to synthesize complete genomes for organisms, we can also write what we want in its individual genes. Andrew Pollack describes several such literary efforts:

You were expecting poetry, perhaps? The secret messages hidden in J. Craig Venter’s synthetic bacterial genome have now been revealed. They are Dr. Venter’s name, and that of his research institute and co-workers....Dr. Venter announced last week in the journal Science that his team had become the first to synthesize the complete DNA of a bacterium. He revealed that the genome had five “watermarks,” sequences of genetic code that would spell words using the letters for the amino acids that would be produced by the DNA...Wired Science reported Monday that it had ferreted out the messages, with help from government scientists. One watermark said “VenterInstitvte,” using the unusual spelling because there is no amino acid represented by the letter “u.”...The other messages were CraigVenter, HamSmith, GlassandClyde and CindiandClyde for his co-authors Hamilton O. Smith, Clyde A. Hutchison III, John I. Glass and Cynthia Andrews-Pfannkoch. A Venter spokeswoman confirmed them...In 2003, scientists from Icon Genetics, a German biotechnology company, engineered the plant Arabidopsis thaliana to contain a line from Virgil’s “Georgics,” with the meaning “Neither can every soil bear every fruit.”

Monday, February 04, 2008

Stronger or weaker brain synapses after sleep?

Why do we spend a third of our lives asleep? The answers suggested so far are varied and controversial. It is well documented that improvement in learning and memory accompanies a night of sleep. One idea is that most new information is discarded during sleep, as diurnal animals are bombarded by stimuli during the day, most of which we want to (or need to) forget. Synapses need to recover. If this is the dominant reason why we sleep, then decreased numbers of synapses or synapse weakening should be a prominent neuronal feature of sleep. Fountain points to an article by Tonini and colleagues (Nature Neuroscience 11, pp. 200 - 208, 2008) that provides evidence for this option. Tononi suggests that after sleep "“we get a leaner brain — there’s a gain in terms of energy, space and supplies, and you are ready to learn anew.” Here is their abstract:

Plastic changes occurring during wakefulness aid in the acquisition and consolidation of memories. For some memories, further consolidation requires sleep, but whether plastic processes during wakefulness and sleep differ is unclear. We show that, in rat cortex and hippocampus, GluR1-containing AMPA receptor (AMPAR) levels are high during wakefulness and low during sleep, and changes in the phosphorylation states of AMPARs, CamKII and GSK3beta are consistent with synaptic potentiation during wakefulness and depression during sleep. Furthermore, slope and amplitude of cortical evoked responses increase after wakefulness, decrease after sleep and correlate with changes in slow-wave activity, a marker of sleep pressure. Changes in molecular and electrophysiological indicators of synaptic strength are largely independent of the time of day. Finally, cortical long-term potentiation can be easily induced after sleep, but not after wakefulness. Thus, wakefulness appears to be associated with net synaptic potentiation, whereas sleep may favor global synaptic depression, thereby preserving an overall balance of synaptic strength.

The algorithms of love...

John Tierney writes an interesting article on internet match finding services in the Jan 29 New York Times.

Online matchmaking has become a boom industry as rival scientists test their algorithms for finding love...The leading yenta is eHarmony, which pioneered the don’t-try-this-yourself approach eight years ago by refusing to let its online customers browse for their own dates. It requires them to answer a 258-question personality test and then picks potential partners...Another company, Perfectmatch.com, is using an algorithm designed by Pepper Schwartz, a sociologist at the University of Washington at Seattle. Match.com, which became the largest online dating service by letting people find their own partners, set up a new matchmaking service, Chemistry.com, using an algorithm created by Helen E. Fisher, an anthropologist at Rutgers who has studied the neural chemistry of people in love.

As the matchmakers compete for customers — and denigrate each other’s methodology — the battle has intrigued academic researchers who study the mating game. On the one hand, they are skeptical, because the algorithms and the results have not been published for peer review. But they also realize that these online companies give scientists a remarkable opportunity to gather enormous amounts of data and test their theories in the field. EHarmony says more than 19 million people have filled out its questionnaire...In the battle of the matchmakers, Chemistry.com has been running commercials faulting eHarmony for refusing to match gay couples (eHarmony says it can’t because its algorithm is based on data from heterosexuals), and eHarmony asked the Better Business Bureau to stop Chemistry.com from claiming its algorithm had been scientifically validated. The bureau concurred that there was not enough evidence, and Chemistry.com agreed to stop advertising that Dr. Fisher’s method was based on “the latest science of attraction.”

Dr. Fisher now says the ruling against her last year made sense because her algorithm at that time was still a work in progress as she correlated sociological and psychological measures, as well as indicators linked to chemical systems in the brain. But now, she said, she has the evidence from Chemistry.com users to validate the method, and she plans to publish it along with the details of the algorithm...“I believe in transparency,” she said, taking a dig at eHarmony. “I want to share my data so that I will get peer review.”
On reading that Chemistry.com didn't discriminate against gay match making, I naturally decided to give it a spin and went through their series of questions (including one on the relative lengths of one's index and ringer finger). It included psychological profile questions and some interesting tests of susceptibility to visual illusions. Alas, the list of prospective mates for a 65 yr. old retired professor was rather lean, and I ended my experiment by withdrawing my chemistry.com profile after one day.

Sunday, February 03, 2008

Super Bowl preliminaries....the anthropoligist from Mars

The description in the header of this blog includes the phrase "and random curious stuff." Well....this post qualifies. I show you one of the videos used Sunday to warm patrons up for the super bowl orgy at my happy hour bar. "Macho Man", the Village People. Watching this did make me feel like Oliver Sacks' anthropologist from Mars.

Friday, February 01, 2008

Will cognition-enhancing drugs become as acceptable as coffee?

In my backlog of blog-postings-to-do is one on an article in the Dec. 27 issue of Nature on the use of cognition-enhancing drugs not only to treat cognitive disabilities, but also to enhance performance in those without medical issues (Nature 450, 1157–1159; 2007). Two drugs commonly used to reduced extraneous activity and focus attention are methylphenidate (Ritalin) and atomoxetine; both increase brain levels of the neurotransmitter noradrenaline. Sahakia and Morein-Zamir pose a series of questions whose answers become increasingly less obvious, and invite responses in an online forum:

-Should adults with severe memory and concentration problems from neuropsychiatric disorders be given cognitive-enhancing drugs?
-If drugs can be shown to have mild side effects, should they be prescribed more widely for other psychiatric disorders?
-Do the same arguments apply for young children and adolescents with neuropsychiatric disorders, such as those with ADHD?
-Would you boost your own brain power?
-How would you react if you knew your colleagues — or your students — were taking cognitive enhancers?
-How should society react?
I have now received a message from the Nature people, sent to a number of bloggers in the brain and behavior area, suggesting that readers check out some responses to this article and also participate in a survey.

Faith and Healing

Jerome Groopman reviews Anne Harrington's new book "The Cure Within - A History of Mind-Body Medicine" in the NY Times Book review of Jan. 27. Harrington is professor and chair of the History of Science department at Harvard. Here is the final section of that review:

Harrington offers close observations of the interactions between the Harvard cardiologist Herbert Benson (and later the neuroscientist Richard Davidson of the University of Wisconsin) and the Dalai Lama and his Tibetan monks. She admits longing for scientific support for what is, in essence, an “Orientalist” conception, that the “Other” holds wisdom and therapeutic treasures beyond those imaginable to us in the West. Some of Harrington’s wish is fulfilled in the biology of the placebo response. Recent studies show that belief, even in inert treatments, can have profound benefits in relieving pain, likely via release of endorphins and other mediators in the brain. But despite several decades of concerted research in the field of psychoneuroimmunology, to my scrutiny no robust effects of meditation or other relaxation techniques that could combat illnesses like cancer or AIDS have been identified.

Harrington concludes with the questions that her students at Harvard regularly ask: Which mind-body narratives are “true”? Are all the stories we tell ourselves about illness equally valuable? Harrington has already answered these queries in part in the voice of the woman with breast cancer in the Stanford study. Yet, she has still been “haunted” over the years by unusual events, like the case of a man whose tumors seemed to melt “like snowballs on a hot stove” in response to a “worthlesss” cancer treatment that he nonetheless believed in. The physicist Freeman Dyson once noted that, to a scientist, an event like the spontaneous remission of a tumor is viewed as occurring at the asymptote of probability, one in several million, but through the eyes of a believer it becomes not mathematics but a miracle. Harrington shows us that, whatever science reveals about the cause and course of disease, we will continue to tell ourselves stories, and try to use our own metaphors to find meaning in randomness.

The fruits of promiscuity...more dancing and food

From the research highlights section of the Jan. 24 issue of Nature, summarizing work by Matilla et al:

A honeybee colony led by a promiscuous queen does better than one led by a faithful queen: the colony forages more, stores more food and grows faster. Heather Mattila and her colleagues at Cornell University in Ithaca, New York, think this happens because genetically diverse colonies dance more....Honeybees 'waggle dance' to tell each other where to fly to find food. Mattila's team compared colonies in which the queen always bred with the same male to colonies ruled by a queen that had been inseminated by 15 drones. On average, worker bees from the latter category performed 36% more dances daily, kept waggling for 62% longer and communicated about food discoveries farther from the nest than did workers from single-father colonies.