There is an interesting brief communication by Moriceau and Sullivan in Nature Neuroscience (vol. 9, pp. 1004 - 1006, 2006) describing how maternal presence can switch fear learning to attraction in preweanling (12–15 days old) rats. In the mother's absence, odor-shock conditioning produces amygdala activation and learned odor avoidance. With maternal presence, this same conditioning yields an odor preference without amygdala activation. Maternal presence acts through suppressing pup corticosterone and thus corticosterone's regulation of amygdala activity. Intra-amygdala corticosterone infusions that over-ride maternal suppression of corticosterone permit fear conditioning and amygdala activation to return.
The data suggest that preweanling pups have two odor-shock learning circuits, with maternal presence providing suppression of stress-induced corticosterone release and engaging the odor-shock circuit for odor preference learning supporting infant-mother attachment. The data suggest a way in which the functional maturation of brain development may be disrupted by stress.. The mother's ability to modify fear learning circuitry may provide clues to abusive attachment and predisposition for mental illness and altered emotional expression later in life. The validity of an animal model of abusive attachment is strengthened by the wide phylogenetic representation of abusive attachment, which has been documented in chicks, infant dogs, rodents and nonhuman primates.
Tuesday, August 08, 2006
Monday, August 07, 2006
How emotions nudge rationality - brain correlates of "framing"
A very elegant report by Martino et al. from Dolan's laboratory has the title: "Frames, Biases, and Rational Decision-Making in the Human Brain"
"Human choices are remarkably susceptible to the manner in which options are presented. This so-called "framing effect" represents a striking violation of standard economic accounts of human rationality, although its underlying neurobiology is not understood. We found that the framing effect was specifically associated with amygdala activity, suggesting a key role for an emotional system in mediating decision biases. Moreover, across individuals, orbital and medial prefrontal cortex activity predicted a reduced susceptibility to the framing effect. This finding highlights the importance of incorporating emotional processes within models of human choice and suggests how the brain may modulate the effect of these biasing influences to approximate rationality."
From the brief review of this article by Miller in the same issue of Science, one example of framing:
Faced with a decision between two packages of ground beef, one labeled "80% lean," the other "20% fat," which would you choose? The meat is exactly the same, but most people would pick "80% lean." The language used to describe options often influences what people choose, a phenomenon behavioral economists call the framing effect. The Martino et al. experiments look directly at brain activity correlating with this effect.
The experiments used a novel financial decision-making task. Participants (20 university students or graduates) received a message indicating the amount of money that they would initially receive in that trial (e.g., "You receive £50"). Subjects then had to choose between a "sure" option and a "gamble" option presented in the context of two different frames. The "sure" option was formulated as either the amount of money retained from the initial starting amount (e.g., keep £20 of the £50; "Gain" frame) or as the amount of money lost from the initial amount (e.g., lose £30 of the £50; "Loss" frame). Subjects - who performed the task while inside an fMRI scanner! - were risk-averse in the Gain frame, tending to choose the sure option over the gamble option and were risk-seeking in the Loss frame, preferring the gamble option.
The amygdala (A, in the figure) was relatively more activated when subjects chose in accordance with the frame effect. When subjects made decisions that ran counter to their general behavioral tendency enhanced activity in the anterior cingulate cortex was observed (C, in the figure). This suggests an opponency between two neural systems, with ACC activation consistent with the detection of conflict between predominantly "analytic" response tendencies and a more "emotional" amygdala-based system.
Decreased susceptibility to the framing effect correlated with enhanced activity in the orbital and medial prefrontal cortex, specifically in the right orbitofrontal cortex (A, in the figure). The findings support a model in which the OMPFC evaluates and integrates emotional and cognitive information, thus underpinning more "rational" (i.e., description-invariant) behavior.
The framing bias occurs because "individuals incorporate a potentially broad range of additional emotional information into the decision process. In evolutionary terms, this mechanism may confer a strong advantage, because such contextual cues may carry useful, if not critical, information. Neglecting such information may ignore the subtle social cues that communicate elements of (possibly unconscious) knowledge that allow optimal decisions to be made in a variety of environments. However, in modern society, which contains many symbolic artifacts and where optimal decision-making often requires skills of abstraction and decontextualization, such mechanisms may render human choices irrational."
"Human choices are remarkably susceptible to the manner in which options are presented. This so-called "framing effect" represents a striking violation of standard economic accounts of human rationality, although its underlying neurobiology is not understood. We found that the framing effect was specifically associated with amygdala activity, suggesting a key role for an emotional system in mediating decision biases. Moreover, across individuals, orbital and medial prefrontal cortex activity predicted a reduced susceptibility to the framing effect. This finding highlights the importance of incorporating emotional processes within models of human choice and suggests how the brain may modulate the effect of these biasing influences to approximate rationality."
From the brief review of this article by Miller in the same issue of Science, one example of framing:
Faced with a decision between two packages of ground beef, one labeled "80% lean," the other "20% fat," which would you choose? The meat is exactly the same, but most people would pick "80% lean." The language used to describe options often influences what people choose, a phenomenon behavioral economists call the framing effect. The Martino et al. experiments look directly at brain activity correlating with this effect.
The experiments used a novel financial decision-making task. Participants (20 university students or graduates) received a message indicating the amount of money that they would initially receive in that trial (e.g., "You receive £50"). Subjects then had to choose between a "sure" option and a "gamble" option presented in the context of two different frames. The "sure" option was formulated as either the amount of money retained from the initial starting amount (e.g., keep £20 of the £50; "Gain" frame) or as the amount of money lost from the initial amount (e.g., lose £30 of the £50; "Loss" frame). Subjects - who performed the task while inside an fMRI scanner! - were risk-averse in the Gain frame, tending to choose the sure option over the gamble option and were risk-seeking in the Loss frame, preferring the gamble option.
The amygdala (A, in the figure) was relatively more activated when subjects chose in accordance with the frame effect. When subjects made decisions that ran counter to their general behavioral tendency enhanced activity in the anterior cingulate cortex was observed (C, in the figure). This suggests an opponency between two neural systems, with ACC activation consistent with the detection of conflict between predominantly "analytic" response tendencies and a more "emotional" amygdala-based system.
Decreased susceptibility to the framing effect correlated with enhanced activity in the orbital and medial prefrontal cortex, specifically in the right orbitofrontal cortex (A, in the figure). The findings support a model in which the OMPFC evaluates and integrates emotional and cognitive information, thus underpinning more "rational" (i.e., description-invariant) behavior.
The framing bias occurs because "individuals incorporate a potentially broad range of additional emotional information into the decision process. In evolutionary terms, this mechanism may confer a strong advantage, because such contextual cues may carry useful, if not critical, information. Neglecting such information may ignore the subtle social cues that communicate elements of (possibly unconscious) knowledge that allow optimal decisions to be made in a variety of environments. However, in modern society, which contains many symbolic artifacts and where optimal decision-making often requires skills of abstraction and decontextualization, such mechanisms may render human choices irrational."
Saturday, August 05, 2006
Cortical Plasticity and Recovery from Brain Injury
Ramanathan et al have made some interesting observations on the recovery of complex movement patterns after focal damage to the rat motor cortex. They used "behaviorally relevant," long-duration (500-msec) intracortical microstimulation of rat motor cortex that causes complex, multijoint movements. A consistent topographic distribution of these complex motor patterns is present across the motor cortex in naïve rats. They documented the plasticity of these complex movement patterns after focal cortical injury by measuring a significant expansion of specific complex movement representations in response to rehabilitative training after injury. (The rehabilitative training task required animals to use the forepaw to reach through a small slit in a Plexiglas chamber and grasp and retrieve a small food pellet positioned on a platform near the chamber.) The degree of functional recovery attained after cortical injury and rehabilitation correlated significantly with a specific feature of map reorganization, the ability to reexpress movement patterns disrupted by the initial injury. This suggests the existence of complex movement representations in the rat motor cortex that exhibit plasticity after injury and rehabilitation. Thus there is a significant correlation between the reorganization of disrupted complex representations and behavioral recovery after brain injury.
The graphic shows the types of complex movement elicited by long-duration microstimulation. The maps of motor cortex regulating these movements are a bit complex to show in this posting.
Figure: Complex movements elicited by long-duration microstimulation. (A–C) Three types of complex movements evoked by long-duration stimulation within motor cortex. Complex movements elicited by long-duration microstimulation occur across multiple joints. (A) Reaching movement characterized by rostral displacement of the elbow and shoulder, without change in wrist configuration. (B) Retraction characterized by caudal displacement of the elbow and forepaw. (C) Grasping movement characterized by contraction of all digit joints simultaneously. Credit: PNAS.
The graphic shows the types of complex movement elicited by long-duration microstimulation. The maps of motor cortex regulating these movements are a bit complex to show in this posting.
Figure: Complex movements elicited by long-duration microstimulation. (A–C) Three types of complex movements evoked by long-duration stimulation within motor cortex. Complex movements elicited by long-duration microstimulation occur across multiple joints. (A) Reaching movement characterized by rostral displacement of the elbow and shoulder, without change in wrist configuration. (B) Retraction characterized by caudal displacement of the elbow and forepaw. (C) Grasping movement characterized by contraction of all digit joints simultaneously. Credit: PNAS.
Friday, August 04, 2006
Social Class and Values - an inversion?
A humorous Op-Ed piece in the Aug 3 NYTimes by David Brooks notes a recent trend in America that he considers a blow to the natural order of the universe. "In all healthy societies, the middle-class people have wholesome middle-class values while the upper-crust bluebloods lead lives of cosseted leisure interrupted by infidelity, overdoses and hunting accidents. But in America today we’ve got this all bollixed up... Through some screw-up in the moral superstructure, we now have a plutocratic upper class infused with the staid industriousness of Ben Franklin, while we are apparently seeing the emergence of a Wal-Mart leisure class — devil-may-care middle-age slackers who live off home-equity loans and disability payments so they can surf the History Channel and enjoy fantasy football leagues...For the first time in human history, the rich work longer hours than the proletariat"...(the piece then documents a number of middle aged men who have dropped out of the work force).. "What I see is a migration of values. Once upon a time, middle-class men would have defined their dignity by their ability to work hard, provide for their family and live as self-reliant members of society. But these fellows, to judge by their quotations, define their dignity the same way the subjects of Thorstein Veblen’s “The Theory of the Leisure Class” defined theirs... by the loftiness of their thinking. They define their dignity not by their achievement, but by their personal enlightenment, their autonomy, by their distance from anything dishonorably menial or compulsory."
And, in a bit of a non-sequitur: "The only comfort I’ve had from these disturbing trends is another recent story in The Times. Joyce Wadler reported that women in places like the Hamptons are still bedding down with the hired help. R. Couri Hay, the society editor of Hamptons magazine, celebrated rich women’s tendency to sleep with their home renovators..."Nobody knows,” he said. “The contractor isn’t going to tell because the husband is writing the check, the wife isn’t going to tell, and you get a better job because she’s providing a fringe benefit. Everybody wins.”...Thank God somebody is standing up for traditional morality."
And, in a bit of a non-sequitur: "The only comfort I’ve had from these disturbing trends is another recent story in The Times. Joyce Wadler reported that women in places like the Hamptons are still bedding down with the hired help. R. Couri Hay, the society editor of Hamptons magazine, celebrated rich women’s tendency to sleep with their home renovators..."Nobody knows,” he said. “The contractor isn’t going to tell because the husband is writing the check, the wife isn’t going to tell, and you get a better job because she’s providing a fringe benefit. Everybody wins.”...Thank God somebody is standing up for traditional morality."
Thursday, August 03, 2006
The Gender Wars Continuing - retort from Pinker
Here is the latest exchange between Steven Pinker and his detractors, from the Aug 3 issue of Nature Magazine:
The gender debate: science promises an honest investigation of the world
Steven Pinker1
- Department of Psychology, Harvard University, Cambridge, Massachusetts 02138, USA
Sir:
Ben Barres's Commentary article "Does gender matter?" (Nature 442, 133–136; 2006) misrepresents my position.
In my book The Blank Slate (Allen Lane, London, 2002), and in a published debate (http://www.edge.org/3rd_culture/debate05/debate05_index.html), I reviewed a large empirical literature showing differences in mean and variance in the distributions of talents, temperaments and life priorities among men and women. Given these differences, some favouring men, some women, it is unlikely that the proportions of men and women in any profession would be identical, even without discrimination. That is probably one of several reasons that the sex ratio tips towards women in some scientific disciplines (such as my own, developmental psycholinguistics) and towards men in others. Barres renders this conclusion as "a whole group of people is innately wired to fail" — an egregious distortion.
Barres claims that I have denied that sex discrimination is a significant factor in professional life, whereas I have repeatedly stated the opposite, and indeed provided a jacket endorsement for Virginia Valian's book Why So Slow? (MIT Press, Cambridge, 1998) that summarized the evidence.
As for encouraging women in science: in my experience, students of both sexes are attracted to science because it promises an honest investigation into how the world works, an alternative to the subjectivity, simplistic dichotomies and moralistic name-calling that characterize politics and personal quarrels. Let's hope Barres's Commentary article does not discourage them.
Readers are encouraged to add their comments to the Ben Barres Commentary on the Nature News Blog at: http://blogs.nature.com/news/blog/2006/07/
does_gender_matter.html.
Personality Predicts Responsivity of the Brain Reward System
The Journal of Neuroscience has started a new feature: short reviews of a recent paper in the Journal, written exclusively by graduate students or postdoctoral fellows. They are meant to mimic the journal clubs that exist in many academic department or institutions.
A recent entry by J. B. Engelmann discusses a paper by Beaver et al. that examines the relationship between a personality trait, reward sensitivity, and activity of the brain reward system measured by functional magnetic resonance imaging. A study like this is relevant to understanding the over-consumption of appetizing high-caloric foods that has contributed to the dramatic increase in obesity within the past 20 years, making obesity a top 10 global health threat. Here are some clips from the review and article:
Figure - A highly simplified schematic diagram outlines the connections between central nodes in the brain reward system (modified from Berridge and Robinson, 2003). Animal as well as human neuroimaging studies have implicated this network in the hedonic and motivational effects of natural rewards and drugs of abuse, such as food and amphetamine. AMYG, Amygdala; NAC, nucleus accumbens; OFC, orbitofrontal cortex; VP, ventral pallidum; VTA/SN, ventral tegmental area/substantia nigra.
Beaver et al. showed that reward sensitivity, as assessed by the Behavioral Inhibition Scale/Behavioral Activation Scale, predicted neural responses to pictures of appetizing foods in the network of the brain regions outlined in the Figure. Functional magnetic resonance imaging, in conjunction with a blocked experimental design, was used to record blood oxygenation-level dependent (BOLD) responses while participants passively viewed pictures of foods from four different categories...The authors found increased activation in orbitofrontal cortex (appetizing vs nonfood objects) and bilateral ventral striatum (appetizing vs bland foods). Interestingly, there was a dissociation between left and right orbitofrontal cortex such that appetizing food stimuli activated the left orbitofrontal cortex, whereas disgusting food stimuli activated the right orbitofrontal cortex.
Beaver et al. provide an important link between human behavioral research that has demonstrated an association between trait reward sensitivity and unhealthy eating habits and animal research implicating the reward network in hyperphagia and increased intake of high-caloric foods. Their findings thus offer a possible explanation for why some individuals overeat compulsively. It will be interesting to establish a more direct link between compulsive overeating and responsivity of the reward system, for instance by correlating activity in the reward system in response to images depicting appetizing foods and body mass index. Finally, an abundance of parallels between obesity and drug addiction points to similarities in the underlying brain mechanisms and neural adaptations that accompany these two conditions
A recent entry by J. B. Engelmann discusses a paper by Beaver et al. that examines the relationship between a personality trait, reward sensitivity, and activity of the brain reward system measured by functional magnetic resonance imaging. A study like this is relevant to understanding the over-consumption of appetizing high-caloric foods that has contributed to the dramatic increase in obesity within the past 20 years, making obesity a top 10 global health threat. Here are some clips from the review and article:
Figure - A highly simplified schematic diagram outlines the connections between central nodes in the brain reward system (modified from Berridge and Robinson, 2003). Animal as well as human neuroimaging studies have implicated this network in the hedonic and motivational effects of natural rewards and drugs of abuse, such as food and amphetamine. AMYG, Amygdala; NAC, nucleus accumbens; OFC, orbitofrontal cortex; VP, ventral pallidum; VTA/SN, ventral tegmental area/substantia nigra.
Beaver et al. showed that reward sensitivity, as assessed by the Behavioral Inhibition Scale/Behavioral Activation Scale, predicted neural responses to pictures of appetizing foods in the network of the brain regions outlined in the Figure. Functional magnetic resonance imaging, in conjunction with a blocked experimental design, was used to record blood oxygenation-level dependent (BOLD) responses while participants passively viewed pictures of foods from four different categories...The authors found increased activation in orbitofrontal cortex (appetizing vs nonfood objects) and bilateral ventral striatum (appetizing vs bland foods). Interestingly, there was a dissociation between left and right orbitofrontal cortex such that appetizing food stimuli activated the left orbitofrontal cortex, whereas disgusting food stimuli activated the right orbitofrontal cortex.
Beaver et al. provide an important link between human behavioral research that has demonstrated an association between trait reward sensitivity and unhealthy eating habits and animal research implicating the reward network in hyperphagia and increased intake of high-caloric foods. Their findings thus offer a possible explanation for why some individuals overeat compulsively. It will be interesting to establish a more direct link between compulsive overeating and responsivity of the reward system, for instance by correlating activity in the reward system in response to images depicting appetizing foods and body mass index. Finally, an abundance of parallels between obesity and drug addiction points to similarities in the underlying brain mechanisms and neural adaptations that accompany these two conditions
Wednesday, August 02, 2006
How do we persist when our molecules do not?
John McCrone wrote a brief essay on this topic several years ago in the now-defunct Science and Consciousness Review (or, can anyone point me to a newer URL that works??). I thought that it is worth repeating and abstracting here:
Our entire brain is recycled about every two months, and different components of the synapses that transmit information between nerve cells replace themselves, molecular for molecule, on a time scale of hours to days. All of these synapses and the intricate network of trillions of connections that they form have been crafted by our experience to make us who we are. How can all this remain stable when the large molecules that make synapses seem to be boiling, falling apart nearly as soon as they are made?
Synapses turn out to be reflecting a living confluence of top-down and bottom-up pressures.. (Bottom up: gene or RNA expression patterns remembering what the state of a synapse should be; top down: a constant replaying, or jangling trace, that helps keep labile synapses stabilized). The information is out there in the whole system and it is making the synaptic patterns we observe.
"This kind of topsy-turvey picture can only be resolved by taking a more holistic view of the
brain as the organ of consciousness. The whole shapes the parts as much as the parts shape
the whole. No component of the system is itself stable but the entire production locks together
to have stable existence. This is how you can manage to persist even though much of you is
being recycled by day if not the hour."
Our entire brain is recycled about every two months, and different components of the synapses that transmit information between nerve cells replace themselves, molecular for molecule, on a time scale of hours to days. All of these synapses and the intricate network of trillions of connections that they form have been crafted by our experience to make us who we are. How can all this remain stable when the large molecules that make synapses seem to be boiling, falling apart nearly as soon as they are made?
Synapses turn out to be reflecting a living confluence of top-down and bottom-up pressures.. (Bottom up: gene or RNA expression patterns remembering what the state of a synapse should be; top down: a constant replaying, or jangling trace, that helps keep labile synapses stabilized). The information is out there in the whole system and it is making the synaptic patterns we observe.
"This kind of topsy-turvey picture can only be resolved by taking a more holistic view of the
brain as the organ of consciousness. The whole shapes the parts as much as the parts shape
the whole. No component of the system is itself stable but the entire production locks together
to have stable existence. This is how you can manage to persist even though much of you is
being recycled by day if not the hour."
Tuesday, August 01, 2006
Whale Song and Wavelets.... and some piano
An article by G. Cuda in today's NYTimes points out interesting work by Mark Fischer that transforms whale song from what sounds like a series of clicks into a visual art form using wavelet technology. Several beautiful videos of his work can be seen at Google Video. Intricate detail is captured without losing the bigger picture, and presentation in circular form makes repeated patterns more evident. Patterns are unique to different whale species, and even to individuals in a group. Presentation in this form might aid researcher trying to show that repetitions in whale songs follow grammatical rules similar to those of human language.And, speaking of sounds, I might mention the totally unrelated point that I am starting to put some of my piano recordings and videos from this summer on my website.
Graphic credit, copyright: NYTimes
Monday, July 31, 2006
Living longer and better.....
The July 30 Sunday New York Times has a fascinating article comparing longevity and health in men over the period 1850-2000 (data taken mainly from military records).
"Humans in the industrialized world have undergone a form of evolution that is unique not only to humankind, but unique among the 7,000 or so generations of humans who have ever inhabited the earth. The difference does not involve changes in genes, as far as is known, but changes in the human form. It shows up in several ways, from those that are well known and almost taken for granted, like greater heights and longer lives, to ones that are emerging only from comparisons of health records. The biggest surprise emerging from the new studies is that many chronic ailments like heart disease, lung disease and arthritis are occurring an average of 10 to 25 years later than they used to. There is also less disability among older people today, according to a federal study that directly measures it. And that is not just because medical treatments like cataract surgery keep people functioning. Human bodies are simply not breaking down the way they did before. Even the human mind seems improved. The average I.Q. has been increasing for decades, and at least one study found that a person’s chances of having dementia in old age appeared to have fallen in recent years. The proposed reasons are as unexpected as the changes themselves. Improved medical care is only part of the explanation; studies suggest that the effects seem to have been set in motion by events early in life, even in the womb, that show up in middle and old age."
"In 1900, 13 percent of people who were 65 could expect to see 85. Now, nearly half of 65-year-olds can expect to live that long. People even look different today. American men, for example, are nearly 3 inches taller than they were 100 years ago and about 50 pounds heavier."
"Today’s middle-aged people are the first generation to grow up with childhood vaccines and with antibiotics. Early life for them was much better than it was for their parents, whose early life, in turn, was much better than it was for their parents. And if good health and nutrition early in life are major factors in determining health in middle and old age, that bodes well for middle-aged people today. Investigators predict that they may live longer and with less pain and misery than any previous generation."
There is also the concern, however, that obesity could lead to so much diabetes and heart disease that life expectancy could level off or even decline within the first half of this century.
Graphic: credit and copyright, N.Y. Times
"Humans in the industrialized world have undergone a form of evolution that is unique not only to humankind, but unique among the 7,000 or so generations of humans who have ever inhabited the earth. The difference does not involve changes in genes, as far as is known, but changes in the human form. It shows up in several ways, from those that are well known and almost taken for granted, like greater heights and longer lives, to ones that are emerging only from comparisons of health records. The biggest surprise emerging from the new studies is that many chronic ailments like heart disease, lung disease and arthritis are occurring an average of 10 to 25 years later than they used to. There is also less disability among older people today, according to a federal study that directly measures it. And that is not just because medical treatments like cataract surgery keep people functioning. Human bodies are simply not breaking down the way they did before. Even the human mind seems improved. The average I.Q. has been increasing for decades, and at least one study found that a person’s chances of having dementia in old age appeared to have fallen in recent years. The proposed reasons are as unexpected as the changes themselves. Improved medical care is only part of the explanation; studies suggest that the effects seem to have been set in motion by events early in life, even in the womb, that show up in middle and old age."
"In 1900, 13 percent of people who were 65 could expect to see 85. Now, nearly half of 65-year-olds can expect to live that long. People even look different today. American men, for example, are nearly 3 inches taller than they were 100 years ago and about 50 pounds heavier."
"Today’s middle-aged people are the first generation to grow up with childhood vaccines and with antibiotics. Early life for them was much better than it was for their parents, whose early life, in turn, was much better than it was for their parents. And if good health and nutrition early in life are major factors in determining health in middle and old age, that bodes well for middle-aged people today. Investigators predict that they may live longer and with less pain and misery than any previous generation."
There is also the concern, however, that obesity could lead to so much diabetes and heart disease that life expectancy could level off or even decline within the first half of this century.
Graphic: credit and copyright, N.Y. Times
Friday, July 28, 2006
Cracking the Language Code...
An interesting article by McNealy et al. in J. Neuroscience begins to look at the neural basis of detecting word boundaries in continuous speech using functional magnetic resonance imaging (fMRI). From their abstract: "the neural substrate of word segmentation was examined on-line as participants listened to three streams of concatenated syllables, containing either statistical regularities alone, statistical regularities and speech cues, or no cues. Despite the participants’ inability to explicitly detect differences between the speech streams, neural activity differed significantly across conditions, with left-lateralized signal increases in temporal cortices observed only when participants listened to streams containing statistical regularities, particularly the stream containing speech cues. In a second fMRI study, designed to verify that word segmentation had implicitly taken place, participants listened to trisyllabic combinations that occurred with different frequencies in the streams of speech they just heard ("words," 45 times; "partwords," 15 times; "nonwords," once). Reliably greater activity in left inferior and middle frontal gyri was observed when comparing words with partwords and, to a lesser extent, when comparing partwords with nonwords. Activity in these regions, taken to index the implicit detection of word boundaries, was positively correlated with participants’ rapid auditory processing skills. "
Figure: left superior temporal gyrus activity associated with listening to the artificial language conditions (compared with the random syllables condition) during the speech stream exposure task was significantly correlated with participants’ ability to discriminate words that occurred in the artificial languages. Credit: J. Neuroscience
These findings provide a neural signature of on-line word segmentation in the mature brain and an initial model with which to study developmental changes in the neural architecture involved in processing speech cues during language learning.
Figure: left superior temporal gyrus activity associated with listening to the artificial language conditions (compared with the random syllables condition) during the speech stream exposure task was significantly correlated with participants’ ability to discriminate words that occurred in the artificial languages. Credit: J. Neuroscience
These findings provide a neural signature of on-line word segmentation in the mature brain and an initial model with which to study developmental changes in the neural architecture involved in processing speech cues during language learning.
Thursday, July 27, 2006
Face Blindness - hereditary prosopagnosia
One of the most striking consequences of damage to the medial occipitotemporal region of the brain can be the loss of the ability to recognize familiar faces. Patients know only that a face is a face, and can name its parts. There is a website devoted to this disorder. The accquired condition is rare, and inherited or congenital forms of prosopagnosia have been assumed to be even more rare. Kennerknecht et al., however, have now shown that in one group of 689 students, 17 (~2.5%) had congenital prosopagnosia. It turns out that this condition can easily go undiagnosed, because subjects develop alternate strategies for identifying people — they remember their clothes, mannerisms, gait, hairstyle or voice, and by using such techniques, many can compensate quite well. Bakalar, in a review of this work in the July 18 New York Times, notes that people with face blindness can typically understand facially expressed emotions — they know whether a face is happy or sad, angry or puzzled. They can detect subtle facial cues, determine gender and even agree with everyone else about which faces are attractive and which are not. In other words, they see the face clearly, they just do not know whose face they are looking at, and cannot remember it once they stop looking. A specific gene for the disorder has not been found, but evidence is mounting that the trait is inherited. The pedigrees that have been established so far are compatible with autosomal dominant inheritance.”
Tuesday, July 25, 2006
Nice and Nasty Rats.... Religion and Science
Today's science section of the New York Times has several articles worth noting.
Some remarkable experiments were started in the former Soviet Union in 1959 by Dmitri Belyaev, who decided to study the genetics of domestication and find what qualities were selected for by the neolithic farmers who developed most major farm species about 10,000 years ago. He decided to select for a single criterion: tameness. Starting by breeding silver foxes from the wild, after only eight generations animals that would tolerate human presence became common, and after 40 years and the breeding of 45,000 foxes, a group had emerged that were as tame and as eager to please as a dog. The tame silver foxes had begun to show white patches on their fur floppy ears, rolled tails and smaller skulls, like many other domesticated species. They also exhibited the unusual ability of dogs to understand human gestures (something Chimpanzees can't manage at all). Belyaev also bred a parallel colony of vicious foxes, but realizing that genetics can be better studied in smaller animals, he started working with local wild rats. In only sixty generations separate breeds of very tame and very ferocious rats were obtained. Paabo's laboratory in Germany is now crossing the tame and aggressive strains to find genetic sites that correlate with these behaviors. Such sites could then be examined in tame and aggressive individuals in other mammalian species, including humans... Perhaps an important part of homminid evolution was a human self-domestication that involved ostracizing (blocking the breeding of) individuals who were too aggressive.
The article by Dean in the same NYTimes issue provides a review of recent books on the clash between religion and science, and the debate over whether faith in God can coexist with faith in the scientific method. Professors of either faith or science acknowledge that they cannot prove that God either does or does not exist. Evolutionary psychological explanation of why religious belief seems to be universal among Homo sapiens are still "just-so" stories, very far from being proved.
The book by Lewis Wolpert "Six Impossible Things Before Breakfast: The Evolutionary Origins of Belief" (published in England, due in the U.S. in January) looks quite interesting:
Some remarkable experiments were started in the former Soviet Union in 1959 by Dmitri Belyaev, who decided to study the genetics of domestication and find what qualities were selected for by the neolithic farmers who developed most major farm species about 10,000 years ago. He decided to select for a single criterion: tameness. Starting by breeding silver foxes from the wild, after only eight generations animals that would tolerate human presence became common, and after 40 years and the breeding of 45,000 foxes, a group had emerged that were as tame and as eager to please as a dog. The tame silver foxes had begun to show white patches on their fur floppy ears, rolled tails and smaller skulls, like many other domesticated species. They also exhibited the unusual ability of dogs to understand human gestures (something Chimpanzees can't manage at all). Belyaev also bred a parallel colony of vicious foxes, but realizing that genetics can be better studied in smaller animals, he started working with local wild rats. In only sixty generations separate breeds of very tame and very ferocious rats were obtained. Paabo's laboratory in Germany is now crossing the tame and aggressive strains to find genetic sites that correlate with these behaviors. Such sites could then be examined in tame and aggressive individuals in other mammalian species, including humans... Perhaps an important part of homminid evolution was a human self-domestication that involved ostracizing (blocking the breeding of) individuals who were too aggressive.
The article by Dean in the same NYTimes issue provides a review of recent books on the clash between religion and science, and the debate over whether faith in God can coexist with faith in the scientific method. Professors of either faith or science acknowledge that they cannot prove that God either does or does not exist. Evolutionary psychological explanation of why religious belief seems to be universal among Homo sapiens are still "just-so" stories, very far from being proved.
The book by Lewis Wolpert "Six Impossible Things Before Breakfast: The Evolutionary Origins of Belief" (published in England, due in the U.S. in January) looks quite interesting:
"Dr. Wolpert writes about the way people think about cause and effect, citing among other work experiments on how we reason, how we assess risk, and the rules of thumb and biases that guide us when we make decisions. He is looking into what he calls “causal belief” — the idea that events or conditions we experience have a cause, possibly a supernatural cause.
Human reasoning is “beset with logical problems that include overdependence on authority, overemphasis on coincidence, distortion of the evidence, circular reasoning, use of anecdotes, ignorance of science and failures of logic,” he writes. And whatever these traits may say about acceptance of religion, they have a lot to do with public misunderstanding of science.
So, he concludes, “We have to both respect, if we can, the beliefs of others, and accept the responsibility to try and change them if the evidence for them is weak or scientifically improbable.”
This is where the scientific method comes in. If scientists are prepared to state their hypotheses, describe how they tested them, lay out their data, explain how they analyze their data and the conclusions they draw from their analyses — then it should not matter if they pray to Zeus, Jehovah, the Tooth Fairy, or nobody.
Their work will speak for itself."
Remembering past rewards - anterior cingulate cortex needed
Here is the abstract from an interesting paper in Nature Neuroscience by Kennerley et al.
"Learning the value of options in an uncertain environment is central to optimal decision making. The anterior cingulate cortex (ACC) has been implicated in using reinforcement information to control behavior. Here we demonstrate that the ACC's critical role in reinforcement-guided behavior is neither in detecting nor in correcting errors, but in guiding voluntary choices based on the history of actions and outcomes. ACC lesions did not impair the performance of monkeys (Macaca mulatta) immediately after errors, but made them unable to sustain rewarded responses in a reinforcement-guided choice task and to integrate risk and payoff in a dynamic foraging task. These data suggest that the ACC is essential for learning the value of actions."
Here is a graphic (credit: Ann Thomson, Nature Neuroscience) in an accompanying review of this work by Haydn and Platt.
Monkeys with lesions in the anterior cingulate cortex (ACC) correct errors but fail to maintain the new rewarded behavior. (a) Medial view of the right hemisphere in the macaque. Shading, location of the lesion in the ACC. (b) Behavioral responses of monkeys with ACC lesions in experiment 1. After one action—in this case, lift—was rewarded for 25 consecutive trials, the rewarded action was switched—in this case, to turn. Following an unrewarded lift response, lesioned monkeys switched to turning, but could not sustain this response on subsequent trials. Intact monkeys, however, had no difficulty with this task. Similar lesion-induced disruptions in behavioral performance were found in a reward probability matching task in a second experiment.
"Learning the value of options in an uncertain environment is central to optimal decision making. The anterior cingulate cortex (ACC) has been implicated in using reinforcement information to control behavior. Here we demonstrate that the ACC's critical role in reinforcement-guided behavior is neither in detecting nor in correcting errors, but in guiding voluntary choices based on the history of actions and outcomes. ACC lesions did not impair the performance of monkeys (Macaca mulatta) immediately after errors, but made them unable to sustain rewarded responses in a reinforcement-guided choice task and to integrate risk and payoff in a dynamic foraging task. These data suggest that the ACC is essential for learning the value of actions."
Here is a graphic (credit: Ann Thomson, Nature Neuroscience) in an accompanying review of this work by Haydn and Platt.
Monkeys with lesions in the anterior cingulate cortex (ACC) correct errors but fail to maintain the new rewarded behavior. (a) Medial view of the right hemisphere in the macaque. Shading, location of the lesion in the ACC. (b) Behavioral responses of monkeys with ACC lesions in experiment 1. After one action—in this case, lift—was rewarded for 25 consecutive trials, the rewarded action was switched—in this case, to turn. Following an unrewarded lift response, lesioned monkeys switched to turning, but could not sustain this response on subsequent trials. Intact monkeys, however, had no difficulty with this task. Similar lesion-induced disruptions in behavioral performance were found in a reward probability matching task in a second experiment.
Monday, July 24, 2006
The Middle East - contribution of basic cognitive errors to cycles of retribution.
Daniel Gilbert, whose book (Stumbling on Happiness) I abstracted in a series of posts on 6/29/06, has a fascinating Op-Ed piece in today's New York Times that seems particularly relevant to the current maelstrom of violence in the middle east. Here are a few clips from his writing:
"He hit me first" provides an acceptable rationale for doing that which is otherwise forbidden. Both civil and religious law provide long lists of behaviors that are illegal or immoral — unless they are responses in kind, in which case they are perfectly fine...a punch thrown second is legally and morally different than a punch thrown first....That’s why participants in every one of the globe’s intractable conflicts — from Ireland to the Middle East — offer the even-numberedness of their punches as grounds for exculpation.
The problem with the principle of even-numberedness is that people count differently...In a study conducted by William Swann and colleagues at the University of Texas, pairs of volunteers played the roles of world leaders who were trying to decide whether to initiate a nuclear strike. The first volunteer was asked to make an opening statement, the second volunteer was asked to respond, the first volunteer was asked to respond to the second, and so on. At the end of the conversation, the volunteers were shown several of the statements that had been made and were asked to recall what had been said just before and just after each of them...The results revealed an intriguing asymmetry: When volunteers were shown one of their own statements, they naturally remembered what had led them to say it. But when they were shown one of their conversation partner’s statements, they naturally remembered how they had responded to it...
What seems like a grossly self-serving pattern of remembering is actually the product of two innocent facts. First, because our senses point outward, we can observe other people’s actions but not our own. Second, because mental life is a private affair, we can observe our own thoughts but not the thoughts of others. Together, these facts suggest that our reasons for punching will always be more salient to us than the punches themselves — but that the opposite will be true of other people’s reasons and other people’s punches...Examples aren’t hard to come by. Shiites seek revenge on Sunnis for the revenge they sought on Shiites; Irish Catholics retaliate against the Protestants who retaliated against them; and since 1948, it’s hard to think of any partisan in the Middle East who has done anything but play defense. In each of these instances, people on one side claim that they are merely responding to provocation and dismiss the other side’s identical claim as disingenuous spin. But research suggests that these claims reflect genuinely different perceptions of the same bloody conversation.
If the first principle of legitimate punching is that punches must be even-numbered, the second principle is that an even-numbered punch may be no more forceful than the odd-numbered punch that preceded it. Legitimate retribution is meant to restore balance, and thus an eye for an eye is fair, but an eye for an eyelash is not. When the European Union condemned Israel for bombing Lebanon in retaliation for the kidnapping of two Israeli soldiers, it did not question Israel’s right to respond, but rather, its “disproportionate use of force.” It is O.K. to hit back, just not too hard.
Research shows that people have as much trouble applying the second principle as the first. In a study conducted by Sukhwinder Shergill and colleagues at University College London, pairs of volunteers were hooked up to a mechanical device that allowed each of them to exert pressure on the other volunteer’s fingers.
The researcher began the game by exerting a fixed amount of pressure on the first volunteer’s finger. The first volunteer was then asked to exert precisely the same amount of pressure on the second volunteer’s finger. The second volunteer was then asked to exert the same amount of pressure on the first volunteer’s finger. And so on. The two volunteers took turns applying equal amounts of pressure to each other’s fingers while the researchers measured the actual amount of pressure they applied.
The results were striking. Although volunteers tried to respond to each other’s touches with equal force, they typically responded with about 40 percent more force than they had just experienced. Each time a volunteer was touched, he touched back harder, which led the other volunteer to touch back even harder. What began as a game of soft touches quickly became a game of moderate pokes and then hard prods, even though both volunteers were doing their level best to respond in kind.
Each volunteer was convinced that he was responding with equal force and that for some reason the other volunteer was escalating. Neither realized that the escalation was the natural byproduct of a neurological quirk that causes the pain we receive to seem more painful than the pain we produce, so we usually give more pain than we have received.
Research teaches us that our reasons and our pains are more palpable, more obvious and real, than are the reasons and pains of others. This leads to the escalation of mutual harm, to the illusion that others are solely responsible for it and to the belief that our actions are justifiable responses to theirs.
None of this is to deny the roles that hatred, intolerance, avarice and deceit play in human conflict. It is simply to say that basic principles of human psychology are important ingredients in this miserable stew. Until we learn to stop trusting everything our brains tell us about others — and to start trusting others themselves — there will continue to be tears and recriminations in the wayback.
"He hit me first" provides an acceptable rationale for doing that which is otherwise forbidden. Both civil and religious law provide long lists of behaviors that are illegal or immoral — unless they are responses in kind, in which case they are perfectly fine...a punch thrown second is legally and morally different than a punch thrown first....That’s why participants in every one of the globe’s intractable conflicts — from Ireland to the Middle East — offer the even-numberedness of their punches as grounds for exculpation.
The problem with the principle of even-numberedness is that people count differently...In a study conducted by William Swann and colleagues at the University of Texas, pairs of volunteers played the roles of world leaders who were trying to decide whether to initiate a nuclear strike. The first volunteer was asked to make an opening statement, the second volunteer was asked to respond, the first volunteer was asked to respond to the second, and so on. At the end of the conversation, the volunteers were shown several of the statements that had been made and were asked to recall what had been said just before and just after each of them...The results revealed an intriguing asymmetry: When volunteers were shown one of their own statements, they naturally remembered what had led them to say it. But when they were shown one of their conversation partner’s statements, they naturally remembered how they had responded to it...
What seems like a grossly self-serving pattern of remembering is actually the product of two innocent facts. First, because our senses point outward, we can observe other people’s actions but not our own. Second, because mental life is a private affair, we can observe our own thoughts but not the thoughts of others. Together, these facts suggest that our reasons for punching will always be more salient to us than the punches themselves — but that the opposite will be true of other people’s reasons and other people’s punches...Examples aren’t hard to come by. Shiites seek revenge on Sunnis for the revenge they sought on Shiites; Irish Catholics retaliate against the Protestants who retaliated against them; and since 1948, it’s hard to think of any partisan in the Middle East who has done anything but play defense. In each of these instances, people on one side claim that they are merely responding to provocation and dismiss the other side’s identical claim as disingenuous spin. But research suggests that these claims reflect genuinely different perceptions of the same bloody conversation.
If the first principle of legitimate punching is that punches must be even-numbered, the second principle is that an even-numbered punch may be no more forceful than the odd-numbered punch that preceded it. Legitimate retribution is meant to restore balance, and thus an eye for an eye is fair, but an eye for an eyelash is not. When the European Union condemned Israel for bombing Lebanon in retaliation for the kidnapping of two Israeli soldiers, it did not question Israel’s right to respond, but rather, its “disproportionate use of force.” It is O.K. to hit back, just not too hard.
Research shows that people have as much trouble applying the second principle as the first. In a study conducted by Sukhwinder Shergill and colleagues at University College London, pairs of volunteers were hooked up to a mechanical device that allowed each of them to exert pressure on the other volunteer’s fingers.
The researcher began the game by exerting a fixed amount of pressure on the first volunteer’s finger. The first volunteer was then asked to exert precisely the same amount of pressure on the second volunteer’s finger. The second volunteer was then asked to exert the same amount of pressure on the first volunteer’s finger. And so on. The two volunteers took turns applying equal amounts of pressure to each other’s fingers while the researchers measured the actual amount of pressure they applied.
The results were striking. Although volunteers tried to respond to each other’s touches with equal force, they typically responded with about 40 percent more force than they had just experienced. Each time a volunteer was touched, he touched back harder, which led the other volunteer to touch back even harder. What began as a game of soft touches quickly became a game of moderate pokes and then hard prods, even though both volunteers were doing their level best to respond in kind.
Each volunteer was convinced that he was responding with equal force and that for some reason the other volunteer was escalating. Neither realized that the escalation was the natural byproduct of a neurological quirk that causes the pain we receive to seem more painful than the pain we produce, so we usually give more pain than we have received.
Research teaches us that our reasons and our pains are more palpable, more obvious and real, than are the reasons and pains of others. This leads to the escalation of mutual harm, to the illusion that others are solely responsible for it and to the belief that our actions are justifiable responses to theirs.
None of this is to deny the roles that hatred, intolerance, avarice and deceit play in human conflict. It is simply to say that basic principles of human psychology are important ingredients in this miserable stew. Until we learn to stop trusting everything our brains tell us about others — and to start trusting others themselves — there will continue to be tears and recriminations in the wayback.
Friday, July 21, 2006
A ‘Senior Moment’ or a Self-Fulfilling Prophecy?
This is the title of an article by Benedict Carey in last Tuesday's NYTimes science section (7/18/06) pointing to work reported in the current issue of the journal Social Cognition. Men and women in late middle age (48-62) underperformed on a standard memory test when told they were part of a study including people over age 70. Inclusion with an older group — an indirect reminder of the link between age and memory slippage — was enough to affect their scores, especially for those who were most concerned about getting older. Scores were higher when participants were told they were competing with a group in their 20's. The findings “show how negative images of aging on TV, in other media and in jokes reinforce negative stereotypes that can affect performance even before people reach retirement age."
This self-undermining is a stereotype effect, of the sort that has been documented it in many groups. Other studies have shown that women perform less well on math exams after reading that men tend to perform better on them. Similarly, white men perform less well when they are told that they are competing in math against Asian students.
This self-undermining is a stereotype effect, of the sort that has been documented it in many groups. Other studies have shown that women perform less well on math exams after reading that men tend to perform better on them. Similarly, white men perform less well when they are told that they are competing in math against Asian students.
Thursday, July 20, 2006
The Locus Ceruleus Is Involved in the Retrieval of Emotional Memories in Humans
Emotional events are usually remembered better than neutral ones, and the amygdala is involved in this enhancement. The level of the amygdala's response during encoding of either emotional events or neutral stimuli encoded in an emotional contex is related to the ease of subsequent recall. Retrieving such memories is accompanied by significant amygdalar responses. Sterpenich et. al. have now shown that successful recognition of stimuli encoded in emotional context is accompanied by a significant response not only in the amygdala and parahippocampal gyrus but also in central arousing structures of the brainstem and the diencephalon (centered on the locus ceruleus). They found that locus ceruleus responses at retrieval, as a constituent element of the emotional memory, could be related to the arousal induced during encoding.
A Right amygdala. C Parahippocampus gyrus
A. Locus ceruleus.
Credit: J. Neuroscience
A Right amygdala. C Parahippocampus gyrus
A. Locus ceruleus.
Credit: J. Neuroscience
Wednesday, July 19, 2006
Attention Deficit Hyperactivity Disorder, how Ritalin might be working.
Ruth Williams, in Nature Reviews Neuroscience, points out an article by Drouin et al in The Journal of Neurophysiology that suggests a potential brain mechanism for the action of methylphenidate (Ritalin) in relieving attention deficit hyperactivity disorder (ADHD). ADHD sufferers essentially "pay attention to too many things." They find it difficult to filter out unwanted distractions and focus one issue at a time. Behavioral experiments with rats have shown that Ritalin improves behavior in a sustained attention task, just as it does in humans. Drouin et al found that administering Ritalin to rats (at a dose equivalent to that used in human therapy) caused an increase in the levels of the neurotransmitter noradrenaline in the rat's sensory cortex and reduced a long-latency phase of the brain's response to sensory stimuli. This latter effect may be important in filtering out sensory noise.
Tuesday, July 18, 2006
Free Will, Free Won't, or Neither? A refinement of Libet's work on the conscious control of spontaneous actions.
In a famous paper published in 1983, Libet et al. showed that the recordable cerebral activity (readiness-potential) that precedes a freely voluntary motor act occurs at least several hundred milliseconds before the reported time of conscious intention to act. The actual movement occurs 200-250 msec after the reported time of intention to act. The data are pretty spooky when you think about it. They say that your brain ("it") has started working on a action well before "you" think you are initiating it! This article has sparked a continuing debate on whether we actually have free will. Libet has suggested that the ~200-250 msec period between awareness of intention and the actual action was sufficient to permit a "veto" of the action if it was judged inappropriate. In this interpretation, we might be said to be "free won't" rather than "free will".
Lau et al. have now done a more nuanced version of LIbet's experiments. In a previous paper they showed that, when participants were required to estimate the onset of their intentions using Libet's procedure, the activity in the presupplementary motor area (pre-SMA) was enhanced ~228 msec before motor execution. In their most recent work they show that when participants were required to estimate the onset of their motor executions (instead of their intentions), the activity in the cingulate motor area was enhanced. This latter condition, judged to be more natural and have less task-demanding instructions. The perceived onset of intention could be as late as ~120 msec before the motor execution . "Together, these findings raise the question of whether the conscious control of spontaneous action can be done within a much shorter time window than we had expected, or whether, as suggested by Wegner (The illusion of conscious will Cambridge, MA: MIT Press, 2002), our impression of conscious control is simply illusory."
I think Wegner has it right. His book, and his interpretation of our sense of agency as an after the fact ' emotion of authorship' is a must-read for anyone interested in issues of conscious volition.
Lau et al. have now done a more nuanced version of LIbet's experiments. In a previous paper they showed that, when participants were required to estimate the onset of their intentions using Libet's procedure, the activity in the presupplementary motor area (pre-SMA) was enhanced ~228 msec before motor execution. In their most recent work they show that when participants were required to estimate the onset of their motor executions (instead of their intentions), the activity in the cingulate motor area was enhanced. This latter condition, judged to be more natural and have less task-demanding instructions. The perceived onset of intention could be as late as ~120 msec before the motor execution . "Together, these findings raise the question of whether the conscious control of spontaneous action can be done within a much shorter time window than we had expected, or whether, as suggested by Wegner (The illusion of conscious will Cambridge, MA: MIT Press, 2002), our impression of conscious control is simply illusory."
I think Wegner has it right. His book, and his interpretation of our sense of agency as an after the fact ' emotion of authorship' is a must-read for anyone interested in issues of conscious volition.
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