Wednesday, December 31, 2008

Genetics of successful placebo response to stress.

Here is a fascinating piece of work from Furmark et al., showing that placebo treatment of stress in subjects with social anxiety disorder (reflected by reducted amygdala activity during public speaking) was successful only in individuals with particular forms of serotonin transporter and tryptophan hydroxylase genes. This demonstrates a link between genetically controlled serotonergic modulation of amygdala activity and placebo-induced anxiety relief. The experiments were done in the context of a study evaluating a potential anti-anxiety drug and matching placebo provided by GlaxoSmithKline.

Placebo may yield beneficial effects that are indistinguishable from those of active medication, but the factors underlying proneness to respond to placebo are widely unknown. Here, we used functional neuroimaging to examine neural correlates of anxiety reduction resulting from sustained placebo treatment under randomized double-blind conditions, in patients with social anxiety disorder. Brain activity was assessed during a stressful public speaking task by means of positron emission tomography before and after an 8 week treatment period. Patients were genotyped with respect to the serotonin transporter-linked polymorphic region (5-HTTLPR) and the G-703T polymorphism in the tryptophan hydroxylase-2 (TPH2) gene promoter. Results showed that placebo response was accompanied by reduced stress-related activity in the amygdala, a brain region crucial for emotional processing. However, attenuated amygdala activity was demonstrable only in subjects who were homozygous for the long allele of the 5-HTTLPR or the G variant of the TPH2 G-703T polymorphism, and not in carriers of short or T alleles. Moreover, the TPH2 polymorphism was a significant predictor of clinical placebo response, homozygosity for the G allele being associated with greater improvement in anxiety symptoms. Path analysis supported that the genetic effect on symptomatic improvement with placebo is mediated by its effect on amygdala activity. Hence, our study shows, for the first time, evidence of a link between genetically controlled serotonergic modulation of amygdala activity and placebo-induced anxiety relief.

Upper limb amputees can sense a rubber hand as their own

A further observation on the brain plasticity shown during the rubber hand illusion (mentioned in the Dec. 24 posting) is made by Ehrsson et al., who find that the illusion can induced in upper limb amputees:

We describe how upper limb amputees can be made to experience a rubber hand as part of their own body. This was accomplished by applying synchronous touches to the stump, which was out of view, and to the index finger of a rubber hand, placed in full view (26 cm medial to the stump). This elicited an illusion of sensing touch on the artificial hand, rather than on the stump and a feeling of ownership of the rubber hand developed. This effect was supported by quantitative subjective reports in the form of questionnaires, behavioural data in the form of misreaching in a pointing task when asked to localize the position of the touch, and physiological evidence obtained by skin conductance responses when threatening the hand prosthesis. Our findings outline a simple method for transferring tactile sensations from the stump to a prosthetic limb by tricking the brain, thereby making an important contribution to the field of neuroprosthetics where a major goal is to develop artificial limbs that feel like a real parts of the body.

Tuesday, December 30, 2008

Musing on the topic of well-being or happiness...

On seeing this Op-Ed piece by Lyubomirsky in the NYTimes I realized that this is the author, an academic researcher, who has put out a book that I am currently scanning titled "The How of Happiness: A Scientific Approach to Getting the Life You Want." The NYTimes Op-Ed piece notes that the reason that most of us are not more dejected than one might expect by the market meltdown and recession is that the fortunes of virtually everyone have been compromised, and we care more about social comparison, status and rank than about the absolute value of our bank accounts or reputations.

With regard to the book, Ms. Lyubomirsky can not be accused of being a skilled prose stylist, but her writing does offer a meat and potatoes list of behavioral tips on activities that have been shown in double blind studies on fairly large groups of real people to enhance well-being, namely:

Expressing gratitude
Cultivating Optimism
Avoiding over thinking and social comparison
Practicing acts of kindness
Nurturing relationships
Developing strategies for coping.
Learning to forgive
Doing more activities that truly engage you.
Savoring Life’s joys
Committing to your goals
Practicing religion and spirituality
Taking care of your body.

She suggests taking the four of these that seem most congenial to you, and working on those rather than tackling the whole list.

My take on this well-being stuff is that it does boil down to some fairly discrete mental operations, being a matter of executive (frontal lobe) function - to put some things in your mind and not others - images of coherence and well being versus random input from the environment and the old pandora’s box of your past. This is essentially cognitive therapy, letting one thing express rather than another (making a distinction such as: ‘this is a part of my brain that is not working to my advantage’). It does not have to be an energy draining self-coercion of one part of ourselves going to war with another, but rather is a self choosing of one option over another. You are what you spend your time doing.

Hemispheric shift of categorical color perception during brain development.

Franklin et al. show an interesting shift in categorical perception of colors from right to left hemisphere as infants learn the words that distinguish the relevant category boundaries, showing an influence of language on the functional organization of the brain.

Categorical perception (CP) of color is the faster and more accurate discrimination of two colors from different categories than two colors from the same category, even when same- and different-category chromatic separations are equated. In adults, color CP is lateralized to the left hemisphere (LH), whereas in infants, it is lateralized to the right hemisphere (RH). There is evidence that the LH bias in color CP in adults is due to the influence of color terms in the LH. Here we show that the RH to LH switch in color CP occurs when the words that distinguish the relevant category boundary are learned. A colored target was shown in either the left- or right-visual field on either the same- or different-category background, with equal hue separation for both conditions. The time to initiate an eye movement toward the target from central fixation at target onset was recorded. Color naming and comprehension was assessed. Toddlers were faster at detecting targets on different- than same-category backgrounds and the extent of CP did not vary with level of color term knowledge. However, for toddlers who knew the relevant color terms, the category effect was found only for targets in the RVF (LH), whereas for toddlers learning the color terms, the category effect was found only for targets in the LVF (RH). The findings suggest that lateralization of color CP changes with color term acquisition, and provide evidence for the influence of language on the functional organization of the brain.

Monday, December 29, 2008

Sharing today's New York Times

How social status shapes race.

Penner and Saperstein carry out an interesting analysis of data from the National Longitudinal Survey of Youth (NLSY), which contains multiple measures of interviewer-classified and self-identified race over a twenty-year period. Their abstract, followed by one figure from the paper:

We show that racial perceptions are fluid; how individuals perceive their own race and how they are perceived by others depends in part on their social position. Using longitudinal data from a representative sample of Americans, we find that individuals who are unemployed, incarcerated, or impoverished are more likely to be seen and identify as black and less likely to be seen and identify as white, regardless of how they were classified or identified previously. This is consistent with the view that race is not a fixed individual attribute, but rather a changeable marker of status.


Figure - Racial self-identification and cumulative social status, 2002. Source: National Longitudinal Survey of Youth. (A) The percentage of respondents who self-identified as white in 2002, restricted to respondents who identified as white in 1979. (B) The percentage of respondents who identified as black in 2002, restricted to respondents who identified as black in 1979. Ever-incarcerated refers to whether the respondent was ever interviewed while in prison; ever-unemployed refers to whether the respondent was ever unemployed for more than 4 months in a calendar year; and ever-impoverished refers to whether the respondent's household income was ever below the poverty line. Error bars, ± 1SE.

Altering our self-face recognition

In the wake of several recent posts on the rubber hand illusion, which alters our sense of where our hand is in space, I thought this observation by Tsakiris was interesting: multisensory input to our face (Synchronous tactile stimulation while watching another person's face being similarly touched) causes a bias in recognizing our own face. Here is the abstract:

How do I know the person I see in the mirror is really me? Is it because I know the person simply looks like me, or is it because the mirror reflection moves when I move, and I see it being touched when I feel touch myself? Studies of face-recognition suggest that visual recognition of stored visual features inform self-face recognition. In contrast, body-recognition studies conclude that multisensory integration is the main cue to selfhood. The present study investigates for the first time the specific contribution of current multisensory input for self-face recognition. Participants were stroked on their face while they were looking at a morphed face being touched in synchrony or asynchrony. Before and after the visuo-tactile stimulation participants performed a self-recognition task. The results show that multisensory signals have a significant effect on self-face recognition. Synchronous tactile stimulation while watching another person's face being similarly touched produced a bias in recognizing one's own face, in the direction of the other person included in the representation of one's own face. Multisensory integration can update cognitive representations of one's body, such as the sense of ownership. The present study extends this converging evidence by showing that the correlation of synchronous multisensory signals also updates the representation of one's face. The face is a key feature of our identity, but at the same time is a source of rich multisensory experiences used to maintain or update self-representations.

Friday, December 26, 2008

The net generation

Hurt offers a review of Tapscott's recent book "Growing up Digital", which defines the 81 million people born between 1977 to 1997 that make up 27% of the population as the "net generation" (following generations X and Y).

"As the first global generation ever, the Net Geners are smarter, quicker and more tolerant of diversity than their predecessors,” Tapscott writes. “They care strongly about justice and the problems faced by their society and are typically engaged in some kind of civic activity at school, at work or in their communities."

Mr. Tapscott devotes an entire chapter to examining how Net Geners are already using their collective power to transform society — as evidenced by their impact on Barack Obama’s presidential campaign...He documents how Mr. Obama capitalized on interactive social networking sites like Facebook and MySpace that inspired the participation of millions of small donors, while Hillary Rodham Clinton relied on relatively old broadcast-style media like television and e-mail to attract much lower numbers of mostly large donors.

Mr. Tapscott identifies eight norms of many members of the Net Generation: they prize freedom; they want to customize things; they enjoy collaboration; they scrutinize everything; they insist on integrity in institutions and corporations; they want to have fun even at school or work; they believe that speed in technology and all else is normal; and they regard constant innovation as a fact of life.

He cites recent brain-imaging and childhood-development studies to buttress his contention that Internet use by Net Geners has fundamentally changed — and improved — the way their brains are wired. Noting that raw I.Q. scores have been climbing by three points a decade since World War II across racial, income and regional boundaries, Mr. Tapscott asserts that Net Geners are also developing valuable skills that do not show up on standard I.Q. tests.

“Not only do video game players notice more, they have highly developed spatial skills that are useful for architects, engineers and surgeons,” he says.

Men are red, women are green.

Here is a curious bit which I pass on from the Random Samples section of the Dec. 19 Science Magazine, describing the work of researchers at Brown University:

Men are colored like Mars, but women are greenish--and the difference may help explain how people perceive la difference...Cognitive scientist Michael Tarr and grad student Adrian Nestor made the discovery by averaging mug shots of 200 white males and females into a single androgynous face. They then obscured it further with randomly placed red and green pixels.

Three volunteers looked at 20,000 different versions of the image--some redder, others greener--and told the researchers which sex they thought each face represented. The result: Faces with green pixels were tagged as female and those with more red pixels as male. The color of the cheekbones, nose, and sides of the mouth were particularly important to decisions, says Tarr, whose paper is in press in Psychological Science.

Marlene Behrmann, a psychologist at Carnegie Mellon University in Pittsburgh, Pennsylvania, says the fact that people subconsciously recognize the red-green distinction "means there is something evolutionarily and ecologically important about color that extends even into the human central nervous system."

Thursday, December 25, 2008

Bach oratorio on period instruments.

Cognitive benefits of a walk in the woods

An article by Berman et al. in Psychological Science (PDF here) shows that immersion in a natural environment leads to more than simply a sense of feeling refreshed, it also recharges our cognitive batteries:

We compare the restorative effects on cognitive functioning of interactions with natural versus urban environments. Attention restoration theory (ART) provides an analysis of the kinds of environments that lead to improvements in directed-attention abilities. Nature, which is filled with intriguing stimuli, modestly grabs attention in a bottom-up fashion, allowing top-down directed-attention abilities a chance to replenish. Unlike natural environments, urban environments are filled with stimulation that captures attention dramatically and additionally requires directed attention (e.g., to avoid being hit by a car), making them less restorative. We present two experiments that show that walking in nature or viewing pictures of nature can improve directed-attention abilities as measured with a backwards digit-span task and the Attention Network Task, thus validating attention restoration theory.

Wednesday, December 24, 2008

Seasonal Nostalgia

I alternatively want to feel warm and cushy or gag myself with a spoon on watching this.

Knowing where and knowing how to get there - a dissociation in the rubber hand illusion.

Kammers et al. show that during the rubber hand illusion (in which watching a rubber hand being stroked while our own unseen hand is synchronously stroked induces a relocation of the sensed position of our own hand towards the rubber hand) our actual ballistic hand movements resist the illusion. Their abstract contains some useful references:

In the well-known rubber hand illusion (RHI), watching a rubber hand being stroked while one's own unseen hand is synchronously stroked, induces a relocation of the sensed position of one's own hand towards the rubber hand [Botvinick, M., & Cohen, J. (1998). Rubber hands ‘feel’ touch that eyes see. Nature, 391(6669), 756]. As one has lost the veridical location of one's hand, one should not be able to correctly guide one's hand movements. An accurate representation of the location of body parts is indeed a necessary pre-requisite for any correct motor command [Graziano, M. S. A., & Botvinick, M. M. (1999). How the brain represents the body: Insights from neurophysiology and psychology. In D. Gopher, & A. Koriat (Eds.), Attention and performance XVII—Cognitive regulation of performance interaction of theory and application (pp. 136–157)]. However, it has not yet been investigated whether action is indeed affected by the proprioceptive drift towards the rubber hand, nor has the resistance of visual capture in the RHI to new proprioceptive information been assessed. In the present two kinematic experiments, we show for the first time that action resists the RHI and that the RHI resists action. In other words, we show a dissociation between illusion-insensitive ballistic motor responses and illusion-sensitive perceptual bodily judgments. Moreover, the stimulated hand was judged closer to the rubber hand for the perceptual responses, even after active movements. This challenges the view that any proprioceptive update through active movement of the stimulated hand erases the illusion. These results expand the knowledge about representations of the body in the healthy brain, and are in line with the currently most used dissociation between two types of body representations so far mainly based on neuropsychological patients [Paillard, J. (1991). Knowing where and knowing how to get there. In J. Paillard (Ed.), Brain and space (pp. 461–481); Paillard, J. (1999). Body schema and body image: A double dissociation in deafferented patients. In G. N. Gantchev, S. Mori, & J.Massion (Eds.), Motor control, today and tomorrow (pp. 197–214)].

Tuesday, December 23, 2008

Effect of candidate appearance on election outcomes - neural correlates

An interesting open access article from Adolphs and collaborators:

Election outcomes correlate with judgments based on a candidate's visual appearance, suggesting that the attributions viewers make based on appearance, so-called thin-slice judgments, influence voting. Yet, it is not known whether the effect of appearance on voting is more strongly influenced by positive or negative attributions, nor which neural mechanisms subserve this effect. We conducted two independent brain imaging studies to address this question. In Study 1, images of losing candidates elicited greater activation in the insula and ventral anterior cingulate than images of winning candidates. Winning candidates elicited no differential activation at all. This suggests that negative attributions from appearance exert greater influence on voting than do positive. We further tested this hypothesis in Study 2 by asking a separate group of participants to judge which unfamiliar candidate in a pair looked more attractive, competent, deceitful and threatening. When negative attribution processing was enhanced (specifically, under judgment of threat), images of losing candidates again elicited greater activation in the insula and ventral anterior cingulate. Together, these findings support the view that negative attributions play a critical role in mediating the effects of appearance on voter decisions, an effect that may be of special importance when other information is absent.

Enhanced perception of threat during limited attention

This open access article from Dolan's and collaborators builds on previous studies on the role of the amygdala in pre-attentive processing of potential threats, noting parts of the brain that become active during threat identification during periods of compromised attention. Their abstract:

The ability to process stimuli that convey potential threat, under conditions of limited attentional resources, confers adaptive advantages. This study examined the neurobiology underpinnings of this capacity. Employing an attentional blink paradigm, in conjunction with functional magnetic resonance imaging, we manipulated the salience of the second of 2 face target stimuli (T2), by varying emotionality. Behaviorally, fearful T2 faces were identified significantly more than neutral faces. Activity in fusiform face area increased with correct identification of T2 faces. Enhanced activity in rostral anterior cingulate cortex (rACC) accounted for the benefit in detection of fearful stimuli reflected in a significant interaction between target valence and correct identification. Thus, under conditions of limited attention resources activation in rACC correlated with enhanced processing of emotional stimuli. We suggest that these data support a model in which a prefrontal "gate" mechanism controls conscious access of emotional information under conditions of limited attentional resources.

In the same issue of Cerebral Cortex, another Dolan collaboration uses a masked face priming paradigm to show that face responsive regions of the brain become active in the absence of awareness of faces that are presented.

Monday, December 22, 2008

Our motor cortex responds to musical rhythms.

From Chen et al. :

Perception and actions can be tightly coupled; but does a perceptual event dissociated from action processes still engage the motor system? We conducted 2 functional magnetic resonance imaging studies involving rhythm perception and production to address this question. In experiment 1, on each trial subjects 1st listened in anticipation of tapping, and then tapped along with musical rhythms. Recruitment of the supplementary motor area, mid-premotor cortex (PMC), and cerebellum was observed during listen with anticipation. To test whether this activation was related to motor planning or rehearsal, in experiment 2 subjects naively listened to rhythms without foreknowledge that they would later tap along with them. Yet, the same motor regions were engaged despite no action–perception connection. In contrast, the ventral PMC was only recruited during action and action-coupled perceptual processes, whereas the dorsal part was only sensitive to the selection of actions based on higher-order rules of temporal organization. These functional dissociations shed light on the nature of action–perception processes and suggest an inherent link between auditory and motor systems in the context of rhythm.

Video Introduction to Experimental Philosophy

A MindBlog reader points us to this site, which uses a a YouTube video to better explain the concept of intention and the role our moral judgments play in our perception of intent.

Friday, December 19, 2008

Avian Dancing

From the New York Times Magazine special issue on 'Year in Ideas 2008', slightly edited:

Here you see a large white bird balanced on the back of an office chair, bobbing his head, stomping his feet and ... dancing just like a human. Snowball’s videos are changing the way researchers understand the neurology of music and dancing.

Aniruddh Patel, senior fellow at the Neurosciences Institute in California, got the link from a friend. He saw not just a funny bird but also a potential solution to a scientific argument dating back to Darwin: some researchers say that human brains have been specially wired by natural selection for dancing, because dancing confers survival benefits through group bonding. If that were true, according to Patel, you would see dancing only in animals that, like humans, have a long history of music and dance, which no other species has. The fact that only humans dance has long been seen as evidence supporting the evolution argument.

So Patel sent an e-mail message to Snowball’s owner, Irena Schulz, and asked to study her bird. “The obvious question was whether he was just mimicking somebody,” Patel said. To answer that, he made CDs of Snowball’s favorite song (“Everybody (Backstreet’s Back)” by the Backstreet Boys) at various speeds. Schulz videotaped Snowball dancing to each version, and then Patel graphed Snowball’s movement against the music’s beat. “Like a child, he synched to the music for stretches of time, then danced a little faster or a little slower, but always in a rhythmic way,” Patel says. “Statistically those periods when he’s locked onto the beat are not by chance — they really do indicate sensitivity to the beat and an ability to synchronize with it.”

What’s most interesting to Patel is that this ability is present in birds but not in primates, our closest animal relatives. “This is no coincidence,” he says. Patel says dancing is associated with our vocal abilities, not musical hard wiring. Humans and parrots are two of the few species with brains wired for vocal learning — hearing sounds (like words), then coordinating complex movements (lips, tongues, vocal cords) to reproduce those sounds. Other animals who have this ability: dolphins, seals and whales. “In theory,” he says, “they may be able to dance, too. We just don’t know it yet.”

Crisis of Confidence for Masters of the Universe

An interesting article by Friedman in the NYTimes on psychological effects of the market meltdown.

Over the last few months, I have seen a group of patients, all men, who experienced a near collapse in their self-esteem, though none of them were clinically depressed...
Another patient summed it up: “I used to be a master-of-the-universe kind of guy, but this cut me down to size.”

I have plenty of female patients who work in finance at high levels, but none of them has had this kind of psychological reaction. I can’t pretend this is a scientific survey, but I wonder if men are more likely than women to respond this way. At the risk of trading in gender stereotypes, do men rely disproportionately more on their work for their self-esteem than women do? Or are they just more vulnerable to the inevitable narcissistic injury that comes with performing poorly or losing one’s job?

A different patient was puzzled not by his anxiety about the market, but by his total lack of self-confidence. He had always had an easy intuitive feel for finance. But in the wake of the market collapse, he seriously questioned his knowledge and skill.

On Wall Street, though, a rising tide lifts many boats and vice versa, which means that there are many people who succeed — or fail — through no merit or fault of their own.

This observation might ease a sense of personal responsibility for the economic crisis, but it was of little comfort to my patients. I think this is because for many of them, the previously expanding market gave them a sense of power along with something as strong as a drug: thrill.

The human brain is acutely attuned to rewards like money, sex and drugs. It turns out that the way a reward is delivered has an enormous impact on its strength. Unpredictable rewards produce much larger signals in the brain’s reward circuit than anticipated ones. Your reaction to situations that are either better or worse than expected is generally stronger to those you can predict.

My patients lost more than money in the market. Beyond the rush and excitement, they lost their sense of competence and success. At least temporarily: I have no doubt that, like the economy, they will recover. But it’s a reminder of just how fragile our self-confidence can be.

Thursday, December 18, 2008

Why are we so nice? ...because generosity wins.

Here is a further entry in Nature's "Being Human" series, in which Martin Nowak points out that mathematical models predict, and experiments confirm, that generosity is an essential feature of winning strategies in games that explore human interactions. 'Prosocial behaviour' has evolved within a framework of direct or indirect reciprocity, and the latter may have provided selection pressure for social intelligence and language. A few excerpts:

Only if certain mechanisms are involved can natural selection favour individuals who reduce their own fitness to increase that of a competitor. One such mechanism is direct reciprocity: my strategy depends on what you have done to me. Another is indirect reciprocity: my strategy depends on what you have done to me and on what you have done to others.

In both, mathematical analysis shows that winning strategies tend to be generous, hopeful and forgiving. Generous here means not seeking to get more than one's opponent; hopeful means cooperating in the first move or in the absence of information; and forgiving means attempting to re-establish cooperation after an accidental defection. These three traits are related. If I am generous, it is easier for me to forgive, and also to be hopeful and take the risk of cooperating with newcomers.

Experiments have confirmed the success of generosity. A typical set-up involves students and computer screens. The computer pairs random individuals. One person, the donor, is asked if she wishes to transfer some money to the recipient. She is informed about the recipient's decisions in previous rounds with other players. The experiment shows that people base their decision on what the recipient has done before. Generous people are more likely to receive donations.

Similar reputation-based systems operate in e-commerce. When buying a camera online, you might consider both the price and the seller's reputation. Consumers are willing to pay higher prices if the seller is thought to be reliable. Successful websites are those with good reputations.

So why aren't humans always 'generous, hopeful and forgiving'? Part of the explanation may be that cooperation is never a stable state. Mathematical studies show that it is constantly challenged by defection. In a society of defectors where no-one helps, a cluster of cooperating individuals can emerge if, by chance, a few people start playing a direct reciprocity strategy called tit-for-tat: I do whatever you have done to me. Tit-for-tat can't persist for long because its appetite for revenge is self-destructive. It is soon replaced by 'generous tit-for-tat'. Here, I cooperate whenever you have cooperated, but sometimes even when you have defected. In other words, I am forgiving. For a while, cooperation thrives. But in a generous tit-for-tat population, the emergence of unconditional cooperators eventually invites the invasion of defectors. This leads to cycles of cooperation and defection — which could account, at least in part, for the mix of cooperators and defectors that persists in human societies.

Mathematical models allow a precise investigation of fundamental aspects of human behaviour. The games described here occur in every society. Ancestral humans spent most of their time in small groups where interactions were repeated. The same is true for most dealings in modern life: repeat encounters are always possible and reputation is typically at stake. The evolution of prosocial behaviour cannot be understood outside the framework of direct or indirect reciprocity. Indeed, I believe that games of indirect reciprocity have provided the crucial selection pressures for social intelligence and language.

In such games, social intelligence is needed to monitor and interpret the interactions of others. We follow with great interest what our fellow creatures do to us and to others. When deciding how to act, we take into account — often subconsciously — the possible consequences for our own reputation. Moreover, our own observations are often not enough; we want to learn from the experiences of others. Spreading the rumours of indirect reciprocity requires language. As my colleague David Haig once remarked "for direct reciprocity you need a face, for indirect reciprocity you need a name".

Wheel of life.

I recently came across this interesting graphic demonstration of the Buddha's wheel of life, narrated by Robert Thurman.

Wednesday, December 17, 2008

How a cognition enhancing drug works.

Minzenberg et. al. find that brain images of humans treated with a cognitive enhancing drug show increased task-oriented activity in a brainstem nucleus and confirm that this region controls cognition. Their abstract:

Models of cognitive control posit a key modulatory role for the pontine locus coeruleus–norepinephrine (LC-NE) system. In nonhuman primates, phasic LC-NE activity confers adaptive adjustments in cortical gain in task-relevant brain networks, and in performance, on a trial-by-trial basis. This model has remained untested in humans. We used the pharmacological agent modafinil to promote low-tonic/high-phasic LC-NE activity in healthy humans performing a cognitive control task during event-related functional magnetic resonance imaging (fMRI). Modafanil administration was associated with decreased task-independent, tonic LC activity, increased task-related LC and prefrontal cortex (PFC) activity, and enhanced LC-PFC functional connectivity. These results confirm in humans the role of the LC-NE system in PFC function and cognitive control and suggest a mechanism for therapeutic action of procognitive noradrenergic agents.

Advocacy of cognition enhancing drugs.

Stimulants such as methyl-phenidate (Ritalin) and modafinil (Provigil), familiar as treatments for attention deficit hyperactivity disorder and narcolepsy respectively, are increasingly used as 'smart drugs' by students and more widely as a boost to intellectual creativity. Should society recognize the demand for cognitive enhancement? The trend has been resisted by some on the grounds of safety, 'medicalization' and social inequality. Urging responsible use of cognitive-enhancing drugs by the healthy, Greely et al., in an open access article, think that society must respond to the growing demand for cognitive enhancement. A few clips from their article:

Ritalin (methyphenidate) and Adderall (mixed amphetamine salts), and are prescribed mainly for the treatment of attention deficit hyperactivity disorder (ADHD). Because of their effects on the catecholamine system, these drugs increase executive functions in patients and most healthy normal people, improving their abilities to focus their attention, manipulate information in working memory and flexibly control their responses...A newer drug, modafinil (Provigil), has also shown enhancement potential. Modafinil is approved for the treatment of fatigue caused by narcolepsy, sleep apnoea and shift-work sleep disorder....laboratory studies have shown that modafinil enhances aspects of executive function in rested healthy adults, particularly inhibitory control.

Many people have doubts about the moral status of enhancement drugs for reasons ranging from the pragmatic to the philosophical, including concerns about short-circuiting personal agency and undermining the value of human effort. Kass, for example, has written of the subtle but, in his view, important differences between human enhancement through biotechnology and through more traditional means. Such arguments have been persuasively rejected. Three arguments against the use of cognitive enhancement by the healthy quickly bubble to the surface in most discussions: that it is cheating, that it is unnatural and that it amounts to drug abuse.

In the context of sports, pharmacological performance enhancement is indeed cheating. But, of course, it is cheating because it is against the rules. Any good set of rules would need to distinguish today's allowed cognitive enhancements, from private tutors to double espressos, from the newer methods, if they are to be banned.

As for an appeal to the 'natural', the lives of almost all living humans are deeply unnatural; our homes, our clothes and our food — to say nothing of the medical care we enjoy — bear little relation to our species' 'natural' state. Given the many cognitive-enhancing tools we accept already, from writing to laptop computers, why draw the line here and say, thus far but no further?

Like all new technologies, cognitive enhancement can be used well or poorly. We should welcome new methods of improving our brain function. In a world in which human workspans and lifespans are increasing, cognitive enhancement tools — including the pharmacological — will be increasingly useful for improved quality of life and extended work productivity, as well as to stave off normal and pathological age-related cognitive declines. Safe and effective cognitive enhancers will benefit both the individual and society.

But it would also be foolish to ignore problems that such use of drugs could create or exacerbate. With this, as with other technologies, we need to think and work hard to maximize its benefits and minimize its harms.

Tuesday, December 16, 2008

This is so kewl.....

From Science Magazine's 'Random Samples' feature:

Meet the Pivo 2, Nissan's compact electric concept car, designed for urban travel with a 360° rotating cabin and wheels that allow the car to scoot sideways for parking. It's one of the stars of the new exhibit "Japan Car: Designs for the Crowded Globe" at London's Science Museum, spotlighting "mobile cells"--small cars fueled by low-polluting electricity or hydrogen and equipped with intelligent driver interfaces.

Other examples include Toyota's iREAL, a sitting version of a Segway that looks like a futuristic wheelchair, with sensors that alert a driver to obstacles down the road, and Mitsubishi's electrical iMiEV, planned for release next year, that can go 160 kilometers on an overnight charge.

Key features of these vehicles are their brains. Pivo 2 has a talking "robotic agent" that offers traffic updates and route information and has voice-recognition capability to answer a driver's questions. The agent is personified by a swiveling head mounted beside the instrument panel that nods and shakes to keep the driver in a "positive frame of mind." "It infers the driver's mood through conversation and facial-monitoring technology," Nissan says. But can you make it shut up? Nissan doesn't say.

Crazy Money

An article by Chelsea Wald continues to make the case that financial theories can not assume that investor behavior is rational. Some clips from that article:

Even the experts seem bewildered by the current economic crisis. Quantitative analysts (quants)--the whiz-kid financial engineers whose algorithms have dominated Wall Street trading in recent years--have watched those algorithms fail. Former Federal Reserve Chair Alan Greenspan acknowledged in October that there was "a flaw in the model that I perceived … defines how the world works."...the classical theory of finance simply does not address human psychology. It looks more like a physical science than a social science--relying on the premises that markets are "efficient,"

Blame has fallen on quants for various aspects of the crisis. First, mathematical models were increasingly used to determine whether someone deserved a loan, bypassing individual judgments. "In the end, there was very little sound credit judgment going into making these credit calls," says Bjorn Flesaker, a senior quant at Bloomberg in New York. Then, quant models were used to rate the riskiness of financial instruments, including the CDOs. "We never necessarily viewed the rating agencies as having the greatest rocket scientists around," says Flesaker, yet investors accepted those ratings, taking on more risk than even they realized...like many of the elements that economists and the media have focused on, the quant models are simply "proximate causes." Ultimately, experts must examine human behavior to find out why the crisis happened. Why did so many people take on mortgages that they would not be able to pay? Why did the best minds of Wall Street ignore warnings about a housing bubble? "The bottom-line question that economists, I think, still are struggling with is: 'Did anybody know that the risks were so great and, if so, why did they continue investing?'

The madness of crowds

Classical finance theory's model of speculative bubbles, such as the dot-com bubble of the late '90s and the recent housing bubble, does not match real-life observations. Classical finance contends that rational investors will always have the best possible portfolio, so they will not buy or sell unless they have extra money to invest or need to cash in their investments. However, researchers have observed that people buy and sell much more often than that during a bubble--with the rate of transactions becoming increasingly manic the bigger the bubble gets.

Lacking a good classical model for stock-market bubbles, Scheinkman, whose work is primarily classical, turned to a concept in behavioral finance. Psychologists have found that people often overestimate the precision of their knowledge. Scheinkman and his Princeton colleague Wei Xiong guessed that overconfident investors would trust their own opinions about the price of an asset, so they would consider others' opinions, if different, a little "crazy," says Scheinkman. Looking to make money off others' crazy opinions, investors would be willing to pay more than they think an asset is actually worth because they believe that they will be able to sell it in the future to an overeager buyer. This process would inflate prices and cause a trading frenzy. Incorporating investor overconfidence into a theoretical model published in 2003 in the Journal of Political Economy, Scheinkman and Xiong were able to recreate more accurately the hyperactive trading in bubbles.
Andrew Lo, a financial economist at MIT, is developing alternative models:
Lo's species behave differently based on what part of their brains they are using. When things go well and people make money, as they did for the past decade, the experience stimulates investors' reward circuitry. This causes them to seek more profits and ignore possible risk, leading, for example, to a bubble. When things take a turn for the worse, panic overrides rational decision-making, leading to a crash. Only when the market is steady does the rational brain take over. Lo is starting to use functional magnetic resonance imaging and other tools of neuroscience to quantify these behaviors and incorporate them into his models. He also needs more real-world data on the way different funds invest money--data that are now secret or that no one bothers to collect.

Although Lo's idiosyncratic approach lies outside of the behavioral and classical theories, he says it reconciles them. "If you were an efficient-markets type, I think you'd be hard-pressed to explain what happened over the last few weeks. And if you were an irrational finance person, you'd be hard-pressed to explain what happened over the previous 10 years. So I think that the only way to reconcile the two is to acknowledge that both are different aspects of the exact same truth."

Behavioral researchers are eager to prove that their ideas mirror nature by using quantitative methods to link them directly to real-life data... Stock pricing lends itself to such studies, because valuing a stock involves conjecture--which is subject to psychological factors--and a lot of stock-market data have recently become available to academic researchers.

In a 2007 paper in the Journal of Economic Perspectives, Wurgler and co-author Malcolm Baker, a financial economist at Harvard Business School, looked for signatures of investor sentiment--irrational optimism or pessimism--in stock-market data since the 1960s. They hypothesized that certain stocks would be more subject to sentiment than others: broadly speaking, stocks for which the true value is difficult to determine. For example, a young, promising company would fit the bill. "The combination of no earnings history and a highly uncertain future allows investors to defend valuations ranging from much too low to much too high," they write.

Comparing the stock-market data with their measure of investor sentiment, they found what they had expected. In optimistic times, difficult-to-value stocks were wildly popular and therefore made much more money than average. In pessimistic times, they were wildly unpopular and therefore made much less money than average. On the other hand, easy-to-value stocks, which are considered safer, were more popular in pessimistic times than optimistic ones, but their prices stayed much closer to average. This helps explain past bubbles in certain types of stocks--say, dot-com stocks in the 1990s--and is also useful for making predictions for the future

Monday, December 15, 2008

Conflict: Altruism's midwife

Bowles has an interesting article in the Nature "Being Human" series. From the editor's comments:

The historical and archaeological records reveal that humans became especially good at killing 'outsiders' from other groups, tribes or nations. Some animals do engage in such conflicts, but humans excel. We are also uniquely receptive to socialization and learning, and can achieve the heights of altruistic behaviour. Economist Samuel Bowles argues that these two extremes may be related: generosity and solidarity towards one's own may have emerged only in combination with hostility towards outsiders. Both may be part of what it is to be human. All essays in the 'Being human' series are available free via http://tinyurl.com/55ncjj.
From the article:
Among ancestral humans, parochial altruists may have provoked conflicts between groups over scarce natural and reproductive resources, and at the same time contributed to a group's success in these conflicts. Altruism would have facilitated the coordination of raiding and ambushing on a scale known in few other animals, while parochialism fuelled the antipathy towards outsiders. Additionally, with the development of projectile weapons, humans became adept at killing from a distance, which would have reduced the costs of aggression.

Support for this idea comes from artificial histories of early human evolution that my co-authors and I simulated by computer. In these simulations, we allowed groups of agents, tolerant or parochial, altruistic or selfish, to interact over thousands of generations under conditions likely to have been experienced by our Late Pleistocene and early Holocene ancestors. We designed the simulations so that violent conflict between two groups is likely if at least one group contains a preponderance of parochialists. We also made each group's fighters the parochial altruists (non-altruists are happy to let someone else do the fighting; tolerant members prefer to stay on friendly terms with outsiders). Thus, the groups with the most parochial altruists tend to win conflicts. Our objective was to see how the frequency of warfare, and the fraction of the different types of agent, would evolve.

In millions of simulated evolutionary histories, the populations emerging after thousands of generations of selection tend to be either tolerant and selfish, with little warfare, or parochial and altruistic with frequent and lethal encounters with other groups. Occasional transitions occur between the selfish peaceful states and the warring altruistic states. But neither altruism nor parochialism ever proliferate singly; they share a common fate, with war the elixir of their success.

Dogs have sense of fairness.

Fountain points to work by Range et al. showing that dogs, like monkeys and chips, have a sense of equity and fairness. A dog may stop obeying a command if it sees that another dog is getting a better deal. Thus, species other than primates show at least a primitive version of inequity aversion, perhaps a precursor of a more sophisticated sensitivity to efforts and payoffs of joint interactions.

I wonder if this behavior also might possibly be related to the extensive breeding selection carried out on dogs over the past several thousand years which has made them, unlike monkeys and apes, very attentive to human moods and intentions.

(Note: I usually compose these blog postings several days in advance of their actual appearance, to keep free of deadline pressure. The downside of this is that I frequently see something I want to mention appearing immediately on, for example, the Op-Ed page of the New York Times. This bit on fairness in dogs is referenced by Gail Collins as relevant to the current U.S. automakers bailout controversy.)

Friday, December 12, 2008

If I Were You: Perceptual Illusion of Body Swapping

The title of this post is also the title of a fascinating article published in PLoS ONE. When tricked by some simple optical and sensory illusions, we can adopt any other human form, no matter how different, as our own. From Carey's review:

The technique is simple. A subject stands or sits opposite the scientist, as if engaged in an interview. Both are wearing headsets, with special goggles, the scientist’s containing small film cameras. The goggles are rigged so the subject sees what the scientist sees: to the right and left are the scientist’s arms, and below is the scientist’s body...To add a physical element, the researchers have each person squeeze the other’s hand, as if in a handshake. Now the subject can see and “feel” the new body. In a matter of seconds, the illusion is complete. In a series of studies, using mannequins and stroking both bodies’ bellies simultaneously, the Karolinska researchers have found that men and women say they not only feel they have taken on the new body, but also unconsciously cringe when it is poked or threatened.
Here is the abstract from the article:
The concept of an individual swapping his or her body with that of another person has captured the imagination of writers and artists for decades. Although this topic has not been the subject of investigation in science, it exemplifies the fundamental question of why we have an ongoing experience of being located inside our bodies. Here we report a perceptual illusion of body-swapping that addresses directly this issue. Manipulation of the visual perspective, in combination with the receipt of correlated multisensory information from the body was sufficient to trigger the illusion that another person's body or an artificial body was one's own. This effect was so strong that people could experience being in another person's body when facing their own body and shaking hands with it. Our results are of fundamental importance because they identify the perceptual processes that produce the feeling of ownership of one's body.

I would love to try this...

My own personal helicopter.

Thursday, December 11, 2008

Spread of Happiness - a network analysis.

A report by Fowler and Christakis, as noted by Belluck, is generating interest and controversy. In an analysis covering 20 years of the well known Framington Heart Study they find that happiness spreads like a contagion, that one's happiness is influence by the happiness of friends of friends. The issue is whether the study proved that people became happy because of their social contacts or some unrelated reason. In the same issue of the British Medical Journal, Cohen-Cole and Fletcher critique the work, showing that the statistical analysis used in network studies can detect implausible social network effects in acne, height, and headaches. Here is a summary graphic based on the work provided by the New York Times:

Cool Brain Trick....

I pass on this link to you because of my interest in music, a scale that always seems to be going down, but not getting much lower. It’s an auditory equivalent of an old-fashioned barber pole.

Compendium of brain blogs...

MindBlog reader Kelly points us to this recent posting of "101 Fascinating Brain Blogs"

Wednesday, December 10, 2008

Changing our body image can change pain perception.

Some remarkable observations by Moseley et al. :

The feeling that our body is ours, and is constantly there, is a fundamental aspect of self-awareness. Although it is often taken for granted, our physical self-awareness, or body image, is disrupted in many clinical conditions. One common disturbance of body image, in which one limb feels bigger than it really is, can also be induced in healthy volunteers by using local anaesthesia or cutaneous stimulation. Here we report that, in patients with chronic hand pain, magnifying their view of their own limb during movement significantly increases the pain and swelling evoked by movement. By contrast, minifying their view of the limb significantly decreases the pain and swelling evoked by movement. These results show a top-down effect of body image on body tissues, thus demonstrating that the link between body image and the tissues is bi-directional.

Larger hippocampus and superior pathfinding in the blind

From Fortin et al, work that confirms how unnecessary vision is for the construction of spatial concepts:

In the absence of visual input, the question arises as to how complex spatial abilities develop and how the brain adapts to the absence of this modality. We explored navigational skills in both early and late blind individuals and structural differences in the hippocampus, a brain region well known to be involved in spatial processing. Thirty-eight participants were divided into three groups: early blind individuals (n = 12; loss of vision before 5 years of age; mean age 33.8 years), late blind individuals (n = 7; loss of vision after 14 years of age; mean age 39.9 years) and 19 sighted, blindfolded matched controls. Subjects undertook route learning and pointing tasks in a maze and a spatial layout task. Anatomical data was collected by MRI. Remarkably, we not only show that blind individuals possess superior navigational skills than controls on the route learning task, but we also show for the first time a significant volume increase of the hippocampus in blind individuals [F(1,36) = 6.314; P ≤ 0.01; blind: mean = 4237.00 mm3, SE = 107.53; sighted: mean = 3905.74 mm3, SE = 76.27], irrespective of whether their blindness was congenital or acquired. Overall, our results shed new light not only on the construction of spatial concepts and the non-necessity of vision for its proper development, but also on the hippocampal plasticity observed in adult blind individuals who have to navigate in this space.

Tuesday, December 09, 2008

Neural mechanisms underlying memory failure in older adults

Here is a fascinating bit of work from Stevens et al. When failing to encode information older, but not younger, adults show increased activity in brain regions mediating distraction. This continues the developing consensus that aging brains (as I woefully note for mine) have increasing difficulty ignoring distracting information that is irrelevant to the task at hand :

Older adults have reduced memory, primarily for recall, but also for recognition, particularly for unfamiliar faces. Behavioral studies have shown that age-related memory declines are due in part to distraction from impaired inhibition of task-irrelevant input during encoding. Functional magnetic resonance imaging (fMRI) has been used to uncover the sources of memory deficits associated with aging. To date, this work has focused on successful encoding, while the neural correlates of unsuccessful encoding are unknown. Here, we provide novel evidence of a neural mechanism underlying memory failures exclusively affecting older adults. Whereas both younger and older adults showed reduced activation of brain regions important for encoding (e.g., hippocampus) during unsuccessful encoding, only older adults showed increased activity in brain regions mediating distraction (e.g., auditory cortex) and in left prefrontal cortex. Further, these regions were functionally connected with medial parietal areas, previously identified as default mode regions, which may reflect environmental monitoring. Our results suggest that increased distraction from task-irrelevant input (auditory in this case), associated with the unfamiliar and noisy fMRI environment, may increase environmental monitoring. This in turn could hinder suppression of default mode processing, resulting in memory failures in older adults. These findings provide novel evidence of a brain mechanism underlying the behavioral evidence that impaired inhibition of extraneous input during encoding leads to memory failure in older adults and may have implications for the ubiquitous use of fMRI for investigating neurocognitive aging.

Prefrontal regions mediating resistance versus vulnerability to depression.

Koenigs et al., in a study of humans with focal brain lesions, address the causality of depressive symptoms by showing that lesions to different parts of our prefrontal cortex can either enhance or decrease our expression of those symptoms:

The neuroanatomical correlates of depression remain unclear. Functional imaging data have associated depression with abnormal patterns of activity in prefrontal cortex (PFC), including the ventromedial (vmPFC) and dorsolateral (dlPFC) sectors. If vmPFC and dlPFC are critical neural substrates for the pathogenesis of depression, then damage to either area should affect the expression of depressive symptoms. Using patients with brain lesions we show that, relative to nonfrontal lesions, bilateral vmPFC lesions are associated with markedly low levels of depression, whereas bilateral dorsal PFC lesions (involving dorsomedial and dorsolateral areas in both hemispheres) are associated with substantially higher levels of depression. These findings demonstrate that vmPFC and dorsal PFC are critically and causally involved in depression, although with very different roles: vmPFC damage confers resistance to depression, whereas dorsal PFC damage confers vulnerability.

Monday, December 08, 2008

Degraded surroundings degrade behavior

Keizer et al. find support for the "Broken Windows Theory," that suggests that signs of disorderly and petty criminal behavior trigger more disorderly and petty criminal behavior, thus causing the behavior to spread. They find that if people see one norm or rule being violated (such as graffiti or a vehicle parked illegally), they're more likely to violate others--such as littering, or even stealing. Groningen citizens were given the opportunity to steal an envelope that obviously contained a 5 Euro note from a postbox. When the postbox was clean and tidy 13% took the bait; by contrast, 27% stole from a graffitied postbox and 25% from one with litter around it. Other tests showed that people are more likely to litter in the presence of graffiti or abandoned shopping trollies, and after hearing the crackle of illegal fireworks.

Does your cell phone signal damange your DNA? - round two

An exchange in the letters to the editor section of the Nov. 28 Science Magazine:

In her widely cited News of the Week story "Fraud charges cast doubt on claims of DNA damage from cell phone fields" (Science, 29 August, p. 1144), G. Vogel writes, "The only two peer-reviewed scientific papers showing that electromagnetic fields (EMFs) from cell phones can cause DNA breakage are at the center of a misconduct controversy at the Medical University of Vienna." Notwithstanding the allegations on both sides of the fence in this unresolved controversy, Vogel's opening comment and the title of her article are misleading. In fact, there are many other peer-reviewed papers from laboratories in at least seven countries, including the United States, showing that cell phone or similar low-intensity EMFs can break DNA or modulate it structurally [e.g., (1-9)].

Vini G. Khurana
Department of Neurosurgery
The Canberra Hospital
Australian National University
Canberra, ACT, Australia
E-mail: vgkhurana@gmail.com

References

1. R. J. Aitken, L. E. Bennetts, D. Sawyer, A. M. Wiklendt, B. V. King, Int. J. Androl. 28, 171 (2005).
2. W. Baohong et al., Toxicology 232, 311 (2007).
3. J. Y. Kim et al., Environ. Toxicol. 23, 319 (2008).
4. H. Lai, N. P. Singh, Int. J. Radiat. Biol. 69, 513 (1996).
5. S. Lixia et al., Mutat. Res. 602, 135 (2006).
6. R. Paulraj, J. Behari, Mutat. Res. 596, 76 (2006).
7. J. L. Phillips et al., Bioelectrochem. Bioenerget. 45, 103 (1998).
8. T. Nikolova et al., FASEB J. 19, 1686 (2005).
9. M. Mashevich et al., Bioelectromagnetics 24, 82 (2003).

Response
My intention was not to imply that there were only two papers showing any effects of EMFs. There are many publications that show effects of EMFs on DNA, but the citations listed here do not directly contradict the quoted sentence. Some see an effect in combination with other known agents that damage DNA. One finds an effect of microwaves, but in the range of microwave ovens and wireless LANs, not cell phones. Others look at DNA damage (for example, chromosome duplications), but not breakage. Several show mixed results: One finds a decrease in DNA breaks in three sets of exposed cells and an increase in one. Since the story was published, however, I have been made aware of a paper by Yao et al. (1), which also reported single-strand DNA breaks caused by EMFs equivalent to those from cell phones. I regret any misunderstanding the sentence caused.

Gretchen Vogel

Reference

1. K. Yao et al., Mol. Vision 14, 964 (2008).


Sunday, December 07, 2008

MindBlog has moved south...

A personal note...I've spent the last week in transition between Madison Wisconsin (where it is 7 degrees farenheit right now) and Fort Lauderdale (where it is 72). I'll be here until mid-April. The picture is of one of my two Abyssinian kittens, looking out my condo window. The cats were great travelers in the car, watched the passing countryside as if they were dogs.

Friday, December 05, 2008

Foundations of neuroeconomics.

Clithero et al. offer an analysis and critique of the foundations of Neuroeconomics, the attempt to understand human economic behaviors in terms of underlying brain mechanisms.

Cyberchondria

An article by Markoff reminds me of the recent post on an example of the nocebo effect (Reading the drug side-effects label can make you sick). He describes a study by Microsoft suggesting that self-diagnosis by search engine frequently leads Web searchers to conclude the worst about what ails them.

They found that Web searches for things like headache and chest pain were just as likely or more likely to lead people to pages describing serious conditions as benign ones, even though the serious illnesses are much more rare...For example, there were just as many results that linked headaches with brain tumors as with caffeine withdrawal, although the chance of having a brain tumor is infinitesimally small.

Thursday, December 04, 2008

Resveratrol promotes repair of DNA breaks that occur on aging

Nicholas Wade reports on work of Sinclair and collaborators (reported in Cell) that sirtulin, an enzyme activated by the red wine compound resveratrol, promotes the repair of breaks in DNA that occur on aging. (Ten previous MindBlog posts on resveratrol can be retrieved by entering "resveratrol" in the search box in the left column.) Resveratrol has many different effects, only some of which are exerted through sirtuin. While some people have been taking resveratrol with no apparent side effects, Mindblog's self-experiment found it causing arthritic symptoms, and that experience was reported by several who commented on that post.

Ventral and dorsal pathways for language

Finding an analogy to our visual system's partition of visual information into dorsal 'where' and ventral 'what' streams, Saur et al combine MRI and diffusion tensor imaging to provide support for a language processing model in which a dorsal stream is involved in mapping sound to articulation, and a ventral stream in mapping sound to meaning. Here is their abstract:

Built on an analogy between the visual and auditory systems, the following dual stream model for language processing was suggested recently: a dorsal stream is involved in mapping sound to articulation, and a ventral stream in mapping sound to meaning. The goal of the study presented here was to test the neuroanatomical basis of this model. Combining functional magnetic resonance imaging (fMRI) with a novel diffusion tensor imaging (DTI)-based tractography method we were able to identify the most probable anatomical pathways connecting brain regions activated during two prototypical language tasks. Sublexical repetition of speech is subserved by a dorsal pathway, connecting the superior temporal lobe and premotor cortices in the frontal lobe via the arcuate and superior longitudinal fascicle. In contrast, higher-level language comprehension is mediated by a ventral pathway connecting the middle temporal lobe and the ventrolateral prefrontal cortex via the extreme capsule. Thus, according to our findings, the function of the dorsal route, traditionally considered to be the major language pathway, is mainly restricted to sensory-motor mapping of sound to articulation, whereas linguistic processing of sound to meaning requires temporofrontal interaction transmitted via the ventral route.

Wednesday, December 03, 2008

Destroying memories to strengthen them

Lee reports work with rats showing that the core mechanisms that strengthen memories have more in common with the mechanisms that support memory reconsolidation than those that participate in initial memory storage. Memories are dynamic, rather than static, in nature. The reactivation of a memory through re-exposure to salient training stimuli results in its destabilization, necessitating a restabilization process known as reconsolidation, a disruption of which leads to amnesia. He finds that one normal function of hippocampal memory reconsolidation in rats is to modify the strength of a contextual-fear memory as a result of further learning.

A summary figure from Rudy's review of the article:


(a) The contextual-fear conditioning procedures that were used to study reconsolidation and memory strengthening are very similar. Note that the only difference between them is that the shock unconditioned stimulus was presented in phase II of the memory strengthening procedure, but the subject was only exposed to the context in the reconsolidation procedure. (b) Exposure to just a retrieval cue or a second conditioning trial will retrieve the established memory trace from long-term memory. This will result in the activation of the UPS, which will uncouple the synapses that support the trace, and the activation of Zip268 and the subsequent production of molecules, protein synthesis (PS), needed to rebuild or strengthen the trace.

The idea that retrieval can disrupt the synaptic basis of an established memory trace is counterintuitive. Nevertheless, the ubiquitin-proteasome system (UPS) has recently been identified as a key component of this process. Ubiquitin tags proteins for degradation and the proteasome degrades them. Retrieval of a contextual-fear memory is associated with polyubiquitinization of important postsynaptic density scaffolding proteins in the hippocampus.If proteolysis is prevented, then the memory trace should not degrade and would not have to be rebuilt from new protein.

Measuring the real-time chemistry of reward and aversion

fMRI studies suggest that nucleus accumbens (NAc) activation increases in response to stimuli of different hedonic valence, whereas physiological evidence suggests that NAc neurons show increases in activity for rewarding stimuli and pauses for aversive stimuli. Using cyclic voltammetry, Roitman et al. find that patterns of dopamine release and metabolic activity differentiate between rewarding and aversive stimuli. From their text:

It is controversial whether dopamine release in the NAc exclusively signals aspects of reward or serves a more broad purpose for signaling novelty or salience regardless of hedonic value...To dissociate salience or novelty from hedonic valence, we delivered brief intra-oral infusions of sucrose and quinine solutions to naive behaving rats and measured changes in dopamine concentration and pH in the NAc every 100 ms using fast-scan cyclic voltammetry. The pH measurements provide a measure of metabolic activity and thus an indirect measure of general neuronal activity.Appetitive (0.3 M sucrose) and aversive (0.001 M quinine) stimuli were delivered intra-orally to ensure equal exposure and transduction via the same sensory modality: the taste system. Each animal received both appetitive and aversive stimuli at unpredictable times to ensure comparable novelty and salience but opposing hedonic valence. This design elicited strong and consistent behavioral differences in hedonic expression with no evidence of anticipatory or conditioned responses. Voltammetric recordings permitted real-time detection of dopamine release and NAc activity, elucidating their role in signaling hedonic valence. The work makes clear that dopamine signaling and general activity in the NAc is exquisitely sensitive to both rewarding and aversive taste stimuli.

Tuesday, December 02, 2008

Teaching robots right from wrong

Cornelia Dean writes a brief article on people trying to develop intelligent battle robots that can behave more ethically in the battlefield than humans currently can. It focuses on the work of Ronald Arkin at Georgia Tech.

In the heat of battle, their minds clouded by fear, anger or vengefulness, even the best-trained soldiers can act in ways that violate the Geneva Conventions or battlefield rules of engagement. Now some researchers suggest that robots could do better...some of the potential benefits of autonomous fighting robots: For one thing, they can be designed without an instinct for self-preservation and, as a result, no tendency to lash out in fear. They can be built without anger or recklessness, Dr. Arkin wrote, and they can be made invulnerable to what he called “the psychological problem of ‘scenario fulfillment,’ ” which causes people to absorb new information more easily if it agrees with their pre-existing ideas.

Dr. Arkin’s approach involves creating a kind of intellectual landscape in which various kinds of action occur in particular “spaces.” In the landscape of all responses, there is a subspace of lethal responses. That lethal subspace is further divided into spaces for ethical actions, like firing a rocket at an attacking tank, and unethical actions, like firing a rocket at an ambulance....because rules like the Geneva Conventions are based on humane principles, building them into the machine’s mental architecture endows it with a kind of empathy. He added, though, that it would be difficult to design “perceptual algorithms” that could recognize when people were wounded or holding a white flag or otherwise “hors de combat.”
Noel Sharkey, a computer scientist at the University of Sheffield in Britain, has written that this is not a ‘Terminator’-style science fiction but grim reality. He would ban lethal autonomous robots until they demonstrate they will act ethically, a standard he said he believes they are unlikely to meet. Meanwhile, he said, he worries that advocates of the technology will exploit the ethics research to allay political opposition.

Daniel C. Dennett, a philosopher and cognitive scientist at Tufts University:
“If we talk about training a robot to make distinctions that track moral relevance, that’s not beyond the pale at all,” he said. But, he added, letting machines make ethical judgments is “a moral issue that people should think about.”

The Psychology of Transcending the Present

Liberman and Trope suggest an underlying similarity in all of our mental operations that are not dealing with the here and now:

People directly experience only themselves here and now but often consider, evaluate, and plan situations that are removed in time or space, that pertain to others' experiences, and that are hypothetical rather than real. People thus transcend the present and mentally traverse temporal distance, spatial distance, social distance, and hypotheticality. We argue that this is made possible by the human capacity for abstract processing of information. We review research showing that there is considerable similarity in the way people mentally traverse different distances, that the process of abstraction underlies traversing different distances, and that this process guides the way people predict, evaluate, and plan near and distant situations.
Here is one clip from the article on the interrelations among psychological distance dimensions:
Try to complete the sentence "A long time ago, in a ____ place." The tendency to complete it with "far away" rather than with "nearby" reflects not only a literary convention but also an automatic tendency of the human mind. Indeed, people use spatial metaphors to represent time in everyday language and reasoning. More generally, if psychological distance is reflected in different dimensions, then these dimensions should be mentally associated. Remote locations should bring to mind the distant rather than the near future, other people rather than oneself, and unlikely rather than likely events. Initial support for this hypothesis comes from a set of studies in which participants viewed landscape photographs containing an arrow that was pointing to either a proximal or a distal point on the landscape. Each arrow contained a word denoting either psychological proximity (e.g., tomorrow, we, sure) or psychological remoteness (e.g., year, others, maybe) (Figure below). Participants had to respond by pressing one of two keys as quickly and as accurately as possible. In one version of the task, they had to indicate whether the arrow pointed to a proximal or distal location. In another version, they had to identify the word printed in the arrow [Stroop task]. In both versions, participants responded faster to (i.e., processed more efficiently) distance-congruent stimuli (in which the spatially distant arrow contained a word that denoted large temporal distance, large social distance, or low likelihood and the spatially proximal arrow contained words that denoted temporal proximity, social proximity or high likelihood) than to distance-incongruent stimuli (in which spatially distal arrows contained words denoting proximity and spatially proximal arrows contained words denoting remoteness).

Figure: Two examples of incongruent visual stimuli: a word denoting social proximity, "us," located far from the observer, and a word denoting social remoteness, "them," located near the observer. Because spatial distance is associated with temporal distance, social distance, and hypotheticality, participants are slower to indicate the location of the arrow and to identify the word on it with incongruent stimuli than with congruent stimuli "us" located near the observer and "them" located far from the observer.

Monday, December 01, 2008

Superorganisms

Steve Jones writes an interesting review of E.O. Wilson's latest book, a collaboration with Bert Hölldobler: "THE SUPERORGANISM -The Beauty, Elegance, and Strangeness of Insect Societies"

Social insects have often been co-opted as models of human society. The right uses them to celebrate the power of hierarchy, the left that of community. Bees attract the liberal and optimistic (the spirit of the beehive), ants the conservative and the anything but (the city as ant heap).

Hölldobler and Wilson’s central conceit is that a colony is a single animal raised to a higher level. Each insect is a cell, its castes are organs, its queens are its genitals, the wasps that stung me are an equivalent of an immune system. In the same way, the foragers are eyes and ears, and the colony’s rules of development determine its shape and size. The hive has no brain, but the iron laws of cooperation give the impression of planning. Teamwork pays; in a survey of one piece of Amazonian rain forest, social insects accounted for 80 percent of the total biomass, with ants alone weighing four times as much as all its mammals, birds, lizards, snakes and frogs put together. The world holds as much ant flesh as it does that of humans.

A few simple rules produce what appears to be intelligence, but is in fact entirely mindless. Individuals are automatons. An ant stumbles on a tasty item and brings a piece back to the nest, wandering as it does and leaving a trail of scent. A second ant tracks that pathway back to the source, making random swerves of its own. A third, a fourth, and so on do the same, until soon the busy creatures converge on the shortest possible route, marked by a highway of pheromones. This phenomenon has some useful applications for the social animals who study it. Computer scientists fill their machines with virtual ants and task them with finding their way through a maze, leaving a coded signal as they pass until the fastest route emerges. That same logic helps plan efficient phone networks and the best use of the gates at J.F.K. In the phone system each message leaves a digital “pheromone” as it passes through a node, and the fastest track soon emerges. Swarm intelligence does wondrous things.

Neurotech

Virginia Gewin offers a report on the growing neurotechnology industry.

Last year, global neurotechnology industry revenues rose 8.3% to US$130.5 billion, says NeuroInsights, a market-analysis firm based in San Francisco, California. Its Neurotechnology Industry 2008 Report, which profiled 500 public and private companies, divided the industry into three sectors: neuropharmaceuticals, neurodevices and neurodiagnostics.

Medtronic in Minneapolis, Minnesota...is developing deep-brain stimulation devices, the latest ones for epilepsy and depression.

The budding area of neurogenesis research..has prompted drug companies to look to start-ups and academia for talent... the development of small molecules to encourage neurogenesis — in which endogenous stem cells mature into neurons — is a "breakthrough area". Swiss-based drug giant AstraZeneca announced last month that it will collaborate with Columbia University's René Hen to explore novel neurogenesis-related depression and anxiety treatments.