An E.Coli toxin can stimulate learning and memory

Diana et al show (at least for mice) that intracerebral injection of cytotoxic necrotizing factor 1 (CNF1) - a protein toxin from Escherichia coli that constitutively activates Rho GTPases and leads to remodeling of the cerebral actin cytoskeleton - enhances neurotransmission and synaptic plasticity, and improves learning and memory in various behavioral tasks. The effects persist for weeks and are not observed in mice treated with a recombinant CNF1 inactivated by a single amino acid replacement. The results suggest that learning ability can be improved through pharmacological manipulation of neural connectivity.

Two parallel (and sometimes conflicting) brain systems for evaluating others.

The Editor's Choice section of the Jan. 5 Science magazine has a brief review of interesting work by Rydell et al. at Miami University:

"One emerging theoretical view posits two systems of reasoning: a slow-learning system that acquires and classifies associations over long periods of time, and a fast-learning module that emphasizes higher-order conscious cognition. A stimulus--for example, the negatively valenced word "hate"--can be paired in a subliminal fashion with a person's face (for example, Bob's); this association will induce subjects to regard Bob unfavorably, as assessed by their poststimulus choice of positive or negative adjectives, yet they will be unaware of having evolved this implicit attitude. Similarly, written descriptions of Bob's praiseworthy behavior will result in subjects expressing a liking for Bob, where this evaluation reflects a studied and thoughtful appraisal--that is, the formation of an explicit attitude. Rydell et al. show that these mental processes can be accessed separately and appear to operate independently. Not only are subjects capable of developing apparently inconsistent negative implicit attitudes and positive explicit attitudes about the same individual, but they can actually be influenced to invert their preferences by the subsequent presentation of subliminal (positive) words and supraliminal (negative) descriptions."

Attention and consciousness are not the same thing.

I would like to point you to an excellent article by Christof Koch and Naotsugu Tsuchiya in Trends in Cognitive Science arguing that attention and consciousness are two distinct brain processes. They do a much more thorough job than I managed in my "Biology of Mind" book. A PDF form of the article can be obtained from the Koch laboratory web site. Here is their abstract:

The close relationship between attention and consciousness has led many scholars to conflate these processes. This article summarizes psychophysical evidence, arguing that top-down attention and consciousness are distinct phenomena that need not occur together and that can be manipulated using distinct paradigms. Subjects can become conscious of an isolated object or the gist of a scene despite the near absence of top-down attention; conversely, subjects can attend to perceptually invisible objects. Furthermore, top-down attention and consciousness can have opposing effects. Such dissociations are easier to understand when the different functions of these two processes are considered. Untangling their tight relationship is necessary for the scientific elucidation of consciousness and its material substrate.

At the end of their paper the authors comment on the implications their consclusions hold for real life:

It could be contested that top-down attention without consciousness and consciousness with little or no top-down attention are arcane laboratory curiosities that have little relevance to the real world. We believe otherwise. A lasting insight into human behavior – eloquently articulated by Friedrich Nietzsche – is that much action bypasses conscious perception and introspection. In particular, Goodale and Milner isolated highly trained, automatic, stereotyped and fluid visuomotor behaviors that work in the absence of phenomenal experience. As anybody who runs mountain trails, climbs, plays soccer or drives home on automatic pilot knows, these sensorimotor skills – dubbed zombie behaviors – require rapid and sophisticated sensory processing. Confirming a long-held belief among trainers, athletes perform better at their highly tuned skill when they are distracted by a skill-irrelevant dual task (e.g. paying attention to tones) than when they pay attention to their exhaustively trained behaviors.

The history of any scientific concept (e.g. energy, atoms or genes) is one of increasing differentiation and sophistication until its action can be explained in a quantitative and mechanistic manner at a lower, more elemental level. We are far from this ideal in the inchoate science of consciousness. Yet functional considerations and the empirical and conceptual work of many scholars over the past decade make it clear that these psychologically defined processes – top-down attention and consciousness – so often conflated, are not the same. This empirical and functional distinction clears the deck for a concerted neurobiological attack on the core problem – that of identifying the necessary and sufficient neural causes of a conscious percept.

A key to life satisfaction? Lower your expectations.

Why do citizens of Denmark have score higher than any other Western country on measures of life satisfaction? A brief article in today's Science section of the New York Times points to a study suggesting an answer: the country’s secret is a culture of low expectations. "...on surveys, Danes continually report lower expectations for the year to come, compared with most other nations... If you’re a big guy, you expect to be on the top all the time and you’re disappointed when things don’t go well. But when you’re down at the bottom .. you hang on, you don’t expect much, and once in a while you win, and it’s that much better....year after year, they are pleasantly surprised to find that not everything is getting more rotten in the state of Denmark,”

Become an Evo Warrior

From the Jan. 5 issue of Science Magazine:

What can you do if your local school board proposes a curriculum that downplays evolution? Or if your hometown newspaper runs an editorial supporting "intelligent design"?

This new site from the Federation of American Societies for Experimental Biology in Rockville, Maryland, offers advice and resources for scientists who want to defend Darwinism. Downloadable documents provide pointers on meeting with public officials, testifying at school board hearings, and related topics. Much of the advice is common sense, but some of it may be counterintuitive for scientists. For example, although you want your papers to run in prestigious journals, an op-ed will probably have more impact if it appears in the local paper than if it's accepted by The Wall Street Journal. The site also furnishes PowerPoint files on topics such as the importance of learning about evolution.

Movement errors can rise in the brain before the movement starts.

Churchland et al report in Neuron Magazine that variations in firing of the motor cortical neurons that plan and preceed trained skilled physical movement (like throwing a dart at a dart board) are responsible for a large fraction of the variability of the movement. This contradicts our usual assumption that something goes wrong during the movement. Recording from monkey motor and pre-motor cortex neurons, they found that variations in the velocity of trained reaches correlated with fluctuations in brain activity during the preparatory period — hundreds of milliseconds before the movement started.

Constructive memory a tool for anticipating futures.

Daniel Schacter writes a brief essay in the Jan. 4 issue of Nature Magazine on why our memory is not a literal reproduction of the past, but is instead constructed by pulling together pieces of information from different sources.

"One clue comes from studies indicating that memory errors can reveal the operation of adaptive rather than defective processes. For example, consider the following words: tired, bed, awake, rest, dream, night, blanket, doze, slumber, snore, pillow, peace, yawn and drowsy. When asked whether 'blanket'; was on the list (a few minutes after seeing the words), most people correctly recognize that it was; when asked about 'point';, they correctly remember that it was not. When asked about 'sleep';, most people confidently remember having seen it — but they are wrong. They falsely recognize 'sleep'; because they remember that many associated words were present, and mistakenly rely on their accurate memory for the general theme of the list."

"Future events are not exact replicas of past events, and a memory system that simply stored rote records would not be well-suited to simulating future events. A system built according to constructive principles may be a better tool for the job: it can draw on the elements and gist of the past, and extract, recombine and reassemble them into imaginary events that never occurred in that exact form. Such a system will occasionally produce memory errors, but it also provides considerable flexibility."

"Taken together, neurological and neuroimaging studies suggest that false-recognition errors reflect the healthy operation of adaptive, constructive processes supporting the ability to remember what actually happened in the past. Many researchers believe that remembering the gist of what happened is an economical way of storing the most important aspects of our experiences without cluttering memory with trivial details. We agree. But we also see another important function for constructive memory, one that emerges from an idea that a growing number of researchers are embracing — that memory is important for the future as well as the past."

Watching the brain make up its mind about an ambiguous stimulus.

On looking at an ambiguous visual stimuli, we can experience frequent spontaneous transitions between two competing percepts while physical stimulation remains unchanged (see example in the top section of Figure 1)... a key question has remained unresolved: Does perceptual rivalry result merely from local bistability of neural activity patterns in sensory stimulus representations (i.e. mainly in posterior visual cortical areas), or do higher-order areas (i.e. frontal cortex) play a causal role by shifting inference and, thus, initiating perceptual changes? Sterzer and Kleinschmidt have used functional MRI to measure brain activity while human observers reported successive spontaneous changes in perceived direction for an ambiguous apparent motion stimulus (Fig 1, top). In a control condition, the individual sequences of spontaneous perceptual switches during bistability were replayed by using a disambiguated version of the stimulus (Fig. 1, bottom).


Fig. 1. Stimulus display. Ambiguous and disambiguated versions of the apparent motion quartet used in the rivalry and replay conditions, respectively, are shown. The single frames alternated at 4 Hz. When looking at the rivalry stimulus, perception is bistable and fluctuates spontaneously between periods of horizontal and vertical apparent motion perception. Disambiguated versions of the stimulus were used to change participants' perception of apparent motion with the same temporal sequence as during the rivalry condition.


Fig. 2. Transient activation during perceptual switches. (A) Regions commonly activated in response to both spontaneous and stimulus-driven perceptual switches are rendered in blue onto a standard anatomical template image Numbers 1–6 indicate the regions that were subsequently used for detailed analyses of signal time courses. (B) Greater response amplitudes during spontaneous as opposed to stimulus-driven switches were observed in bilateral inferior frontal regions and are shown in red. (C) Earlier responses during spontaneous as opposed to stimulus-driven switches were observed in the right inferior frontal gyrus.

Greater activations during spontaneous compared with stimulus-driven switches were observed in inferior frontal cortex bilaterally. Subsequent chronometric analyses of event-related signal time courses showed that, relative to activations in motion-sensitive extrastriate visual cortex, right inferior frontal cortex activation occurred earlier during spontaneous than during stimulus-driven perceptual changes. The temporal precedence of right inferior frontal activations suggests that this region participates in initiating spontaneous switches in perception during constant physical stimulation. Their findings can thus be seen as a signature of when and where the brain "makes up its mind" about competing perceptual interpretations of a given sensory input pattern.

Brain correlates of "flashbulb memory" of 9/11

The term "flashbulb memory" is used to describe the recall of shocking, consequential events such as hearing news of a presidential assassination. Sharot et al test the idea that the vivid detail of such memories results from the action of a unique neural mechanism. They study personal recollections of the terrorist attacks of September 11, 2001 (9/11) in New York City, combining behavioral and brain imaging techniques, with two goals: (i) to explore the neural basis of such memories and (ii) to clarify the characteristics of the emotional events that may give rise to them. Three years after the terrorist attacks, participants were asked to retrieve memories of 9/11, as well as memories of personally selected control events from 2001. At the time of the attacks, some participants were in Downtown Manhattan, close to the World Trade Center; others were in Midtown, a few miles away. The Downtown participants exhibited selective activation of the amygdala as they recalled events from 9/11, but not while they recalled control events. This was not the case for the Midtown participants. Moreover, only the Downtown participants reported emotionally enhanced recollective experiences while recalling events from 9/11, as compared with control events. These results suggest that close personal experience may be critical in engaging the neural mechanisms that underlie the emotional modulation of memory and thus in producing the vivid recollections to which the term flashbulb memory is often applied.

Figure: Blood oxygen level-dependent (BOLD) response and proximity to the WTC. (a) Coronal slice of the structurally defined left amygdala (outlined in red) that includes the peak active voxel. (b) Mean percentage signal change from the peak active voxel in the left amygdala, revealing a two-way interaction of trial type (9/11 vs. summer) x group (Downtown vs. Midtown). (c and d) ANCOVA contrasting activation during 9/11 trials vs. summer trials, with participants' distance from the WTC as a covariate, in voxels within the structurally defined amygdala (c) and posterior parahippocampal cortex (d). Warm colors indicate positive correlation, and cool colors indicate negative correlation. Participants who were closer to the WTC showed decreased activation in the posterior parahippocampal cortex and increased activation in the amygdala bilaterally during retrieval of 9/11 memories relative to summer memories.

Being happy broadens your scope of attention.

Rowe et. al. have measured the "effect of positive mood states ... in two different cognitive domains: semantic search (remote associates task) and visual selective attention (Eriksen flanker task). In the conceptual domain, positive affect enhanced access to remote associates, suggesting an increase in the scope of semantic access. In the visuospatial domain, positive affect impaired visual selective attention by increasing processing of spatially adjacent flanking distractors, suggesting an increase in the scope of visuospatial attention. During positive states, individual differences in enhanced semantic access were correlated with the degree of impaired visual selective attention. These findings demonstrate that positive states, by loosening the reins on inhibitory control, result in a fundamental change in the breadth of attentional allocation to both external visual and internal conceptual space."

Alcohol and Arthritis

Jonsson et. al. show (at least in mice) that "low but persistent ethanol consumption delays the onset and halts the progression of collagen-induced arthritis by interaction with innate immune responsiveness."

An Autistic Savant - The Living Camera

Steven is an autistic savant living in London who did not speak until he was five and now has great difficulty with language as an adult. When he was eleven he drew a perfect aerial view of London after flying over it only once. Here is a windows media player movie describing his Rome flyover and drawing.

The Free Will debate...

Any of you who have read my "I-Illusion" piece or followed this blog will know that I have a continuing interest in the issue of free will. The science section in the Jan. 2 issue of The New York Times has a beautifully written essay by Dennis Overbye - "Free Will: Now You Have It, Now You Don't" - which gives the views of Dennett, Wegner, Libet, Silberstein and others. I'm tempted to give you huge chunks of the article, but will retrain myself to just a few clips:

Overbye: A bevy of experiments in recent years suggest that the conscious mind is like a monkey riding a tiger of subconscious decisions and actions in progress, frantically making up stories about being in control.

Silberstein: If people freak at evolution, etc., how much more will they freak if scientists and philosophers tell them they are nothing more than sophisticated meat machines, and is that conclusion now clearly warranted or is it premature?

Dennett: When we consider whether free will is an illusion or reality, we are looking into an abyss. What seems to confront us is a plunge into nihilism and despair.

Overbye: Dennett...is one of many who have tried to redefine free will in a way that involves no escape from the materialist world while still offering enough autonomy for moral responsibility, which seems to be what everyone cares about. ... Dennett argues, it is precisely our immersion in causality and the material world that frees us. Evolution, history and culture, he explains, have endowed us with feedback systems that give us the unique ability to reflect and think things over and to imagine the future. Free will and determinism can co-exist.

Dennett: All the varieties of free will worth having, we have...We have the power of imagination, to see and imagine futures...That’s what makes us moral agents...You don’t need a miracle to have responsibility.

Overbye also reviews the idea of freedom as a possible emergent phenomena that grows naturally in accordance with the laws of physics - like stock markets, brains, or the rules of democracy - that play by new rules once they are here.

The distinction between sincerity and authenticity

I want to pass on clips from an essay by Orlando Patterson in the Dec. 26 New York Times. He cites Lionel Trilling, the cultural critic, as having in the 1970s "encouraged us to take seriously the distinction between sincerity and authenticity. Sincerity, he said, requires us to act and really be the way that we present ourselves to others. Authenticity involves finding and expressing the true inner self and judging all relationships in terms of it."

Patterson suggests that "Authenticity now dominates our way of viewing ourselves and our relationships, with baleful consequences. Within sensitive individuals it breeds doubt; between people it promotes distrust; within groups it enhances group-think in the endless quest to be one with the group’s true soul; and between groups it is the inner source of identity politics...the primacy of the self has penetrated major areas of government: emotivist arguments trump reasoned discourse in Congressional hearings and criminal justice; and in public education."

"Social scientists and pollsters routinely belittle results showing growing tolerance; they argue that Americans have simply learned how to conceal their deeply...Harvard social psychologist Mahzarin Banaji and her collaborators claim to have evidence, based on more than three million self-administered Web-based tests, that nearly all of us are authentically bigoted to the core with hidden “implicit prejudices” — about race, gender, age, homosexuality and appearance — that we deny, sometimes with consciously tolerant views ingrained prejudices."

"I couldn’t care less whether my neighbors and co-workers are authentically sexist, racist or ageist. What matters is that they behave with civility and tolerance, obey the rules of social interaction and are sincere about it. The criteria of sincerity are unambiguous: Will they keep their promises? Will they honor the meanings and understandings we tacitly negotiate? Are their gestures of cordiality offered in conscious good faith?...Sincerity rests in reconciling our performance of tolerance with the people we become. And what it means for us today is that the best way of living in our diverse and contentiously free society is neither to obsess about the hidden depths of our prejudices nor to deny them, but to behave as if we had none."

Explaining away the supernatural as brain misfirings?

Several of my posts have mentioned work suggesting a basis for phenomena like out of body experiences or sensing the presence of phantom others: in the temporary perturbation of brain processes that normally arrange our perception of the external world and others in it. These perturbations have been observed during epileptic seizures and electrical or magnetic stimulation of regions of the brain. Deborah Blum, author of “Ghost Hunters: William James and the Scientific Search for Life After Death.” weighs in on this issue in a Op-Ed piece in the Dec. 30 New York Times. She cites work from Blanke's laboratory that I mentioned in my Oct. 3 post. She seems critical of scientists who "concluded that ghosts are mere “bodily delusions,” electrical misfirings and nothing more" and cites work done on psychic phenomena by respected scientists in the late 19th century. Blum says "Dr. Blanke believes that even this one subject’s experience serves as an example of how we may mistake errant signals in the brain for something more. Humans tend, he points out, to seek explanation, to impose meaning on events that may have none. The pure rationalists among us suggest that our need to add meaning to a basic, biological existence easily accounts for the way we organize religions and find evidence of otherworldly powers in the stuff of everyday life."

Blum then continues: "The nonpurists suggest a different conclusion: willful scientific blindness. And there’s no reason Dr. Blanke’s study can’t support their theories of the paranormal. Perhaps his experimental electric current simply mimics the work of an equally powerful spirit. Much of the psychical research done today applies similar principles: brain-imaging machines highlight parts of the brain that respond to psychic phenomena, while other devices are used to search for infrared radiation or increased electrical activity in haunted houses."

Wait a minute... Equally powerful spirit? Will someone please measure this spirit with a physical instrument, because it is altering physical processes in the brain! Or, "parts of the brain that respond to psychic phenomena?" What is cause and what is effect here? Are we presupposing the existence of psychic phenomena as causes? Then please measure them. I'm sorry, but I can't give up my skepticism about things that alter material physical processes in the brain, how can a non-physical process (spirit, ectoplasm, soul, whatever) change them? We're back to Descartes putting the soul in the pineal gland.


Photo credit: New York Times.

"Web 2.0"...both feel-good and wicked

I want to pass on two articles on "Web 2.0", the first by Celeste Biever in the Dec. 23 Issue of New Scientist, and the second by David Pogue in the Dec. 31 issue of the New York Times.

First, Biever:

"USER participation is crucial to the survival of popular websites like YouTube and Flickr. But how do these sites ensure that new videos, photos and comments keep flooding in?

It all comes down to persuasion strategies, says B. J. Fogg at Stanford University in California, who is analysing the techniques employed by websites that rely on their users for content, known collectively as Web 2.0. The secret is to tie the acquisition of friends, compliments and status – spoils that humans will work hard for – to activities that enhance the site, such as inviting new users and contributing photos, he says. “You offer someone a context for gaining status, and they are going to work for that status.”

If you offer people a chance to gain status, they will work for it

Fogg and his colleagues analysed hundreds of such sites and identified three stages to their success, which they called discovery, superficial involvement and true commitment.

They found that the first two stages are easily achieved, for example by making it simple for existing users to email their friends with something they have posted online. In this way other people discover the site and become superficially involved through activities such as rating a posted video or photo. What separates successful from unsuccessful websites is the ability to get these people to create content of their own, involve yet more friends, and remain active and loyal (see “Watch yourself”).

By studying over 150 videos of people using successful sites, Fogg identified key strategies that persuade users to get involved. One incentive is to give people the opportunity to increase their status. For example, the photo-sharing website Flickr assigns images an “interestingness” score depending on how many people view them and whether they comment. This encourages users to email their friends with links to their photos. This is good for the site as it improves the quality of Flickr's search engine by ensuring the most interesting photos are ranked most highly.

Sites also keep people involved by giving them the chance to earn rewards. For bloggers these could come in the form of comments from other users, while on the business networking site Linked-In they might be endorsements that potential contacts can read. Again, these benefit the websites by engaging other users.

The effects of both status and rewards are increased because they are doled out unpredictably – new people joining your friendship group on MySpace say, or a new comment on your blog. This ensures users frequently return to the site to check for changes.

Fogg hopes that by studying how well these strategies work, he will be able to quantify them and discover new ways in which people are open to persuasion. “The web is a huge lab for studying human psychology,” he says. “I think what we are seeing with Web 2.0 is which persuasion technologies work and which do not.”

And the next article, by Pogue:

"IN 2006, the big Internet news was “Web 2.0” — that is, participatory Web sites, like YouTube, MySpace, Wikipedia, Digg and Flickr, which relied on material supplied by the audience itself. On these explosively popular sites, the Web is not so much a publication as a global conversation.

In 2007, the challenge may be keeping that conversation from descending into the muck.

As a Web 2.0 site or a blog becomes more popular, a growing percentage of its reader contributions devolve into vitriol, backstabbing and name-calling (not to mention Neanderthal spelling and grammar). Participants address each other as “idiot” and “moron” (and worse) the way correspondents of old might have used “sir” or “madam.”

The New Nastiness may be no different from the incivility people can show each other in everyday life. It may be inspired by the political insultfests on TV and radio. Or it may be that anonymity online removes whatever self-control they might have exhibited when confronting their subjects in person.

Internet veterans scoff at the notion that there’s any increase in hostility online. They point to similar “flame wars” dating back to the earliest days of the Internet, even before there was a Web.

Instead, these observers note that rudeness increases disproportionately with a site’s popularity. That is, the decline of comment quality on YouTube doesn’t reflect a decline on the Internet in general, only of YouTube’s wider appeal.

One thing is clear, however: the uncivil participants are driving away the civil ones. The result is an acceleration of the cycle, and an increasing proportion of hostile remarks.

Requiring commenters to use their real names might work to add some civility, but such a radical change might drive away a big chunk of the audience. It’s more likely that the citizens of the Internet will simply learn to accept the poison on the comment boards as an unfortunate side effect of free speech online, much the way they grumblingly tolerate spam in their e-mail in-box."

Challenging the link between the human microcephalin gene, evolution, and cognition.

Michael Balter writes an interesting account in Science Magazine over the controversy over the interpretation of data on the microcephalin gene, a gene that regulates brain size. (Microcephaly is the congenital or developmental disorder in which the circumference of the head is smaller than normal because the brain has not developed properly or has stopped growing. )

"...in two papers in Science last year, Lahn reported that variants of the two genes appear to have been strongly favored by recent natural selection (Science, 9 September 2005, pp. 1717 and 1720). That implies that the variants conferred a survival or reproductive benefit, perhaps a cognitive one. In media interviews, Lahn conceded that there was no real evidence natural selection had acted on cognition or intelligence. But both papers pointed out that the mutations arose when key events in human cultural development occurred: The microcephalin variant was dated to about 37,000 years ago, when the first art and symbolism showed up in Europe, and the ASPM variant to 5800 years ago, when the first cities arose.


Lahn's papers also reported the skewed geographic distribution of the genetic variants. Variants in microcephalin turned up in 75% or more of some Europeans and Asians Lahn studied, but in less than 10% of some African groups. The ASPM variant was also much less frequent in Africa. (click on graphic to enlarge).

Bloggers jumped on the news, trumpeting the papers as support for the idea that African Americans have lower intelligence than whites. Two months later, in the conservative National Review Online, columnist John Derbyshire wrote that the research implied that "our cherished national dream of a well-mixed and harmonious meritocracy … may be unattainable."

"Soon after the Science papers were published, Lahn set out to see whether the variants give a cognitive advantage. In one study, Lahn helped controversial psychologist Philippe Rushton of the University of Western Ontario in London, Canada, test whether people who carry the favored variants have higher IQs. Rushton is well known for his claims that African Americans have lower intelligence than whites, and Lahn had found that some genetic variants are common in Europeans and Asians but less frequent among sub-Saharan Africans. But Rushton reported last week at the annual meeting of the International Society for Intelligence Research in San Francisco, California, that he had struck out: The variants conferred no advantage on IQ tests. "[We] had no luck," Rushton told Science, "no matter which way we analyzed the data." Lahn was not a co-author, but his group genotyped the 644 adults of differing ethnicity in the study."

Among some geneticists, there was consternation. "There was no evidence whatsoever that these [genetic variants] have any effect" on differences between people, Altshuler says, adding that the controversy over the work was "easily anticipated." Harvard geneticist Richard Lewontin goes further, criticizing both Lahn and Science for publishing such speculative links to cultural advances. "These two papers are particularly egregious examples of going well beyond the data to try to make a splash," he says. And archaeologist Scott MacEachern of Bowdoin College in Brunswick, Maine, says the archaeological links in the papers are simplistic and outdated. The symbolic revolution, agriculture, and urbanism developed "over many thousands of years, and none was restricted to Europe and the Middle East," he says."

Actions speak louder than brain images.

There is growing concern over the pseudoscientific use of brain imaging to predict behaviors or assign a character type. Apoorva Mandavilli writes a short essay on this topic in the Dec. 7 issue of Nature Magazine.

"Can brain scans of a racist, liar or psychopath accurately tell whether that person will persecute, fib or kill? No, say experts in the ethics of neuroscience, who are increasingly concerned that such images will be used to make dangerous legal or social judgements about people's behaviour. They say it is time for scientists, lawyers and philosophers to speak up about the limitations of such techniques....interpreting brain scans, and correlating them to actions, is inaccurate at best. All we can really gain from such studies is a more nuanced understanding of behaviour...studies of behavioural or physical responses — for example, a person's reaction to different races in real life — should trump imaging every time...The legal and moral claims being made[ from imaging studies involving very few people] are far too extensive."

" In a landmark case in the US Supreme Court in March 2005, several leading scientific groups, including the American Medical Association, the American Psychiatric Association and the National Mental Health Association, filed briefs to support the premise that teenagers are less rational than adults.

The data included a brain-imaging study showing that the prefrontal cortex, which governs impulse control and reasoning, develops late in adolescence (see Nature 442, 865–867; 2006), and could explain some irrational aspects of teenage behaviour."

"Many groups thought this study could help rule against the death penalty. But although the court ruled against the death penalty for those younger than 18, it chose not to cite the brain-imaging study, relying instead on behavioural studies that showed adolescents are more impulsive, more vulnerable to peer pressure and more affected by stress."

Brain self repair

Jan's laboratory at UCSF (Cell Volume 127, Issue 6, 15 December 2006) has looked at an area of the brain known as the subventricular zone (SVZ). They showed that a gene called Numb regulates how stem cells from the SVZ become neurons, and instructs these cells to maintain the walls of the lateral ventricles, the brain's central cavities.

With Numb knocked out, mice developed large holes in these walls. But, rather than worsening over time, the holes were repaired within 6 weeks. The team suggests that stem cells that escaped the knockout were able to shore up the walls. Such capacity for do-it-yourself repair might be harnessed to treat brain damage.

A bull market in Brain Fitness and Calisthenics

I've been meaning for some time to do a post on the avalanche of interest in aging baby boomers not loosing their marbles any faster than absolutely necessary. An article on this topic by Pam Belluck in the 12/27/06 New York Times prompts me to go ahead. We are seeing a blooming of blogs and start up companies that focus on techniques for preserving memory and mental acuity (Posit Science, Third Age, Vigorous Mind, Rocky Mountain Learning, Sharp Brains, Happy Neuron, My Brain Trainer, to mention just a few). The Developing Intelligence blog has a post that discusses the Sharp Brains company, and the Sharp Brains Blog and the Brain Reserves Blog are among several that focus on brain fitness.

There are positive individual testimonials to the effectiveness of brain exercises, and a number of group studies are underway, but we are still absent any hard data that brain exercises bring a benefit that is distinguishable from general cardiovascular exercise. Belluck notes "human studies have generally relied on observations of people with healthier brains, but have not tested whether a particular behavior improves brain health. Perhaps people with healthier brains are more likely to do brain-stimulating activities, not the reverse." She also makes the point: "Certainly most brain-healthy recommendations are not considered bad for people. They do not have the potential risks of drugs or herbal supplements... The challenge we have is it’s going to be a lot like the anti-aging industry: how much science is there behind this?"