Although the concept of whole numbers is intuitive and well suited for counting and ordering, it is with the invention of fractions that the number system gained precision and flexibility. Absolute magnitude is encoded by single neurons that discharge maximally to specific numbers. However, it is unknown how the ratio of two numbers is represented, whether by processing numerator and denominator in separation, or by extending the analog magnitude code to relative quantity. Using functional MRI adaptation, we now show that populations of neurons in human fronto-parietal cortex are tuned to preferred fractions, generalizing across the format of presentation. After blood oxygen level-dependent signal adaptation to constant fractions, signal recovery to deviant fractions was modulated parametrically as a function of numerical distance between the deviant and adaptation fraction. The distance effect was invariant to changes in notation from number to word fractions and strongest in the anterior intraparietal sulcus, a key region for the processing of whole numbers. These findings demonstrate that the human brain uses the same analog magnitude code to represent both absolute and relative quantity. Our results have implications for mathematical education, which may be tailored to better harness our ability to access automatically a composite quantitative measure.
This blog reports new ideas and work on mind, brain, behavior, psychology, and politics - as well as random curious stuff. (Try the Dynamic Views at top of right column.)
Tuesday, June 02, 2009
Parietal brain neurons tuned to fractions
Interesting work from Jacob and Nieder:
Monday, June 01, 2009
More Chopin, the Polonaise No. 1
Here is a further piece I have recorded recently on my Steinway B at Twin Valley.
Liberals and Conservatives feel differently
Kristoff reviews evidence that our political stances start with flash moral intuitions that our brains then find evidence to support. For liberals, morality derives mostly from fairness and prevention of harm. For conservatives, morality places relatively more emphasis on upholding authority and loyalty — and revulsion at disgust.
Psychologists have developed a “disgust scale” based on how queasy people would be in 27 situations, such as stepping barefoot on an earthworm or smelling urine in a tunnel. Conservatives systematically register more disgust than liberals. (To see how you weigh factors in moral decisions, take the tests at http://yourmorals.org/.)...One experiment involved hypnotizing subjects to expect a flash of disgust at the word “take.” They were then told about Dan, a student council president who “tries to take topics that appeal to both professors and students.” The research subjects felt disgust but couldn’t find any good reason for it. So, in some cases, they concocted their own reasons, such as: “Dan is a popularity-seeking snob.”
Blog Categories:
acting/choosing,
attention/perception,
emotion,
social cognition
Friday, May 29, 2009
Hugs
Given the unhealthy phobia about physical contact in this country, in addition to litigious paranoia about sexual harassment or improper touching, I was really heartened to read this account of a new trend among teenagers in high school of giving hugs on greeting: male-female, female-female, even male-male (given sanction by recent 'Bromance' movies). Some prune faced administrators have banned it, but I think it reflects that kids are more inclined to nuture each other, perhaps as an antidote to comparative aridity of a world of Facebook 'friends.' (By the way, I wrote this brief post on reading the NYTimes article yesterday morning, then set it to be actually posted next Monday. Then I see the bloody story featured on the NBC Evening News yesterday evening, interviews with experts and all that, and so I guess I have to stay with the news cycle and post while its fresh!).
Blog Categories:
culture/politics,
happiness,
social cognition
The coming superbrain?
John Markoff offers a timely essay - given the recent release of the movie "Terminator Salvation" - on the future of artificial intelligence. There seems to be little doubt that we will eventually be able to design machines that have the emergent property, like ourselves, of being aware of their own internal states. Metzinger suggests that this will happen once the neural underpinnings of his "Ego Tunnel" are made more clear.
Thursday, May 28, 2009
Your own brain gym.
Passing on this link emailed to me this morning: Build Your Own Brain Gym: 100 Tools, Exercises, and Games. The blog on this website (which, curiously, is a health care administration career site) contains a veritable orgy of self-help links.
Subcortical enhancement of musical intervals in musicians
From Lee et al:
By measuring the auditory brainstem response to two musical intervals, the major sixth (E3 and G2) and the minor seventh (E3 and F#2), we found that musicians have a more specialized sensory system for processing behaviorally relevant aspects of sound. Musicians had heightened responses to the harmonics of the upper tone (E), as well as certain combination tones (sum tones) generated by nonlinear processing in the auditory system. In music, the upper note is typically carried by the upper voice, and the enhancement of the upper tone likely reflects musicians' extensive experience attending to the upper voice. Neural phase locking to the temporal periodicity of the amplitude-modulated envelope, which underlies the perception of musical harmony, was also more precise in musicians than nonmusicians. Neural enhancements were strongly correlated with years of musical training, and our findings, therefore, underscore the role that long-term experience with music plays in shaping auditory sensory encoding.
The amusic brain
Peretz et al. find that people with congenital amusia (~4% of the population unable to distinguish different tones) have the essential neural circuitry to perceive fine-grained pitch differences, but limited awareness of this ability and the lack of responsiveness to semitone changes that violate musical keys. Apparently the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.
Like language, music engagement is universal, complex and present early in life. However, ~4% of the general population experiences a lifelong deficit in music perception that cannot be explained by hearing loss, brain damage, intellectual deficiencies or lack of exposure. This musical disorder, commonly known as tone-deafness and now termed congenital amusia, affects mostly the melodic pitch dimension. Congenital amusia is hereditary and is associated with abnormal grey and white matter in the auditory cortex and the inferior frontal cortex. In order to relate these anatomical anomalies to the behavioural expression of the disorder, we measured the electrical brain activity of amusic subjects and matched controls while they monitored melodies for the presence of pitch anomalies. Contrary to current reports, we show that the amusic brain can track quarter-tone pitch differences, exhibiting an early right-lateralized negative brain response. This suggests near-normal neural processing of musical pitch incongruities in congenital amusia. It is important because it reveals that the amusic brain is equipped with the essential neural circuitry to perceive fine-grained pitch differences. What distinguishes the amusic from the normal brain is the limited awareness of this ability and the lack of responsiveness to the semitone changes that violate musical keys. These findings suggest that, in the amusic brain, the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.
Wednesday, May 27, 2009
The management of our attention
Here is another of the many nuggets (from Chapter 9) from Metzinger's new book that hit me as an excellent summary. He discusses the problem we face in the management of our attention:
The ability to attend to our environment, to our own feelings, and to those of others is a naturally evolved feature of the human brain. Attention is a finite commodity, and it is absolutely essential to living a good life. We need attention in order to truly listen to others - and even to ourselves. We need attention to truly enjoy sensory pleasures, as well as for efficient learning. We need it in order to be truly present during sex or to be in love or when we are simply contemplating nature. Our brains can generate only a limited amount of this precious resource every day.Having just forced myself to watch the recent American Idol show climax, these points have struck me as particularly cogent. Metzinger suggests we counter the attacks on our reserves of attention by introducing classes in meditation in our high schools, by making the young aware of our limited capacity for attention, and the need to learn techniques to sustain it and enhance mindfulness.
Today, the advertisement and entertainment industries are attacking the very foundations of our capacity for experience, drawing us into the vast and confusing media jungle. They are trying to rob us of as much of our scarce resource as possible, and they are doing so in every more persistent and intelligent ways. Of course, they are increasingly making use of the new insights in the human mind offered by cognitive and brain science to achieve their goals ("neuromarketing" is one of the ugly new buzzwords). We can see the probable result in the epidemic of attention-deficit disorder in children and young adults, in midlife burnout, in rising levels of anxiety in large parts of the population. If I am right that consciousness is the space of attentional agency, and if (as discussed in chapter 4) it is also true that the experience of controlling and sustaining your focus of attention is one of the deeper layers of phenomenal selfhood, then we are currently witnessing not only an organized attack on the speace of consciousness per se but a mild form of depersonalization. New medial environments many create a new form of waking consciousness that resembles weakly subjective states - a mixture of dreaming, dementia, intoxication, and infantilization.
Semantic versus behavioral deficits in left versus right fronto-temporal lobe atrophies
Chan et al. provide a survey of the deficits observed in people with left versus right fronto-temporal lobe atrophies, which cause, respectively mainly semantic (left) versus behavioral (right) disorders. Their summary:
Frontotemporal lobar degeneration is currently associated with three syndromic variants. Disorders of speech and language figure prominently in two of the three variants, and are associated with left-sided frontotemporal atrophy. The detailed characterization of these syndromes contrasts with the relative paucity of information relating to frontotemporal lobar degeneration primarily affecting the right cerebral hemisphere. The objective of this study was to identify the clinical profile associated with asymmetrical, predominantly right-sided, temporal lobe atrophy. Twenty patients with predominant right temporal lobe atrophy were identified on the basis of blinded visual assessment of the MRI scans. The severity of right temporal lobe atrophy was quantified using volumetric analysis of the whole temporal lobes, the amygdala and the hippocampus. Profiles of cognitive function, behavioural and personality changes were obtained on each patient. The pattern of atrophy and the clinical features were compared with those observed in a group of patients with semantic dementia and predominant left-sided temporal lobe atrophy. The mean right temporal lobe volume in the right temporal lobe atrophy group was reduced by 37%, with the mean left temporal lobe volume reduced by 19%. There was marked atrophy of the right hippocampus and right amygdala, with mean volumes reduced by 41 and 51%, respectively (left hippocampus and amygdala volumes were reduced by 18 and 33%, respectively). The most prominent cognitive deficits were impairment of episodic memory and getting lost. Prosopagnosia was a symptom in right temporal lobe atrophy patients. These patients also exhibited a variety of behavioural symptoms including social disinhibition, depression and aggressive behaviour. Nearly all behavioural disorders were more prevalent in the right temporal lobe atrophy patient group than the semantic dementia group. Symptoms particular to the right temporal lobe atrophy patient group included hyper-religiosity, visual hallucinations and cross-modal sensory experiences. The combination of clinical features associated with predominant right temporal lobe atrophy differs significantly from those associated with the other syndromes associated with focal degeneration of the frontal and temporal lobes and it is, therefore, proposed that this right temporal variant should be considered a separate syndromic variant of frontotemporal lobar degeneration.
Blog Categories:
acting/choosing,
attention/perception,
emotion,
language
Tuesday, May 26, 2009
A musical offering for this week - Chopin Nocture in C minor
Here is the posthumous Chopin Nocture in C minor.
Neural correlates of vicarious reward.
Interesting observations from Mobbs et al. The experiments involved brain imaging of participants reacting to game winning by contestants with whom they were or were not sympathetic. Their abstract (slightly edited):
Humans appear to have an inherent prosocial tendency toward one another in that we often take pleasure in seeing others succeed. This fact is almost certainly exploited by game shows, yet why watching others win elicits a pleasurable vicarious rewarding feeling in the absence of personal economic gain is unclear. One explanation is that game shows use contestants who have similarities to the viewing population, thereby kindling kin-motivated responses (for example, prosocial behavior). Using a game show–inspired paradigm, we show that the interactions between the ventral striatum and anterior cingulate cortex subserve the modulation of vicarious reward by similarity, respectively. Our results support studies showing that similarity acts as a proximate neurobiological mechanism where prosocial behavior extends to unrelated strangers.
Evidence for separate semantic and syntactic processing in deaf native signers.
Adding to evidence from written and spoken language suggesting that nonidentical brain networks support semantic and syntactic processing, Capek et al now find a similar distinction in native deaf signers:
Studies of written and spoken language suggest that nonidentical brain networks support semantic and syntactic processing. Event-related brain potential (ERP) studies of spoken and written languages show that semantic anomalies elicit a posterior bilateral N400, whereas syntactic anomalies elicit a left anterior negativity, followed by a broadly distributed late positivity. The present study assessed whether these ERP indicators index the activity of language systems specific for the processing of aural-oral language or if they index neural systems underlying any natural language, including sign language. The syntax of a signed language is mediated through space. Thus the question arises of whether the comprehension of a signed language requires neural systems specific for this kind of code. Deaf native users of American Sign Language (ASL) were presented signed sentences that were either correct or that contained either a semantic or a syntactic error (1 of 2 types of verb agreement errors). ASL sentences were presented at the natural rate of signing, while the electroencephalogram was recorded. As predicted on the basis of earlier studies, an N400 was elicited by semantic violations. In addition, signed syntactic violations elicited an early frontal negativity and a later posterior positivity. Crucially, the distribution of the anterior negativity varied as a function of the type of syntactic violation, suggesting a unique involvement of spatial processing in signed syntax. Together, these findings suggest that biological constraints and experience shape the development of neural systems important for language.
Monday, May 25, 2009
Massage stimulates brain development
I've always been a massage nut. Many years ago I had some formal training, and I always feel totally rejuvenated by the too-infrequent massages I occasionally get. This item in the Journal of Neuroscience from Guzzetta et al. makes perfect sense to me. I'll bet that a shadow of these early effects of massage seen in infants still occur in adults. The brain growth factor (IGF-1) enhanced by massage in infants is also associated with brain plasticity in adult humans:
Environmental enrichment (EE) was shown recently to accelerate brain development in rodents. Increased levels of maternal care, and particularly tactile stimulation through licking and grooming, may represent a key component in the early phases of EE. We hypothesized that enriching the environment in terms of body massage may thus accelerate brain development in infants. We explored the effects of body massage in preterm infants and found that massage accelerates the maturation of electroencephalographic activity and of visual function, in particular visual acuity. In massaged infants, we found higher levels of blood IGF-1. Massage accelerated the maturation of visual function also in rat pups and increased the level of IGF-1 in the cortex. Antagonizing IGF-1 action by means of systemic injections of the IGF-1 antagonist JB1 blocked the effects of massage in rat pups. These results demonstrate that massage has an influence on brain development and in particular on visual development and suggest that its effects are mediated by specific endogenous factors such as IGF-1.
Blog Categories:
attention/perception,
human development
SenseCam - a device for restoring and protecting memories
While scanning my lost list of articles that might become the topic of MindBlog posts, I re-encountered this description from Science Magazine of research on autobiographical memory which has subjects wear a small camera mounted on their chests. The work has expanded to involve patients with memory problems due to Alzheimer's or brain injuries. On viewing the camera's data six months later:
...many SenseCam users...report a sudden flood of memories of thoughts and sensations, ... "Proustian moments," when they review images taken by the device. SenseCam's images correspond to the nature of human memory--they're fragmentary, they're formed outside conscious control, they're visual in nature, they're from the subject's perspective. All these features are very like what we call episodic memory.A research team:
SenseCam records images passively, permitting a person to go about their day without interruption. The latest version is about the size and weight of a clunky mobile phone and appears to observe the world through two unmatched eyeballs. One is a passive infrared sensor, tuned to trigger the camera whenever another person passes by. The other is a wide-angle camera lens, set to capture most of the user's field of view. The device is also equipped with an ambient light sensor that triggers the camera when its user moves from one room to another, or goes in or out of doors. The camera can also be set to snap an image if the sensors haven't triggered a photo after an arbitrary number of seconds. A typical wearer might come home with 2000 to 3000 fragmentary, artless images at the end of a day.
...under the direction of neuropsychologist Georgina Brown, has followed five additional people with memory problems over a nearly 3-year period, exploring the difference between the memory boost provided by visual and written diary-keeping. Establishing a baseline of how fast these people lose their memories, the team asked each about an event every other day for 2 weeks after the event, and then again after 1 month and after 3 months. Then they asked the patients to keep a diary of a separate event and review it every other day during an initial 2-week assessment, but not during subsequent months. Finally, patients reviewed their SenseCam's images for 2 weeks following a third event.
The preliminary results suggest that SenseCam use strengthened these patients' memories more than diary-keeping did. A full analysis of the data is in preparation, says Brown, whose team plans to submit it to the journal Memory for a special issue devoted to SenseCam research.
Friday, May 22, 2009
What we will never be able to talk about - Ineffability
At numerous points during my reading of Thomas Metzinger's new book "The Ego Tunnel" I have come across writing that seems such a crisp description of core ideas (as well as being directly relevant to my own experience) that I want to try to condense and pass the material on to you. I found the following mix of summary, paraphrase, and quotes from chapter 2 to be a calming antidote to my implicit and constant "I can understand this" temperament. (By the way, I first bought this book for my Kindle but then found that the kind of jumping back and around, checking references, that I want to do in reading such a book was impossible, so I purchased the hard copy.) Here's a chunk on the ineffability problem:
In between 430 and 650 nanometers, we can discriminate (make same/different judgements about) more than 150 different wavelengths, or different subjective shades of color. But, if asked to reidentify single colors with a high degree of accuracy, we can do so for fewer than 15. The same is true for other sensory experiences. We can discriminate about 1,400 steps of pitch difference across the audible frequency range, but we can recognize these steps as examples of only about 80 different pitches... Thus we are much better at discriminating perceptual values than we are at identifying or recognizing them.
Metzinger uses a simplest example of two similar shades of green to spell through the consequences of this situation (he calls them Green No. 24 and Green No. 25, nearest possible neighbors on the color chart, such that there's no shade of green between them that you could discriminate). We can experience their difference, but are unable consciously to represent the sameness of Green No. 25 over time. We do not possess introspective identity criteria for this simplest state of consciousness, and we can not pinpoint a minimally sufficient neural correlate of Green No. 25 in the brain if we can not correctly identify the phenomenal aspect of Green No. 25 over time, in repeated trials in a controlled experimental setting. This is why it may be impossible to do what most hard scientists in consciousness research would like to do: show that Green No. 25 is identical with a state in your head.
These simple findings show that there is a depth in pure perception that cannot be grasped or invaded by thought or language. This ineffability problem arises for the simplest forms of sensory awareness, for the finest nuances of sight and touch, of smell and taste, and for those aspect of conscious hearing that underlie the magic and beauty of a musical experience. It almost certainly appears also for empathy, for emotional and intrinsically embodied forms of communication.
Money doesn't make us happy, certainty does.
A nice Op-Ed piece from Daniel Gilbert in the N.Y. Times. It is found on the New York Time's blog "Happy Days" - a discussion about the search for contentment in its many forms — economic, emotional, physical, spiritual. This blog was running postings through 2006, and then curiously lapsed until this Gilbert article. Gilbert's conclusions:
Our national gloom is real enough, but it isn’t a matter of insufficient funds. It’s a matter of insufficient certainty. Americans have been perfectly happy with far less wealth than most of us have now, and we could quickly become those Americans again — if only we knew we had to.
Why would we prefer to know the worst than to suspect it? Because when we get bad news we weep for a while, and then get busy making the best of it. We change our behavior, we change our attitudes. We raise our consciousness and lower our standards. We find our bootstraps and tug. But we can’t come to terms with circumstances whose terms we don’t yet know. An uncertain future leaves us stranded in an unhappy present with nothing to do but wait.
Thursday, May 21, 2009
Status is everything?
Tierney describes how Geoffrey Miller continues the arguments he started in "The Mating Mind" which seek to reduce much of our behavior to a quest for sex and status. His new book is “Spent: Sex, Evolution and Consumer Behavior.” This is a complementary approach to the sort of material mentioned in Monday's post on Gopnik's article.
If marketers (or their customers) understood biologists’ new calculations about animals’ “costly signaling,” ... they’d see that Harvard diplomas and iPhones send the same kind of signal as the ornate tail of a peacock....Sometimes the message is as simple as “I’ve got resources to burn,” the classic conspicuous waste demonstrated by the energy expended to lift a peacock’s tail or the fuel guzzled by a Hummer. But brand-name products aren’t just about flaunting transient wealth. The audience for our signals — prospective mates, friends, rivals — care more about the permanent traits measured in tests of intelligence and personality.
In a series of experiments, Dr. Miller and other researchers found that people were more likely to expend money and effort on products and activities if they were first primed with photographs of the opposite sex or stories about dating...After this priming, men were more willing to splurge on designer sunglasses, expensive watches and European vacations. Women became more willing to do volunteer work and perform other acts of conspicuous charity — a signal of high conscientiousness and agreeableness, like demonstrating your concern for third world farmers by spending extra for Starbucks’s “fair trade” coffee.
To get over your consuming obsessions, Dr. Miller suggests exercises like comparing the relative costs and pleasures of the stuff you’ve bought. (You can try the exercise at nytimes.com/tierneylab.) It may seem odd that we need these exercises — why would natural selection leave us with such unproductive fetishes? — perhaps because evolution is good at getting us to avoid death, desperation and celibacy, but not that good at getting us to feel happy...our desire to impress strangers may be a quirky evolutionary byproduct of a smaller social world...“We evolved as social primates who hardly ever encountered strangers in prehistory,” Miller says. “So we instinctively treat all strangers as if they’re potential mates or friends or enemies. But your happiness and survival today don’t depend on your relationships with strangers. It doesn’t matter whether you get a nanosecond of deference from a shopkeeper or a stranger in an airport.”
Bad drives reactions, Good propels behaviors
From Wang et al., slightly edited:
Research across disciplines suggests that bad is stronger than good and that individuals punish deception more than they reward honesty. However, methodological issues in previous research limit the latter conclusion. Three experiments resolved these issues and consistently found the opposite pattern: In the first experiment individuals rewarded honesty more frequently and intensely than they punished deception. The second experiment extended these counter-intuitive findings by revealing a divergence between evaluation and behavior: Evaluative reactions to deception were stronger than those to honesty, but behavioral intentions in response to honesty were stronger than those in response to deception. In addition, individuals wanted to avoid deceivers more than they wanted to approach honest actors. The third experiment found that punishment, but not reward, frequencies were sensitive to costs. Moderated-mediation tests revealed the role of different psychological mechanisms: Negative affect drove punishments, whereas perceived trustworthiness drove rewards. Overall, bad appears to be stronger than good in influencing psychological reactions, but good seems to be stronger than bad in influencing behavior.
Wednesday, May 20, 2009
Why I am loyal to Wisconsin...
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