Tuesday, June 30, 2009

Metzinger: introduction to "The Ego Tunnel"

Thomas Metzinger is one of my heroes, a philosopher and polymath who has a deep understanding also of neurobiology and cognitive psychology and neuroscience. His model of the mind is one that I find most sane and accessible. I strongly recommend that you read his recent book, "The Ego Tunnel," which casts the arguments in his much longer and more technical book - "Being No One" - in layman's terms. I have decided to pass on to you my own (quite imprecise and idiosyncratic) abstracting of Part I (The Consciousness Problem) and a bit of Part III (The Consciousness Revolution) of "The Ego Tunnel" book in a series of daily posts, today starting with the Introduction to the book. I am not dealing with Part II on the actual science, which relates many of the same experiments I have covered in this blog (on body image, agency and ownership, dreaming, empathy, etc.)

INTRODUCTION

Why is there always someone having the experience? Who is the the feeler of your feelings and the dreamer of your dreams?

Metzinger's phenomenal self-model (PSM) is the conscious model of the organisms as a whole that is activated by the brain. It is, for example, shifted in the rubber hand illusion and in out of body experiences (OBEs). The content of PSM is the ego. Our PSM is unique among animals in that we mentally represent ourselves as representational systems in real time. Whatever is part of PSM has the feeling of “mineness”

The central metaphor of “The Ego Tunnel” is that: “Conscious experience is like a tunnel. Modern neuroscience has demonstrated that the content of our conscious experience is not only an internal construct but also and extremely selective way of representing information. This is why it is a tunnel: What we see and hear, or what we feel and smell and taste, is only a small fraction of what actually exists out there. Our conscious model of reality is a low-dimensional projection of the inconceivably richer physical reality surrounding and sustaining us...our brains generate a world-simulation and an inner image of ourselves as a whole so perfect that we do not recognize it as an image in our minds...We are not in direct contact with outside reality or with ourselves, but we do have an inner perspective. We can use the word “I.” We lives our conscious lives in the ego tunnel.

Our PSM can become the Ego only because you are constitutionally unable to realize that all this is just the content of a simulation in your brain...the Ego is a transparent mental image: You - the physical person as a whole - look right through it. Transparency means that we are unaware of the medium through which information reaches us. We do not see the window but only the bird flying by. We do not see neurons firing away in our brain but only what they represent for us. The central claim of this book - and the theory behind it, the self-model theory of subjectivity- is that the conscious experience of being a self emerges because a large part of the PSM in your brain is transparent.

Yes, there is an outside world, and yes, there is an objective reality, but in moving through this world, we constantly apply unconscious filter mechanisms, and in doing so, we unknowingly construct our own individual world, which is our “reality tunnel.”

One way of looking at the Ego Tunnel is as a complex property of the global neural correlate of consciousness (NCC).

On becoming cultural - models for evolution of human behavior

Ruth Mace describes articles by Bowles and by Powell et al. on the origins of altruism toward one's own social group and the emergence of cultural complexity. They invoke evolution and selection of behavioral traits at the level of groups, a topic I've mentioned in numerous previous posts (enter 'group selection' in the search box at left to review them). Clips from Mace's review:

...Genetic and cultural traits are both heritable and subject to evolutionary processes, but cultural traits are not transmitted in a Mendelian way; they can be inherited from almost anyone, including people who may not share your genetic interests...Perhaps the central difference between genetic and cultural transmission is that we can change our cultural phenotype during our lives—for example, to conform to group norms. Cultural differences between groups might be easier to maintain than are genetic ones, due to processes such as conformist social learning and punishment; several models show that if these processes occur, cultural group selection could explain the evolution of prosocial or altruistic behavior.
In what is essentially an extension of the Baldwin Hypothesis (again, check the blog's search box) Bowles makes the claim that:
...the demographic structure of hunter-gatherer populations allowed group-selected genetic traits to evolve in humans. He argues that lethal warfare was endemic and that altruistic, group-beneficial behaviors that hurt the survival chances of individuals but improved the likelihood for groups to win conflicts could emerge by group selection. This argument was originally espoused by Darwin, but few formal tests of it have been done.

In his model, Bowles identifies two key determinants of whether group selection can favor altruistic behavior: the individual and group costs and benefits of altruism in warfare, and the extent of genetic differentiation among groups. An array of ethnographic and archaeological evidence shows that hunter-gatherers certainly did kill each other. How much of this killing was within or between groups is tricky to ascertain (especially from archaeological data) and varies among sites, but on average, 14% of adult deaths appear to have been due to warfare...based on genetic studies of extant hunter-gatherers, the model shows that a realistic level of inbreeding within groups allows group benefits to offset fitness costs of roughly 3% associated with being an "altruistic warrior" relative to nonaltruists. Ironically, lethal hostility toward other groups could thus underpin cooperation and support within human communities.
Powell et al. argue:
...that changes in population size and structure can explain the patterns of acquisition (and loss) of culturally inherited skills (like the ~10,000-40,000 year old harpoon shown) ...[Their model]..examines a structured population, in which individuals live in groups (subpopulations) and inherit (learn) skills from others in the group or by contact due to migration between groups. The results show that the time since first occupation of a region is a far less reliable predictor of the accumulation of cultural skills than is the density of subpopulations and the degree of migration between them.

The two models paint rather different pictures of Pleistocene life. Were early modern humans in frequent contact with neighboring groups to exchange cultural innovations, or were they inward looking, unwilling to travel, and constantly engaging their neighbors in lethal conflict? Probably both, at different times and in different places (although it may be possible to steal someone's cultural innovations and kill them too).

Nonverbal Status Cues Alter Perceived Size

Marsh et al. show that nonverbal cues associated with social dominance also affect the perceived size of the displayer.

Monday, June 29, 2009

Regret in animals

In That Tucked Tail, Real Pangs of Regret?

No evidence for mirror neurons in humans?!

Given all the hype over the mirror neuron system in humans (basis for constructing social cognition, empathy, mind reading, and the development of language, etc. - this blog has mostly joined the chorus) , this recent work by Lingnau would seem to be quite a bombshell. Their introduction explains the logic, context and basic results:

There are 2 conditions that must be fulfilled by any study that aims to address the existence of mirror neurons in humans. First, it must be demonstrated that execution and recognition of a specific motor act activate a common set of neurons in so-called mirror neuron areas (condition I). Importantly, this overlap must be act specific. Second, it must be demonstrated that activation of neurons within potential mirror neuron areas results from direct activation and not from a prior nonmotor categorization on the basis of inferences about potential motor acts from minimal visual cues, e.g., seeing a hand move toward a familiar graspable object, inviting the inference that the actor's intention may be to grasp the object (condition II).
Their study meets these conditions:
We studied within- and cross-modal adaptation for simple intransitive motor acts that are not associated with a particular meaning, such that any observed adaptation effect could not be attributed to adaptation of the same semantic representation or the same object. Furthermore, to ensure that participants would not be able to guess the target motor act from initial features of a movement, we used 8 different unpredictable movements that could be distinguished from each other only at a relatively late phase of the movement.

We found adaptation for executed motor acts, when these were preceded by execution or observation of the same motor act, as would be expected if a previously executed or observed motor act were to prime the subsequent execution of that act. Importantly, we found no sign of adaptation when motor acts were first executed and then observed. ...our data do not support the direct matching account, according to which neurons exist that selectively respond to actions irrespective of whether these are observed or executed. Our data are compatible with the assumption that responses in mirror neuron areas reflect the facilitation of the motor system because of learned associations between semantic representation of actions and their generating motor programs.

Positive and negative emotions bias the earliest stages of our visual processing.

Opposing Influences of Affective State Valence on Visual Cortical Encoding

Hardwired human nature?

David Brooks repeats some of the arguments needed as an antidote to the evolutionary psychology craze that is reinforced by books such as Geoffrey Miller's "The Mating Mind" and more recently, "Spent."

Friday, June 26, 2009

The Stonewall Riots

The Stonewall riots that started on June 27, 1969, have achieved iconic status as the start of my tribe's 'liberation.' Here is an interesting recollection by an observer.

Risky behaviors: genetic predisposition countered by behavioral intervention

Work by Brody et al. is summarized by Jasny in the Editor's Choice section of the June 5 issue of Science:

There have been many discussions of how genes and environment might interact in the context of human behavior. Brody et al. have studied the effects of a randomized behavioral intervention on adolescents who have a genetic polymorphism associated with the initiation of risky behavior. Roughly 600 11-year-olds were randomly assigned to the Strong African American Families (SAAF) program or to a control group. The SAAF group (and their caregivers, usually mothers) participated in separate and joint training sessions on parenting practices, stress management, dealing with racism, setting goals, and norms for the use of alcohol and other substances. Sessions occurred over the course of 1 year, and the initiation of risky behaviors was assessed at the beginning of the program and for the next 2.5 years. Two years later, saliva samples were collected to look for a polymorphism in the promoter region of the serotonin transporter. Possession of a short form of the allele has been associated previously with impulsivity, substance abuse, and early sexual activity. In the control group, adolescents with the short allele were twice as likely to have engaged in risky behaviors as those assigned to the SAAF group or those with the long allele in either group. Only one genetic polymorphism was examined, and the results need to be confirmed in a variety of populations; however, this provides further evidence of the value of this intervention and the mutability of the effects of genetic predisposition.

Pretty Please....

Why are we more friendly towards the pleading behavior of very young humans or animals? The Nature "Research Highlights" section notes a study on the pleading behavior of young meerkats by Madden et al.:

Many young animals beg for food from their elders. But, eventually, the pleading stops or the charity dries up. Joah Madden, at the University of Cambridge, UK, and his team looked to find the biological triggers that put an end to begging behaviour by studying free-ranging meerkats (Suricata suricatta) of the Kalahari Desert in South Africa over an 18-month period.

The group analysed the begging calls of meerkat pups aged between 40 and 60 days — the peak of their begging behaviour — and compared them with the calls of the same individuals aged 100–120 days. Experimental playback to adults revealed that lower-pitched juvenile calls reaped fewer rewards than the pleading of pups.

An evolutionary rationale for blushing.

An article from Benedict Carey covers work suggesting the blushing evolved to to strengthen social bonds.

Gender, culture, and mathematics performance

Janet Hyde at Wisconsin continues her crusade against the proposition that there are gender differences in mathematical performance and talent. (Unfortunate comments on this issue got Larry Summers fired - or more accurately, he 'resigned under pressure' - as Harvard President.)

Thursday, June 25, 2009

Unconscious motor control that conflicts with conscious awareness.

During my recent Europe vacation, on stepping onto an escalator in the Munich metro that I knew was stopped, I noticed that odd sensation accompanied by clumsy movements that is probably also familiar to you, as if my motor behavior and sensations were being guided by a “phantom” of a moving escalator. Fukui et al. show that this is the consequence of an unconscious automatic habitual motor program cued by the escalator itself. Their results suggest a dissociation between conscious awareness and subconscious motor control: the former makes us perfectly aware of the current environmental situation, but the latter automatically emerges as a result of highly habituated visual input no matter how unsuitable the motor control is.

Boosting your serotonin reduces responsiveness to aggression

From Berman et al.:

We tested the theory that central serotonin (5-hydroxytryptamine, or 5-HT) activity regulates aggression by modulating response to provocation. Eighty men and women (40 with and 40 without a history of aggression) were randomly assigned to receive either 40 mg of paroxetine (to acutely augment serotonergic activity) or a placebo, administered using double-blind procedures. Aggression was assessed during a competitive reaction time game with a fictitious opponent. Shocks were selected by the participant and opponent before each trial, with the loser on each trial receiving the shock set by the other player. Provocation was manipulated by having the opponent select increasingly intense shocks for the participant and eventually an ostensibly severe shock toward the end of the trials. Aggression was measured by the number of severe shocks set by the participant for the opponent. As predicted, aggressive responding after provocation was attenuated by augmentation of serotonin in individuals with a pronounced history of aggression.

Questioning the link between brain size and sociality

Almost any lecture on brain evolution includes the assertion that larger brains evolved to serve communication demands of larger social groups. Finarelli and Flynn question this for the carnivores (cats, dogs, bears, weasels, and their relatives).

Anticipating monetary and social reward - differing brain activations in men and women.

Spreckelmeyer et al. show a wider network of brain regions is activated by the prospect of monetary reward in men than in women.

Wednesday, June 24, 2009

Lost in the sauce - alcohol and mind wandering

Great.... all I need is another reason to question the daily happy hour that I use to take the edge off the TV evening news. From Sayette et al:

Alcohol consumption alters consciousness in ways that make drinking both alluring and hazardous. Recent advances in the study of consciousness using a mind-wandering paradigm permit a rigorous examination of the effects of alcohol on experiential consciousness and metaconsciousness. Fifty-four male social drinkers consumed alcohol (0.82 g/kg) or a placebo beverage and then performed a mind-wandering reading task. This task indexed both self-caught and probe-caught zone-outs to distinguish between mind wandering inside and outside of awareness. Compared with participants who drank the placebo, those who drank alcohol were significantly more likely to report that they were zoning out when probed. After this increase in mind wandering was accounted for, alcohol also lowered the probability of catching oneself zoning out. The results suggest that alcohol increases mind wandering while simultaneously reducing the likelihood of noticing one's mind wandering.

Mathematical and linguistic syntax: different brain areas

Contra the suggestion of Hauser, Chomsky, and Fitch that the hierarchical processing required for syntactical operations requires Broca's area, central to language, Friedrich and Friederici find MRI evidence that syntactic processing of abstract mathematical formulae involves mainly intraparietal and prefrontal regions:

Theory predicts a close structural relation of formal languages with natural languages. Both share the aspect of an underlying grammar which either generates (hierarchically) structured expressions or allows us to decide whether a sentence is syntactically correct or not. The advantage of rule-based communication is commonly believed to be its efficiency and effectiveness. A particularly important class of formal languages are those underlying the mathematical syntax. Here we provide brain-imaging evidence that the syntactic processing of abstract mathematical formulae, written in a first order language, is, indeed efficient and effective as a rule-based generation and decision process. However, it is remarkable, that the neural network involved, consisting of intraparietal and prefrontal regions, only involves Broca's area in a surprisingly selective way. This seems to imply that despite structural analogies of common and current formal languages, at the neural level, mathematics and natural language are processed differently, in principal.

Money, social distress, and physical pain

The Symbolic Power of Money: Reminders of Money Alter Social Distress and Physical Pain

Aging, isolation, and internet social networks

An article by Stephanie Clifford on isolated older adults finding social sustenance through internet social sites.

Tuesday, June 23, 2009

Why we pig out.

Parker-Pope describes how the food industry combines and creates foods in a way that taps into our brain circuitry to stimulate our desire for more.

Do we trust our eyes or our ears?

Interesting Angier article on our visual versus sound time resolution, and how situations with conflicting visual and auditory stimuli are resolved. You can hear 20 clicks per second, but twenty visual frames per second is a movie.

Models of life's origins - great videos

Check out Wade's article that has, and links to, some great videos illustrating how a synthetic cell might be made by getting a protocell formed of lipids and a genetic molecule to grow and divide in parallel, with the molecules being encapsulated in the cell. If the molecules gave the cell a survival advantage over other cells, the outcome would be a sustainable, autonomously replicating system, capable of Darwinian evolution.

Gene for depression debunked...

Benedict Carey writes on how a compelling study showing a correlation between a particular variant of a gene involved in Serotonin regulation and the probability of sinking into depression after a stressful event has not been replicated. A coalition of researchers identified 14 studies that gathered the same kinds of data as the original study. They reanalyzed the data and found no evidence of an association between the serotonin gene and the risk of depression, no matter what people’s life experience was.

Zap your brain to enhance your planning ability

Enhancement of Planning Ability by Transcranial Direct Current Stimulation.

Prayer in devoutly religious people recruits social cognition brain areas.

Schjoedt et al. suggest that praying to God is an intersubjective experience comparable to ‘normal’ interpersonal interaction.

Monday, June 22, 2009

Back from vacation - A new variety of MindBlog post....reader poll.

Back from vacation...I had thought that a sudden halt in the daily habits surrounding blog production might cause some withdrawal symptoms. But no... nothing, zip. Now I face a very long accumulated list of potential post topics, which brings home the point that my ritual of doing two blog posts per day forces me to choose only a fraction of the articles that I find interesting as I scan the tables of contents of a number of journals. Among those discarded articles are many that I am sure a subset of MindBlog readers would like to be aware of, even if only given a minimal description of content along with the link to the journal. So, for the next week or two at least, I am going to experiment with sprinkling in more tiny posts, in much the same way that Andrew Sullivan's blog does. The reason for making each a separate post is that the titles then appear in the list presented by RSS readers. (On a typical weekday there are ~200-250 significant post viewings, out of ~1,150 RSS feed subscribers.)

I can think of arguments against doing this (overload, spamming), so I would be grateful for feedback on whether readers think this is a good or bad idea. How many topics/day would you find most useful?

Stress triggers our habitual behaviors

Schwabe and Wolf at Ruhr University in Bochum show that stress promotes habits at the expense of goal-directed performance in humans. Converging lines of evidence show that stress and the glucocorticoid stress hormones (mainly cortisol in humans) released from the adrenal cortex can operate as a switch between "cognitive" (mediated by prefrontal cortex) and "habit" (mediated by striatum)learning systems.

You want to know the truth? Then don't mimic!

We usually feel that expressing empathy by mimicking another person's face and body movements facilitates our understanding of their true emotions. Not so, apparently, if they are lying. Stel et al. have done experiments with two interacting people as follows:

...targets either lied or told the truth, while observers mimicked or did not mimic the targets' facial and behavioral movements. Detection of deception was measured directly by observers' judgments of the extent to which they thought the targets were telling the truth and indirectly by observers' assessment of targets' emotions. The results demonstrated that nonmimickers were more accurate than mimickers in their estimations of targets' truthfulness and of targets' experienced emotions. The results contradict the view that mimicry facilitates the understanding of people's felt emotions. In the case of deceptive messages, mimicry hinders this emotional understanding.

Economy still at the brink

I found this article by two professional Wall Street traders (one out of prison, pardoned by Clinton), to be fascinating.

Brain Music

Wu et al. transform EEG signals during REM sleep and slow wave sleep into musical 'melodies' that induce in listeners (so they say) happy emotions (REM) or drowsy peaceful feelings (SWS). Click on the audio links in the article to judge for yourself.

Monday, June 08, 2009

MindBlog is taking a vacation

For the next 10 days I will be in Amsterdam and Munich on vacation with my daughter Sarah. I think I will suspend blog posting for about two weeks. I have been doing regular weekday postings continuously since February of 2006, and I'm curious to see what life is like in their absence!

Friday, June 05, 2009

The genetics of musical aptitude

Ukkola et al. attempt to understand the neurobiological basis of music in human evolution and communication, motivated by the idea that a main function of music is human social communication. They find a correlation between variations in groups of genes associated with social bonding and cognitive functions and musical aptitude and creativity. They suggest that the neurobiology of music perception and production is likely to be related to the pathways affecting intrinsic attachment behavior. (By the way, in the same issue of PLoS ONE, Israel et al. correlate variations the vasopressin 1a receptor gene (AVPR1a) also monitored by Ukkola et al. with prosocial behavior in several game tasks).

Language influence on color perception.

Here is an interesting bit of work that shows that our brain's language regions can exert a top down influence on early color processing in the visual cortex. The experiments show that colors from different linguistic categories presented to the right visual field (which projects to the left linguistic cortex) caused much stronger activation of visual areas 2 and 3 than stimuli presented to the left visual field (which projects to the right hemisphere). Here is the abstract:

The effect of language on the categorical perception of color is stronger for stimuli in the right visual field (RVF) than in the left visual field, but the neural correlates of the behavioral RVF advantage are unknown. Here we present brain activation maps revealing how language is differentially engaged in the discrimination of colored stimuli presented in either visual hemifield. In a rapid, event-related functional MRI study, we measured subjects' brain activity while they performed a visual search task. Compared with colors from the same lexical category, discrimination of colors from different linguistic categories provoked stronger and faster responses in the left hemisphere language regions, particularly when the colors were presented in the RVF. In addition, activation of visual areas 2/3, responsible for color perception, was much stronger for RVF stimuli from different linguistic categories than for stimuli from the same linguistic category. Notably, the enhanced activity of visual areas 2/3 coincided with the enhanced activity of the left posterior temporoparietal language region, suggesting that this language region may serve as a top-down control source that modulates the activation of the visual cortex. These findings shed light on the brain mechanisms that underlie the hemifield- dependent effect of language on visual perception.

Thursday, June 04, 2009

Cognitive Illusions

My son Jon pointed me to this engaging TED talk on cognitive illusions by Dan Ariely.

Genes to cognition

Here is an educational site you might enjoy checking out, supported by the Cold Spring Harbor Laboratory.

Wednesday, June 03, 2009

Attention training and attention state training

Tang and Posner (PDF here) examine two different approaches that have been shown to improve attention and self-regulation: computer based exercises in children and adults (attention training, AT); and exposure to nature, mindfulness and integrative body-mind training (IBMT, or attention state training, AST). Here is their summary of the characteristics of these two approaches:

AT
• Trains executive attention networks
• Requires directed attention and effortful control
• Targets non-autonomic control systems
• Produces mental fatigue easily
• Training transfers to other cognitive abilities

AST
• Produces changes of body-mind state
• Requires effortful control (early stage) and effortless exercise (later)
• Involves the autonomic system
• Aims at achieving a relaxed and balanced state
• Training transfers to cognition, emotion and social behaviors

Activation of the anterior cingulate cortex appears to be central with both approaches, with AT involving involving changes in anterior cingulate and lateral prefrontal areas, perhaps mainly through increased connectivity between the two. AST involves increased interaction between anterior cingulate cortex and the autonomic nervous system. Increase in activity in the ACC in AST is similar to what is found in AT during task performance and could account for the improved executive attention with both methods.

It is worth noting that both aerobic exercise (A.F. Kramer and K.I. Erickson, Capitalizing on cortical plasticity: influence of physical activity on cognition and brain function, Trends Cogn. Sci. 11 (2007), pp. 342–348) and music education (E.G. Schellenberg, Music and cognitive abilities, Psychol. Sci. 14 (2004), pp. 317–320.) have also been shown to enhance cognitive processes

Lucid old age.

Want to live past 90 without dementia? Check out this article by Benedict Carey describing a retirement community in Los Angeles.

Tuesday, June 02, 2009

Empathy Marketing 101

I pass on this interesting review on "neuromarketing" that Gary Ohlson has just emailed to me.

Stress pathways that impair prefrontal cortex.

Arnsten offers a focus article (one among several) in Nature Reviews Neuroscience that describes how stress impairs the top-down cognitive control functions of the prefrontal cortex, and enhances bottom-up amygdala-limbic emotional influences. I'm passing on the abstract and a summary figure with its text that might be useful for teaching:

The prefrontal cortex (PFC) — the most evolved brain region — subserves our highest-order cognitive abilities. However, it is also the brain region that is most sensitive to the detrimental effects of stress exposure. Even quite mild acute uncontrollable stress can cause a rapid and dramatic loss of prefrontal cognitive abilities, and more prolonged stress exposure causes architectural changes in prefrontal dendrites. Recent research has begun to reveal the intracellular signalling pathways that mediate the effects of stress on the PFC. This research has provided clues as to why genetic or environmental insults that disinhibit stress signalling pathways can lead to symptoms of profound prefrontal cortical dysfunction in mental illness.


The prefrontal cortex (PFC) has extensive connections with other cortical and subcortical regions that are organized in a topographical manner, such that regions that regulate emotion are situated ventrally and medially (green area in part a of the figure) and regions that regulate thought and action are situated more dorsally and laterally (blue and blue–green areas in part a). The dorsolateral PFC (DLPFC) has extensive connections with sensory and motor cortices and is key for regulating attention, thought and action1. In humans, the right inferior PFC (rIPFC) seems to be specialized for inhibiting inappropriate motor responses. By contrast, the ventromedial PFC (VMPFC) has extensive connections with subcortical structures (such as the amygdala, the nucleus accumbens and the hypothalamus) that generate emotional responses and habits and is thus able to regulate emotional responses. Finally, the dorsomedial PFC (DMPFC) has been associated with error monitoring9 and, in human functional MRI studies, reality testing. These PFC regions extensively interconnect to regulate higher-order decision making and to plan and organize for the future. Under non-stress conditions (see part a of the figure), the extensive connections of the PFC orchestrate the brain's activity for intelligent regulation of behaviour, thought and emotion. The PFCalso has direct and indirect connections to monoamine cell bodies in the brainstem, such as the locus coeruleus (LC) (where noradrenaline projections arise) and the substantia nigra (SN) and ventral tegmental area (VTA) (where the major dopamine projections originate), and thus can regulate its own catecholamine inputs. Optimal levels of catecholamine release in turn enhance PFC regulation, thus creating a 'delicious cycle'. Under conditions of psychological stress (see part b of the figure) the amygdala activates stress pathways in the hypothalamus and brainstem, which evokes high levels of noradrenaline (NA) and dopamine (DA) release. This impairs PFC regulation but strengthens amygdala function, thus setting up a 'vicious cycle'. For example, high levels of catecholamines, such as occur during stress, strengthen fear conditioning mediated by the amygdala. By contrast, stress impairs higher-order PFC abilities such as working memory and attention regulation. Thus, attention regulation switches from thoughtful 'top-down' control by the PFC that is based on what is most relevant to the task at hand to 'bottom-up' control by the sensory cortices, whereby the salience of the stimulus (for example, whether it is brightly coloured, loud or moving) captures our attention5. The amygdala also biases us towards habitual motor responding rather than flexible, spatial navigation. Thus, during stress, orchestration of the brain's response patterns switches from slow, thoughtful PFC regulation to the reflexive and rapid emotional responses of the amygdala and related subcortical structures.

Parietal brain neurons tuned to fractions

Interesting work from Jacob and Nieder:

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.

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.”