Demonstration of plastic body schema by tool use.

Cardinali et al have volunteers use a mechanical grabbing arm that extends reach by 40 centi-meters. Measuring arm movements with a high-resolution motion-tracking system, they show that the volunteers reduce the velocity and acceleration of movements to grab or point at an object after a period of using the tool.

When blindfolded, the volunteers also estimate their arms to be slightly longer after tool use, confirming that our body schema — the sense of where our body parts are in space — is plastic.

Mental arithmetic uses brain's eye movement circuitry

Given the cultural link in left-to-right readers between small numbers and the left side of space, and large numbers and the right side of space, Knops et al predicted that mental addition, which increases number size, would be associated with a rightward shift of attention and subtraction with a leftward shift. Hence, the activation pattern in the parietal cortex (especially regions associated with saccadic eye movements) observed with MRI during addition would resemble the activation pattern associated with a rightward eye movement, whereas subtraction would resemble a leftward eye movement.

Here is their abstract:

Throughout the history of mathematics, concepts of number and space have been tightly intertwined. We tested the hypothesis that cortical circuits for spatial attention contribute to mental arithmetic in humans. We trained a multivariate classifier algorithm to infer the direction of an eye movement, left or right, from the brain activation measured in the posterior parietal cortex. Without further training, the classifier then generalized to an arithmetic task. Its left versus right classification could be used to sort out subtraction versus addition trials, whether performed with symbols or with sets of dots. These findings are consistent with the suggestion that mental arithmetic co-opts parietal circuitry associated with spatial coding.

Metzinger: The appearance of a world

Continuing the abstracting begun yesterday, this is Chapter One of Metzinger's "The Ego Tunnel" - The appearance of a world.

Consciousness is the appearance of a world. Mammals, birds, and probably octopi have appropriate brain structures (for color vision, for example) and a primitive transparent PSM. “Higher -order” levels of the PSM in humans may be only a couple of thousand years old, higher levels attending to lower ones.

Human beings in other historical epochs - during the Vedic period of ancient India, say, or during the European Middle Ages, when God was still perceived as a real and constant presence - likely knew kinds of subjective experience almost inaccessible to us today. Theories change social practice, and practice eventually changes brains, the way we perceive the world.

The conscious brain is a biological machine - a reality engine - that purports to tell us what exists and what doesn’t. It is unsettling to discover that there are no colors out there in front of your eyes...they are models created by your brain...The world is not inhabited by colored objects at all..there is just an ocean of electromagnetic radiation, a wild and raging mixture of different wavelengths. Most of them are invisible to you and can never become part of your conscious model of reality. ...the visual system is your brain is drilling a tunnel through this inconceivably rich physical environment and in the process is painting the tunnel walls in various shades of color. Phenomenal color. Appearance. For your conscious eyes only...cognitive neuroscience has shown that the process of conscious experience is just an idiosyncratic path through a physical reality so unimaginably complex and rich in information that it will always be hard to grasp just how reduced our subjective experience is.

Shadows do not have an independent existence. And the book you are holding right now...is just a shadow, a low-dimensional projection of a higher-dimensional object ‘out there’...What is the fire that causes the projection of flickering shadows of consciousness, dancing as activation patterns on the walls of your neural cave? The fire is neural dynamics.”

The idea is that the content of consciousness is the content of a simulated world in our brains, and the sense of “being there” is itself a simulation...the conscious experience of knowing, acting, and being connected is an exclusively internal affair.

Any convincing theory of consciousness will have to explain why this does not seem so to us.

Induction of empathy by the smell of anxiety

Prehn-Kristensen et al. show that show that chemosensory anxiety signals (in the sweat of people awaiting and academic examination) activate brain areas involved in the processing of social anxiety signals (fusiform gyrus), and structures which mediate the empathetic internal representation of the emotional state of others (insula, precuneus, cingulate cortex), even though participants could not distinguish the smell of 'anxious sweat' form the smell of sweat produced by the same sweat donors during exercise.

REM sleep improves creativity by priming associative networks

From Cai et al:

The hypothesized role of rapid eye movement (REM) sleep, which is rich in dreams, in the formation of new associations, has remained anecdotal. We examined the role of REM on creative problem solving, with the Remote Associates Test (RAT). Using a nap paradigm, we manipulated various conditions of prior exposure to elements of a creative problem. Compared with quiet rest and non-REM sleep, REM enhanced the formation of associative networks and the integration of unassociated information. Furthermore, these REM sleep benefits were not the result of an improved memory for the primed items. This study shows that compared with quiet rest and non-REM sleep, REM enhances the integration of unassociated information for creative problem solving, a process, we hypothesize, that is facilitated by cholinergic and noradrenergic neuromodulation during REM sleep.

The evolution of God

Paul Bloom reviews Robert Wright's new book, which gives a historical account of how God has mellowed over time:

In sharp contrast to many contemporary secularists, Wright is bullish about monotheism. In “Nonzero: The Logic of Human Destiny” (2000), he argued that there is a moral direction to human history, that technological growth and expanding global interconnectedness have moved us toward ever more positive and mutually beneficial relationships with others. In “The Evolution of God,” Wright tells a similar story from a religious standpoint, proposing that the increasing goodness of God reflects the increasing goodness of our species.

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.

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."

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.)

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.