Intellectual performance and the efficiency of functional brain networks.

From van den Heuvel et al., an analysis that strongly suggests that our intellectual performance is likely to be related to how efficiently our brain integrates information between multiple brain regions:

Our brain is a complex network in which information is continuously processed and transported between spatially distributed but functionally linked regions. Recent studies have shown that the functional connections of the brain network are organized in a highly efficient small-world manner, indicating a high level of local neighborhood clustering, together with the existence of more long-distance connections that ensure a high level of global communication efficiency within the overall network. Such an efficient network architecture of our functional brain raises the question of a possible association between how efficiently the regions of our brain are functionally connected and our level of intelligence. Examining the overall organization of the brain network using graph analysis, we show a strong negative association between the normalized characteristic path length of the resting-state brain network and intelligence quotient (IQ). This suggests that human intellectual performance is likely to be related to how efficiently our brain integrates information between multiple brain regions. Most pronounced effects between normalized path length and IQ were found in frontal and parietal regions. Our findings indicate a strong positive association between the global efficiency of functional brain networks and intellectual performance.

Most prominent effects between IQ and the level of global connectivity efficiency (as expressed by a shorter node specific normalized path length) were found in the medial prefrontal cortex (yellow box), bilateral inferior parietal cortex (red box depicts effect in right hemisphere), and precuneus/posterior cingulate regions (orange box) of the functional brain network. Shown are correlation coefficient values of those voxels that had a significant negative association between IQ and normalized path length for T = 0.45 (linear regression, p less than 0.05 uncorrected for multiple comparisons, df = 18, corrected for age).

The synchronization of brains

A relevant follow up to the recent posts on Metzinger's book, which discussed the synchronization of our 'ego tunnels': Bharucha suggests that understanding of how brains synchronize — or fail to do so — will be a game-changing scientific development.

Calming aperitif for a Tuesday morning - a Grieg Arietta

This is the first item in Grieg's Lyrical Pieces series, the Arietta Op. 12 No. 1. I'm thinking I might record a series of these short pieces, each of which has a distinctive emotional tone, to punctuate the regular blog posts....

The computation of social behavior

I point out this article by Behrens et al. on the quest to compute social behavior, mainly to pass on their nice summary graphic, preceded by their abstract. They review the recent application of formal behavioral models in the area of social cognitive neuroscience, and the challenge of identifying which behaviors are causes, which are effects, and which are epiphenomena.

Neuroscientists are beginning to advance explanations of social behavior in terms of underlying brain mechanisms. Two distinct networks of brain regions have come to the fore. The first involves brain regions that are concerned with learning about reward and reinforcement. These same reward-related brain areas also mediate preferences that are social in nature even when no direct reward is expected. The second network focuses on regions active when a person must make estimates of another person’s intentions. However, it has been difficult to determine the precise roles of individual brain regions within these networks or how activities in the two networks relate to one another. Some recent studies of reward-guided behavior have described brain activity in terms of formal mathematical models; these models can be extended to describe mechanisms that underlie complex social exchange. Such a mathematical formalism defines explicit mechanistic hypotheses about internal computations underlying regional brain activity, provides a framework in which to relate different types of activity and understand their contributions to behavior, and prescribes strategies for performing experiments under strong control.


Fig. 1 (A) The functional neuroanatomy of social behavior. Primary colors denote brain regions activated by reward and valuation, frequently identified in studies of social interaction within the frame of reference of the subject’s own actions: anterior cingulate cortex sulcus (ACCs), ventromedial prefrontal cortex (VMPFC), amygdala, and ventral striatum (VStr). Pastels denote brain regions activated by considering the intentions of another individual: anterior cingulate cortex gyrus (ACCg), dorsomedial prefrontal cortex (DMPFC), temporoparietal junction (TPJ), and superior temporal sulcus (STS). (B) Schematic of an approach that combines mathematical models of behavior with neural recordings. The model contains parameters that represent specific computations underlying behavior. As the subject/model undergoes different experiences, these parameters will fluctuate. The fluctuation in these parameters is used to find neural correlates of the specific underlying computations. Separately, the same parameter fluctuations come together to predict changes in behavior.

Stumbling blocks on the path of righteousness

I've been meaning to pass on this brief piece by Benedict Carey on studies of the "holier-than-thou effect."

The age of reputation

Gloria Origgi suggests that the internet is ushering in a new 'reputation age', in which the reputation of an item — that is how others value and rate the item — will be the only way we have to extract information about it.

"Internet addiction disorder" in China

An American Psychiatric Association panel is now weighing whether to include Internet addiction in the fifth edition of the field's practices bible, the Diagnostic and Statistical Manual of Mental Disorders, planned for release in 2012. In China, the official view appears to be that Internet addiction is a genuine disorder, but attitudes are shifting about how aggressively it should be treated. Stone describes mild to extreme (military camp) remedies.

Metzinger: A new kind of ethics.

Metzinger's "The Ego Tunnel" - Chapter 9 - A new kind of ethics

In principle, we can design our own Ego Tunnels by tinkering with the hardware responsible for the relevant information-processing: Phenotechnology. (I do not extract at this point a fairly extended section on drugs and altered states of consciousness), which ends with: we must decide which of these altered states can be integrated into our culture and which are to be avoided at all cost.

What is a good state of consciousness?

Metzinger’s intuition is that it should satisfy at least three conditions. It should minimize suffering, in humans and other beings capable of suffering; it should possess an epistemic potential (have component of insight and expanding knowledge; and, should have consequences that increase the probability of future valuable types of experience.

The ego tunnel evolved as a biological system of representation and information processing that is part of a social network of communicating ego tunnels...now embedded in a global data cloud characterized by rapid growth, increasing speed, and an autonomous dynamic of its own....it has begun to reconfigure our brains..perhaps body perception will change as we learn to control multiple avatars in multiple virtual realities, embedding our conscious self into entirely new kinds of sensorimotor loops... we will understand what our social life has been all along - an interaction between images, a highly mediated process in which mental model of persons begin to causally influence one another... communication viewed as estimating and controlling dynamical internal models in other people’s brains.

For those of us intensively working with it, the Internet has already become a part of our self-model. We use it for external memory storage, as a cognitive prosthesis, and for emotional autoregulation...We are learning to multitask, our attention span is becoming shorter, and many of our social relationships are taking on a strangely disembodied character... The integration of hundreds of millions of human brains (and the Ego Tunnels those brains create) into ever new medial environments has already begun to change the structure of conscious experience itself. Where this will lead is unforeseeable.

The new media are also consciousness technologies, and we should ask ourselves again what a good state of consciousness would be.

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.

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 space 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.

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. ]

Riding the tiger: A new cultural context

On normative issues, there is no such thing as expert knowledge.. we must all do this together. Prospects for open and free democratic discussion on global scale are dim. Authoritarian societies growing more rapidly than democratic ones. To protect open societies from irrationalism and fundamentalism, we might try to create a ‘consciousness culture” in which people are free to explore their own minds and design their own conscious reality models, unless the interests of others are directly threatened. How can we increase the autonomy of the individual and protect it from the increasing possibilities of manipulation. If we demystify consciousness, do we automatically lose our sense of human solidarity at the same time?

The interplay of virtual-reality technology, new psychoactive substances, ancient psychological techniques such as meditation, and future neurotechnology will introduce us to a universe of self-exploration barely imaginable today.

Through the naturalistic turn in the image of mind, do we lose our “dignity?” Dignity can be seen in the refusal to humiliate oneself by simply looking the other way or escaping to some metaphysical Disneyland, sliding back into various forms of irrationalism and fundamentalism. We could face the historical transition in our image of ourselves creatively and with a will to clarity.

Old age: always older than you are...

Arnquist notes a recent Pew Research Center study that interviewed 3,000 adults, age 18 and older:

The survey found not just a gap between actual age and the age people say they feel, but also that the gap between reality and perception increases with age. Most adults over age 50 feel at least 10 years younger than their actual age, the survey found. One-third of those between 65 and 74 said they felt 10 to 19 years younger, and one-sixth of people 75 and older said they felt 20 years younger.

On average, survey respondents said old age begins at 68. But few people over 65 agreed; they said old age begins at 75...Respondents under 30 said 60 marks the beginning of old age...Younger people tend to think growing old will be worse than the elderly report...Older adults said they had experienced the negative aspects of aging — including illness, loneliness and financial difficulty — far less often than younger people anticipated. But older participants also said they found less time for family and leisure activities than younger adults expected they would when they reach old age.

Meditation increases brain's gray matter?

Passing this on, but I can't find any published work online. UPDATE: an alert reader just sent a comment, below, with the relevant reference (Neuroimage. 2009 Apr 15;45(3):672-8). PDF is here.

The "acts of kindness" iPhone app

A group of University of Michigan students has created an iPhone app, called DoGood, that challenges users to do a different good deed each day, and reports the total number of users who have done this...

Metzinger: Consciousness technologies and the image of humankind

Abstracted Chapter 8 of "The Ego Tunnel" - Consciousness Technologies and the image of humankind.

The central claim of this book is that the conscious experience of being a self emerges because a large portion of the self-model in your brain is, as philosophers would say, transparent....Ultimately, subjective experience is a biological data format, a highly specific mode of presenting information about the world, and the Ego is merely a complex physical event - an activation pattern in your central nervous system...we are “selfing” organisms: at the very moment we wake up in the morning, the physical system starts the process of “selfing” ...A new chain of conscious events begins; once again, on a higher level of complexity, the life process comes to itself....Today, the key phrase is “dynamical self-organization”.. there is no essence within that stays the same across time...we are selfless ego machines.

We cannot believe this, we are continuously mistaking ourselves for the content of the self model currently activated by our brains. We have only the dynamical self-organization of a new coherent structure, the transparent self-model in the brain, this is what it means to be no one and an Ego Machine at the same time. The conscious self is neither a form of knowledge nor an illusion. It just is what it is.

It is important not to confuse the descriptive (what is a human being?) with the normative (what should it become?). The ego evolved as an instrument in social cognition, and one of its greatest functional advantages was that it allowed us to read the minds of other animals or conspecifics - and then to deceive them. Or deceive ourselves...Psychological evolution endowed us with the irresistible urge to satisfy our emotional need for stability and emotional meaningfulness by creating metaphysical worlds and invisible persons. Religious belief seems to be one of the most successful ways to achieve a stable state... Now science seems to be taking all this away from us. The emerging emptiness may be one reason for the current rise of religious fundamentalism, even in secular societies. A new and comprehensive anthropology must synthesize the knowledge we have gained about ourselves to create a rational basis for normative decision about how we want to be in the future.

The Third Phase of the Revolution...

The first phase is about understanding consciousness as such, as with the ‘ego tunnel’ metaphor. The second phase details the first person perspective, research on agency, free will, emotions, mind-reading, self-consciousness in general. The third phase is dealing with what we want to do with this new knowledge about ourselves, the normative dimension. As with Max Weber’s “disenchantment of the world” we are now witnessing the disenchantment of the self. We are in a dangerous situation, with an anthropological and ethical vacuum created as neuroscience has dissolved Judeo-Christian images that secured a minimal moral consensus before there is a neuroscientific-philosophical consensus on the nature of the self, free will, mind and brain, what makes a person a person... A vulgar materialism might take hold. “It’s all a crock, I’ll just go on pretending I’m an old-fashioned believer in moral values.”....scientists have an obligation to not just be curious, but confront the normative void they have created by destroying everything humankind has believed in for the past twenty-five hundred years.

Putting aside that most humans are firmly rooted in prescientific cultures, with fundamentalism on the rise due to anxiety over scientific findings, suppose a strong version of materialism develops. We will have to assume that the universe has an intrinsic potential for subjectivity. Not only organisms, but consciousness, world models, evolution of ideas, billions of conscious brains like billions of eyes with which the universe can look at itself as being present.

A consciousness ethics is required to deal with issues of altered states (drugs, meditation), as well as neurotechnology and phenotechnology that can redesign the ego-tunnel.

Tool use and the evolution of intelligence.

Bird and Emery make the fascinating observation that rooks, who do not use tools in the wild, are capable of insightful problem solving related to sophisticated tool use, including spontaneously modifying and using a variety of tools, shaping hooks out of wire, and using a series of tools in a sequence to gain a reward. They suggest that the ability to represent tools may be a domain-general cognitive capacity rather than an adaptive specialization and question the relationship between physical intelligence and wild tool use. That is, they question the common invoking of tool use as a candidate trait (together with language, cumulative culture, and excessive prosociality) for promoting the development of human intellectual uniqueness. (I might point to the ongoing debate on whether animals other than humans have causal beliefs, see Wolpert and Shettleworth's letters to nature which comment on an essay by Bolhuis and Wynne, mentioned in a previous MindBlog post.

Bending wire into hooks by rooks. (Left) Fry extracting the bucket containing a worm using a piece of wire she had just bent. This photo was taken after the experiment was completed but the hook and posture are typical of experimental trials. (Right) Photographs of the successful hooks used by all 4 subjects (excluding the 2 trials where the straight wire was used to stab the bucket), with the successfully used end facing right. Numbers indicate trial number.

Increases and decreases in neural synchrony during our development

Uhlhaas, Singer, and others use EEG measurements of neural synchrony to illustrate instabilities of cognitive performance during the adolescent period, instabilities that contrast with earlier and later periods of increasing cognitive performance. They suggest that changes in neural synchrony seen during the transition from late adolescence to early adulthood reflect a critical developmental period that is associated with a rearrangement of functional networks and with an increase of the temporal precision and spatial focusing of neuronal interactions:

Brain development is characterized by maturational processes that span the period from childhood through adolescence to adulthood, but little is known whether and how developmental processes differ during these phases. We analyzed the development of functional networks by measuring neural synchrony in EEG recordings during a Gestalt perception task in 68 participants ranging in age from 6 to 21 years. Until early adolescence, developmental improvements in cognitive performance were accompanied by increases in neural synchrony. This developmental phase was followed by an unexpected decrease in neural synchrony that occurred during late adolescence and was associated with reduced performance. After this period of destabilization, we observed a reorganization of synchronization patterns that was accompanied by pronounced increases in gamma-band power and in theta and beta phase synchrony. These findings provide evidence for the relationship between neural synchrony and late brain development that has important implications for the understanding of adolescence as a critical period of brain maturation...The changing patterns of synchronous, oscillatory activity during adolescence seem to reflect a major reorganization of cortical networks that may have profound implications for the understanding of both normal development and developmental disorders, such as schizophrenia, that typically emerge during this period.

When our brains short-circuit.

An Op-Ed piece by Kristoff on how our 'hot buttons' that evolved for paleolithic life blow away rationale responses in public policy.

Metzinger: A tour of the ego tunnel

Metzinger's "The Ego Tunnel" - Abstracted Chapter Two - A tour of the tunnel
(This chapter has really fascinating ideas)

1- The One-World problem: the unity of consciousness.
2- The Now Problem - the appearance of a lived moment
3-The Reality Problem - why you were born as a naive realist
4-The Ineffability Problem - what we will never be able to talk about
5-The Evolution Problem - what consciousness was good for
6-The Who Problem - what is the entity that has conscious experience

1- The One-World problem: the unity of consciousness.

What binds things together in a comprehensive, simultaneous whole? In apperceptive agnosia, no coherent visual model emerges on the level of conscious experience, despite the fact that all the patient’s low-level visual processes are intact. An intact visual field is perceived, but not its content.

To sum up, it would seem that feature-binding occurs when the widely distributed neurons that represent the reflection of light, the surface properties, and the feel of the device you are using to read at this moment start dancing together, firing at the same time. This rhythmic firing pattern creates a coherent cloud in your brain, a network of neurons representing a single object for you at a particular moment. Holding it all together is coherence in time. Binding is achieved in the temporal dimension. The unity of consciousness is thus seen to be a dynamic property of the human brain. It spans many levels of organization, it self-organizes over time, and it constantly seeks an optimal balance between the parts and the whole as they gradually unfold. It shows up on the EEG as a slowly evolving global property, and, as demonstrated by meditators, it can be cultivated and explored from the inside, from the first-person perspective.

2- The Now Problem - the appearance of a lived moment

One essential function of consciousness is to help an organism stay in touch with the immediate present - and properties in the environment that may change fast and unpredictably...Presence is a necessary condition for conscious experience. If the brain could solve the One-World Prolem but not the Now Problem, a world could not appear to you. In a deep sense, appearance is simply presence, and the subjective sense of temporal immediacy is the definition of an internal space of time. There is an upper limit to what you can consciously experience as taking place in a single moment: It is almost impossible to experience a musical motif, a rhythmic piece of poetry, or a complex thought that lasts for more than three seconds as a unified temporal gestalt...the sense of presence is an internal phenomenon, created by the human brain. Not only are there no colors out there, but there is also no present moment. Physical time flows continuously...neuroscience tells us that we are never in touch with the present, because neural information-processing itself takes time. Signals take time to travel from your sensory organs to your brain and be processed and transformed...the moving window of the conscious now successfully bundles perception, cognition, and conscious will in a way that selects just the right parameters of interaction with the physical work, in environments like those in which our ancestors fought for survival...it is a form of knowledge about what will work with this kind of body and these kinds of eyes, ears, and limbs.

3 - The Reality Problem - why you were born as a naive realist

The pivotal question is how to get from a world-model and a Now-model to exactly what you have as you are reading this: the presence of a world...these models active in the brain are transparent if the brain has no chance of discovering that they are models. ..The brain creates what are called higher order representations - if the first-order process creating the seen object, the book in your hands - integrates its information in a smaller time-window than the second order process (namely, the attention you are directing at this new inner model), then the integration process on the first-order level will itself become transparent...Transparency is not so much a question of the speed of information-processing as of the speed of different types of processing (such as attention and visual perception) relative to each other. The binding of the model of your current reading device with the rest of your experience space, optimized over millions of years, is so fast and reliable that you never notice its existence. It makes your brain invisible to itself. You are in contact only with it content; you never see the representation as such: there you have the illusion of being directly in contact with the world.. you become a naive realist, thinking to be in touch with an observer-independent reality.

The notion of metabolic price is a useful concept. To develop a new cognitive capacity, the brain must pay a metabolic price, if a biological organisms want to develop a conscious self or think in concepts, then this new level of mental complexity must be sustainable. It requires additional neural hardware that requires fuel. Any theory of consciousness must reveal how it paid for itself...This evolutionary perspective helps solve the problem of naive realism.

Our ancestors did not need to know that a bear-representation was currently active in their brains or that they were currently attending to an internal state representing a slowly approaching wolf...All they needed to know was “Bear over there!” or “Wolf approaching from the left!” Knowing that all of this was just a model of the world and of the Now was not necessary for survival. This additional kind of knowledge would have required the formation of what philosophers call meta-representations, or images about other images, thoughts about thoughts. It would have required additional hardware in the brain and more fuel.

Thus, the answer to the question of why our conscious representations of the world are transparent - why we are constitutionally unable to recognize them as representation - and why this proved a viable, stable, strategy for survival and procreation probably is that the formation of meta-representations would not have been cost-efficient: It would have been too expensive in terms of the additional sugar we would have had to find in our environment.

Consciousness is the space of attentional agency, that set of information currently active in our brains to which we can deliberately direct our high level attention. Low level attention is automatic and can be triggered by entirely unconscious events. .. most things we’re aware of are on the fringe of our consciousness and not in its focus. But whatever is available for deliberately directed attention is what is consciously experienced...we are constitutionally unable to apprehend the earlier processing stages.

That is why the walls of the tunnel are impenetrable for us: Even if we believe that something is just an internal construct, we can experience it only as given and never as constructed. We would be overwhelmed if we could apprehend earlier processing stages.

A minimalist concept of consciousness - or how the brain moves from an internal world-model and internal Now-model to the full-blown appearance of a world. If the system in which these models are constructed is constitutionally unable to recognize both the world-model and the experience of the present as models, as only internal constructions, then the system will of necessity generate a reality tunnel. It will have the experience of being in immediate contact with a single, unified world in a single Now, a world appears... the global neural correlate of consciousness (GNCC) will be a dynamic brain state exhibiting large-scale coherence. (Metzinger predicts it will be understood within 50 years).

4 - The Ineffability Problem - what we will never be able to talk about

We are much better at discriminating perceptual values than we are at identifying or recognizing them. For this section, see the May 22, 2009 mindblog posting.

5-The Evolution Problem - what consciousness was good for

There are many potential candidate functions of consciousness: goal hierarchies and long-term plans, enhancement of social coordination,... a long list. A useful idea is of the Global workspace: that subset of active information in the brain that requires monitoring because it’s not clear which of your mental capacities you will need to access next...

Consciousness as a new kind of virtual organ, unlike permanent hardware of liver, kidney, or heart..., that forms for a certain time when needed (like desire, courage, anger, or an immune response)...a new computational strategy, a consciousness tunnel, makes classes of facts globally available and allows attending, flexible reacting, within context.... ‘reality generation’ allowed animals to represent explicitly the fact the something is actually the case, the world is present. (conscious color gives information about nutritional value, red berries among green leaves, empathy gives information about emotional state of conspecifics). Only homo sapiens (and higher apes?) have evolved the additional ability to run offline simulations in the mind, experiencing some things are ‘real’ and other elements of our tunnel as mere thoughts about the world, representing that we are representational systems. Old things in the evolution of consciousness are ultrafast and reliable (like qualities of sensory experience) and transparent: abstract conscious thought is not, it is slow and unreliable, experienced as ‘made.’

6-The Who Problem - what is the entity that has conscious experience

A successful theory of consciousness must match first person phenomenal content to third-person brain content, inner perspective of experiencing self with outside perspective of science... It is likely that consciousness is epistemically irreducible... one reality, one kind of fact, but two kinds of knowledge: first-person knowledge and third-person knowledge, that never can be conflated.

The existence of an experiencing self may not be a necessary component of consciousness... in Cotard’s syndrome, patients sometimes stop using first person pronoun, and claim that they do not really exist. Mystics report deep spiritual experiences in which no ‘self’ exists. Many of the simpler organisms may have a consciousness tunnel with nobody living in it. The need is to understand how in evolution the consciousness tunnel turned into an Ego Tunnel, the experience of being ‘someone’ in a centered model of reality.

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.