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Archive for August 2009

Innate categories

Science Daily reported on a paper, ‘Category-specific Organization in the Human Brain Does Not Require Visual Experience’, by B. Mahon and others. (here) The neural pathway called the ventral stream does a quick visual object categorization process (animals, faces, non-living objects etc). But are the categories the product of visual experience and are they inborn?

The human brain distinctly separates the handling of images of living things from images of non-living things, processing each image type in a different area of the brain. For years, many scientists have assumed the brain segregated visual information in this manner to optimize processing the images themselves, but new research shows that even in people who have been blind since birth the brain still separates the concepts of living and non-living objects.

The research…implies that the brain categorizes objects based on the different types of subsequent consideration they demand—such as whether an object is edible, or is a landmark on the way home, or is a predator to run from. They are not categorized entirely by their appearance.

“If both sighted people and people with blindness (from birth) process the same ideas in the same parts of the brain, then it follows that visual experience is not necessary in order for those aspects of brain organization to develop,” says Mahon, “We think this means significant parts of the brain are innately structured around a few domains of knowledge that were critical in humans’ evolutionary history.”

“When we looked at the MRI scans, it was pretty clear that blind people and sighted people were dividing up living and non-living processing in the same way,” says Mahon. “We think these findings strongly encourage the view that the human brain’s organization innately anticipates the different types of computations that must be carried out for different types of objects.”

Mahon thinks it’s possible that other parts of the human brain are innately structured around categories of knowledge that may have been important in human evolution. For instance, he says, facial expressions need a specific kind of processing linked to understanding emotions, whereas a landmark needs to be processed in conjunction with a sense of spatial awareness. The brain might choose to process these things in different areas of the brain because those areas have strong connections to other processing centers specializing in emotion or spatial awareness, says Mahon.

Clock speeds

Look at the frequency of some events: the gamma waves that synchronize the thalamus and large parts of the cortex happen between 25 and 100 times per second but typically near 40; the saccadic eye vibrations happen between 30 and 70 times per second; the flicker rate of movie projectors that makes the picture stable is between 48 and 72 times per second. This makes one guess that there is a good probability that the discontinuous nature of the ‘frames’ from the eye, from a movie screen and from consciousness all have the same timing centered on about 50 Hz. A group has now shown that the focus of attention shifts about 18 to 34 times a second and averages about 25 Hz. It looks like two frames per focus.

This attention timing is reported by ScienceDaily (here) in an item on a paper by T. Buschman and E. Miller.

You’re meeting a friend in a crowded cafeteria. Do your eyes scan the room like a roving spotlight, moving from face to face, or do you take in the whole scene, hoping that your friend’s face will pop out at you? And what, for that matter, determines how fast you can scan the room?…. you are more likely to scan the room, jumping from face to face as you search for your friend. In addition, the timing of these jumps appears to be determined by waves of activity in the brain that act as a clock. …the study showed that brain waves act as a kind of built-in clock that provides a framework for shifting attention from one location to the next. … Buschman found that the spotlight of the mind’s eye shifted focus at 25 times a second and that this process of switching was regulated by brain waves. …the speed at which the animals searched was related to the speed of their brain waves. When the clock ticked faster, the animals “thought” faster.

The paper’s summary is below:

Attention regulates the flood of sensory information into a manageable stream, and so understanding how attention is controlled is central to understanding cognition. Competing theories suggest visual search involves serial and/or parallel allocation of attention, but there is little direct, neural evidence for either mechanism. Two monkeys were trained to covertly search an array for a target stimulus under visual search (endogenous) and pop-out (exogenous) conditions. Here, we present neural evidence in the frontal eye fields (FEF) for serial, covert shifts of attention during search but not pop-out. Furthermore, attention shifts reflected in FEF spiking activity were correlated with 18–34 Hz oscillations in the local field potential, suggesting a “clocking” signal. This provides direct neural evidence that primates can spontaneously adopt a serial search strategy and that these serial covert shifts of attention are directed by the FEF. It also suggests that neuron population oscillations may regulate the timing of cognitive processing.

Which way is north?

I have just read an article on being lost (here) and I have to say that the people described were ‘not from Saskatchewan’. There are advantages and disadvantages to having been a prairie girl.

When we were first in Kenya, my husband used to look at a map, decide where he was going, and go out the door of the hotel and within a city block he was hopelessly lost. We couldn’t believe what had happened to him. The mystery was solved when we realized he navigated by the sun and had not corrected for being somewhere where the sun can be in the north half of the sky. I, being a prairie girl, did not get lost. I could go on with story after story (I won’t) but the weird ways in which other people navigate.

Of course, I always know which way is north. If I lose this knowledge of my bearing, I suffer from a deeply lost feeling, a type of panic. This is an abstract panic. I can know where I am well enough to manage to get where I am going, or can have a map, or can be with someone who knows where they are. I am not afraid in that sense. What causes the panic is a loss of contact with my mental map of the universe.

Well maybe one more story: my husband was in a fairly large store in Saskatchewan, in the basement. There was a sign that said, ‘Hardware has been moved to the west wall.’ He was amazed. After walking round on the ground floor, taking one of several escalators down to the basement, and walking around there, he was expected to find the west wall in a windowless basement. He was not amused when I suggested that he could have faced north and then turned to his left and walked in that direction.

The article reviews a number of ways that people find their way or get lost, whichever. I am interested in how navigation and the feeling of being lost registers in consciousness.

Every so often, Sharon Roseman rounds a bend in her suburban Colorado neighbourhood and drives into a new world. It’s a lot like the world she knows - same houses, same street names - but with one critical, maddening difference: everything in it has shifted 90 degrees. Familiar stores at well-known intersections are not where she feels they should be, and the Rocky mountains have migrated from the north to the east.

Roseman’s world has been turning like this since she was 5 years old, and the only sure-fire way to set things right is to close her eyes and spin until everything “clicks” back into place, a remedy she jokingly calls her “Wonder Woman cure”. Despite countless visits to a doctor, prescriptions and brain scans over more than 50 years, nobody has offered a diagnosis. Nobody, Roseman suspects, really believed her. Until now.

Giuseppe Iaria of the University of Calgary, Alberta, and Jason Barton at the University of British Columbia in Vancouver, both in Canada, may have finally put a name to Roseman’s condition. They call it developmental topographical disorientation. While people with the disorder have no obvious brain injury or other cognitive problem, they are chronically unable to orient themselves, even in places they know well. The pair have found 400 or so people who may have the disorder, some of whom are so prone to getting lost they fear leaving the house alone.

Well just maybe one more story - When my Grandmother and her children came to Saskatchewan to join Grandfather, the children were mixed up in their directions. So Grandfather’s brother took them out in a horse and sled. He covered them with a blanket. He went round in circles and figure eights and zig-zags on the featureless prairie snow. He would stop the horse (facing north) and ask, ‘is anyone sure they are facing north?’. If anyone was, that child and only them could come out from under the blanket. This was done several times until all the children had emerged and had the correct orientation. And I believe they had it more or less for the rest of their lives.

3D revisited

A comment to the post Time and Space started me thinking about whether our perception is more 2D and less 3D than we realize.

The following excerpt is slightly off the subject of the comment, but still interesting in this regard. It is from a Scientific American interview by Lehrer of Sue Barry. She learned to see stereoscopically after 40 years of seeing two dimensionally. (here)

LEHRER: What was it like to see the world in 3-D? Could you describe your first reactions?

BARRY: Many people tell me that the world looks about the same to them whether they look with one eye or with two. They don’t think stereovision is all that important. What they don’t realize is that their brain is using a lifetime of past visual experiences to fill in the missing stereo information. Seeing in 3-D provides a fundamentally different way of seeing and interpreting the world than seeing with one eye. When I began to see in stereo, it came as an enormous surprise and a great gift.

For the first time, I could see the volumes of space between different tree branches, and I liked immersing myself in those inviting pockets of space. As I walk about, leaves, pine needles, and flowers, - even light fixtures and ceiling pipes - seem to float on a medium more substantial than air. Snow no longer appears to fall in one plane slightly in front of me. Now, the snowflakes envelope me, floating by in layers and layers of depth. It’s been seven years since I gained stereovision, but ordinary views like these still fill me with a deep sense of wonder and joy.”

Her description implies that although she had not automatically perceived three dimensions in her life, she definitely thought in 3D. She did not have to learn how to use this extra ingredient in her perception although it was definitely novel and surprising.

Another recent research report in ScienceDaily gives indications of where and how 3D calculations are done. ( here )

They found, surprisingly, that 3-D motion processing occurs in an area in the brain—located just behind the left and right ears—long thought to only be responsible for processing two-dimensional motion (up, down, left and right). This area, known simply as MT+, and its underlying neuron circuitry are so well studied that most scientists had concluded that 3-D motion must be processed elsewhere. Until now…

For the study, Huk and his colleagues had people watch 3-D visualizations while lying motionless for one or two hours in an MRI scanner fitted with a customized stereovision projection system…The fMRI scans revealed that the MT+ area had intense neural activity when participants perceived objects (in this case, small dots) moving toward and away from their eyes. Colorized images of participants’ brains show the MT+ area awash in bright blue…

The tests also revealed how the MT+ area processes 3-D motion: it simultaneously encodes two types of cues coming from moving objects…There is a mismatch between what the left and right eyes see. This is called binocular disparity… For a moving object, the brain calculates the change in this mismatch over time. Simultaneously, an object speeding directly toward the eyes will move across the left eye’s retina from right to left and the right eye’s retina from left to right. “The brain is using both of these ways to add 3-D motion up,” says Huk. “It’s seeing a change in position over time, and it’s seeing opposite motions falling on the two retinas.”

Out of body experience

ScienceDaily has an item on the research of O. Blanke’s lab at the EPFL Switzerland (here). The sense of self-identification and self-location can be altered in healthy people under certain experimental conditions, yielding similar sensations to those felt in out-of-body experiences.

research to see whether there are changes in touch perception when humans experience ownership of a whole virtual body. They designed a novel behavioural task in which the experimental participants had to try to detect where on their body vibrations were occurring. At the same time, they viewed their own body via a head-mounted display connected to a camera filming the participant’s back from two metres away. The participants had to ignore light flashes that appeared on their body near the vibrators. To induce the feeling that they were located in the position where they viewed their body (i.e. two metres in front of them), participants were stroked on their backs with a stick. This induced a “full body illusion” in which a person perceives herself as being located outside the confines of her own body.

By measuring how strongly the light flashes interfered with the perception of the vibrations, the researchers were able to show that the mapping of touch sensations was altered during the full body illusion. The mapping of touch in space was shifted towards the virtual body when subjects felt themselves to be located where the virtual body was seen.

This study demonstrates that changes in self-consciousness (’where am I located?’ and ‘what is my body?’) are accompanied by changes in where touch sensations are experienced in space. Importantly, these data reveal that brain mechanisms of multisensory processing are crucial for the “I” of conscious experience and can be scientifically manipulated in order to animate and incarnate virtual humans, robots, and machines.”

Our bodies seem to be inferred in our consciousness as are other sensory perceptions.

Property of Consciousness 4

Consciousness seems more complex than a uniform model: a wide-ranging but low resolution model, and a restricted but detailed portion inside the model. We experience the whole room with the things and people in it, but at this instance we may only have the cat as the focus of the experience. The part of consciousness that is attended to has a vividness that is missing from the rest of consciousness and from memories and imaginings. This implies that it is more complete and raw sensory information that is being used for the focus and more processed, generic and categorized information being used for the bulk of the model.

The location of attention within the model seems to be controlled by the frontal cortex in response to what is novel in the model or what is needed by cognitive processes. It seems that we by attentive to two widely separated things at the same time – perhaps this is a ‘time-slicing’ process, or different sensory modes having independent focuses, or two types of process both of which we call attention, or, least likely, actual conscious attention to two things at once.

Property/function of consciousness #4 – Within the conscious model of reality is a small portion with higher sensory discrimination than the bulk of the model, the focus of attention. This compromise between quantity and quality means we experience detail as needed without using the neural resources that would be required to have that detail available when not being used.

Here are some postings on attention:



Attention 1

Attention 2

Attention brain waves

Inexpressible experience

This is an area I intend to follow in future posts.

Property of Consciousness 3

It is fairly clear that consciousness and explicit memory have a link. Our explicit memories are exclusively memories of conscious experience and when recalled form a conscious-type experience. Forming an explicit memory appears to have at least three stages: first, forming a working memory; second, forming a temporary memory in the hippocampus system awaiting consolidation; and third, forming a long-term memory distributed in the cortex during sleep. It is working memory that is linked to consciousness and it appears to rely to some extent on specific types of cells that can sustain activity for a period of time. Working memory appears to have a limit and can hold only a few consecutive slices of consciousness at a time.

The explicit memory is either episodic or semantic. It gives a narrative to our lives and allows us to learn from experience.

Property/function of consciousness #3 – Consciousness is, or is the immediate source of, working memory and therefore of explicit memory. Explicit memory allows us to recall experience in a conscious-like holistic way. It gives a personal narrative and facilitates particular types of learning.

Here are the previous posting relating to memory and consciousness.

What goes on in dreams

Towards understanding working memory


Memories in time

Implicit and explicit memory

Keeping echoes in mind

Visual memory

There will be more on memory as I find it.

Property of Consciousness 2

Consciousness is discontinuous. Each conscious-cycle builds synchronized activity, locally through to globally, in the thalamus-cortex gamma frequency. This synchronized activity appears to bind information together in one global model. Synchrony between the individual feedback loops, cortex-thalamus and cortex-cortex, probably insures a ‘best fit’ or ‘least free energy’ or ‘most consistent’ model of reality that is the best compromise of sensory data, basic knowledge, immediate past, and immediate expectations. These momentary models of reality follow one another in rapid succession and appear to be a continuous experience.

Property/function of consciousness #2 – Consciousness is the result of brain activity, particularly the synchronous firing of neurons across the cortex and thalamus in the gamma frequency. This produces a integrated, global model of reality which is the basis of our experience. Separate versions of the reality model follow one another and appear continuous.

Here are some previous posting relating to the neural events of consciousness.

Watching the movie

Grand Central Station

Yet more Llinas

Thalamus waves

Neural correlates of consciousness

The global workspace

The P3 wave

Locked in consciousness

More will follow is research is reported.

Property of Consciousness 1

What have we found at the end of a year and a bit? I’ll look at that in the next few posts.

It would seem to me that one idea has been fairly convincingly shown: that consciousness predicts the near future from the near past in order to give us an experienced ‘now’. The possible advantages of this constructed ‘now’ are obvious: we experience life in the present, we have a fluid passage through future-present-past, and most importantly, we can register the error between what we predict will happen and what does happen and use this error signal to correct our actions and perceptions. Further, the error signal can provide input to the ‘reward’ system, input to learning systems and input to controlling the focus of attention. How immensely useful this prediction is!!!

Whether the system is mathematically Bayesian or not, it is certainly philosophically Bayesian. We are creating a high-probability scenario of what the future holds from the ‘priors’ we find in the past.


Property/function of consciousness #1 – Consciousness predicts the near future from the near past in order to give us an experienced ‘now’ which is compared with current sensory input. This comparison gives more accuracy to movements and perceptions, and it facilitates appropriate emotional reactions, learning and attention.

Here are some previous postings indicating the predictive nature of consciousness.

Is the brain Bayesian?

Living in the present

Living in the present 2


Friston’s Law

Up the garden path

Bayesian perception

Error signals

I assume there will be more research to come in the next year that will further elaborate this property.

Reading brain patterns

ScienceDaily has a report ( here ) on research by S. Hanson at Rutgers, R. Poldrack at UCLA and Y. Halchenko at Dartmouth. They have been able to read the type of thought of a person before the person is conscious of the thought.

(They) have provided direct evidence that a person’s mental state can be predicted with a high degree of accuracy through functional magnetic resonance imaging (fMRI). The research also suggests that a more comprehensive approach is needed for mapping brain activity and that the widely held belief that localized areas of the brain are responsible for specific mental functions is misleading and incorrect.

Over the last several years, much of neuroimaging has focused on pinpointing areas of the brain that are uniquely responsible for specific mental functions, such as learning, memory, fear and love. But this latest research shows that the brain is more complex than that simple model. In their analysis of global brain activity, the researchers found that different processing tasks have their own distinct pattern of neural connections stretching across the brain, similar to the fingerprints that distinctively identify each of us. Rather than being a static pattern, however, the brain is able to arrange and rearrange the connections based on the mental task being undertaken…

The research showing that specific mental functions do not correspond directly with certain brain areas but rather a unique pattern of neural connections also provides a more accurate direction for mapping the effective connectivity of the brain. Known as the Connectome Project, the goal of researchers involved in that work is to provide a complete map of the neural circuitry of the central nervous system.

What our research shows is that if you want to understand human cognitive function, you need to look at system-wide behavior across the entire brain,” explains Hanson. “You can’t do it by looking at single cells or areas. You need to look at many areas of the brain to even understand the simplest of functions.”…

The study involved 130 participants, each of whom performed a different mental task, ranging from reading, to memorizing a list, to making complex decisions about whether to take monetary risks, while being scanned using fMRI. The researches were able to identify which of eight tasks participants were involved in with more than 80-percent accuracy by analyzing the participants’ fMRI data against classifications developed from the fMRIs of other individuals. …Unlike most research that has focused on specific areas of the brain, Hanson and his team looked at the pattern of activity across a half million points in the brain.”