follow the beat

ScienceDaily has an item on a paper by R. Canolty and others from the Carmena lab, Oscillatory phase coupling coordinates anatomically dispersed functional cell assemblies. (here)

They looked at data accumulated in other research over a number of years and analyzed the recordings to try to find linkages between firing frequencies. Here is the abstract:

Hebb proposed that neuronal cell assemblies are critical for effective perception, cognition, and action. However, evidence for brain mechanisms that coordinate multiple coactive assemblies remains lacking. Neuronal oscillations have been suggested as one possible mechanism for cell assembly coordination. Prior studies have shown that spike timing depends upon local field potential (LFP) phase proximal to the cell body, but few studies have examined the dependence of spiking on distal LFP phases in other brain areas far from the neuron or the influence of LFP–LFP phase coupling between distal areas on spiking. We investigated these interactions by recording LFPs and single-unit activity using multiple microelectrode arrays in several brain areas and then used a unique probabilistic multivariate phase distribution to model the dependence of spike timing on the full pattern of proximal LFP phases, distal LFP phases, and LFP–LFP phase coupling between electrodes. Here we show that spiking activity in single neurons and neuronal ensembles depends on dynamic patterns of oscillatory phase coupling between multiple brain areas, in addition to the effects of proximal LFP phase. Neurons that prefer similar patterns of phase coupling exhibit similar changes in spike rates, whereas neurons with different preferences show divergent responses, providing a basic mechanism to bind different neurons together into coordinated cell assemblies. Surprisingly, phase-coupling–based rate correlations are independent of interneuron distance. Phase-coupling preferences correlate with behavior and neural function and remain stable over multiple days. These findings suggest that neuronal oscillations enable selective and dynamic control of distributed functional cell assemblies.

And here is an analogy, making the general picture easier to imagine:

“It is like the radio communication between emergency first responders at an earthquake,” Canolty said. “You have many people spread out over a large area, and the police need to be able to talk to each other on the radio to coordinate their action without interfering with the firefighters, and the firefighters need to be able to communicate without disrupting the EMTs. So each group tunes into and uses a different radio frequency, providing each group with an independent channel of communication despite the fact that they are spatially spread out and overlapping.”

For example, the high-beta band — 25 to 40 hertz (cycles per second) — was especially important for brain areas involved in motor control and planning. Other ‘channels’ would be used by other functions.

Memory as a resource

Some people are surprised, even disturbed, by the idea that our vision does not give us an accurate picture of what we look at. For example, the colours we experience are not a measure of the wavelength of the light entering our eyes. But accuracy is not the point of vision; the function is to be useful and colour consistency is far more useful then fidelity to wavelength spectra. The same surprise is shown in the reaction to the idea that our memories are reworked continuously so that over time they lose their accuracy. This is not a fault in memory. Again the reason we store memories is to have a useful resource, not necessarily one with detailed accuracy. A great deal of biological energy is used to create memories and to re-consolidate them and therefore we can assume that they have a very important biological role.

In order to have episodic memory, we first have to have the experiences to remember – we create consciousness experiences which become stored as temporary memories. These are soon made more permanent as an event or an episode. Over weeks, months, years, decades they are continually reworked and re-consolidated. They are packaged together and lose their individuality, they are up-dated by newer memories, they are categorized and lose detail not related to their category. Eventually they lose their character as episodic memory and became more a factual or semantic type of memory. What has happened in all this change is that we have learned from experience. This in itself would probably justify the biological cost of consciousness and memory but more has been proposed by Moshe Bar, Donna Rose Addis, Daniel L. Schacter and others. They have put memory at the center not just of the past and learning but of the present and future, of prediction, understanding and cognition.

Bar envisages a ‘proactive brain’ which builds analogues by examining what something is like. If A is like B then they share an analogy which grows as other like things are remembered. Each memory added to a particular analogy brings associations with it, so the associations of each analogy grows. The associations of an analogy are in effect predictions of what else will be found along with the analogy. Thus memory is the material of prediction and foresight. Between memories, predictions and idle imaginings we have the simulations we need to plan our actions. These simulations can even become ‘scripts’ for guiding behaviour and sets of scripts to determine a ‘mindset’ appropriate for a particular type of situation.

Schacter and Addis call their scheme the ‘prospective brain’.

A rapidly growing number of recent studies show the imagining the future depends on much of the same neural machinery that is needed for remembering the past. These findings have led to the concept of the prospective brain; an idea that a critical function of the brain is to use stored information to imagine, simulate and predict possible future events. We suggest that processes such as memory can be productively re-conceptualized in light of this idea.

In fMRI studies of subjects remembering and imagining events, they have identified what they call the ‘core brain system’ which integrates information from past experiences about relationships and associations and uses the information to construct mental simulations. There is a large overlap between the areas of the brain involved in elaborating past and future events. Further there is a large overlap with the default network we use for day-dreaming.

The cognitive machinery outlined by this line of research would convincingly be worth its biological cost by giving us effective and appropriate behaviour. Memory may not be entirely accurate but it is wonderfully useful.

 

ResearchBlogging.org
ADDIS, D., WONG, A., & SCHACTER, D. (2007). Remembering the past and imagining the future: Common and distinct neural substrates during event construction and elaboration Neuropsychologia, 45 (7), 1363-1377 DOI: 10.1016/j.neuropsychologia.2006.10.016
Schacter DL, Addis DR, & Buckner RL (2007). Remembering the past to imagine the future: the prospective brain. Nature reviews. Neuroscience, 8 (9), 657-61 PMID: 17700624
Bar, M. (2009). The proactive brain: memory for predictions Philosophical Transactions of the Royal Society B: Biological Sciences, 364 (1521), 1235-1243 DOI: 10.1098/rstb.2008.0310

A consciousness meter

Carl Zimmer has a piece in the New York Times on Guilio Tononi’s theory of consciousness (here). Tononi is trying to quantify consciousness in terms of ‘phi’, the amount of integrated information in networks. In simplistic terms, the higher the ‘phi’ – the higher the consciousness. My reaction to the theory is lukewarm – but – the attempt to measure the amount of consciousness in people is a great step forward for medicine. This is Zimmer’s description of the technique:

…he and his colleagues placed a small magnetic coil on the heads of volunteers. The coil delivered a pulse of magnetism lasting a tenth of a second. The burst causes neurons in a small patch of the brain to fire, and they in turn send signals to other neurons, making them fire as well.

To track these reverberations, Dr. Tononi and his colleagues recorded brain activity with a mesh of scalp electrodes. They found that the brain reverberated like a ringing bell, with neurons firing in a complex pattern across large areas of the brain for 295 milliseconds.

Then the scientists gave the subjects a sedative called midazolam and delivered another pulse. In the anesthetized brain, the reverberations produced a much simpler response in a much smaller region, lasting just 110 milliseconds. As the midazolam started to wear off, the pulses began to produce richer, longer echoes. … Dr. Tononi has gotten similar results when he has delivered pulses to sleeping people — or at least people in dream-free stages of sleep. … he and his colleagues reported that dreaming brains respond more like wakeful ones. Dr. Tononi is now collaborating with Dr. Steven Laureys of the University of Liège in Belgium to test his theory on people in persistent vegetative states. … “That would give us a consciousness index,” Dr. Laureys said.

What a fabulous tool that would be, with so many uses. If it comes to be, then we will have to remember that it gives us the ‘how much’ and ‘when’ of consciousness but not the ‘how’ or ‘why’. It does not help us with what information is being integrated, how the integration is done and what the brain does with the result.

Power of faces

Much of what we know of perception has come from studying illusions. Finding situations were the processes reveal themselves in their ‘mistakes’ give clues to how those processes work under ordinary conditions. Of course, our sensory processes have not actually made a mistake; we have misled them.A new illusion is a new departure because it added the specialized perception of faces to visual effects.

Giovanni Caputo from the University of Urbino has developed an experimental setup involving an observer staring for a long time at their face in the mirror under low light conditions, low enough to weaken colour perception. By a minute of fixed staring the face started to change. By 10 minutes, the subjects had seen:

“(a) huge deformations of one’s own face (reported by 66% of the fifty participants); (b) a parent’s face with traits changed (18%), of whom 8% were still alive and 10% were deceased; (c) an unknown person (28%); (d) an archetypal face, such as that of an old woman, a child, or a portrait of an ancestor (28%); (e) an animal face such as that of a cat, pig, or lion (18%); (f ) fantastical and monstrous beings (48%). ”

You will notice that these percentages sum to more that 100% and so the images in the mirror may have gone through more that one transformation.

Under this situation of prolonged staring at a central fixation, the perception of an object is expected to get weaker or vanish. This is not what happens with faces – in situations were an object should disappear, a face does not but instead is free to become another face. Here is another piece of evidence that perception of faces is very special and not like seeing other things. My way of looking at this illusion is that the object ‘face’ remains in place but the attributes bound to that face disappear in the prolonged fixed staring. Other attributes can then take the place of the original ones.

Interestingly the face in the mirror also loses its identification with the subject’s self and becomes a vision of another. Only the face remains – not the look or the identity. Face appears to be a powerful category, which is probably why we see them anywhere (clouds, cracks) and why we spend so much time looking at people’s faces (not feet or shoulders).

ResearchBlogging.org
Caputo, G. (2010). Strange-face-in-the-mirror illusion Perception, 39 (7), 1007-1008 DOI: 10.1068/p6466

Remember doing that?

ScienceDaily has a report on work by I. Lindner and others, Observation Inflation: Your actions or mine. (here) They examine the false memories that people have of actions that they did not do but watched someone else do.

Subjects were asked to do a number of things, simple tasks, and then were shown videos of others doing some of the same tasks as well as some different tasks. After two weeks they were asked to list what tasks they personally had done. And they were warned that it was likely that they might include tasks from the videos and they should try to avoid that. In spite of the warning, they had false memories of having done tasks that they only saw done by someone else.

Echterhoff says you shouldn’t worry that this happens all the time — but it’s worth remembering that your memory isn’t always reliable. “It’s good to have an informed doubt or informed skepticism about your memory, so you don’t just easily trust whatever comes to your mind as true and for granted.”

One explanation of these memories – in watching the videos, the subjects used mirror neurons to identify/understand/simulate the actions and these mirror neurons would have also been active if the subjects did actions themselves.

Without involving mirror neurons specifically, I can still see these false memories arising because the session was very motor performance oriented. The subject was asked to perform specific tasks and so they would be concentrating motor plans and programs. This was followed by videos that encouraged comparison of how a task was performed. In that context the novel tasks would likely be viewed not so much as visual scenes but as stimulated motor performances. In that context they would be more likely to feel owned by the subject when they were remembered.

Another step to understanding self

An open question in neuroscience is “How is the self, the ‘I’ constructed?” The more it is examined, the less simple the idea of the self becomes. There is more than one self for different purposes and the limits of these selves are variable depending on the circumstances. We do not notice these complications because normally our selves coincide, as we would expect. Our bodies can expand to include phantom limbs, fake rubber hands, tools and can shrink with various parts being disowned. There are illusions that affect where we believe we are in space. We can also be fooled to accept actions that are not done by our bodies and not accept ownership of actions that are ours. Menzer and group have investigated a specific illusion: how the timing of footfall sounds affect the feeling of ownership of those sounds. Are the sounds part of the whole experience of walking or do they sound like we are being followed by someone else?

In Menzer’s experiments, subjects walked freely around a course while wearing earphones over which they heard their own foot steps with different delays. They were asked to indicate whether the footsteps were theirs. The walking speeds, auditory delays and agency judgments were recorded.

Confirmatory gait agency judgments (the percentage of “yes” responses) in the experiment decreased rapidly for delays > 120ms and reached a first minimum at 400-500 ms. This is very similar to other reported experiments for various motor tasks and visual as well as audio action signals. This is surprising because the time resolution of auditory and visual systems in different. We can order sounds with an accuracy of about 20ms but agency judgments (both visual and auditory) have values of about 100-200ms. This implies a single mechanism for all the senses – a “who” system. They show that the control of full-body locomotion and the building of a conscious experience of it are at least partially distinct brain processes.

Abstract: A fundamental aspect of the “I” of conscious experience is that the self is experienced as a single coherent representation of the entire, spatially situated body. The purpose of the present study was to investigate agency for the entire body. We provided participants with performance-related auditory cues and induced online sensorimotor conflicts in free walking conditions investigating the limits of human consciousness in moving agents. We show that the control of full-body locomotion and the building of a conscious experience of it are at least partially distinct brain processes. The comparable effects on agency using audio-motor and visuo-motor cues as found in the present and previous agency work may reflect common supramodal mechanisms in conscious action monitoring. Our data may help to refine the scientific criteria of selfhood and are of relevance for the investigation of neurological and psychiatric patients with disturbance of selfhood.

 

ResearchBlogging.org
Menzer, F., Brooks, A., Halje, P., Faller, C., Vetterli, M., & Blanke, O. (2010). Feeling in control of your footsteps: Conscious gait monitoring and the auditory consequences of footsteps Cognitive Neuroscience, 1 (3), 184-192 DOI: 10.1080/17588921003743581

Keeping an open mind

I am trying to keep a small field of inquiry in this blog – just consciousness and mostly from a scientific point of view. Of course, this ignores a lot of very interesting material, but it is consciousness that is most puzzling. I am also trying to keep as open a mind on the subject as possible. By open mind, I mean open scientific mind; there are limits to my open-mindedness. I really have very little interest in ideas that are not based on careful observations. (Even poetry is based on careful observation.) I also avoid ideas that are not about the physical world.

Keeping an open mind always takes some effort. My rules of thumb are:

  • Avoid semantic differences. It is easy to misunderstand and reject ideas that use words that have been defined in a different way than I am used to. The word ‘mind’ illustrates this. I separate consciousness from cognition and thinking from awareness. And I associate the word mind with thinking/cognition and not with consciousness/awareness. Thus when someone uses a phrase like ‘conscious mind’ I have a problem with exactly what they mean. I have to decide from the context and the other ideas they put forward whether that are talking about consciousness, cognition or a combination of these. I don’t want to reject an idea out of hand because they use words differently than I do.

  • Don’t set a lot of store in individual reports. It is not a linear chain of evidence that is convincing but a strongly woven fabric of evidence. If something is shown by a number of different researchers using different tools, methods, situations and subjects, than it is robust. Something shown by a single observation is extremely fragile. The more involved the set-up (as with various scans) the more fragile the results. When a couple of different scan types, EEG, some animal neuron recordings and some anatomical/chemical observations all point in the same direction this is real data as opposed to a single scan.

  • Be careful about what causes what. When two events are correlated that does not mean that the earlier event causes the later one or that the logically simpler causes the more complicated. The arrow may be in a counter-intuitive direction or both events may be caused by a third. The consciousness of will is an example. We can be relatively sure that the desire to move causes the preparation to move causes the movement. But we cannot be sure that our consciousness of desire, intent and action have any causal relationship with each other. In fact it is more reasonable given present data to assume that they do not. We are almost forced to think that desire, intent and action enter consciousness independently with variation in strength, accuracy, and timing, with no direct causal relationship between their conscious appearance.

  • Watch out for other agendas. Sometimes an explanation or description seems to be about consciousness but is really about something else – a dispute in philosophy, politics, sociology, linguistics, religion, computer science etc. It is a lot easier to notice someone else’s agenda then my own. My refusal to treat any part of mental activity as non-physical is a form of bias that I recognize in myself and do not intend to ‘correct’. On the other hand, my separation of consciousness and cognition is somewhat tentative. I could accept the idea of conscious cognition even though I have never experienced it first hand. I have never felt I was aware of the cognitive wheels turning, so to speak, as opposed to receiving the ‘brief summary’. So I am extremely suspicious of conscious cognition but do not reject it out of hand.

  • Be aware that a completely new way of looking at the data is possible. There are scientific revolutions and people do not see them coming. I think that consciousness is ripe for a revolution, but I am sure I have not guessed the shape of the ‘great new theory’.

  • Never trust a single idea because it is self-evident. Even ideas that look obviously true need evidence. For example introspection is not what it seems when examined with careful experiments.

Lamme model – less emphasis on introspection

According to Victor Lamme, the reason that the study of consciousness is so difficult is that it gives priority to introspection and behaviour so, as a result, we are fooled into thinking that we know what we are conscious of. By adding evidence from neuroscience into the mix, he hopes to understand consciousness. He looks at the components of what we call consciousness and teases them apart: the phenomenal experience, the behavioural control, the access to the experience/ability to report it, the working memory, the attention focus. Then he asks what neural events match which aspects of consciousness.

Vision is the sense that Lamme uses to explain his model. The first cut is made between the iconic memory and working memory. The iconic image has more detail, is short-lived and overwritten by a change of scene, is not useful to cognition; while the working memory image has limited detail, can last for some time and is not overwritten by new events, is useful to cognition. The parts of the iconic image that become part of the working memory are those few which are attended to – so this cut can also be seen as consciousness with attention verses consciousness without attention.

Consciousness is then divided into stages using the neural events associated with consciousness. These events are the fast feedforward sweep (FFS) and the recurrent processing (RP). In the FFS, information flows from the visual cortex forward through the dorsal and ventral paths to the motor and frontal cortex area. This sweep starts with purely visual processing and ends with motor and executive processing. In RP, information flows out horizontally in each area and flows back to lower levels, as far back as the original visual cortex. In other words, there is a bottom-up stream followed by a sidewise and top-down spread.

Lamme’s stages are:

Stage 1 – Superficial processing during the FFS. Processing stops at the visual areas if a stimulus is not attended to and is also quickly overwritten by a masking image.

Stage 2 – Deep processing during the FFS. If stimulus is attended to but is quickly overwritten the result is that processing reaches the prefrontal and motor areas but remains unconscious.

Stage 3 – Superficial processing with RP. If the stimulus is not masked and has time to evoke RP but is not attended to or is neglected (inattentional blindness, change blindness, attentional blink), the FFS does not travel far but is followed by RP in the area it has managed to reach.

Stage 4 – Deep or widespread RP. If the stimulus has time for the FFS to travel fully forward and is attended to, the RP will span all levels from original visual to executive areas. This consciousness can be reported.

With this four stage model, Lamme labels Stages 1 & 2 as not having consciousness, Stage 3 as iconic representation and Stage 4 as working memory representation. The travel of the FFS forward is associated with attention and the spread of RP is associated with phenomenality.

Lamme argues that the inclusion of neuroscientific evidence is important.

“My main objection is against a form of cognitive psychology where mental constructs are taken as undeniable truths to which neuroscience has to be fitted. I would argue that in the study of consciousness, there are no undeniable truths.

That is the standard approach in science. Intuition told us the sun revolves around the earth, while in fact it is the other way around. Intuition dictated creation, where evolution is the counterintuitive scientific answer. To make scientific headway in our science of consciousness, we need to acknowledge that our intuitions may be wrong and need to be set aside. The upshot is that – finally – we may start solving the questions that have been bothering us for the ages.”

What a breathe of fresh air to have introspection taken off its pedestal!

I have my own list of what explanations of consciousness should address and Lamme touches most of them. My disappointment is the sparse mentions of the role of the thalamus and the nature of synchronous activity as well as the lack of a mention of the apparent projection into the near future of the representation of moving objects.

 ResearchBlogging.org
Lamme, V. (2010). How neuroscience will change our view on consciousness Cognitive Neuroscience, 1 (3), 204-220 DOI: 10.1080/17588921003731586

Worms and us


ScienceDaily reports on a recent paper in Cell by R. Tomer and group (here) looks at the similarities between the vertebrate cortex and the mushroom bodies in insects and marine worms.

He developed a new technique, called cellular profiling by image registration (PrImR), which is the first to enable scientists to investigate a large number of genes in a compact brain and determine which are turned on simultaneously. This technique enabled Tomer to determine each cell’s molecular fingerprint, defining cell types according to the genes they express, rather than just based on their shape and location as was done before.

Using this new method, they found similarities that imply an evolutionary common ancestor (rather than independent evolution) of mushroom bodies and the pallium (cerebral cortex). The common ancestor would be living about 600 million years ago.

As well as having the similar cell types, developing in a similar way, it is interesting that mushroom bodies and palliums have similar functions.

This ancestral structure was likely a group of densely packed cells, which received and processed information about smell and directly controlled locomotion. It may have enabled our ancestors crawling over the sea floor to identify food sources, move towards them, and integrate previous experiences into some sort of learning.

It appears that the general pattern is: taking in sensory information and integrating it in sensory-associative areas, using this ‘perception’ to orientate movement, and learning/remembering its environment. This part of various brains is a good candidate to product whatever amount or degree of consciousness the animal possesses.

Cognitive science and Neurobiology


What use is philosophy to science, or science to it? Paul Thagard thinks they have something important to offer one another, especially in the field of cognitive science. What philosophy offers science is a perspective on questions of theory, explanation and evaluation that allow scientists to think about these areas rather than just carry into their work implicit, unexamined, old philosophical notions. What science offers philosophy is a constraint on the possible theories that can be defended. Here is the abstract of a 09 paper (pdf here).

Contrary to common views that philosophy is extraneous to cognitive science, this paper argues that philosophy has a crucial role to play in cognitive science with respect to generality and normativity. General questions include the nature of theories and explanations, the role of computer simulation in cognitive theorizing, and the relations among the different fields of cognitive science. Normative questions include whether human thinking should be Bayesian, whether decision making should maximize expected utility, and how norms should be established. These kinds of general and normative questions make philosophical reflection an important part of progress in cognitive science. Philosophy operates best, however, not with a priori reasoning or conceptual analysis, but rather with empirically informed reflection on a wide range of findings in cognitive science.

Cognitive science is interdisciplinary – a collaboration in their areas of overlap of Philosophy, Linguistics, Anthropology, Neuroscience, Artificial Intelligence and Psychology according to Thagard. The disciplines have their own historical notions of what a theory looks like, and an explanation or evaluation. They deal with different levels of hierarchy from social to molecular. This is not unusual. Biology, itself, spans the hierarchy from the ecosystem to the molecular. Each biological science has its own theories, methods and ways of thinking but each does try to fit comfortable between the levels below and above their own. Physics has layers in harmony from particles to the cosmos. Cognitive science has not yet found that comfort.

My aim in this paper is to show that philosophy is essential to the interdisciplinary study of mind, but not for the reasons that many philosophers assume. Philosophy does not provide foundations for cognitive science and is incapable of generating the a priori truths that many philosophers have sought. Philosophy is not the queen of the sciences. Nor does philosophy have a special role in clearing up conceptual confusions about the study of mind, as this alleged role misunderstands the nature of concepts.

Along with many interesting ways he feels philosophy can be of use to cognitive science, he looks at the causal relations relations as they appear to various players.

A. reductionist: molecular – explains neural – explains psychological – explains social

Reductive reasoning is the normal sort of scientific explanation in other areas of science but has become a no-no in some cognitive science circles. Thagard is generous to those that bad-mouth reductionism but I wonder if a scholarly enterprise that does not accept a reductionist approach can be called a science.

B. downward: social – explains psychological, but neural and molecular are ignored

This is basically an anti-science approach and holds that the study of cognition is not concerned with the working of the brain. Perhaps it is an extreme post-modern stance.

C. autonomy: social, psychological, neural and molecular are three independent explanations

    This is completely non-reductionist. Thagard believes it is motivated by two things: an attempt to protect psychology from encroachment, and making cognition more general for robotics and AI.

    D. interactive: molecular – explains neural – explains psychological – explains social – explains molecular in a circle.

    Thagard does not want to call this reductionist although it would certainly be recognized as home to most reductionists. It may be that it is necessary for him to not label himself with the taboo name.

He is very even handed but I am afraid that I am not so generous, no doubt because of recent conversations with a artificial intelligence person and on the other hand someone with a postmodern outlook. I was becoming very puzzled by how two people who professed to be extremely interested in thinking, cognition and mind, had no interest in neurobiology. If we are to understand thought and consciousness then it will be through science, Neurobiology especially.