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Archive for the ‘consciousness’ Category

In an interesting paper in the latest version of Progress in Neurobiology, Yuri I. Arshavsky from UCSD writes about the epistemological dualism that exists in modern neuroscience. basically, Arshavsky claims that there is a covert dualism in the way that neuroscientists are treating mind-related topics, especially the study of “consciousness”. Indeed, as he claims:

This covert dualism seems to be rooted in the main paradigm of neuroscience that suggests that cognitive functions, such as language production and comprehension, face recognition, declarative memory, emotions, etc., are performed by neural networks consisting of simple elements.

This might initially sound a bit strange. Is not cognitive functions such as face perception due to operational simple elements? Face perception as such is a combination of many simple processes that operate in unison. So what is Arshavsky proposing? Indeed he suggests the existence of a certain kind of brain cells:

(The) performance of cognitive functions is based on complex cooperative activity of “complex” neurons that are carriers of “elementary cognition.” The uniqueness of human cognitive functions, which has a genetic basis, is determined by the specificity of genes expressed by these “complex” neurons. The main goal of the review is to show that the identification of the genes implicated in cognitive functions and the understanding of a functional role of their products is a possible way to overcome covert dualism in neuroscience.

So there should exist a subset of neurons that integrate information from a variety of input. This sounds strange, since all neurons integrate inputs from thousands of inputs, many from a large variety of inputs. So what are complex neurons? Here, we are told that:

(…) neural networks involved in performing cognitive functions are formed not by simple neurons whose function is limited to the generation of electrical potentials and transmission of signals to other neurons, but by complex neurons that can be regarded as carriers of “elementary” cognition. The performance of cognitive functions is based on the cooperative activity of this type of complex neurons.

In this way, complex neurons seem to be integrative neurons, i.e. cells that integrate information from a variety of processes. This could include the multi-modal neurons found in the functional sub-structures of the medial temporal lobe, such as the hippocampus, perirhinal, entorhinal and temporopolar cortex. But would it not mean the colour processing nodes in the visual cortex? Which IMO leads us back to a basic question: what is a functional unit in the brain. yes, the neuron is a basic building block of information processing in the brain. But what is special about language, memory and so forth in the brain?

It is possible that Arshavsky is not radical enough: what we should seek out is to avoid using generalistic and folk-psychological concepts in the first place. We should possibly not study “language”, “memory” or “consciousness”, since these concepts will always allude to fundamental assumptions of “language-ness”, “memory-ness” and “consciousness-ness”, IOW that there is something more to explain after we have found out how the brain produces what we recognize and label a cognitive function.

Maybe neuroscientists are not using a poor strategy after all? Maybe ignoring the past history of philosophy of mind is the best solution. I’m not sure (nor am I sure that I represent Arshavsky’s view properly). But how we choose to label a cognitive function depend on our past historical influence and learning, as well as our current approach.

-Thomas

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pvs.jpgIt’s all in the news these days. A man who has been in a coma (or is it “coma-like”, “almost coma” or what?) since a car accident in 1984 has now regained consciousness, and cognitive abilibties such as his speech. It’s already been written so much about this topic, but little is actually addressing the science. Often, the sensationalism is only covered. You can get them all by this simple google.

So why start writing about this here at BrainEthics? The story should have been covered by now? I think there are several reasons to address this story in a bit more detail, one of them being that the science, ethics and philosophical consequences are not – or very superfluously – noted. Another good reason is that the article describing this case has come out, and it’s available for free (PDF). Before we get to it, let me briefly let you know what I’d like to mention here:

  • the diagnosis – coma, vegetative state and related mental states are still very hard to tell apart, even to specialists
  • the development – much has happened to our knowledge about these states, but this knowledge has neither reached the general public, science writers nor always professionals dealing with these patients
  • the future – in addition to developments in traditional diagnosis, neuroimaging is already having a significant impact on our understanding on the relations and distinctions between these different states
  • the ethics – should we reach a scientifically valid model about states of consciousness the next step is to determine who is conscious and who is not – but still we are likely to ask “are our judgements correct?

The Diagnosis

If you are involved in a car accident and lose consciousness, the time from when you lose consciousness until you wake up is characterized by different stages where the brain’s level of functioning changes; from improved primitive reflexes to cognitive and mental restoration. A soon as you reach a state where you become aware of your surroundings, even the feeblest sensation, you have reach a state that is called post-traumatic amnesia (PTA). The person is conscious and appears responsive and they may even be able to talk to family members and medical staff, however after a short time, the person will forget all recollection of conversations and actions. The person will be disorientated and may not know the date, where they are, or why they are there.

The important discussion here is that we are discussing whether a person is conscious, or if he has any chance of becoming conscious again. A person in a coma is not conscious – he cannot be awakened, fails to respond normally to pain or light, does not have sleep-wake cycles, and does not take voluntary action. Coma is separate from vegetative state, in which the patient still has no cognitive neurological function or awareness of the environment. However, he has noncognitive function and a preserved sleep-wake cycle. Even more perplexing, the patient may exhibit spontaneous movements and he may open his eyes in response to external stimuli, and even track moving objects (or people) with his eyes. So why is this person not conscious? We know this from the fact that 1) he does not respond to verbal commands; 2) he shows no voluntary movements, only reflexes; 2) reports from people in this stage that have awakened show that they have had no experience. This, of course, is coupled to a variety of theory-bound measures of preserved vs. non-operative reflexes, and more recently neuroimaging.

What makes the diagnosis of coma and vegetative state so hard is that there are cases where patients show almost exactly the same symptoms as these conditions, only that they are aware. Patients in a minimally conscious state are indeed conscious, they may drift in and out of awareness, but they show signs of voluntary movement and communication. Terry Wallis is thought to be in this state, not coma, nor vegetative state. Another condition is locked-in syndrome, in which the patient is aware and awake, but cannot move or communicate due to complete paralysis of all voluntary muscles in the body.

The frequency of misdiagnosis of these patients has not been reviewed in full, but the fear is that it happens more often that we would like to. The misdiagnosis goes both ways: sometimes a patient is thought to be conscious while actually being in a persistent vegetative state. Other times – and this is the most problematic error – a patient that has some level of awareness (e.g. locked-in) is diagnosed with a coma or vegetative state.

The Development

How can we be so wrong about these patients? One reason is that we have just began to explore this field at the level of detail that we do today, incorporating better diagnostic tools and multi-modal assessment tools such as EEG, SPECT and MRI. A willingness to study consciousness, that mongrel concept that we still really don’t know what means, is another reason for the recent developments in this field. In all, our ability to distinguish between conscious and unconscious states has gone from a dichotomic distinction to a range of possibilities that are sometimes hard to distinguish.

This development is often the reason to the sensational awakenings that we can hear from time to time. News about a person regaining consciousness after 20 years from a coma (!) should be taken with a grain of salt. 20 years ago the diagnosis and distinctions to other (conscious) conditions was notas developed as today. So we should maybe think of this rather as a sensational awakening of the science surrounding these patients, not the patients themselves. That’s a bit harsh, but it is true that the conceptual and diagnostic improvements in this fueld has come through the past few years only.

The Future

What can we expect to happen in this field? First of all we can expect that neuroimaging tools will be used more. Today we can record EEG to exclude ideas about brain death; we use MRI images to see where in the brain we find lesions. But studies showing differences in the brain’s activity between these different patients have been emerging – see this article (PDF). The problem with these studies are that they are group studies. As I have argued previously, going from group study mean differences to the ability to identify individual differences – and diagnosing people on this ground – is not a straightforward thing. So tools needs to be developed that makes it possible to look at an individual scan to determine whether a person is conscious or not. As Steven Laureys from the University of Liège says:

Chronically unconscious or minimally conscious patients represent unique problems for diagnosis, prognosis, treatment, and everyday management. They are vulnerable to being denied potentially life-saving therapy….. This case shows that old dogmas need to be oppugned.

It should be noted that efforts are already being made for developing a “consciousness meter“. This stems from the finding of mid-operational awakenings; people undergoing surgery that are put into anaesthesia nevertheless wake up during surgery yet without the ability to notify others about their presence, often suffering pain as their sensations are restored. In other words; an induced locked-in syndrome. However, interesting as it has been it’s been hard to find any updates on the effectiveness of this apparatus. But we should probably think along these lines. Saying that, the consciousness meter suggested is based on EEG, and any measurement of a traumatised brain is bound to show different signals. That needs to be kept in mind.

What, then, about treatment? This is bound to follow the trace of our enhanced knowledge of these conditions. But what is interestig with the case of Terry Wallis is that he showed signes of rewiring of fibres in the brain. While these findings are in no way conclusive, they suggest that new intervention tools can be developed that focus on the regeneration of fibres in the brain. Not only general restitution, but maybe more focal, to the regions in which we have seen Wallis’ brain change (see changes in cerebellum, as indicated by white arrow below).

17103-singer-070506-brainscan.jpg

Diffusion tensor images of a brain at the first scan (left) and 18 months later (right). Color shows direction of white matter fibers, e.g., green for anterior-posterior fiber tracts. Large red area in second scan (arrow) shows what scientists think is growth of new neural processes in a part of the brain that controls movement. (Credit: Weill Cornell Citigroup Biomedical Imaging Center/Henning U. Voss.)

The Ethics

The growing knowledge about brain function and diagnosis of these cases should make us ask whether we are using the most up to date knowledge about these stages and states. Even more troublesome, spreading the knowledge to the entire world is a problematic affair, and even within the developed world. One thing is having an operational diagnostic system; an entirely different thing is seeing it implemented throughout the world. While the diagnosis of brain death is more or less universal across regions, cultures and religions, spreading the news about differential mental state diagnosis is only now beginning to spread. Hopefully, the use of evidence based medicine will provide the tools for such a knowledge dispersal.

Understanding that there is a tight relationship between the brain and the mind has a deep impact on our self-knowledge. Knowing how the brain works and breaks is a tale about yourself. It’s a direct relationship, not only a superficial association of flesh and mind. A loss of brain function is a loss of mental life (or part of it). All in all, the scientific study of unconscious states such as coma and persistent vegetative states are one part of the story that ties the brain and mind together tightly to a coherent picture of our minds as natural, biological phenomena.

-Thomas

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dennett.gifDan Dennett is interviewed by Robert Wright about his views on evolution and consciousness. Their views on evolution differ, especially with Wright's contention that evolution is goal-oriented in someway, and that history progresses in a predictable direction and points toward a certain end: a world of increasing human cooperation where greed and hatred have outlived their usefulness. All in the name of evolution — and game theory, that is. IMHO it's a lot of gibberish. Evolution is not teleology. It's a gross misunderstanding of the principles of evolution. I think Dennett does a nice job at pointing this out. Wright is not all ears, though.

On the second topic, consciousness, Wright and Dennett disagree profoundly. I'm not entirely sure whether Wright takes on the job as a Devil's advocate, or if he really means that epiphenomenalism is a logical possibility. I think the latter: Wright seems totally agnostic towards Dennett's thoughts. They simply won't penetrate Wright's mind.

If you listen carefully (with earphones, like me) you'll hear Dennett make a dozen sighs along the talk. I can understand why. It's a Sisyphean task to discuss these topics, and you're bound to run into people with the same scientific agnosticism or even atheism that hinders true progress in our understanding of topics such as evolution and consciousness.

You can find the interview here.

-Thomas 

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Update. If you haven't already noticed it, yesterday a reader posted a reply by Henry Stapp to Christof Koch's recent Nature article in the comments-section to my post on Koch's paper. I don't know if it is Dr Stapp himself who has graced our blog with a visit, but you should take the time to read through his rebuttal of Koch's arguments!

- Martin

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Our forthcoming article in NeuroImage is now available as an in press paper. Here is the info:

An fMRI study of the neural correlates of graded visual perception • ARTICLE
In Press, Corrected Proof, Available online 19 April 2006
Mark S. Christensen, Thomas Z. Ramsøy, Torben E. Lund, Kristoffer H. Madsen and James B. Rowe
SummaryPlus | Full Text + Links | PDF (1116 K)

You (or your library / institution) need to subscribe to the journal to download the article. If you can't download it, send me an email.

- Thomas

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I have a short review of the late Robert Solso's book "The Psychology of Art and the Evolution of the Conscious Brain" up at the excellent Science and Consciousness Review. Go check it out!

- Martin

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In the most recent issue of Nature (March 30) Christof Koch and Klaus Hepp offer a critique of theories, such as Roger Penrose and Stuart Hameroff's, that human consciousness invoke quantum principles. Most interestingly, they suggest a new thought experiment:

We challenge those who call upon consciousness to carry the burden of the measurement process in quantum mechanics with the following thought experiment. Visual psychology has caught up with magicians and has devised numerous techniques for making things disappear. For instance, if one eye of a subject receives a stream of highly salient images, a constant image projected into the other eye is only seen infrequently. Such perceptual suppression can be exploited to study whether onsciousness is strictly necessary to the collapse of the wave function. Say an observer is looking at a superimposed quantum system, such as Schrödinger’s box with the live and dead cat, with one eye while his other eye sees a succession of faces. Under the appropriate circumstances, the subject is only conscious of the rapidly changing faces, while the cat in the box remains invisible to him. What happens to the cat? The conventional prediction would be that as soon as the photons from this quantum system encounter a classical object, such as the retina of the observer, quantum superposition is lost and the cat is either dead or alive.This is true no matter whether the observer consciously saw the cat in the box or not. If, however, consciousness is truly necessary to resolve the measurement problem, the animal’s fate would remain undecided until that point in time when the cat in the box becomes perceptually dominant to the observer. This seems unlikely but could, at least in principle, be empirically verified. The empirical demonstration of slowly decoherent and controllable quantum bits in neurons connected by electrical or chemical synapses, or the discovery of an efficient quantum algorithm for computations performed by the brain, would do much to bring these speculations from the ‘far-out’ to the mere ‘very unlikely’. Until such progress has been made, there is little reason to appeal to quantum mechanics to explain higher brain functions, including consciousness.

The end of quantum theories of consciousness? Well, I suspect a rebuttal from Hamroff is forthcoming!
Reference

Koch, C. & Hepp, K. (2006): Quantum mechanisms in the brain. Nature 440: 611-612.

- Martin

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