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Archive for the ‘consciousness’ Category

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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Traumatic brain injury distorts the brainFrom time to time I receive emails from people who have relatives or other loved ones that suffer from a neurological or psychiatric condition. I respond to these the best that I can. Today, I'd like to share with you one such response. This is why neuroscience is important; it opens up a better understanding of diseases and treatments. Is your loved one suffering from a vegetative state – is he unconscious all the time, even though being awake – or is he in a minimally conscious state – actually emerging into awareness? Even worse: is he in a locked-in state – being fully aware but unable to communicate, and treated as unconscious?

The email below is anonymized in order to avoid identification. The text is otherwise unedited.

Hello, my name is RD. My 27 year old son, P was in a car accident 3 years ago. He was age 23 at the time of the accident. P suffered a traumatic brain injury. He now lives in a nursing home. In his medical records he is diagnosed as persistent vegetative state. I would call it minimally conscious state, especially these past several months.

We, his family have been very active in his life. I have searched everywhere I can think of for help, in-depth information, clinical trials, anything that may help him. He is aware of his surroundings. He is using his arms now, where 6 months ago he couldn't. He plays ball with his little girl. She was 5 months old when he had his accident. She plays pic-a boo with him. He smiles…especially when someone who he hasn't seen for a while comes to see him, his uncles for instance.

I am looking for someone to take interest in his condition, to see if he can be help. I just pray that someone will give him a chance. I know he has the potential to improve. We just need to be pointed in the right direction. Can you help or do you know who someone who can?

And here is my response:

Dear RD,

Thank you for your email and please excuse my much belated reply.

I am deeply sympathetic to your son's condition and your problem. We are all moved by these tragic accidents. Through my previous work as a clinical neuropsychologist, I have seen people suffering from the same condition that your son is now.

My own shortcomings to be of any serious help to you is that I am living in Copenhagen, Denmark. Although you do not mention explicitly, I think you are living in the US. The medical treatment of post-traumatic amnesia, ranging from coma through vegetative state and to minimally conscious states, is still being improved from day to day. In countries such as the US and Denmark the treatment should be similar, on average. However, there may be places that are more focused and knowledgeable on these cases.

On your feelings that your son is actually better than vegetative state, I would suggest trying to find professionals that deal with the diagnosis of these problems daily. You should always bear in mind four (opposing) facts:

  • Vegetative state patients display signs and behaviours that makes us think that they are aware, conscious and responding. However, if a patient is truly in a vegetative state these signs are automatic responses, and not signs of conscious mental life
  • Vegetative state is often misdiagnosed (publications by e.g. Steven Laureys in Belgium). Many patients are at a higher level of function, such as minimally conscious or locked-in
  • Although a diagnosis is set at vegetative state, the condition of a patient might still improve. The rule is often that that the longer a person stays in a coma or vegetative state the worse the diagnosis. Saying that, one should never lose hope. We do not fully understand the mechanisms behind loss of consciousness, and even less about the awakening from such states.
  • Should a person regain consciousness after a vegetative state, one should always remember that the loss of consciousness had a specific and dramatic cause. Although consciousness may be restored (even as episodes) the brain is often significantly damaged. The person might still be unable to speak, attend, see etc. Many psychological and cognitive functions may be severely distorted or non-functioning

You do not mention where your son's diagnosis has been set, or where in the US you live, but I will suggest some names below. Unfortunately, I have no personal correspondence with Fins or Schiff, but know them through the scientific literature I read. Steven Laureys I know a bit, but I would suggest going to Schiff or Fins first, or the place (university / hospital) they are situated.

Joseph Fins at the Center for Bioethics, Colombia University (homepage)
Nicholas D. Schiff at the Department of Neurology and Neuroscience, Weill Medical College of Cornell University (E-mail)

Steven Laureys (Belgium, for further US directions) at the Cyclotron Research Centre (E-mail)

I hope this could be of any help to you and your family.

Sincerely,
Thomas

References

Laureys S. (2005). Science and society: death, unconsciousness and the brain. Nat Rev Neurosci, 6(11), 899-909

Laureys S. (2005). The neural correlate of (un)awareness: lessons from the vegetative state. Trends Cogn Sci

Laureys S, Pellas F, Van Eeckhout P, Ghorbel S, Schnakers C, Perrin F, Berre J, Faymonville Me, Pantke Kh, Damas F, Lamy M, Moonen G, and Goldman S. (2005). The locked-in syndrome : what is it like to be conscious but paralyzed and voiceless? Prog Brain Res, 150, 495-511

Laureys S, Perrin F, Schnakers C, Boly M, and Majerus S. (2005). Residual cognitive function in comatose, vegetative and minimally conscious states. Curr Opin Neurol, 18(6), 726-733

- Thomas

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Synaesthesia is a rare condition where people experience some percepts as a different sensory modality than the one they normally belong to – e.g., numbers as colours, or tones as shapes. It is, thus, a positive (and rather bizarre!) syndrome, where an abnormal trait is present, not absent, in the affected person.

Synaesthetes clearly posses brains that are differently wired up than non-synaesthetes. It has been speculated by some neuropsychologists, such as V.S. Ramachandran, that the sensory areas of the synaesthetes' brains are connected in an abonormal fashion, such that, for example, signals normally destined for their number areas end up in the colour area.

Experimental work casting light on such hypotheses is finally forthcoming, and a lot of what is presently known has now been collected in the new issue (February 2006) of the journal Cortex. Edited by Jamie Ward and Jason Mattingley, it contains contributions by just about every researcher currently working on synaesthesia. And remember: Cortex doesn't require a subscription to access!

Reference

Ward, J. & Mattingley, J., eds. (2006): "Cognitive neuroscience perspectives on synaesthesia. Cortex, vol. 42, issue 2.

- Martin

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Becoming conscious of a visual input

Click on the image to see full size

What happens in the brain when we become conscious of something? What processes and structures are responsible for becoming aware? Is consciousness an either-or process or can we have in-between forms of perception?

We have recently attempted to put those questions into empirical terms. In a study that is now in press in NeuroImage, we asked subjects to report how clearly they saw visual stimuli. The stimuli were simple geometrical shapes (circle, square, triangle) that were presented at different durations, from approximately 16 msec to about 150 msec.

From a previous behavioural study, we have concluded that conscious perception is not an either-or, and that there are instances where subjects report having “vague” percepts. That is, some stimuli are experienced as “something being presented” withouth being able to determine what was presented. Detection without identification.

Question is, how does the brain work under these conditions? In this study we have showed that vague perception shares much of the same network of fronto-parieto-temporal and cortico-thalamo-cortical network as seen during conscious perception. However, we also identify some unique activity in the brain during vague perception, especially in the prefrontal cortex.

I’ll leave this news hanging in the air/ear (…) just for now. When the article is published, I will link to the PDF. I’ll leave it to Mark Christensen, the PI of this project, to put it in his own words. Take also time to look at the image below.

NOTE: Why is this research important to neuroethical consideations? First of all, it demonstrates that specific types of experience are closely related to what happens in the brain. It shows that questions about the mind can be asked — and answered — by neuroscience. And it strengthens our view that conscious vs. unconscious perception is not a clear dichomotic distinction. Rather, we need to make use of more elaborate ways to study reports of conscious perception. Finally, this finding strengthens models suggesting the necessity of a widespread brain network to support consciousness (see also this article, PDF). Knowing what it means to be conscious tells a lot about what it means to be human.

_/_/_/_/_/_/_/_/_/

Subjective reports of graded perception
by Mark S. Christensen
In an fMRI, which is to be published in NeuroImage, we have shown that subjective reports of perceptual clarity correlates with graded neural activation within a parietal, premotor, basal ganglia and frontal operculum network.

In a simple visual masking experiment, we asked subjects to report their subjective experience of perceptual clarity of masked visual stimuli on a graded scale ranging from no perceptual experience, over a vague/glimpse like experience, to a clear perceptual experience. This was done during an event-related fMRI experiment.
Within fronto-parietal-thalamic areas where the activity was increased for clear perceptual experiences compared to no perceptual experience, we found a network, where the activation varied in a gradual way, following the subjective report. Furthermore, we found areas in insula and frontal cortex outside the fronto-parietal-thalamic network, where the intermediate, fringe-state showed unique activation.
The results provide the first evidence of sensory fringe states, and that the subjective experience of conscious perception has a counterpart in graded neural activation. Furthermore, they strengthen the scientific value of subjective reports. Finally, we show that within a network for conscious perception that includes the parietal and premotor cortices, the subjective experience resides.

Reference:

Christensen MS, Ramsøy TZ, Lund TE, Madsen KH, Rowe JB (in press). An fMRI study of the neural correlates of graded visual perception. Neuroimage

The neural correlates of clearly perceived visual stimuli have been reported previously in contrast to unperceived stimuli, but it is uncertain whether intermediate or graded perceptual experiences
correlate with different patterns of neural activity. In this study, the subjective appearance of briefly presented visual stimuli was rated individually by subjects with respect to perceptual clarity: clear, vague
or no experience of a stimulus. Reports of clear experiences correlated with activation in a widespread network of brain areas, including parietal cortex, prefrontal cortex, premotor cortex, supplementary
motor areas, insula and thalamus. The reports of graded perceptual clarity were reflected in graded neural activity in a network comprising the precentral gyrus, intraparietal sulcus, basal ganglia and the insula. In addition, the reports of vague experiences demonstrated unique patterns of activation. Different degrees of perceptual clarity were reflected both in the degree to which activation was found within parts of the network serving a clear conscious percept, and additional unique activation patterns for different degrees of perceptual clarity. Our findings support theories proposing the involvement of a widespread network of brain areas during conscious perception.

-TZR-

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