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anhinga_anhingaRecently, I reread a number of papers in neuro. The one I liked the most is "Towards a Neurobiological Theory of Consciousness" by Francis Crick and Christof Koch in Seminars in the Neurosciences (1990), Volume 2, pages 263–275:
http://profiles.nlm.nih.gov/SC/B/C/F/D/_/scbcfd.pdf
*****
The "Crick-Koch Conjecture" is that the difference between conscious and unconscious processing is that in the conscious processing the relevant neurons fire in synch, producing (gamma) oscillations. Basically, the conjecture is that the temporal synchrony of the relevant action potentials is what creates a conscious sensation.
This is not the first time people were trying to link neural oscillations and synchrony with consciousness. However, whether this conjecture is right or wrong, after this paper it again became acceptable to address and study the issues of consciousness in the mainstream neuroscience. The reason is probably the combination of Crick's reputation (he achieved seminal breakthroughs quite a few times in his life) and of the fact that this paper is very well and clearly written. If someone wants to read one paper in theoretical neuroscience, this is probably the paper to read.
Crick and Koch remark that one does not need to formally define consciousness in order to study it: "Everyone has a rough idea of what is meant by consciousness. We feel that it is better to avoid a precise definition of consciousness because of the dangers of premature definition. Until we understand the problem much better, any attempt at a formal definition is likely to be either misleading or overly restrictive, or both."
*****
I hope the next year will be better than the outgoing one...
Good luck in the New Year!
http://profiles.nlm.nih.gov/SC/B/C/F/D/_/scbcfd.pdf
*****
The "Crick-Koch Conjecture" is that the difference between conscious and unconscious processing is that in the conscious processing the relevant neurons fire in synch, producing (gamma) oscillations. Basically, the conjecture is that the temporal synchrony of the relevant action potentials is what creates a conscious sensation.
This is not the first time people were trying to link neural oscillations and synchrony with consciousness. However, whether this conjecture is right or wrong, after this paper it again became acceptable to address and study the issues of consciousness in the mainstream neuroscience. The reason is probably the combination of Crick's reputation (he achieved seminal breakthroughs quite a few times in his life) and of the fact that this paper is very well and clearly written. If someone wants to read one paper in theoretical neuroscience, this is probably the paper to read.
Crick and Koch remark that one does not need to formally define consciousness in order to study it: "Everyone has a rough idea of what is meant by consciousness. We feel that it is better to avoid a precise definition of consciousness because of the dangers of premature definition. Until we understand the problem much better, any attempt at a formal definition is likely to be either misleading or overly restrictive, or both."
*****
I hope the next year will be better than the outgoing one...
Good luck in the New Year!
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no subject
Date: 2009-01-01 04:12 am (UTC)Интересно, кто из современных ловцов истины в этой области опирался на такую мысль, и был ли такой вообще...(кроме Хобсона, разумеется) ;-)
no subject
Date: 2009-01-01 04:25 am (UTC)Уж кто из них действительно опирается на идеи оттуда, это, конечно, так сразу не скажешь ;-)
no subject
Date: 2009-01-01 06:29 am (UTC)no subject
Date: 2009-01-01 03:48 pm (UTC)no subject
Date: 2009-01-01 05:17 pm (UTC)Happy New Year!
Date: 2009-01-02 03:38 am (UTC)that synchronizations are emergent phenomena
of the small cortical sub-networks:
http://am.livejournal.com/180054.html
this kind of synchronizations are manifested
in pathological brain states, (funcionally
similar to the highly synchronized epilepsy
induced (or influenced) by hippocampus).
no subject
Date: 2009-01-02 06:14 am (UTC)> synchronizations are emergent phenomena of the small cortical sub-networks
yes, I think everyone believes that synchronizations are emergent phenomena. I doubt that there is a uniform scale or type of neural tissue..
> this kind of synchronizations are manifested in pathological brain states
there are literally dozens, if not hundreds, of various synchronization modes in the brain; even if we consider a fixed frequency, we still have a great variety, both in models and in experiments (in slices and in vivo)..
Nancy Kopell told an impressive story about some of that variety a few years ago, and in particular, about a large variety of Gammas, here are some papers from her site:
http://cbd.bu.edu/members/nkopell.html
I don't think a unified point of view on this diversity of phenomena has many chances. Neither attributing this great variety uniformly to consciousness, nor attributing it all to pathology or to superficial phenomena seems reasonable; we do certainly know some synchronization modes which are pathological, and some might be superficial.. But it's virtually certain, that many of synchronization modes have cognitive significance of various kind..
I consider the Crick-Koch conjecture itself as more of a stimulating food for thought, as opposed to something likely to become "the True Theory". At the same time, many neurons do seem to behave as synchronicity detectors to some extent due to the tendency to relax to the rest state rather quickly, so I don't think the focus on synchronization is unreasonable..
no subject
Date: 2009-01-02 08:14 am (UTC)>I think everyone believes that synchronizations are emergent phenomena..
Not all types of synchronizations. People believed that slow-waves are driven by vigilance level rise served by feedbacks in thalamocortical loops:
http://www.jneurosci.org/cgi/content/short/13/8/3284
but today it is stil not so clear, what impact is provided 1) by the biochemical state changes in single neuron; 2) by cortical microcolumnar circuit dynamics.
Here are earlier discussions of gamma-range synchronizations origin:
http://www.jneurosci.org/cgi/content/short/16/1/392
- "coherence of fast spontaneous rhythms was spatially limited, being confined within a cortical column and among closely located neocortical sites."
The focus on synchronization is very reasonable, especially due the practical, pharmaceutical purposes. Synchronization plays an extremely important role in subcortical circuits functioning and their illness.
I agree that due to the diversity of cortical areas and their local architectures synchronizations may not necessarily drive the cortical dynamics to the totalitarian pathological states. What may allow the synchronizations to subserve some mechanisms of awareness and vigilance uprise.