The Survival of the Wittiest

Count Artby Count_Artblay at hotmail.com
Tue Jan 15 19:54:34 EST 2002


Anno Domini <2001>, verba <Count_Artblay at hotmail.com> hic et nunc in publicae
tabellae collectae , in foro <bionet.neuroscience>(et alii) atque :

Would anybody be so kind to mail or post here some authors
that wrote about "Science" on itself (like Karl Popper) :
I'm aiming 'what about' :

- Neurobiology - Chemistry
- the infinte - infinitecimal problem
- Modern Science after the Nuclear Discoveries

Thanks a lot,

>minsky at media.mit.edu (Marvin Minsky) wrote:
The real one ?
The one that said :" As often teachers only understand what they teach after
explaining it for the first time" ?
>> marko_amnell at hotmail.com (Marko Amnell) wrote: 
>
>> > HOW BRAINS THINK: THE EVOLUTION OF INTELLIGENCE 
>> > by William Calvin is a good exposition of the 
>> > "neural Darwinism" thesis by the man who coined 
>> > the term "Darwin machines". Occasional RAB contributor 
>> > Marvin "The Society of Mind" Minsky gets a mention in 
>> > a footnote for his 1994 Scientific American article 
>> > "Will robots inherit the earth?". 
>> 
>> I've put that on my home page at 
>> http://www.media.mit.edu/people/minsky/.  
>> Actually it's more about the prospects for human immortality.
>
>Thanks. _Consciousness: How Matter Becomes Imagination_ by 
>Gerald Edelman and Giulio Tonori is another good book on 
>Neural Darwinism. It's more comprehensive than William Calvin's 
>_How Brains Think_ (and even contains a few mathematical 
>equations). I believe Edelman actually was the first to propose 
>the Neural Darwinism hypothesis in the late 1970s. What is it? 
>Well, just listing a few principles doesn't explain much, but 
>this is how Edelman and Tononi introduce Neural Darwinism 
>(pp. 79-85):
>
>"In considering the origin of species, Charles Darwin made a 
>great contribution that centered on population thinking: the 
>idea that variation or diversity among individuals in a population 
>provides a basis for competition during natural selection. Natural 
>selection is reflected in the differential reproduction of fitter 
>individuals in a species. In principle, selective events require 
>the continual generation of diversity in repertoires of individual 
>variants, the polling by environmental signals of these diverse 
>repertoires, and the differential amplification or reproduction 
>of those repertoire elements or individuals that match such 
>signals better than their competition. Could it be that the 
>brain follows such principles? We believe it does, and in this 
>chapter we briefly review some aspects of neuronal group selection, 
>or Neural Darwinism. This theory embraces these selective principles 
>and applies them to the functioning brain. Its main tenets are
>
>(1) the formation during brain development of a primary repertoire 
>of highly variant neuronal groups that contribute to neuroanatomy 
>(developmental selection),
>
>(2) the formation during experience of a secondary repertoire of 
>facilitated neural circuits as a result of changes in the strength 
>of connections or synapses (experiental selection), and
>
>(3) a process of reentrant signaling along reciprocal connections 
>between and among distributed neuronal groups to assure the 
>spatiotemporal correlation of selected neural events.
>
>Together, the three tenets of this global brain theory provide a 
>powerful means for understanding the key neural interactions that 
>contribute to consciousness. ...
>
>This theory of neuronal group selection (TNGS), or Neural Darwinism, 
>has three main tenets ...
>
>1. Developmental selection. During the early development of 
>individuals in a species, formation of the initial anatomy of 
>the brain is certainly constrained by genes and inheritance. 
>But from early embryonic stages onward, the connectivity at the 
>level of synapses is established, to a large extent, by somatic 
>selection during each individual's ongoing development. For 
>example, during development, neurons extend myriads of branching 
>processes in many directions. This branching generates extensive 
>variability in the connection patterns of that individual and 
>creates an immense and diverse repertoires of neural circuits. 
>Then, neurons strengthen and weake their connections according 
>to their individual patterns of electrical activity: Neurons 
>that fire together, wire together. As a result, neurons in a 
>group are more closely connected to each other than to neurons 
>in other groups.
>
>2. Experiental selection. Overlapping this early period and 
>extending throughout life, a process of synaptic selection 
>occurs within the repertoire of neuronal groups as a result 
>of behavioral experience. It  is known, for example, that 
>maps of the brain corresponding to tactile inputs from the 
>fingers can change their boundaries, depending on how much 
>different fingers are used. These changes occur because 
>certain synapses within and between groups of locally
>coupled neurons are strengthened and others are weakened 
>without changes in the anatomy. This selectional process 
>is constrained by brain signals that arise as a result of the 
>activity of diffusely projecting value systems, a constraint 
>that is continually modified by successful output.
>
>3. Reentry. The correlation of selective events across the 
>various maps of the brain occurs as a result of the dynamic 
>process of reentry. Reentry allows an animal with a variable 
>and uniquely individual nervous system to partition an 
>unlabeled world into objects and events in the absence of a 
>homunculus or computer program. As we have already discussed, 
>reentry leads to the synchronization of the activity of 
>temporally coherent output. Reentry is thus the central 
>mechanism by which the spatiotemporal coordination of
>diverse sensory and motor events takes place.
>
>The first two tenets, developmental and experiental selection, 
>provide the bases for the great variability and differentiation 
>of distributed neural states that accompany consciousness. The 
>third tenet, reentry, allows for the integration of those states. ...
>
>It is important to emphasize that reentry is not feedback. Feedback 
>occurs along a *single* fixed loop made of reciprocal connections 
>using previous *instructionally* derived information for control 
>and correction, such as an error signal. In contrast, reentry 
>occurs in selectional systems across *multiple* parallel paths 
>where information is not prespecified. Life feedback, however, 
>reentry can be local (within a map) or global (among maps and
>whole regions).
>
>Reentry carries out several major functions. For example, it can 
>account for our ability to discern a shape in a display of moving 
>dots, based on interactions between brain areas for visual movement 
>and shape. Thus, reentry can lead to the construction of new 
>response properties. It can also mediate the synthesis of brain 
>functions by connecting one submodality, such as color, to another, 
>such as motion. It can also resolve conflicts among competing
>neural signals. Reentry also ensures that changes in the efficacy 
>of synapses in one area are affected by the activation patterns 
>of distant areas, thereby making local synaptic changes context-
>dependent. Finally, by assuring the spatiotemporal correlation 
>of neuronal firing, reentry is the main mechanism of neural integration.
>
>Since the formulation of the TNGS, considerable evidence to support 
>the theory has accumulated."
>
>Unfortunately, Edelman and Tononi are not very explicit about 
>the nature of this evidence. Does anyone know what is the best 
>current evidence in support of the hypothesis of Neural Darwinism?
>Or is there some crucial evidence against the theory? Can anyone
>recommend other good books on Neural Darwinism, for or against?
>Are there good articles or papers on the subject that are
>available on the world wide web? Thanks in advance.
>




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