yan king yin <y.k.y(at)lycos(dot)com> wrote in message news:9e5qij$cle2 at imsp212.netvigator.com...
> "maxwell" <mmmaxwell at hotmail.com>:
>> >> [Babies] display the full spectrum of behavior. Then the feedback of
> >> emotions / drives etc causes "bad" circuits to be eliminated.
> >
> > Your evidence?
>> This is just a vague idea where alot of work is needed to make it more
> substantial...
Okay. Realize "full spectrum" needs a trim, for starts. <g>
>> I gave one example where a person needs sleep after great expectations
> followed by disappointment: During the "generative phase" (eg Bob
> thinks that he has won the lottery) the brain is "wired-up" by an
> additive process. In the "eliminative phase" (Bob finds out he's made
> a mistake) the previous circuits have to be eliminated (which i suggest
> is done during (?slow-wave?) sleep).
Seems improbable in respect to episodic memories, though there's been
a relation claimed between SWS and procedural (as in implicit) memory.
>> The generation of new circuits may be achieved by synaptogenesis or by
> birth of new neurons (though the latter is rare in post-natal CNS).
Also, by modifying the strength of already-existent synapses, and also
by local action of neuropeptides. Hmm, well, there's a few more.
>> >> (Postnatal brain development is characterized by a "rise and fall"
> >> pattern, eg total number of synaptic connections plotted against age.
> >
> > _Prenatal_-- by postnatal the declining function is prevalent, though
> > not in all CNS regions-- some are still on the upslope.
>> Yes... but the overall trend could be a result of both additive and
> eliminative processes.
Sure.
>> >> ie a feedback loop in multiple dimensions of love/hate/fear/etc/etc.
> >
> > Evidence?
>> On the one hand this statement is almost self-evident -- eg how kids
> learn to walk (by trial and error), or in language acquisition (by
> rewarding imitation), etc. The question is whether we can find the
> physical correlate of such a feedback mechanism:
>> ie brain circuits generated randomly and subsequently eliminated/
> stabilized by molecular signals that are correlates of "emotions".
There's quite a lot of evidence of correlation between emotional experiences
and memory formation; however, that doesn't mean the memories are necessarily
veridical ones.
>> From the evolutionary perspective it is quite plausible that cognitive
> function is achieved through feedback mechanisms, since it has the
> advantage of being 1) completely flexible, and 2) economical in terms
> of number of genes required to "code" it.
As to #1, not completely, and as to #2, most assuredly so.
>> >> ...when one experiences great expectations followed by great
> >> disappointment, one usually does not adjust to it immediately, but
> >> has to "sleep it off".
> >
> > Presumably, in the self-same armchair from which you hypothesize?
>> go back to YOUR seat and calm down! =)
I'm entirely calm, thanks! ;~)
However, 'tis not from the armchair.
>> >> So maybe the brain is trying to rewire itself during sleep.
> >
> > Some support for this, but note that though hippocampal theta waves
> > are most noticeably present in sleep, they are not absent in wakeful
> > states, especially subsequent to perceptions of novel stimuli/circumstances.
> > Frankly, the 'restorative/reorganizational' notion of sleep functionality
> > has _some_ merit-- but surely fails to explain the ubiquity of sleep, or
> > the wide cross-species and intraspecific variation in sleep stages, and
> > absolute durations of sleep.
>> 1. What do theta waves represent? I dont know much about them except
> that they characterize various levels of wakefulness.
For the purposes here, they are the frequency at which long-term-potentiation
of hippocampal synapses is observed.
>> 2. If sleep is a process of reorganization, then surely all organisms that
> has a complex CNS need sleep (in order for adaptive behavior to occur).
Presuming it is the only process, that would be true.
>> >> If the Hebbian view is correct, ...
> >
> >Which Hebbian view?
>> Hebb proposed in 1949 that "excitatory synapses are stabilized when they
> successfully trigger action potentials in the postsynaptic cell". That
> formed the basis of the Hopfield (1982) learning rule, for artificial
> neural networks. Recently the discovery of NO and canabinoid (sp?) as
> retrograde signaling molecules might prove that the brain does make use
> of this type of learning rules.
That one. Good one.
>> Im suggesting that there might be generative/stabilizing/eliminative
> processes acting on the synaptic level, and they are mediated by molecular
> signals that correlate to our emotions. i think this hypothesis can give
> useful insight to cognitive behavior, modelling, and also be verified by
> experiments.
Sounds good.
>> Some claims:
>> 1. massive synaptic connections were generated randomly at some point
> (periodically (?during REM sleep?) or at birth).
Continually, though non-randomly, and for many months before birth.
>> 2. this "primordial soup" generates totally random behavior (eg the baby
> is not hungry, but it cries or kicks its legs everywhere etc).
The behavior is non-random-- quasi random is what is described here, and
it is an important distinction.
>> 3. molecular signals (whether intrinsic or extrinsic to the brain) are
> the correlates of emotions and drives. Such as availability of ATP or
> glucose, hormones, growth factors, etc.
Yes.
>> 4. synapses are stabilized/eliminated according to these signals.
Hmm. Let's say that these signals decidedly impact, but 'according to'
suggests determination-by-emotion, which, though it would delight
a slew of psychodynamicists, is not determined. Consider that many
traumatic experiences may cause PTSD, in which the person _can't_
forget what they'd wish to, OR cause amnesic 'repression.'
Apparently, we need to look at much more than the emotively driven
components of memory formation.
The effect of the signal *defines* the corresponding emotion as good/bad.
> The 2 things are equivalent. (From the evolutionary point of view,
> each neuron/synapse carries the burden to prove that it is good for
> the survival of the individual).
>> 5. higher cognitive functions are possible when "reward" signals can
> also be issued inside the brain, by complex networks of neurons that
> function like an endocrine organ.
Sure.
>> 6. when a certain behavior gets an adverse response (pain, fear, etc),
> all the recently generated circuits get "punished". That they dont
> get eliminated at once, allows for higher-order circuits to be
> established.
Hmm. Perhaps.
>> 7. this process goes on without the subject being conscious of it.
Sure. We do a lot of post-experiential processing quite unawares of
content.
> "Consciousness" emerges when enough molding has occured.
>> 8. memory might be a by-product of this process when elimination is
> spared for early established networks (just speculation!).
Thanks. <g>
>> well.. i admit this is all very imprecise. I'm digging up more info to
> elaborate on it. please give your comments as well!
Well, I've left a few, up-page.
>> >> there should be some "basic" emotions that form the "basis set" of more
> >> complex feelings. For example, the feeling of fear is somewhat similar
> >> to hunger and also to that of looking down from a tall building
> >> (a thing known as synesthesia).
> >
> > You totally misuse the word.
>> I was trying to say that sometimes "abstract" feelings could get mixed up
> with "gut" feelings. It does not qualify the use of "synesthesia" defined
> as the psychological disorder, but i think that word can be used in a
> broader sense.
Better not to introduce the imprecision. I'm curious how you relate the
phenomenology of altitudes to hunger. Sure, there's arousal in both,
but?
>> >> To answer the original question -- there is as yet no way at all, to
> >> stimulate the brain in any localized and noninvasive manner. When new
> >> techniques are available to do that, things might be alot different.
> >
> > This does not answer the original question, and your answer also reveals
> > your ignorance of trans-cranial magnetic stimulation. Also, why in the
> > world do you think that being able to locally stimulate the brain might
> > help you "read someone's mind?"
>> i think TMS has low spatial resolution and it is also somewhat invasive
> in that the subject feels an unpleasant pinch on the scalp. I think the
> diffusion of magnetic waves through the medium (brain) makes it very
> difficult to get high resolution. Maybe MRI techniques will provide a
> solution because there is much progress there.
Okay, but even if we were able to refine fMRI to a spatial/temporal resolution
as exacting as implantable arrays, how would that get us to being able to "mind read?"
>> Well, I'm more interested in understanding the mechanisms of cognitive
> function than to create the "mind-reading" machine. That is just too
> speculative from our standpoint at present. But, nothing is impossible =)
Well, since we started with dreams, I'll affrim that dreaming anything, whether
asleep or awake, is possible, but I'm of the belief that reading someone's
mind is not possible. However, I can't of course prove non-existence,
because non-observance is no proof.
-maxwell
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