On Fri, 6 Feb 2004 02:04:56 +0000 (UTC), kola9809{at}aol.com (Kola9809)
wrote:

>
>
>On Wed, 4 Feb 2004 06:18:25 +0000 (UTC) r norman wrote:
>
>>(Kola9809)
>>wrote:
>
>>>I will break down my question by trying to explain
"Why?" the information
>>for
>>>activation of melatonin genes is necessary, as well as
"Where?" and "How?"
>>is
>>>it generated.
>
>(I apologize for trying to summarize and not reproduce here our  previous
>discussion in their entirety.) 
>
>While it seems that both of us agree on the first question, as far as the
>second question goes: "Where does this information for activating melatonin
>genes in the pineal come from" my explanation was:
>
>>>The suprachiasmatic signal itself is the chemical output of processing in
>>the
>>>above-mentioned circuit of the electrical signal into which
retinal neurons
>>>have converted an external stimulus, the day-night (circadian) cycle.
>>>This conversion as well, is not a random process, but very specific and
>>results
>>>from a computational process taking place in those neurons. It turns an
>>>otherwise neutral stimulus intu a cue, an instruction for activating a
>>signal
>>>cascade that leads to specific gene activation for an adaptive phenotypic
>>>result.
>>>The processing takes place in the above mentioned neural
circuit and it is
>>the
>>>neural circuit that generates the information. Correct me if I'm wrong.
>
>Even though you neither directly address that question nor express any
>reservations on my response, you argue: 
>
>>So there are three kinds (at least) of information involved --
>>specificity of nerve pathways, neuronal signals, and cell responses to
>>stimulation.  Each of these is known in many details. 
>
>Even though I would consider the above elements of an "information
channel"
>rather than proper information, if I got it right, your statement implies that
>not one but three types of epigenetic information are necessary for expression
>of genes in the CNS ("specificity of the nerve pathways, neuronal
signals, and
>cell responses" are clearly not genetic information; only the sequence of
>nucleotides in the DNA is).
>
>As for the third question on how this epigenetic information is generated in
>the neural circuits, my response was:
>
>>>Experimental evidence shows that the chemical output, or information for
>>>activating genes in neurons is generated computationally, by processing
>>>internal and external stimuli according to a general model that
essentially
>>>comprises:
>>>-reception of internal/external signals by interoceptors/exteroceptors,
>>>-conversion of those stimuli into specific patterns of
electrical signals, 
>>>-reconfiguration of synaptic morphology of the neural circuit
and resulting
>>>change in the computational properties of the circuit, which
>>> changes  the electrical/chemical output of the circuit, leading to
>>>- specific activation/inactivation of target genes in neurons.
>>>
>
>Even though you do not address this question, I am indeed very interested to
>know your expert opinion on whether the above epigenetic mechanism is real or
>supported by neurobiological data.
>
Again I have trouble following your logic because I think we are not
thinking at all on the same line.

My impression is that you somehow think that there is a neural code
that tells a pineal cell "activate a melatonin gene" as opposed to a
different code that tells a pineal cell to do something else.  In
other words, somehow the neural circuit has to figure out (compute)
somehow just how to code a signal to activate a gene.

That is not the way it works.  When a melatonin secreting cell in the
pineal receives a nerve signal, any nerve signal, it secretes
melatonin and, if appropriate, also activates whatever genes are
necessary to synthesize melatonin.  That is simply the nature of the
cell.

When a muscle cell receives a nerve signal, it contracts.  When a
gland cell receives a nerve signal, it secretes.  That is simply the
way those cells are built.  There is nothing special about the
message.  Any old message will do.  That is, any message using the
same nerve transmitter and activating the same synaptic receptors.
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