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JAM



Posts: 503
Joined: July 2007

(Permalink) Posted: Sep. 23 2007,11:54   

Quote (Thought Provoker @ Sep. 23 2007,10:20)
from the peer reviewed paper  Orchestrated Objective Reduction of Quantum Coherence in Brain Microtubules: The "Orch OR" Model for Consciousness

TP, let me explain some of the silliness in this paper:

   
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Several types of studies suggest cytoskeletal involvement in cognition.

What Penrose omits is the fact that the evidence supporting the involvement of the ACTIN cytoskeleton is an order of magnitude greater than the evidence supporting the involvement of the MICROTUBULE cytoskeleton.

This alone trashes Penrose's credibility in my eyes.

   
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For example long term potentiation (LTP) is a form of synaptic plasticity that serves as a model for learning and memory in mammalian hippocampal cortex. LTP requires MAP-2, a dendrite-specific, MT-crosslinking MAP which is dephosphorylated as a result of synaptic membrane receptor activation (e.g. Halpain and Greengard, 1990).

But what else does it require? Penrose doesn't say, and you aren't reading carefully enough to be skeptical.
   
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In cat visual cortex, MAP-2 is dephosphorylated when visual stimulation occurs (Aoki and Siekevitz, 1985).

Is that a cause or an effect, TP? Is this provoking any thought in your head?
   
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Auditory Pavlovian conditioning elevates temporal cortex MAP-2 activity in rats (Woolf et al, 1994). Phosphorylation/ dephosphorylation of MAP-2 accounts for a large proportion of brain biochemical energy consumption (e.g. Theurkauf and Vallee, 1983) and is involved in functions which include strengthening specific networks, such as potentiating excitatory synaptic pathways in rat hippocampus (Montoro et al, 1993).

This is trivial relative to the known roles of CaM kinase II, receptor phosphorylation, and receptor trafficking in LTP. Only the last of these (one of the things we study) is known to have any dependence on MTs, and the role of MTs and MAPs may still be constituitive.
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The mechanism for regulating synaptic function appears related to rearrangement of MAP-2 connections on MTs (Bigot and Hunt, 1990; Friedrich, 1990)

Think, TP. "Appears related...," is sufficiently convincing to someone who has the audacity to call himself "Thought Provoker"?

I suggest that you read some LTP reviews from folks in the LTP field and look at the primary literature cited. Very little of it has to do with MTs or MAPs.

  
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