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qetzal



Posts: 308
Joined: Feb. 2006

(Permalink) Posted: Sep. 25 2007,00:23   

Quote (JAM @ Sep. 24 2007,23:51)
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Disruption of intra-neuronal cytoskeletal structures impairs cognition, such as tangling of the tau MAP linking MTs in Alzheimerís disease (Matsuyama and Jarvik, 1989, Iqbal and Grundke-Iqbal 2004).

This is an irresponsible case of stating hypothesis as fact. It's not yet known whether the plaques and NFTs of AD cause cognitive impairment or are the effects of a more subtle mechanism that causes cognitive problems. It's one of the major issues in AD research, and claiming that it is already solved is ludicrous.

Hameroff seems to do that rather a lot. Consider this claim:

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To gauge how single neuron functions may exceed simple input-output activities, consider the single cell organism paramecium. Such cells swim about gracefully, avoid obstacles and predators, find food and engage in sex with partner paramecia. They can also learn; if placed in capillary tubes they escape, and when placed back in the capillary tubes escape more quickly.


A quick PubMed search suggests this is arguable at best:

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Behav Neurosci. 1994 Feb;108(1):94-9.

Is tube-escape learning by protozoa associative learning?

Hinkle DJ, Wood DC.

Department of Behavioral Neuroscience, University of Pittsburgh, Pennsylvania 15260.

The ciliate protozoa, Stentor and Paramecium, have been reported to escape from the bottom end of narrow capillary tubes into a larger volume of medium with increasing rapidity over the course of trials. This change in behavior has been considered an apparent example of associative learning. This decrease in escape time is not due to a change in the protozoa's environment, their swimming speed, frequency of ciliary reversals, or the proportion of time spent forward or backward swimming. Instead, most of the decrease results from a decrease in the proportion of time spent in upward swimming. However, a similar decrease in upward swimming occurs when the task is altered to require escape from the upper end of the capillary tubes. Because the protozoa exhibit the same change in behavior regardless of the reinforcing stimulus, tube-escape learning is not associative learning.

PMID: 8192854


Skimming through some of the links on Hameroff's site, he seems to repeatedly oversimplify unsettled questions in ways that conveniently fit his preferred hypothesis. As one more example, he states that gaseous anesthetics work by binding to hydrophobic pockets in proteins, and argues that this supports his model of superposition of states in tubulin. Here again, a quick search suggests that this is just one possible model of how such anesthetics work.

None of this is actual evidence against Hameroff's claims, of course, but I'm always more suspicious of someone who's willing to employ such dubious arguments.

  
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