TEMPERATURE REGULATION "CENTERS" 
DR. FREEMAN: I guess if we could afford it, we would be a 
twenty-five-channel thinker. 
DR. CLARK: I have one comment. You brought up the question 
of plasticity. Now, plasticity to me is a good deal like the spread 
of current. One may use spread of current to explain why the other 
man got results different from yours. Plasticity is to me just a 
recognition of lack of knowledge. For example, if you take out the 
motor cortex in a cat, and wait about ei^t months, he behaves 
quite normally. You do the same thing with a chimpanzee and eight 
months later he will still have the same paralysis that he began 
with. If you do it with a spider- monkey, the paralysis remains. 
Now, if you explain the return of functioning in the cat by invoking 
the term "plasticity", why does it not occur in these other two 
species? 
DR. FREEMAN: I take it that this is a rhetorical question? 
DR. CLARK: It is. And the same is true of the posterior 
columns. You damage those and the damage is apparently permanent, 
but as all of you clinicians know, the operation for relief of pain is 
not uniformly successful. If you invoke plasticity to explain the 
return of pain, why does function not return in the posterior 
columns? I think as far as return of shivering in those animals is 
concerned, there is a question of the probability of hitting a cell or 
a fiber. Where there is a fair collection of theiii this is easy, but 
when they are scattered throughout a large area, the probability of 
hitting enou^ of them becomes much less. 
DR. FREEMAN: I quite agree. It is a term to describe essen- 
tially the recovery process, but it does no more than show that we 
do not know what it is. 
DR. CLARK: It is worse than that, because when you invoke 
the term plasticity, you assume then that there is no localization, 
no permanent localization. 
DR. FREEMAN: I agree it is a loose term that one could take 
to mean that, but I would not go that far. 
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