TEMPERATURE REGULATION "CENTERS" 
DISCUSSION 
DR. STUART: Is it true that the posterior hypothalamus is out- 
side the dipole field generated by the prepyriform cortex? 
DR. FREEMAN: Excuse me. It does extend into that area. 
DR. STUART: I thought you showed its most posterior aspect 
as anterior to the posterior hypothalamus. 
DR. FREEMAN: That is somewhat different. It is mixed there 
with another field. 
DR. STUART: There is no perceptible disturbance of tempera- 
ture regulation in cats with the prepyriform cortex ablated. Could 
it be that the activity you recorded in the hypothalamus with macro- 
electrodes was masking the unitary activity of small hypothalamic 
cells whose activity is related to temperature regulation? 
DR. FREEMAN: If such activity exists, yes, but one would have 
to prove that it exists. This is precisely what we were looking for 
by means of various types of recording. I did not find it. I do not 
know of anybody else who has. I know several people who looked 
but were unable to find anything definite. This applies not only to 
EEG waves, but also to unit activity, which we also inade a serious 
attempt to find, and could not. We could find action potentials, but 
they came from other structures such as the optic tracts. In other 
words, they stopped and started with the opening and closing of the 
eyes, and, therefore, were irrelevant to this area. As far as I could 
find to date, this structure is electrically silent. I would hope that 
Dr. Hensel would be able to modify his techniques for recording C 
fibers to record from small cells in that area, since there are cells 
there and they can be presumed to generate electrical activity; but 
before you can say it is being masked, you have to know whether it 
is there. I have not been able to see it; as far as I am concerned, 
we cannot yet say that it exists. 
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