STUART, D. G. 
lay the groundwork for an eventual neurological explanation of 
Gressler and Hansen's (1927) report of the activation and suppression 
of shivering by hypnotic suggestion and the Russian work, recently 
reviewed by Bykov (1957), that has illustrated classical Pavlovian 
conditioning of temperature regulatory responses. 
The suppression of shivering by ventrolateral posterior hypo- 
thalamic stimulation is in agreement with the previous work from 
our laboratory reported by Hemingway, Forgrave, and Birzis 
(1954). (See their Table I and Figure 2.) This locus is within the 
medial forebrain bundle's projection to and from the midbrain. It 
seems that stimulation of this locus evokes suppression of shivering, 
not via the anterior hypothalamus but via a level more caudal than 
the h3T)othalamus. This is because the intensity of stimulus neces- 
sary to suppress shivering during stimulation of this locus is not 
greater than that needed during anterior hypothalamic stimulation. 
Additionally, there are no known connections in the posterior hypo- 
thalamus between the ventrolateral and dorsomedial regions that by 
activation of the suppressive locus could result in attenuation or 
activity of dorsomedial neurons presumed on the basis of our exper- 
iments to be active during shivering. 
We have evidence of a second system of suppressive neurons 
that perhaps originate in the anterior hypothalamus and terminate in 
the posterior hypothalamus after dorsal periventricular passage. 
Stimulation of the most medial dorsal posterior hypothalamus sup- 
presses shivering with stimulus intensities greater than those 
necessary to stimulate the ventrolateral posterior hypothalamus. 
Since this dorsal region is within that whose activation produces 
shivering, there was a possibility that the stimulus was disrupting 
activity related to the production of shivering (Wedensky inhibition). 
This proved not to be the case in that stimulation of loci 0.25 
mm to 0.5 mm more lateral than the third ventricle augmented 
rather than suppressed shivering. Additionally, shivering could 
be suppressed at all loci within the dorsomedial posterior hypo- 
thalamus with 200 pulses/sec stimuli. Conversely, stimuli of 
25 to 100 pulses/sec augmented shivering at all dorsomedial loci 
except those immediately adjacent to the third ventricle. 
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