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Introduction
Page 1
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Results
Pages 5 - 6 - 7 - 8 - 9
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Discussion
Pages 10 - 11
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References
Page 12
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Added figures
Pages 13 - 14 - 15
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Figures
Figures 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10
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2. Negative data from the hypothalamus.
It was surprising that no cells recorded from the perifornical and ventromedial regions of the hypothalamus responded specifically during affective defense, despite the fact that 15 cells were recorded from in these regions at sites where affective defense could be elicited by electrical stimulation. This is in contrast to the midbrain where 7 out of 21 cells recorded at sites where affective defense could be elicited by electrical stimulation responded specifically during affective defense. It is unlikely that the difference could be a statistical sampling error; the probability of obtaining both the above proportions from the same population is less than .02 according to a X² test.
If there are cells in the hypothalamus which mediate affective defense, perhaps they are fewer in number than the corresponding cells in the midbrain, or perhaps they are smaller in size and cannot be recorded by the technique used here. It is also possible that the hypothalamus is not involved in affective defense which is elicited by an attacking animal, but only in affective defense elicited by other conditions, such as frustration. What we know about the role of the hypothalamus in affective defense has been learned primarily from electrical stimulation which bypasses the use of natural eliciting stimuli. It has not been possible to abolish affective defense elicited by an attacking animal with lesions of the hypothalamus (8).
3. Other types of cells.
The most surprising results, in addition to those related to affective defense, came from the many cells in the hypothalamus and especially the ventromedial nucleus which stopped firing altogether whenever the cat was manipulated by the experimenter or distracted by repetitive sensory stimulation. Inhibition of firing rate has previously been obtained in the hypothalamus by experimenters observing anesthetized preparations (3), but the effects seen in this study are more complete, more consistent across various manipulations of the cat and present in a higher percentage of cells than has previously been indicated.
Most of the other data observed in this experiment have been described by many previous investigators. It is well known that many cells from the superior colliculus and region of the oculomotor nucleus respond to visual motion and many cells from the midbrain reticular formation respond especially to auditory stimuli. It is also well known that cells of the midbrain reticular formation respond to a variety of sensory modalities, and it has been pointed out that cells of this type may also be found in the hypothalamus (4). It was less expected, however, that cells from nucleus centralis lateralis of the thalamus should be particularly related to head turning.
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