97° 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



periodic stimulation of the hypothalamus in rats was 

 associated with increased drinking. 



There is usually some decline in metaljolism and in 

 general bodily activity in animals with lesions of the 

 ventromedial nuclei but not enough to account for 

 more than a limited portion of the positive food bal- 

 ance because the obesity can be controlled to a great 

 degree by restricted diet. If the lesions are sufficiently 

 extensive, there may also be gonadal atrophy. On the 

 other hand, with restricted lesions the gonads may 

 remain quite normal. It is of considerable interest 

 that very frequently these obese and hyperphagic 

 animals develop a state of 'savageness.' Appetite and 

 thirst are considered in Chapter XL\'II of this 

 volume by Brobeck. 



PATTERNS OF EMOTIONAL BEH.\viOR. It has long been 

 known that patients with lesions encroaching upon 

 the diencephalon occasionally have spells of senseless 

 crying or laughing unassociated with appropriate 

 subjective feelings. Neurosurgeons manipulating the 

 hypothalamic region in patients without general 

 anesthesia have noted manic outbursts. Stimulation 

 of suitable areas of the hypothalamus in unanesthe- 

 tized animals evokes an expression of rage accom- 

 panied by all the usual autonomic phenomena (74, 

 92) which quickly subside when stimulation ceases. 

 Such responses are most easily produced by stimula- 

 tion of the lateral hypothalamic area near the fornix. 

 Autonomic signs include pupil dilatation, horripila- 

 tion, and sometimes urination and defecation. It is 

 said that response patterns of this type do not become 

 conditioned, i:>ut there is recent evidence that animals 

 will attempt to avoid receiving stimuli of this type 

 (41). The response may be greatly reinforced if the 

 animal sees persons or objects at which it can be 

 directed and an actual attack may result. 



Somewhat similar, but almost paroxysmal, rage 

 reactions may be observed in animals after removal of 

 large areas of the forebrain. Such behavior develops 

 in response to innocuous external stimuli, is ill- 

 directed, subsides quickly and has been called 'sham 

 rage.' Again all the usual autonomic components 

 accompany the somatic response (12). The complete 

 picture of sham rage does not appear unless the pos- 

 terior part of the hypothalamus is intact. Incomplete 

 rage may, however, appearafter massive iiypothalamic 

 destruction in animals with intact forebrains. 



After relatively restricted bilateral lesions in the 

 region of the ventromedial nuclei, animals may be- 

 come extremely, chronically and incurably savage, 

 developing a malevolent attitude towards men and 

 other animals which is not unmixed with fear reac- 



tions (86, 172). During times of violent affective 

 response, all usual overt signs of autonomic discharge 

 are seen. When undisturbed, the activity level is sub- 

 normal. Animals with such behavior frequently show 

 gluttonous appetites as mentioned previously and 

 become very obese, but this is not an invariable corre- 

 late of the changed behavior pattern. 



VVe have here a situation in which loss of the fore- 

 brain and the presence of the hypothalamus predis- 

 poses to senseless rage responses to mild stimuli while, 

 on the other hand, appropriate lesions of the hypo- 

 thalamus in otherwise intact brains effect a complete 

 change in attitude and personality, typified by well- 

 directed defensive and offensive attitudes, and 

 crowned by the appearance of extreme anger with all 

 of its autonomic correlates. This pattern of disturbed 

 personality and behavior following restricted basal 

 lesions may be considered as a true organic psychosis. 



The locations of the mechanisms released by these 

 lesions have not been determined and the areas in- 

 volved may be extensive. Hunsperger (83) has found 

 that lesions of the periaqueductal gray matter prevent 

 the occurrence of the rage pattern in response to 

 hypothalamic stimulation. \Vhether this involves 

 simply a descending pathway for the total pattern 

 response is not clear. The rage and savageness asso- 

 ciated with ventromedial lesions has not as yet been 

 found to be prevented by lesions of the piriform areas 

 which ordinarily produce very bland and tame ani- 

 mals (149). Nor does administration of ataractic 

 drugs eliminate the savageness. It is interesting that 

 brain injuries in this region in man are often asso- 

 ciated with personality changes and swings of mood 

 between euphoria and depression, aggressiveness, 

 Korsakoff-like responses (140) and paranoid delu- 

 sions. The operation of prefrontal lobotomy for de- 

 pressed and withdrawn psychotic patients has been 

 in part predicated on release of hypothalamic influ- 

 ences from suppression exerted by the prefrontal 

 cortex. On this basis efforts have been made to oi)tain 

 similar results by producing bilateral lesions in the 

 dorsomedial thalamic nuclei in such patients (156, 

 176). It will be recalled that the latter nuclei partici- 

 pate in communication between the frontal lobe and 

 hypothalamus. 



If alterations in emotional behavior patterns can 

 result from disturbed hypothalainic-forebrain circuits 

 or from restricted lesions within the hypothalamus, 

 what happens to the emotional patterns if the hypo- 

 thalamus is destroyed or its descending efferent ele- 

 ments are destroyed or interrupted? In higher mam- 

 mals destruction of the hypothalamus produces a 

 somnolent, semicomatose animal with profound lack 



