

li wiiiii ii ik ill- pir. sii i| i >i;v 



NEIROPHYSIOLOCIY III 



pothalamic influences to the more primitive reticular 

 ai n\ ating mechanisms. 



The continuing emphasis upon hypothalamic 

 mechanisms in the development of neurophysiological 

 approaches to the experimental analysis of emotional 

 behavior has shown no diminution over the several 

 decades that have intervened since these early ex- 

 plorations. Subsequent efforts have provided con- 

 vincing evidence of the central but somewhat compli- 

 cated role played by hypothalamic portions of the 

 forebrain in the elaboration of affective phenomena. 

 The monumental studies of Hess and his collaborators 

 (152, 155, 1 81—183) have demonstrated the broad 

 range of emotional response patterns which can be 

 selectively elicited from discretely localized electrical 

 stimulation of carefully mapped diencephalic regions. 

 The behavior changes observed following such direct 

 stimulation of the hypothalamus have been com- 

 pared with alterations seen in emotional responses 

 of normal animals conventionally associated with 

 'fear," 'anger' and 'pleasure,' as well as with such 

 phenomena as 'exploratory tendencies, feeding 

 tendencies, cleaning tendencies and continuous rest- 

 lessness.' In general, the results of these studies have 

 indicated that more anterior and lateral portions of 

 the diencephalon, including the basal septal nuclei, 

 the preoptic area, the lateral hypothalamus and part 

 ol the basal medial thalamus, may be associated 

 with hostile and aggressive 'rage' responses, or 

 'affective defense reactions' as Hess prefers to call 

 them. As stimulation is carried more posteriorly, 

 changes in oral behavior, increased restlessness and 

 escape responses appear, although no clear-cul 

 topographical arrangement of hypothalamic nuclei 

 with specific functional significance for affective 

 processes has \<-i been discerned. Indeed, Ranson 



;i|, ;i-,i, Ingram (197, '98), Masserman (271- 

 l) and others (1H7, 207) have also demonstrated 

 the emotionally exciting effects ('fear' and 'rage 1 

 responses with multiple sympathetic manifestations) 

 of direct hypothalamic stimulation in cats and 

 monkeys, and al least some partial confirmation of 

 hypothalamic involvement in emotional activities 

 has been obtained b) White (395) with electrical 

 stimulation methods in conscious human patients 

 under local anesthesia. In addition, Grinker (159) 

 also recorded selective electrical activity from deep- 

 lying hypothalamic electrodes in man in response 

 to 'emotional probing.' And, of course, the recent 

 emergence of experimental emphasis upon results 

 1. Li. imed with intracranial self-stimulation tech- 

 niques, following the interesting demonstration by 



Olds & Milner | [Ol 1 of the rewarding effects asso- 

 ciated with direct electrical stimulation of selective 

 forebrain structures, has suggested the intimate par- 

 ticipation of hypothalamic influences, anions; others, 

 in the presumably affective components of this 

 phenomenon in a wide variety of species (46, 299, 

 300). 



That the hypothalamic role in the mediation of 

 affective behavior is not to be regarded as unitary 

 or uncomplicated, however, has been even more 

 clearly emphasized by the results of numerous 

 ablation studies involving relatively discrete de- 

 struction of selected diencephalic nuclei and the 

 analysis of behavioral changes. Bilateral lesions in 

 the caudal part of the hypothalamus of cats and 

 dorsolateral to the mammillary bodies in the monkey 

 were early reported by Ingram et al. (198) and by 

 Ranson (314) to produce complete loss of emotional 

 responsiveness (masklike faces, stolidity), and some- 

 times somnolence and sleep. Similar results were 

 also obtained by Masserman (270), although reports 

 of his own experiments in this area stress metabolic 

 and homeostatic changes in accounting for the appar- 

 ently transient emotional effects of such lesions. In 

 contrast, Kessler (213) and Wheatley (394) have 

 shown that destruction of the more medial aspects 

 of this diencephalic region can result in dramatic 

 rage reactions. In the more extensive study by 

 Wheatley, relatively small lesions in the ventro- 

 medial hypothalamic nuclei were observed to pro- 

 duce "extremely, chronically and incurably savage' 

 behavior in cats. Interestingly, however, the rage 

 reactions in these animals (which appeared 'not 

 unmixed with tear') were not blind or senseless, 

 but well-directed and coordinated, complete with 

 all the normal autonomic phenomena and well- 

 calculated defensive and offensive activities. Nor 

 were these ventromedial rage reactions altered 

 appreciably b) superimposition of partial or total 



frontal lobectomy, removal of the temporal neo- 

 cortex, or destruction of the mamrnillothalamic 

 tracts, tin- fornices at the septal level, the dorsomedial 

 thalamic nuclei or the mammillary bodies (197). 

 Differential changes in cerebral cortie.il potential 

 patterns have also been recorded with implanted 

 electrodes from such ventromedial hypothalamic 

 preparations 1 1 99)- 



I'r.icticallv all the behavioral alterations observed 



in follow ablation and stimulation hi the hypothala- 

 mus in experimental animals have also been reported 

 in man alter trauma, operative manipulation, tumor, 



vascular lesions and infections of the hypothalamus. 



