I4I2 



HANDBOOK OF PHYSIOLOGY ^ NEUROPHYSIOLOGY II 



et al. (236) were savage immediately after the opera- 

 tion and that Bard & Mountcastle (24) never ob- 

 served hypersexuahty in their cats. Another explana- 

 tion for the discrepancy of results is gi\-en by Green 

 et al. (105) who belie\e that inadvertent interference 

 with the blood supply to the anterior hippocampus 

 may produce savage behavior, whereas similar vascu- 

 lar disturbances in the basal ganglia may produce a 

 state of apathy resembling placiditv. 



Observations in man on the effects upon emotional 

 behavior produced by bilateral amygdaloid lesions 

 were mostly made in assaulti\'e psychotics in whom 

 these lesions were placed in an attempt to curb the 

 patients' aggressiveness. In most cases there was a 

 definite decrease in aggressive behavior (106, 202, 

 226, 228, 240, 244). Some however showed an initial 

 increase in aggressiveness (220), and still others 

 became emotionally labile. Usually quite docile when 

 left alone, they were nevertheless easilv provoked 

 into short-lived anger by minor frustrations (220, 227). 

 This and other aspects of these patients' behavior, 

 such as their manner of speech, their motor restless- 

 ness and their abnormal interest for such food items 

 as candies and cake, struck some observers as tanta- 

 mount to a regression to a childish level of behavior 

 (220, 227, 240). Some authors however failed to 

 observe any obvious change in emotional behavior in 

 patients after bilateral amygdalectomy (67, 68, 253). 



The development of hypersexuality was a promi- 

 nent feature in some experimental series (29, 72, 222- 



FiG. 9. Hypersexuality produced by bilateral amygdaloid 

 lesions in male cats; attempts at copulation with animals of 

 other species or with other males. Note also that no aggressive- 

 ness is displayed towards a dog which is approached as a 

 potential sexual mate just as any other animal. [From Schreiner 

 & Kling (223).] 



224), whereas in others it was not, or only occa- 

 sionally, noticed (24, 199, 204, 252J and in still 

 others there was a decrease in sexual impulse (241, 

 249). Green et al. (105) found hypersexuality only 

 when the lesion involved the piriform cortex. Amygda- 

 loid lesions sparing this area did not alter sexual be- 

 havior. Hypersexuality follows the placement of 

 bilateral lesions only after a long latent period of 

 several weeks. It leads both in the male and the 

 female to increased copulatory and to abnormal 

 sexual behavior (fig. 9), such as homosexual activities, 

 masturbation and attempts at copulation with ani- 

 mals of other species or outside territory. Preoperative 

 castration prevents development of hypersexuality. 

 Once developed, it will gradually disappear when 

 castration is carried out after amygdalectomy (224). 

 This does not prove, however, that increased sex 

 hormone production is the underlying cause of 

 hypersexuality in amygdalectomized animals. It may 

 merely demonstrate that sex hormones are a necessary 

 prerequisite for the manifestation of sexual behavior. 

 Corroborative evidence in favor of this view is the 

 observation that irritative lesions of the rhinencepha- 

 lon in man, although producing diminution of libido 

 and potency, are not associated with any signs of 

 hypogonadism (77). 



Bilateral amygdaloid lesions in man produced a 

 clear effect on sexual behavior in only one patient 

 who became exhibitionistic (240), whereas a few 

 others seemed to show only a very slight release of 

 sexual impulse and the majority showed no change at 

 all in sexual behavior (67, 68, 106, 220, 227, 253). 



In a female monkey it was noticed that bilateral 

 amygdalectomy also affects maternal behavior, since 

 this animal ceased to care for or defend her offspring 

 after the operation (241, 249). 



Different types of changes occurring in general 

 motor behavior after amygdalectomy are described. 

 Fairly often, motor restlessness is noted (29, 204, 220, 

 223, 236) which may (29, 202, 223, 227, 234, 240, 

 -49' 252) or may not (220, 236) follow upon an 

 initial period of apathy. Logorrhea" frequently seen 

 in patients after bilateral amygdalectomy may be 

 related to this motor restlessness (220, 240). In con- 

 trast to these obser\ations however are reports that 

 in rats bilateral amygdalectom\- is followed bv a 

 permanent decrease in spontaneous activity (10). 



.\ special form of increased motor activity is that 

 which Kliiver & Bucy (143-145) described as 'hyper- 



' Vocalization was increased in cats (223) but decreased in 

 monkeys (143-145) after bilateral amygdaloid lesions. 



