CINGULATE, POSTERIOR ORBITAL, ANTERIOR INSULAR AND TEMPORAL POLE CORTEX 



1365 



background activity, actually represent an abortive 

 arousal effect (r26, p. 207). Further, the "depression" 

 and 'elimination of strychnine and unelicited spikes' 

 mainly represent unspecific extinction phenomena 

 which can be oiatained froin any cortical area (126, 

 p. 231 and 244). 



EFFECTS OF ABLATION 



No conclusion concerning the functional signifi- 

 cance of a particular portion of the brain can be 

 drawn solely on the basis of stimulation experiments. 

 A better understanding is reached by comparing the 

 results of stimulation and ablation. In the past 5 to 10 

 years a considerable amount of data on ablation of 

 the cortical areas under discussion has accumulated. 

 Important contributions have come also from clinical 

 studies in connection with surgical intervention of 

 these portions of the brain in psychiatric and epileptic 

 patients. Only clinical papers which may contribute 

 to an understanding of the functional role of the area 

 concerned will be mentioned. 



An important conclusion which has emerged from 

 all ablation studies, in animals and man, is that 

 neither unilateral nor bilateral lesions of the cingulate 

 and orbitoinsulotemporal polar region interfere with 

 the correct integration of basic elementary somato- 

 motor and autonomic mechanisms (with the excep- 

 tions mentioned below), nor with functions essential 

 for survival. Thus, there has been no change in volun- 

 tary or reflex motor performance, no muscular hyper- 

 or hyporeflexia, no disturbance of respiratory, cardio- 

 vascular and gastrointestinal functions, no pupillary 

 change, etc. This in spite of the fact that the same 

 areas, on stimulation, are able to exert a profound 

 influence upon these very same functions probably as 

 a part of more complex behavior patterns. This influ- 

 ence on basic autonomic and somatic mechanisms 

 therefore is probably not of a tonic character. 



Some exceptions to these essentially negative results 

 are the slight elevation of skin temperature of the 

 extremities and the augmentation of reflex vasodila- 

 tion on exposure to a warm environment following 

 bilateral removal of the posterior orbital surface in 

 monkeys (54, 159). More recently. Showers & 

 Crosby (227) have recorded a transitory drop in body 

 temperature (average 5.5°F = 3°C) in monkeys with 

 lesions of the posterior or anterior cingulate cortex. 

 Also, it was possible to observe piloerection and an 

 increase in sudomotor activity in the 2 to 3 weeks 

 following the operation. Further, Babkin & Kite (15) 



found that bilateral ablation of the cingulate gyrus in 

 acute experiments in dogs produced a moderate 

 increase in the rate of contractions of the pyloric 

 antrum, whereas orbital surface ablations were with- 

 out significant effects. Finally, Turner (256) has 

 shown that remo\al of the posterior orbital cortex in 

 monkeys results in increased resistance to anoxia, 

 possibly because '". . . a protective mechanism had 

 been damaged or destroyed." Davis (52) observed 

 that monkeys with bilateral ablation of area 13 

 quickly collapse when exposed to an altitude equiva- 

 lent of 20,000 ft., while normal unoperated animals 

 are able to maintain normal activity at this altitude 

 for 30 min. or longer. 



The more prominent changes which ensue after 

 bilateral lesion of the cingulate and orbitoinsulo- 

 temporal cortex are all concerned with the behavior 

 of the animal, such as increased motor restlessness 

 and changes in the affective state of the animal. But 

 also in these respects the changes are not very striking 

 and bilateral removal is necessary to obtain any 

 significant effects. 



Anterior Cmgular Region 



Bilateral anterior cingulate ablation in monkeys 

 by Smith (236) and Ward (266) has resulted in 

 behavior changes in the direction of greater lameness 

 and diminution of preoperative fear and rage in re- 

 sponse to man and in lack of 'social consciousness' 

 (Ward). This was confirmed in a general way by Glees 

 et al. (91) but they report that the behavior changes 

 were rather short-lived, disappearing after 6 wk. to 3 

 mos. Pribram & Fulton (201) and Mirsky et al. (178) 

 recently reported that in monkeys resection of the 

 cortex of the anterior cingulate gyrus, and of the pre- 

 and subcallosal and medial frontal areas as well, does 

 not lead to any profound and prolonged alteration in 

 behavior in response to other animals; the effects are 

 transient, apparently minimal and difficult to 

 appraise. However, cingulectomy may have the effect 

 of making monkeys temporarily more aggressive or 

 less fearful of man (178). Bard (26) found that bi- 

 lateral lesion of the cingulate cortex of cats does not 

 per se alter the threshold at which rage provoking 

 stimuli become effective. Further, Rothfield & Har- 

 man (212) concluded that removal of the neocortex 

 plus cingulate cortex in cats does not alter the rage 

 threshold. Some increased motor restlessness, similar 

 to but less than that resulting from posterior orbital 

 ablation (see below), has been observed following 



