CINGULATE, POSTERIOR ORBITAL, ANTERIOR INSULAR AND TEMPORAL POLE CORTEX 



■359 



from the anterior cingulate and pyriform cortex 

 (238, 239), 



Little is known regarding the descending pathways 

 mediating the arterial pressure effects to the cardio- 

 vascular centers of the lower brain stem. A drop in 

 arterial pressure has been obtained from a zone 

 extending from the genual portion of the anterior 

 cingulate cortex and through the septal, preoptic, 

 hypothalamic and mesencephalic areas (102, 136). 

 This "path" appears to coincide closely with that yield- 

 ing inhiljition of cortically and reflexly induced move- 

 ments and respiration (discussed above). According 

 to Wall & Davis (263) the anterior cingulate cortex 

 may possibly influence arterial pressure b)' a mech- 

 anism dependent on the anterior temporal lobe. 

 Bilateral hypothalamic lesions may abolish the arte- 

 rial pressure response from the orbitoinsular cortex 

 without influencing the respiratory response (263). 

 Lund (160) has traced a pressor zone from the base 

 of the forebrain to the septum pellucidum. Arterial 

 pressure effects evoked by stimulation of the temporal 

 pole are possibly mediated via a bundle of fibers 

 which travel with the temporopontine tract to the 

 tegmentum and pons (263) or to the pulvinar {195). 

 Section of the fornix (126) and pyramidal tract (263) 

 leave the arterial pressure responses induced from the 

 medial and basal cortical areas unaltered. 



GASTRIC MOTILITY. On the lateral surface of the cere- 

 bral hemisphere two areas with influence on gastro- 

 intestinal motility have been located, one in the inter- 

 mediate frontal cortex and a second in the parietal 

 lobe. [These have been considered in previous reviews 

 (16, 55, 63, 83, 126).] 



In 1940 Bailey & Sweet (21 ) recorded a fall in tone 

 of the stomach wall on stimulation of the posterior 

 orbital surface of the frontal lobe of monkeys and of 

 the orbital gyrus of cats. The gastric influence of this 

 area was subsequently studied by Babkin et al. (14-16) 

 in the dog, !)y Eliasson (63) in the cat, and by Kaada 

 (126) and Hoffman & Rasmussen (115) in the mon- 

 key. In the latter species alteration in pyloric antral 

 contractions also was obtained by stimulation of the 

 anterior insula, the olfactory tubercle and the tip of 

 the temporal lobe, i.e. the basal continuous cortical 

 zone yielding optimum inhibition of respiratory and 

 other somatomotor activities and arterial pressure 

 changes (the lower encircled area in fig. 65). This 

 finding emphasizes further the homology between the 

 cortex of the orbital gyrus of cats and dogs and the 

 orbitoinsulotemporal cortex in the monkey (see 

 above). 



From the medial surface gastric motility can be 

 influenced by stimulation of the anterior cingulate 

 region in dog (14, 16), cat (63) and monkey (126). 

 In the dog and cat the responsive region is confined to 

 a rather small area in the pre- and subcallosal portion 

 of the anterior cingulate cortex; the corresponding 

 area in the monkey is indicated in figure 6fi. 



Only inhibition of pyloric peristalsis has been ob- 

 tained in all species of animals froin the anterior 

 cingulate cortex. In the cat this inhibition may be 

 associated with a moderate augmentation of the 

 fundic motility (63). Optimum stimulus parameters 

 are frequencies of 30 to 60 cps and prolonged dura- 

 tions of 10 to 20 msec, for all species of animals. 

 Stimulation of the anterior cingulate cortex in humans 

 may be associated with plainly audible borborygmi 

 and violent pas.sage of gas by rectum (197). The effects 

 obtained from the orbitoinsulotemporal polar cortex 

 are essentially similar to those evoked from the ante- 

 rior cingulate except that no augmentation of fundic 

 motility has been reported on stimulating the former 

 area. Further, increase of the stimulus frequency 

 shortens the latency of the orbital response, while it 

 influences only the degree of the effect produced by 

 cingulate stimulation (15). 



Occasionally some augmentation of pyloric peris- 

 taltic contractions has been observed in dogs (15) and 

 monkeys (126) on stimulation of the orbitoinsulo- 

 teinporal polar field. This effect may possibly have 

 been caused by spread of excitation to the neighboring 

 olfactory pathways (the olfactory bulb and tract, 

 rostral pyriform cortex), stimulation of which, accord- 

 ing to Eliasson (63), results in strong contractions and 

 increased peristalsis of the stomach. 



The induced alterations in gastric motility are not 

 caused by concomitant changes in respiratory move- 

 ments or arterial blood pressure (14-16, 63, 126). The 

 anesthetic commonly used by all observers has been 

 chloralose, either alone or in combination with ure- 

 thane or barbiturates. The effects are similar under 

 barbiturates or ether alone (16, 126). Chloralose 

 appears to augment gastric motility by stimulating 

 the vagal centers in the lower brain stem (14). This 

 may account for the difficulties of some observers in 

 obtaining increased contractions by cortical stimula- 

 tion, as the experiments may have been performed 

 under conditions of maximal motility. 



Bilateral cervical vagotomy eliminates the gastric 

 effects evoked from the anterior cingulate (14, 16, 63, 

 126) and orbitoinsulotemporal polar fields (14, 16, 

 63, 1 15, 126), while section of the splanchnic (14, 63, 

 126) or trigeminal (115) nerves leaves the responses 



