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HANDBOOK OF PH^■SIOLOGY 



NEURCJPHYSIOloOV II 



intact. Atropine abolishes the cortically induced 

 responses (63). These observations support the sup- 

 position of a dual vagal representation on the medial 

 and liasal aspects of the cerebral hemisphere (cf 

 above). Each of the two areas may exert its influence 

 on gastric motility in the aijsence of the other (14, 

 63, 126). Cholinergic fiijers running in the splanchnic 

 nerves are responsible for the increase of gastric 

 motility evoked by stimulation of the olfactory path- 

 ways (63). 



The available data give no definite answer to the 

 question whether the responsive cortical fields act 

 directly on the dorsal motor nucleus of the vagus in 

 the medulla oblongata or whether the impulses are 

 transmitted through some intermediate station. 

 Eliasson (63) has traced a pathway mediating the 

 augmentatory effects from the olfactory bulb and 

 tract and pyriform cortex through the amygdaloid 

 nuclear complex. The fibers mediating the effects 

 from the orbital surface pass, according to the same 

 author, caudally and medially through the internal 

 capsule below the anterior commissure. A discrete 

 pathway has further been traced from the anterior 

 cingulate cortex to the vicinity of the anterior com- 

 missure (63). It appears that these paths from the 

 orbital and anterior cingulate areas coincide with 

 those mediating the cardiovascular and somatomotor 

 inhibitory effects from the same areas through the 

 hypothalamus (cf. above). The excitatory effects on 

 the fundus of the stomach evoked from the rostral 

 cingulate region are possibly mediated via the respon- 

 sive area of the motor cortex as they are abolished by 

 aislation and facilitated by strychninization of this 

 area (63). 



The general subject of nervous control of digestive 

 processes is considered by Eliasson in C:hapter XL\' 

 of this Handbook. 



PUPILLARY RESPONSES. Pupillary dilatation, usually 

 of a slight degree and associated with opening of the 

 eyes, may, according to Kaada (126), be obtained 

 from all cortical regions yielding inhibition of respira- 

 tory and other spontaneous somatomotor movements 

 in monkeys (fig. 2A, B), cats (fig. 2C to E) and dogs. 

 These rather extensive zones correspond well with the 

 pupillomotor areas outlined in cats by Hodes & 

 Magoun (113). On the medial surface an optimal 

 zone has been found in the precallosal part of the 

 cingulate gyrus of the cat (229). Pupillary dilatation 

 was also observed by Smith (238), Ward (260) and 

 Showers & Crosby (227) on stimulating the rostral 

 cingulate cortex, by Showers' & Crosby (227) from 

 the posterior cingulate cortex, and by Sachs et al. (215) 



from the posterior oriiital gyrus in the monkey. The 

 response has been said to be due to oculomotor inhibi- 

 tion (113), or sympathetic excitation (266), or both 

 (229). 



Points yielding pupillodilatation were traced 

 caudally by Hodes & Magoun (112, 113) in an unin- 

 terrupted column from the medial and ventral cortical 

 zones through the basal telencephalon to the hypo- 

 thalamus. In addition the septum, the mid-line group 

 of thalamic nuclei, the subthalamus and a large part 

 of the midbrain were found to yield similar responses. 



The functional significance of the pupillodilatation 

 evoked from these widespread cortical areas is ob- 

 scure. It possibly represents an integrated pari of the 

 complex 'arousal" respon.se which in the unanesthe- 

 tized animal can be produced from the same cortical 

 areas and which always is associated witli some 

 pupillodilatation and opening of the eyes. 



Pupilloconstriction has been obtained in cats by 

 stimulation of a narrow zone, 2 to 3 mm ijroad, imme- 

 diately surrounding the genu of the corpus callosum 

 (113, 126). At the thalamic and hypothalamic levels 

 constriction of the pupils as a result of stimulation 

 has, according to Hess (106), been obsersed only in 

 association with drowsiness or sleep and with ady- 

 namia. Since the portion of the cingulate cortex 

 yielding pupilloconstriction appears approximately 

 to coincide with the optimum zone yielding sleep-like 

 reactions with inhibition of somatomotor activities 

 and autonomic "vagal" responses (cf. ai30\e), it may 

 l)e that this cortically induced pupilloconstriction 

 has a functional significance similar to that of the 

 hypnogenic-adynamic areas of the rostral lirain stem. 



OTHER .\UTo.\OMic RESPONSES. PiloeiTction has been 

 induced h\ stimulation of the anterior cingulate 

 (126, 227, 238, 266) and olfactory tuisercle (126) in 

 monkeys but no such effect has been seen in cats as a 

 result of cortical stimulation (113, 126). 



Salivation has been produced on stimulation of the 

 cingulate cortex (227), the olfactory tubercle and 

 pyriform cortex (126, 207) and the adjacent poste- 

 rior orbital and anterior insular regions (fig. &B) 

 (126). Edinger's (62) suggestion that the olfactory 

 tuljercle is eii} Centrum des Oralsinnes should be borne 

 in mind. 



Bladder contraction has been observed on stimula- 

 tion of the posterior portion of the cingulate cortex in 

 dogs (147) and of the pyriform area in monkeys (126, 

 239), cats and dogs (126). Henneman (98) recorded 

 both contraction and relaxation of the bladder from 

 these areas in cats. 



Defecation has occasionalh' resulted from excita- 



