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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY II 



Ericksoii (19), Passouant et al. (17), Passouant et al. 

 {18), Penfield & Jasper (20), Pool (21) and Cladilliac 



(I). 



c) Stimulation of the upper surface of the hippo- 

 campus has been accomplished with minimal inter- 

 ference to surrounding structures by approaching it 

 through the ventricle without severing the anterior 

 or inferior part of the temporal lobe, as has been 

 done by Pampiglione & Falconer (15, 16). 



One must remember that in all these observations 

 the experimental subjects were patients with some 

 disorder of cerebral origin, often involving the 

 stimulated areas. Hence a full evaluation of the re- 

 sults is difhcult. In addition the methods of stimu- 

 lating differed widely from one observer to the other; 

 square wave pulses, sine waves, saw-tooth waves 

 have been used with a variety of pulse frequencies 

 and duration. Furthermore the patients studied 

 were either under general or under local anesthesia. 

 It is not surprising therefore that no uniformity of 

 results has been found. However, some patients 

 with similar disorders were stimulated under com- 

 parable conditions, and in these certain \alid com- 

 parisons may be made. 



In patients in whom electrical stimulation was 

 applied to the inferior surface of the temporal lobe, 

 as in a) above, arrest of respiration appeared to be 

 the most commonly-elicited phenomenon. Kaada 

 (g), quoting his observations with Penfield and Jasper 

 in eight patients stimulated under local analgesia 

 with 4 v. saw-tooth waves at 60 per sec, says that 

 arrest of breathing could be obtained from points 

 on the anterior portion of the hippocampal gyrus 

 and adjacent portion of the temporal lobe. Arrest 

 of breathing however also followed stimulation of the 

 insula. The respiratory arrest was invariably in ex- 

 piration and appeared promptly upon application of 

 the stimulus and lasted during the entire period of 

 stimulation (3 to 30 sec), occasionally interrupted 

 by a deep breath. Mechanical stimulation (suction) 

 in the same area produced respiratory arrest in one 

 patient for 56 sec. This author mentions that his 

 patients were partly able to overcome the respiratory 

 arrest when asked to count, but there was also some 

 tendency to close the eyes and to feel tired and sleepy. 

 This comment appears of particular importance as 

 it suggests that the apparent loss of contact recorded 

 after hippocampal stimulation by Cadilhac ( i ) and 

 Pampiglione & Falconer (16) was probably not 

 related only to respiratory arrest. An interference 

 with breathing was found by Glusman et al. (7) to 

 follow stimulation of the unciis in six psychotic pa- 



tients (4 to 12 V. square pulses lasting 2.5 to 5.0 

 msec, at a rate of 30 to 100 per sec. being used). 

 Arrest of respiration however was also recorded by 

 other workers stimulating not only the hippocampal 

 region (3, 11, 17, 21) but also other regions of the 

 temporal lobe, the frontal lobe, the thalamus, etc. 

 [for discussion see (i)]. Thus, it seems possible that 

 the respiratory arrest appearing after stimulation in 

 man may not be a specific feature of any of the stimu- 

 lated areas. Moreover Pampiglione & Falconer 

 (unpublished observations) noticed that respiratory 

 arrest produced by stimulating the hippocampus 

 appeared only in their patients under general anes- 

 thesia and not in their conscious patients. Similar 

 comments might be made concerning the observation 

 of mydriasis reported by some authors as discussed 

 by Cadilhac ( i ). 



Stimulation of the hippocampus after temporal 

 lobectomy, as in b) above, produced no observable 

 changes according to Penfield & Erickson (19), but 

 Pool (21) and Passouant et al. (17) noted in some 

 cases mydriasis and in others respiratory arrest 

 without fall in arterial pressure. One of the 1 5 pa- 

 tients operated upon under local anesthesia by 

 Passouant et al. (17] clearly appeared to stop his 

 conversation with the anesthetist at the time of the 

 hippocampal discharge, which followed stimulation, 

 and was unresponsi\e when called by name or when 

 sensory stimuli were applied. It is not specified 

 whether the operation had been performed over the 

 dominant or nondominant cerebral hemisphere. In 

 most instances the clinical phenomena produced by 

 electrical stimulation of the hippocampus after re- 

 moval of the surrounding structures of the temporal 

 lobe or e\en after hemispherectomy were few (18). 

 In fact Passouant et al. (17) remark that the impor- 

 tance and complexity of electrical manifestations 

 after stimulation of Amnion's horn contrast with the 

 poverty of concomitant peripheral phenomena. 



In order to assess whether the poverty and incon- 

 sistency of the clinical manifestations elicited might 

 be due mainly to the extensive surgical interference 

 used by other workers, Pampiglione & Falconer (15) 

 devised a new approach to the hippocampus, as in 

 c) above, somewhat reminiscent of that used by 

 Ferrier in a monkey (5). The brain was exposed by 

 a lateral craniotomy and, after preliminary cortico- 

 graphic exploration, an oblique incision about 2 cm 

 long was made in the midtemporal convolution, 5 

 to 6 cm behind the temporal pole, opening into the 

 temporal horn of the lateral ventricle. Under direct 

 vision throuarh this incision a silver-silver chloride 



