1742 



HANDBOOK OF PHYSIOLOGY 



NLtROPHYSIOLOGY III 



to develop predominantly parasympathetic manifesta- 

 tions, whereas those tested at 5-min. intervals showed 

 signs of sympathetic overactivity. In investigations 

 following up this interesting lead it will be of par- 

 ticular interest to discover whether or not, with more 

 prolonged testing, lesions might eventually appear 

 in the variously affected systems. 



Learning and memory. Conditioning methods also 

 have the potentiality of helping to identify neural 

 mechanisms of learning and memory that are con- 

 ducive to psychosomatic dysfunction. It has been sug- 

 gested that learning and memory depend on the inte- 

 gration of internally and externally derived experience 

 (30). If so, there are indications that this would re- 

 quire the integration of the performance of dissimilar 

 mechanisms because conditioning procedures reveal 

 that visceral and locomotor systems are differentially 

 affected in the learning process. Indiscriminate vis- 

 ceral responses regularly appear before an animal 

 learns a discriminative act. Furthermore, in classical 

 trace conditioning in which there is an interval of 

 several seconds between the cessation of the condi- 

 tioned stimulus and the onset of the emotion-inducing 

 unconditioned stimulus, one can readily establish 

 conditioned cardiac and respiratory responses, but 

 not a specific leg response. On the contrary, in condi- 

 tioning where there is a temporal overlap of the condi- 

 tioned and unconditioned stimuli, a leg response is 

 rapidly acquired. 



Such discrepancies have important implications in 

 1 1 gard to learning and the incipience of psychosomatic 

 disorders. It is recognized, for example, that in the 

 house training of a dog, one must punish the animal 

 immediately after it soils or il will fail to learn the 

 significance of the punishment, and may subsequently 

 cower and cringe every time it sees its master. In 

 Other words, it fails to discriminate that the only time 

 it needs to fear the hand of authority is when there 

 has been a specific misdeed. In human affairs, a 

 parallel situation is suggested by the mother who 

 habitually postpones punishment of a child until the 

 lather can return home to administer the whipping. 

 Conceivably, such circumstances would be conducive 

 to the formation of indiscriminate visceral reactions 

 in childhood. Furthermore, through the symbolic 

 process, the father would stand in the position to 



become interchangeable with all authoritative- figures 

 who in turn would Ik- feared regardless of the- circum- 

 stances in which the) appeared 1 1 1 I. 



I low is it to lie explained thai in trace- conditioning 



which 1 .ills tin the association of two temporally sepa- 

 rated events, cardiac and respiratory responses arc 



readily conditioned whereas a specific leg withdrawal 

 is not? It is possible that the dichotomy in function of 

 limbic and neocortical systems bears on this question. 

 As already emphasized, the limbic cortex is strongly 

 interconnected with the hypothalamus. It was also 

 pointed out that sensor) stimulation by way of 

 various intero- and exteroceptive systems evokes 

 rhythmically recurring potentials in certain parts of 

 the limbic cortex that persist for a considerable time 

 after the cessation of the stimulation. Is it possible 

 that the neural perturbations remaining in these 

 structures allow a more ready association of two 

 temporally separated events than is possible in the 

 neocortex where one does not see a comparable phe- 

 nomenon (41 )? If so, it would suggest an explanation 

 of how two temporally separated events might be so 

 related as to impress themselves more readily on the 

 viscera than on the discriminative acts of the skeletal 

 musculature that are presumably dependent on the 

 neocortex. 



A number of clinical observations emphasize the 

 importance of the limbic system in memory mecha- 

 nisms. An inability to recall recent events has been 

 found to be associated with lesions involving any one 

 of the limbic structures forming the neural circuit 

 comprised of the hippocampal formation, mammillary 

 bodies, anterior thalamic nuclei and cingulate gyrus. 

 Sufferers from psychomotor epilepsy, in which the 

 seizure discharge is predisposed to involve limbic 

 structures, have no memory for what they do during 

 their automatisms, some of which may involve a 

 duplication of memorized dexterities and intellectual 

 performance. 



finally, Gantt (21) has made- a highly significant 

 observation that has a fundamental bearing on the 

 foregoing considerations. He has found that condi- 

 tioned cardiac reflexes may persist long after the 

 somatic response conditioned In the same stimulus 

 has been extinguished. In his words, the organism re- 

 members with its heart, but not with specific move- 

 ments. "Thus the emotional basis for action remains 

 after the external and superficial movements of 

 adaptation have been lost. . . ." He refers to this con- 

 dition as 'schizokinesis.' This suggests a mechanism 

 that might account for chronic psychosomatic < lis 

 orders d| the cardiovascular s\stem. In the author's 

 laboratory, an attempt was made- to disc-over whether 

 or not the phenomenon of schizokinesis was possibly 

 rc-lated to a differential influence- of neocortical and 

 limbic- sv stems, respect i\ civ, on "somatic' and 'v isceral 1 

 functions (41). Hippocampal seizures were induced in 

 cats .is -i means of bringing about a massi\<- alteration 



