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Survey of Neurobiology 



Marked recent advances have been in the 

 heredity of dementia praecox, epilepsy, and 

 in analysis of the basis of some hereditary 

 nervous diseases as defects of protein me- 

 tabolism. Studies of normal traits such 

 as those carried out by the Eugenics Rec- 

 ord Office early in the century have been 

 relatively sterile because of the vagueness 

 of the conceptions of mental traits and the 

 lack of exact quantitative measurements. 

 Recent development of more adequate 

 measures of "primary mental abilities" and 

 of personality traits will make possible a 

 more significant approach to the problems 

 of inheritance of individual psychological 

 differences. 



The question of the neural correlates of 

 inherited traits has scarcely been touched. 

 The 1920 monograph of Karplus gives some 

 evidence of the inheritance of minor varia- 

 tions in gross nervous structure. Recent 

 studies have shown marked variations in 

 the histological structure of the thalmus 

 and cerebral cortex within an apparently 

 normal population; structural differences 

 which should result in behavioral differ- 

 ences. No attempt has been made to cor- 

 relate such individual variations in struc- 

 ture with behavior, except in the case of 

 cell deficiency in idiocy. The whole prob- 

 lem of the heredity of nervous structures 

 and their influence on behavior is prac- 

 tically untouched. Such investigations will 

 be difficult and laborious but methods are 

 available and results should repay the in- 

 vestment. 



Neurological Basis of Instincts. Among 

 the most difficult problems of the genetics 

 of behavior is the inheritance of specific 

 modes of action, as illustrated by the spe- 

 cies-constant patterns of the webs of orb- 

 weaving spiders and the recognition of 

 members of their own species by many in- 

 sects, birds, and mammals. Even for man 

 there is some evidence of an innate per- 

 ceptual structuring of certain stimulus pat- 

 terns and further investigation may perhaps 

 reveal a wider range of human instinctive 

 behavior than is at present recognized. The 

 relations of sexual behavior to spinal and 

 cerebral functions and to hormonal ac- 

 tivation has been partially analyzed, and 



these studies set a pattern of investigation 

 that may profitably be applied to other in- 

 stinctive behavior. However, the funda- 

 mental problems of the nature of the react- 

 ing mechanisms and of the mode of action 

 of the sex hormones in inducing behavior 

 remain unsolved. 



As a preliminary to the neurological an- 

 alysis of instinct, exact studies of the nature 

 of the stimuli effective in initiating be- 

 havior and of the motor patterns elicited 

 must be made. The majority of studies of 

 instinct have been in terms of the products 

 rather than of the behavior. Especially im- 

 portant contributions of this sort have been 

 made by Lorenz and his students. These 

 studies are laying a foundation for neuro- 

 logical analysis, but as yet no attempt to- 

 ward neurological correlations has been 

 made by the group. 



Sensory Physiology. The interest of psy- 

 chologists in sensation led to the early de- 

 velopment of methods for studying sensory 

 processes and of physiological theories of 

 sensory mechanisms. As a result, knowl- 

 edge of the physiology of vision, audition, 

 and vestibular functions is far in advance 

 of any other aspect of neuropsychology, 

 with techniques so refined that speciali- 

 zation in these fields almost precludes work 

 on more general problems of neurology. 

 The application of electrical recording 

 methods to analysis of sensory pathways 

 and propogated impulses has given ad- 

 ditional impetus to work in the field, so 

 that the number of investigators engaged 

 is perhaps out of proportion to the relative 

 importance of the topics. The study of 

 other sensory mechanisms, taste, smell, 

 kinesthesis, touch and pain, have lagged 

 far behind, in part as a result of the greater 

 difficulty in controlling the stimuli, in part 

 because of probably more complicated and 

 less sharply defined neural mechanisms. 

 The practical value of studies of vision, 

 audition, and vestibular functions has been 

 demonstrated, especially in connection with 

 military problems, so that research on these 

 topics is receiving increased support. The 

 need is for support of research on the more 

 obscure sensory processes. 



Dynamic Functions. In studies of be- 



