Neuropsychology — Karl S. Lashley 



21 



havior there is frequently evidence of cor- 

 related variation in the level of activity of 

 a number of functions. The organism may 

 be more or less physically active, percep- 

 tually alert, emotionally depressed or ex- 

 cited, intellectually indifferent or curious. 

 Such variations have led psychologists to 

 postulate some general stores of nervous 

 or mental energy, which may be directed 

 into diverse activities. Such postulates are 

 represented in the psychologist's notion of 

 "drives," in the psychoanalytic theory of free 

 libido, in Henry Head's conception of re- 

 duced vigilance in brain injury, and in 

 Spearman's theory of the G factor in in- 

 telligence. In the facts revealed by studies 

 of neurophysiology there is no clear cor- 

 relate for such dynamic concepts. The 

 nearest approach to a neurological theory 

 of the dynamics of behavior is the Head- 

 Cannon theory of thalamic facilitation in 

 emotion. This has been shown to be un- 

 tenable as an explanation of the dynamic 

 aspects of emotion. 



Because of the prevalence of such ideas 

 in psychology there is great need for a 

 systematic investigation of the possible neu- 

 rological and endocrine basis of individual 

 differences in the level of activity. Studies 

 of frontal lobe function both in experi- 

 mental work and in human prefrontal lob- 

 otomies suggest a possible approach to this 

 problem, but the data so far available are 

 inconsistent and uninterpretable. Recent 

 work on the action of the reticular forma- 

 tion suggests a mechanism for general fa- 

 cilitation, but its bearing on problems of 

 behavior is still obscure. Biochemical and 

 hormonal studies perhaps offer a more 

 promising direction of attack. 



Temporal Organization of Action. Inves- 

 tigations of tonic reflexes and of posture 

 have advanced understanding of the spatial 

 organization of the nervous system and of 

 reactions. In contrast, practically nothing 

 is known of the mechanisms by which a 

 predetermined series of acts is carried out 

 or a succession of stimuli, such as a musical 

 phrase or a sentence heard, is condensed 

 into a unitary perception. Yet almost all 

 behavior is based upon such temporal or- 

 ganization. In clinical neurology under- 



standing of apraxia and of syntactical apha- 

 sia or agrammatism depends upon a knowl- 

 edge of the normal mechanisms of serial 

 action. The mechanism of serial ordering 

 is perhaps the most neglected and, for 

 understanding of complex adaptive be- 

 havior, the most important problem in the 

 physiology of the nervous system. 



Neurological Basis of Learning and Mem- 

 ory. Since the pioneer studies of Ebbing- 

 haus 75 years ago, thousands of experi- 

 mental investigations of learning have been 

 reported, yet real understanding of the na- 

 ture of the memory has scarcely advanced. 

 "Laws" of learning have been formulated, to 

 all of which there are contradictory facts, 

 and scores of theories proposed which are 

 inconsistent either with some facts of learn- 

 ing or of neurophysiology. As in other 

 fields of psychology it is increasingly evi- 

 dent that apparent contradictions of fact 

 will be cleared up only when the neurologi- 

 cal m.echanisms underlying the processes 

 are understood. At present there are no' 

 very promising methods for investigation 

 of the neurological basis of memory. The 

 conditioned reflex experiments of Pavlov 

 are scarcely more than a repetition of the 

 old psychological experiments on associa- 

 tion; attempts to discover memory centers 

 or to trace associative paths have been 

 unsuccessful. Theories of memory as a 

 chemical sensitization have little factual 

 support and techniques for testing them 

 are not available. There is little that can 

 be done to advance this topic, pending de- 

 velopment of some new experimental ap- 

 proach. 



Neurology of Intelligence; Analysis of 

 Defects Following Cerebral Injuries. The 

 vast literature on aphasias, agnosias, per- 

 sonality changes, and other results of cer- 

 ebral injury contains few really competent 

 studies of the psychological changes in- 

 volved. Psychological examinations have 

 usually been unsystematic, unreliable, and 

 without adequate normal controls. A re- 

 view of the tests used, even in the elab- 

 orate study of aphasia by Weisenberg and 

 McBride, which is by far the most com- 

 petent investigation of the subject that has 

 been made, reveals that some of the tests 



