254 ARCHIVES OF NEUROLOGY AXD PSYCHIATRY 



motor, but "psychomotor," means no more than that the pyramidal 

 cells excite patterns of spinal motor cells rather than individual cells. 

 It contributes nothing to our understanding of cerebral function. In 

 the present state of psychologic science, we can not do better than fol- 

 low the dictum of Bubnoff and Heidenhain, 40 "Es will uns uberhaupt 

 scheinen als miiste die Untersuchung der physiologischen Processe in 

 dem Gehirn von den jene Vorgange begleitenden Bewusstseinsvorgangen 

 moglichst absehen, wenn es sich urn eine Deutung physischen Gesche- 

 hens handelt," and rigidly exclude from neurologic discussion every 

 subjective concept which cannot be translated into objective terms. 



There is no evidence for the localization of any "mental function" 

 in any part of the cerebrum. All that can be concluded from the 

 existing evidence is that the conducting pathways concerned in par- 

 ticular kinds of behavior lead from receptor to effector through certain 

 cerebral areas. Cerebral motor localization is a problem of the origin . 

 and function of the centrifugal neural impulses of the cortex. Their 

 "volitional" or "automatic"' character can be defined only in terms of 

 their complexity of organization and their relative importance in the 

 total motor integration or kinetic melody, and until so defined the terms 

 are meaningless. The "reflex" conception of cerebral function, although 

 still a theory and notably inadequate to account for all the phenomena 

 of cerebral function because of oversimplification in its formulations, 41 

 is too well supported by evidence on nerve conduction and analogy with 

 spinal functions to be disregarded in favor of any speculations con- 

 cerning the localization of "psychic" functions. 



STATEMENT OF PROBLEM 



Stated objectively, three mutually incompatible theories concerning 

 the function of the precentral gyrus are to be found in the current 

 literature. They are: 1. This area is the only centrifugal outlet from 

 the cerebral cortex for complexly integrated movements or for move- 

 ments acquired as a result of training ( voluntary movements or con- 

 ditioned reflexes). 2. In the intact animal, the Betz cells are the 

 principle centrifugal paths, but some neural impulses of like function 

 may descend by extrapyramidal tracts, and these tracts may assume 

 vicariously all the functions of the motor area. 3. The motor area 

 is a part of the mechanism functioning in the regulation of tonus and 

 posture and is not directly concerned in conditioned reflex activity. 



40. Bubnoff, V. and Heidenhain, R. : Ueber Erregungs- und Hemmungs- 

 vorgange innerhalb der motorischen Hirncentren, Arch. f. d. ges. Physiol. 26: 

 137-200, 1881. 



41. The data on direct adaptation of unpracticed organs to the solution of 

 |irol)lem-boxes presented later in this paper seem wholly inexplicable in terms 

 oi simple conditioned reflexes. 



