LASHLEY— CEREBRAL FUNCTION 271 



explanation is probably to be found in the forced practice which 

 diplegia imposes on the paralyzed limbs (Odin and Franz 4 "). 



Other restricted cerebral areas have also been rather definitely 

 excluded from participation in the vicarious function of the stimulable 

 areas, by the work of Leyton and Sherrington 2,i ( Lashley 49 ) . Luciani : "' 

 has suggested that recovery may be due to the activity of the corpus 

 striatum, which has homologies with the stimulable cortex. This was 

 tested in animal Number 2 of the present series by destruction of the 

 right striatum after recovery from diplegia. Hemiplegia symptoms did 

 not recur, so that we may conclude that the recovery had not been due 

 to the vicarious activity of the striate nucleus. 



THE FUNCTION OF THE ELECTROSTIMULABLE AREAS 



The conclusions which may be drawn from these experiments are 

 wholly negative. They seem to prove that the precentral gyrus does 

 not include the efferent paths for learned activities ; in the current 

 localization terminology, it is not the center for "voluntary movements/' 

 as is almost universally assumed. But if this is true, what is the 

 significance of the movements elicitated by electrical stimulation? How 

 may we interpret the cerebral paralyses, and why do they especially 

 affect the finer manipulative movements? A number of lines of evi- 

 dence may help to answer these questions and clear up tbe function of 

 the precentral gyri. 



The Postural Function of the Stimulable Areas. — Many investi- 

 gators have pointed out the similarity between the movements elicited 

 by cortical stimulation and "voluntary movements." I am convinced 

 that this is an error due to contrasting these movements with those 

 which are elicited by stimulation of motor nerves or spinal cord. In 

 the latter cases, the movements are wholly incoordinated. whereas the 

 movements following cortical stimulation involve synergic groups of 

 muscles. But in all cortical stimulation experiments which I have seen, 

 the movements have been slow and rather massive, i. e., chiefly involving 

 the larger musculature of the limbs. When smaller segments are 

 moved, the movements are never coordinated as they are. for example, 

 in grasping small objects. They never show the fineness of gradation 

 and accuracy of adjustment which is characteristic of the movements 

 of the intact animal. This has been observed by various investigators 

 and interpreted as showing that the finer adjustments are integrated 



48. Odin, R., and Franz, S. I : On Cerebral Motor Control: The Recovery 

 from Experimentally Produced Hemiplegia, Psychobiol. 1:33-50, 1917. 



49. Lashley, K. S.: Studies of Cerebral Function in Learning. Vicarious 

 Function After Destruction of the Visual areas, Am. 1. Physiol. 59:44-71. 1922. 



50. Luciani, L. : Human Physiology, London 3. 1915. 



