Function of Precentral Convolution in Primates 121 



59 (2019) 



Function of the precentral convolution in primates. 

 By K. S. LASHLEY. 



[From the Psychological Laboratory, University of Minnesota, 

 M inneapol is, M i n nesota.] 



Studies of cerebral function in rodents have shown the sur- 

 vival of habitual reactions after bilateral destruction of the 

 electro-stimulable pallium and of the corpora striata. 1 The pres- 

 ent experiments were designed to test the relations of the cor- 

 responding cortical areas in primates to the performance of 

 habitual or voluntary movements. 



Two- Cebus monkeys were trained in manipulative move- 

 ments of the hands; opening various types of latch boxes. When 

 facility in these movements was acquired, the animals were sub- 

 jected to an operation in which all of the electro-stimulable cor- 

 tex anterior to the Rolandic fissure on each side was destroyed 

 by cauterization. The animals were then kept without additional 

 training until they recovered from the resultant paralysis. When 

 recovery was sufficient to permit of grasping movements, reten- 

 tion of the latch-box habit was tested. Both animals showed 

 perfect retention of the habits, reproducing the specific manipu- 

 lative movements acquired through the initial training. 



The experiment seems to prove that destruction of the so- 

 called motor area of the pallium does not destroy the specific pat- 

 terns of neural integration involved in habitual or voluntary 

 movements and hence, that the motor area is not the chief nor- 

 mal efferent path from the cortex for voluntary movement. 



On the basis of earlier work with rodents the suggestion is 

 advanced that the motor pallium is to be considered a relatively 

 primitive center for regulation of postural reflexes, facilitating 

 the neural impulses for voluntary movement, but taking no direct 

 part in their integration or transmission from the cortex. 



iLashler, K. S., Braiv. 1921, xliv. 



