272 ARCHIVES OF NEUROLOGY AXD PSYCHIATRY 



at some higher level and imposed through it on the motor area. But 

 there is no direct evidence that this is the case. The movements fol- 

 lowing excitation are far more like the gross changes of posture which 

 one may observe in the intact animal — the raising of an arm preparatory 

 to snatching at food, bracing against a pressure, or the like. It seems 

 significant that coordinated movements of the eyes are among the most 

 easilv elicited movements on electrical stimulation ( although their stimu- 

 late points lie outside of the precentral areas), and that these move- 

 ments in the intact man or animal are almost always a reflex fixation 

 (postural adjustment) called out directly by exterostimulation and, in 

 fact, can not be accurately performed in the absence of such stimulation, 

 as with lids closed. 



Wilson 51 has pointed out the similarity of the contractures in cere- 

 bral paralysis to the postural reflexes of decerebrate rigidity, and from 

 this it seems certain that a part of the function of the stimulable areas 

 is the regulation of these spinal and cerebellar postures. It seems rather 

 probable that the movements obtained on electrical stimulation are only 

 a further exhibition of this postural activity and are unrelated to the 

 finer coordinations of conditioned motor reflexes, or motor habits. 



The Dynamic Function of the Stimulable Areas. — The condition 

 following lesions to the precentral gyrus or internal capsule, even in 

 man, should be described rather as an enormous difficulty in making 

 movements than as an absolute paralysis of movement. The degree of 

 paralysis varies somewhat from day to day. Excitement seems to 

 increase motor control (Minkowski. 52 Lashley 37 ), and the paralvsis 

 may in part or wholly disappear during emotional disturbance, only to 

 recur when the disturbing situation is past. If we may judge from the 

 tonic condition of the muscles, there must be in excitement a ireneral 

 facilitation of lower motor centers which temporarily reinstates cerebral 

 control. Further, if this is the case, in the intact animal in the absence 

 of emotional stimulation cerebral control must likewise be conditioned 

 by some such facilitation derived from the precentral gvrus. The work 

 of Brown 53 and of Leyton and Sherrington 26 has shown that stimula- 

 tion of the motor area does facilitate the centrifugal paths of other 



51. Wilson, S. A. K. : On Decerebrate Rigidity in Man and the Occurrence 

 of Tonic Fits, Brain 43:220-268, 1920. 



52. Minkowski, M. : Etude physiologique des circonvolutions rolandique et 

 parietal. Arch. Suisse de Neurol, et Psychiat. 1:389-459, 1917. 



53. Brown, T. G. : Studies in the Physiology of the Nervous System. XXV. 

 On the Phenomenon of Facilitation. 4. Its Occurrence in the Subcortical 

 Mechanism by the Action of Which Motor Effects Are Produced on Artificial 

 Stimulation of the "Motor" Cortex. J. Physiol. 9:131-145. 1915; also Footnote 36. 



