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FIO. i I. Electromyographic analysis of the activity of trans- 

 posed muscles in man after posttraumatic section of the radial 

 nerve. Simultaneous recording on a polygraphic inkwriter of 

 muscular activities recorded by coaxial needle electrodes. The 

 three uppet records are from the operated right upper limb. R.P., 

 activit) of the pronator teres attached to the distal part of the 

 extensor carpi tendon; C.A., activity of the cubitalis anterior 

 transplanted to the tendon of the inactive extensor digitorum; 

 P.P., activity oi the palmaris brevis bound to the tendon of the 

 abductor policis. I he three lower records are from the correspond- 

 ing muscles in their normal attachment in the left upper limb. 

 The following movements are carried out simultaneously with 

 the two hands Left I xtension of the wrist. Note the coopi ra 

 tiuii nl these three muscles in normal conditions and the para- 

 sitil participation of the palmaris brevis in the operated limb. 

 The cubitalis anterior is in this subject the chief executor of 

 this movement. (The left photograph shows the fairly good 

 achievement of tliis movement by the operated hand. The 

 position nl the thumb should however be noted, i Right: Kx- 

 tension of the dibits. Mere too a synergistic activity of the pal- 

 maris brevis is avoidable onl) with difficulty by the subject 

 who cannot extend his dibits without abducting his thumb. 

 Abduction of the thumb (not illustrated by a photograph) is 

 c, lined urn with quite perfect achievement bj the palmaris 

 brevis in the operated side with stabilizing cooperation of the 

 pronatot tct es Front Lord : ' i 



pointed oul l>\ Weiss u |o), the lack oi secondary 

 adjustmenl of the hind-limb movements in this 

 species ma) be correlated with the poverty of |>\ 

 i .> 1 1 1 i 1 1 . 1 1 innervation of the spinal hind-limb centers 

 (no). In the same kind of experiments performed 

 mi the tin i liiul i, which is better supplied with py- 

 ramidal fibers, an attempt at adjustment by 'trick' 

 performance can be observed; however, .1 true 



remodeling of the primitive patterns does not occur 

 at all (1 10). 



Where the ral fails, the monkey partly succeeds; 

 man seems capable of an apparently far better 

 performance. The most carefully analyzed cases, 

 either by clinical 1 1114, 1 to) or by electrophysiological 

 means (70, 80, 1 3 1 ) , are not completely conclusive 

 (see hg. 11). The) sometimes have brought to light a 

 real conflict between inborn patterns and newl) 

 learned patterns, while at other times these subjects 

 show true voluntary disruption of old existing patterns. 



Without doubt man can, by exerting the necessar) 

 mental effort and subjecting himself 10 appropriate 

 training, selectively control certain parts of his 

 musculature, most easily the muscles of the hand. 

 Thanks to his will power he can effectively succeed 

 in correcting certain maladaptations and achieve the 

 proper readjustment of his performance l>\ dis- 

 rupting primitive patterns. The p. in played in the 

 success of this process by his corticomotoneural path 

 may obviously be questioned. 



Scherb (105), however, noted that a real difference 

 may be observed in the action of transplanted muscles 

 of the lower limb between a single voluntary move- 

 ment achieved by the patient at rest, on the one hand, 

 and the old patterns of movement which inevitably 

 reappear in an automatic act such as walking. I In- 

 same type of observations with identical conclusions 

 was made b) Weiss & Ruch (132) in a case of 

 functional supernumerary appendages in man Also, 

 Sperry has rightly pointed out, "To what extent such 

 deliberative corrections could eventually become 

 rapid, automatic and generalized, so as to transfer 

 readily to unpractised activities, can onlv be guessed 

 at present" (i 10). 



It is therefore obvious that the corticospinal system 



must be looked upon as the ehiel mediator of such 

 selective voluntary readjustments. Its anatomical 



arrangement may account for the accuracy of the 

 cortical control of spinal structures 



With regard to the mechanisms brought into play 

 to achieve the progressive and selective focusing ol 

 activity during motor learning, the) ma) be com- 

 pared with those which are similarly operative in 

 conditioning processes. It would also be interesting 



to be able to relate the selective localization of 



voluntar) motor activit) to that of perceptive at- 

 tention. These considerations suggest that it might be 

 profitable to search in motor mechanisms foi some 

 kind nl focalizing mechanisms like those- we begin to 

 feel ma) appear in the organization of sensor) ^vs- 

 tems 





