THE PATTERNING OF SKILLED MOVEMENTS 



703 



for the analysis of living organisms as teleological 

 systems of action (36), we will assert for our restricted 

 field its undeniable explicatory power to account for 

 the flexibility of motor performance which, in other 

 respects, is dependent on a prearranged pattern of 

 neuronal interconnections. 



We are now faced with our second problem. How 

 can we conceive the mechanism by which the or- 

 ganism may improve upon its own structure and may 

 invent new forms of action? 



The Acquisition 0] Motor Skills and 

 the Learning Process 1 



A basic fact must be kept in mind when trying to 

 approach the problem of the neural basis of motor 

 learning, namely that the muscular keyboard does not 

 immediately allow all possible chords. The central 

 commands are bound to operate upon it through the 

 pre-existing arrangements of its inherited or mosl 

 usual modes of action. 



Therefore, as also emphasized l>\ the psychologists 

 concerned with learning, to learn a new act does not 

 consist in creating out of nothing a new motor pattern 

 by putting together in proper sequences the ana- 

 tomical units of the motor machinery. Learning 

 requires, before anything else, a disrupting of some 

 pre-existing functional units (45), then a selective 

 choice of the useful motor combinations, and finally 

 their assembling into a new working unit. 



For convenience of anaKsis, it will be 0] some 

 interest to distinguish two complementary aspects, 

 both intimately involved in the learning of a new act 

 The first is more especially related to the initial phase 

 of learning; it concerns the activity required of the 

 higher control to tide over the difficulties encountered 

 and to achieve the proposed end, it implies a selective 

 operation. The second is related to the learning 

 process itself and finds its final expression in the 

 automatically achieved act which becomes almost 

 completely independent of higher control; it implies 

 the stabilization of the fixation of a new pattern of 

 nervous activity. 



ACHIEVEMENT OF A NEW PURPOSEFUL ACT. Perfect as 



the self-regulatory mechanisms may be, they are 

 incapable of executing immediately with the required 

 accuracy a purposeful act having an aim which is 



1 This topic is the subject of Chapter LXI by Galambos and 

 Morgan in this Handbook. 



beyond the limit of flexibility of the individual's motor 

 repertoire. 



The mastering of the basic movements in the first 

 years of childhood and later of the skilled movements 

 or technical abilities is accomplished, first of all, 

 through a process of fumbling and progressive 

 adjustment. Psychologists have defined the essential 

 characters of this progress. The initial phase involves 

 a first inventory of the means to be put into action to 

 attain the proposed goal. From the very outset, the 

 most important part seems to be played by regulatory 

 perception. The improvement in motor performance 

 is essentially characterized by the selective restriction 

 to movements strictly necessary to make the action 

 effective. Psychologists also insist on the importance 

 of the perceptive organization from which the 

 elaboration of the 'motor image' or representation of 

 the act proceeds. A significant part is played in this by 

 the model of the act existing in the subject's central 

 nervous system (45). The achievement of a new act 

 therefore depends upon a complex modulator opera- 

 tion which involves the higher level of integration. 



The main concern for our understanding of the 

 neural mechanism involved is that this selective and 

 adjustive capacity of the higher levels is limited in 

 setting up new patterns of action by its power to 

 remodel or abolish the existing ones. Therefore, the 

 limits of the learning process proper appear to be 

 determined l>\ the extent to which the functional 

 units which produce internal remodelings of higher 

 Origin can operate. The nature and the importance oi 

 these functional units vary with the speeies and in a 

 given species with the different parts of the body, 

 discrimination being more accurate in the forelimb 

 than in the hind limb, and in the distal part of the 

 limb than in the proximal. 



Such facts obviously suggest that motor learning 

 capacities should be closely related to the degree of 

 refinement in the connections between the higher and 

 lower levels of motor arrangements. Such a statement 

 seems fully justified by the data available from the 

 results of experimental as well as therapeutic nerve 

 regeneration or muscle transposition. These opera- 

 tions, which impair the effective performance of a 

 given muscular group, are of interest in imposing on 

 the learning capacities of higher levels the necessitv of 

 remodeling inborn primitive patterns of coordination 

 in order to re-establish the adaptive use of a limb. 



As shown by the now classic experiment of Sperrv 

 (110), a rat fails to re-establish a correct functional 

 adjustment of the action of antagonistic muscles when 

 their tendinous attachments have been reversed. A- 



