THE PATTERNING OF SKILLED MOVEMENTS 



I 70; 



On the other hand, the part played by perceptive 

 or purely sensory regulation should probably be 

 considered as determinant. The accuracy of fine 

 motor adjustments controlled by visual cues, for 

 instance, is much more often limited by perceptual 

 than by motor factors. A possible organization of 

 circuits invoked in these sensorimotor relations is 

 diagrammed in figure 10. 



AUTOMATIZATION OF THE SKILLED ACT. Thus the first 



phase of the learning process requires, to a greater or 

 less degree according to the difficulties invoked, an 

 important mental effort which mobilizes the higher 

 controlling systems. These, indeed, have at the 

 beginning the heavy task of directing almost every 

 part of the act. From the effort of voluntary control 

 there may result a generalized tension. This tension 

 appears in the musculature in the form of stiffness 

 It is as though there were a certain diffusion of the 

 motor command, producing parasitic movements 

 which are prejudicial not so much to the precision as 

 to the economy of performance. The mechanism of 

 this diffusion can now be considered (91 ). On repeti- 

 tion of the act, this initial tension decreases pro- 

 gressively. This decrease in tension seems to be related 

 directly to the degree of participation of the higher 

 control. Voluntary control, as previously stressed, is 

 effected with the help of sensor) feedbacks. It is 

 obvious that the first improvements of the performance 

 are attributable to the reorganization of feed-back 

 control. Initially, and as a rule, such feedbacks arc 

 chiefly visual in manipulative activities. Then the 

 links between certain sequences in the acts find them- 

 selves entrusted to other sensory modalities (chiefly 

 proprioception). Thus, each part of the act becomes 

 the signal which brings the next one into action. The 

 distance receptors are progressively freed from pan of 

 their former duties and from voluntary control as 

 well. Then the latter may concentrate on watching 

 over the most delicate parts of the action and thereby 

 improve their performance. Finally, thcv have to 

 play a part only in bringing the perfectly automatized 

 action into play and turning it off, remaining vigilant, 

 however, to face immediately any emergency beyond 

 the range of flexibility of this automatic act. 



The automatic act becomes perfect only when the 

 'kinetic melody' has, so to speak, its own regulation 

 in hand (45), in other words, when it becomes the 

 output of an organized functional self-regulating 

 unit. This new functional unit owes its structural 

 individuality at least in part to reinforcement and 



maintenance of new patterns of synaptic linkages. It 

 owes its internal cohesion as well as its own range of 

 flexibility to its "systemic' organization. Thus, a new 

 skilled act is added to the 'motor repertoire' of the 

 individual. 



Where must the stabilization of the learned kinetic 

 system be located in the nervous structures? How can 

 the mechanism of preservation of this pattern be 

 understood? These two questions are still far from 

 being answered satisfactorily. Concerning the location 

 of the learned kinetic patterns in the cortical nervous 

 structures we do not presently possess any decisive 

 experimental evidence (57, 66, 87). That these 

 cortical structures are a part of the kinetic functional 

 unit is, however, not to be doubted. The study of 

 motor apraxias has stressed the pattern-disrupting 

 results of destruction of the anterior conical motor 

 regions. We have, however, already mentioned the 

 1 act that in no place where cerebral tissue ma) be 

 electricall) stimulated can learned purposeful motor 

 acts be obtained. In the same connection, however, 

 it is noteworthy that well-organized memories are 

 activated bv stimulation of the temporal region. 



Sperr) asked '-whether the attainment of automa- 

 ticitv bv long practice might not result eventually in 

 descent oi the central reorganization to lower motor 

 levels" I 1 i" Lashley's earlier data on this point (66), 

 although not conclusive, suggesl that the eventual 

 participation of subcortical structures iii the learning 

 process could not in an) ease make an acquired lial.il 

 independent of its cortical organization. Recently, 

 av .11I. 1 1 ilc d.ii,] concerning the mechanisms responsible 

 lor the 'temporary link' in the Pavlovian conditioning 



-eei igree in localizing in nonspecific subcortical 



regions the seat of the so-called 'switching' of such 

 links (42). Nevertheless, such data do not diminish the 

 functional importance of neocortical structures iii the 

 process of selective differentiation, concentration and 

 extinction of a conditioned reflex 



The possibility of learning or reorganization within 

 the spinal structures claimed by the organismic 

 school (Anokhin, Goldstein, Bethe) probabl) remains 

 remote, if ever present, as appears from the pertinent 

 criticisms of Sperry (1 10, 112). The existence of spinal 

 conditioning is also still definitely controversial (87). 

 The interneural relation patterned by learning would 

 seem to be relegated better to the cerebral circuits and, 

 as proposed by certain authorities, particularly to 

 those circuits connecting the cortical with the sub- 

 cortical structures 



