CHAPTER LXVIL 



The patterning of skilled movements 



JACQUES PAILLARD Faculte des Sciences, Universite d'Aix-Marseille, Marseille, Frame 



CHAPTER CONTENTS 



Peripheral Expression of Skilled Movements 

 Conditions of Expression 

 Forms of Expression 

 Executive Pathways of Skilled Movements 

 The Lower Motoneuron Keyboard 

 The Upper Motoneuron Keyboard 

 The Corticomotoneural Tract 



The Pyramidal and Extrapyramidal Contribution 

 Elaborative Activity and Initiation of Volitional Commands 

 Data from Pathology 

 Motor apraxia 

 Idiokinetic apraxia 

 Ideational apraxia 

 Neurophysiological Data 



Cortical participation in the elaboration of voluntary- 

 movement 

 Concept of a centreneephalic system of integration 

 Mechanisms of patterning at the neuronal level 

 Adaptive Plasticity of the System of Action; its Conditions and 

 its Limits 

 Flexibility of Motor Performances 



Regulative role of sensory information 

 Mechanisms of self-adjustment 

 The Acquisition of Motor Skills and the Learning Process 

 Achievement of a new purposeful act 

 Automatization of the skilled act 



the term 'skilled' is employed with various mean- 

 ings. We shall use it here to designate among motor 

 activities a particular category of finely coordinated 

 voluntary movements, generally engaging certain 

 privileged parts of the musculature in the per- 

 formance of various technical acts which have as 

 common characteristics the delicacy of their adjust- 

 ment, the economy of their execution and the ac- 

 curacy of their achievement. 



Such movements belong to the categorv of the 



so-called manipulative activities and have to be 

 set apart from purely locomotor activities. The skill- 

 ful use of certain motor organs for gripping and 

 transforming matter is included in the scale of 

 evolutionary development which leads from the 

 primitive activities of prehension to the more com- 

 plex activities of manipulation, finally culminating 

 in the achievement of manufacture which is the 

 outcome of human dexterity 'i ;;' Manipulation' 

 (like 'manufacture') designates etymologically the 

 work of the hand; 'dexterity' characterizes, in its 

 original scum-, the quality of these skilled actions 

 which are executed by the right hand (and COnse- 

 <|uentlv better than bv the left hand). Such an- 

 thropomorphism in the vocabulary indicates the vei v 

 particular and privileged role of the human hand as 

 the most elaborate instrument for skilled activities. 



Indeed, phv louenctic considerations will show how 

 the human hand, in spite of the bonds which tie it 

 to the animal world, behaves (as does, in another 

 held, the very special apparatus of language expres- 

 sion I in accordance with an absolutely original 

 functional formula. Ever since their origin, the func- 

 tional organization of living creatures has been 

 characterized by a very harmonious coordination 

 between the apparatus for collecting information 

 thanks to which the organism can construct its 

 knowledge of the surrounding world, the locomotor 

 arrangements which permit it to explore and the 

 organs of prehension which condition its acquisition 

 of food. 



Among the nonsessile organisms, for which the 

 exploratory activities become predominant, the 

 organization of the functional components appears 

 identical; the organs for prehension and for securing 

 of information are grouped at the anterior part of an 



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