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II VXDHIMIK (II- I'llYSK il l M. Y 



XllKlll'HYSIOI.OGY III 



complex descending system contributes to the excita- 

 tory siaic of the spinal keyboard. 



Stereotyped patterned movements integrated at 

 lower levels can be utilized as parts of wholes. Pos- 

 tures can be assumed, modified and shifted so that 

 the instant obedience of a muscle to pyramidal 

 demands could appear. The refinement with which 

 the presence of ihe pyramidal system supplements 

 holokinesis is referred to by Hincs as 'idiokinesis 1 



(51). 



I less (50) described the extrapyramidal function 

 as 'ereismatic' ('ereisma' meaning a framework). It 



assures llie inlenlional 'leleokinetic' movemenl 

 (directed u> a i>ivcn end) of its essential frame for 

 economical and precise accomplishment. (This con- 

 cept is developed in detail in Chapter XXXV by 

 Jung i\' I lassler in this work.) 



Thus, the ability to control skeletal muscle for 

 discrete action is dependent upon the organization of 

 a whole complex motor arrangement. The specificity 

 with which the spinal keyboard responds to the 



cortical command depends chielh upon the fineness 

 of organization of the upper motoneuronal keyboard 

 and upon the more or less close connection between 

 the lower motoneuron and the upper one. 



II is also significant to note that electrical stimu- 

 lation of cortical motor areas of unanesthetized 

 monkeys (129) or man (95) never gives forced move 

 ments having a dextrous and purposeful gestural 

 allure. 1 he cortical keyboard appears 10 be only a 



relay station essential to the exec anion of fine control 

 ol the musculature, bul one which receives its activa- 

 tion from other sources. The patterning of com- 

 mands which is elaborated at its level depends upon 

 superior influences which harmonize the conjoined 

 play of pyramidal and extrapyramidal actions. 



1 1 VBOB \i ivi VI 1 ivi n \xi> imii vin>\ 



1 il Vi H I I II IN \l ' 1 'MM \XIIS 



When he tries In pmlie deeper into llie organiza- 

 tion ol the systems devoted to the elaboration and 

 10 the volitional control of the 1 hemes of activity, the 

 neurophysiologisl quickly appreciates the insuffi- 

 ciency of his present knowledge and the imperfec- 

 tions nl his means ol investigation. The complexity 

 of the integrative activities pul into action al this 

 level seems, ai fnsi glance, beyond the reach of the 

 traditional methods of animal experimentation. 

 Normal function seems to be an undissociable com- 

 plex in which immediate sensorial data and traces ol 



acquired experience are blended with complex 

 psychic elaborations into a dynamic synthesis which 

 is constantly being remodeled. It is inward llie 

 clinician and the pathological anatomist that the 

 neurophysiologisl now turns in the hope of finding 

 some phenomena accessible to his experimental 

 methods. 



Data from Pathology 



The clinician gives us a very important clue when 

 he affirms that he can recognize a kind of motor 

 disorder affecting electively the capacity of the pa- 

 tient to move certain parts of the body by intention 

 to attain a given end. This disturbance appears in- 

 dependently of any impairment of the mechanisms 

 for motor execution or of the systems providing 

 sensory information, and of any deficit of intellectual 

 functions. It justifies the concept of a 'praxic' func- 

 tion 



This line of thought becomes still more challenging 

 when ii is realized that the accumulated pathological 

 anatomical documents establish the association of 

 certain localized cortical lesions with the disruption 

 nl this function. But difficulties soon crop up in the 

 face of the number and the disparity of die various 

 clinical manifestations accompanying such lesions. 

 Further confusion arises from the multiplication of 

 theoretical schemes which have been proposed to 

 provide a coherent explanatory framework into 

 which die observed facts may be introduced. With- 

 out entering upon these questions in detail, we shall 

 only consider several aspects useful in our approach 

 to the nervous mechanisms brought into pla\ in the 

 central elaboration of voluntary commands. 



Disorders of praxic function can affect separately 

 all kinds of intentional movements. It is important 

 lor our study to note that they impair most particu- 

 larly die acquired forms of skilled manual mo\ ements 

 .mil the activities of the laryngeal apparatus in its 

 relation In speech. Disturbances of the killer his- 

 torically opened die pathway to the study ol praxii 

 (unctions (171 They are, furthermore, the object of a 



special field ol development (see the chapter bv 



Zangwill on speech in this volume). We shall devote 

 ourselves exclusively therefore to the examination of 

 the former. 

 According to the initial classification of Liepmann 

 and the nine authors who followed him, 

 apraxia represents a disorder of voluntary movement 

 resulting either from a perturbation ol psychic 

 planning of action (ideational apraxia 1, from the 





