THE PATTERNING OF SKILLED MOVEMENTS 



169I 



incapacity to mobilize correctly the kinetic formulas 

 in accordance with the established plan (ideokinetic 

 • apraxia) or finally from the dissolution of the kinetic 

 formulas themselves (motor apraxia). 



In spite of the divergence of views and of the 

 many controversies in which clinicians have been 

 involved concerning the nosologic classification of 

 praxic disorders which, like all classifications, has an 

 artificial character, we shall accept Liepmann's as 

 didactically useful in that it leads us to consider 

 distinctions between different levels of organization 

 in the unitary functional whole involved in praxic 

 functions. 



motor apraxia. This disability corresponds to the 

 gliedkinetische Apraxie of Licpmann (75) or to the 

 innervatorische Apraxie of von Kleist (123). Nielsen (90) 

 also speaks of a 'cortical motor pattern apraxia." It i^ 

 associated with a more or less specific disruption of 

 the kinetic formulas acquired during the learning of 

 certain specialized movements. 



The subject behaves as if he were carrying out, for 

 the first time, these movements which were normalK 

 part of his habitual motor repertory. The disorder 

 can take on curious specificities and affect electively 

 special abilities. Such is the case, often reported, ol 

 the instrumental amusia which leaves the patient 

 disoriented before his habitual musical instrument, 

 incapable of mobilizing his previously acquired 

 automatisms. Agraphia is another frequently given 

 example in which the patient becomes incapable oi 

 directing his pen to form a letter. The same kind of 

 trouble is found in the realm of speech disorders; the 

 buccofacial apraxia which constitutes one of the 

 components of anarthria causes difficulty in the 

 emission of words by a deficit of the corresponding 

 motor patterns. 



These disorders are associated with injuries localized 

 in the frontal region immediately adjacent to area 4. 

 Specialized apraxias are accompanied by elective 

 destructions of certain sectors of area 6. Agraphia, 

 for instance, is associated with a lesion of the second 

 frontal convolution, anterior to the precentral gyrus, 

 and instrumental or vocal amusia with a lesion 

 situated in the neighborhood of Broca's convolution 

 (the pars triangularis of the third frontal convolu- 

 tion). 



The same cortical regions, as we have seen, also 

 control the complex figures of innate holokinetic 

 mechanisms. Injury to these regions situated more or 

 less largely outside the cortical keyboard is accom- 

 panied either by volitional paralysis or by dis- 



turbances in the discrete control of the musculature. 

 It causes a specific deficiency in both the innate and 

 acquired kinetic repertories. 



These facts, at first sight, seem consistent with 

 the early conceptions formulated to explain the 

 phenomena of memory by postulating the existence 

 of engrains, or traces inscribed in the neuronal ar- 

 rangements and containing the prefiguration of 

 given patterns of activity. 



Without subscribing to the excesses of those who 

 accept the cortical localization of such engrains 

 without qualification, we can however retain belief 

 in the unique role played by these nervous structures, 

 immediately adjacent to the cortical keyboard, in 

 the construction and the organization of given de- 

 signs of activity. We may note here the homology of 

 (his organization with that of the gnosis areas which. 

 on tlx- sensor) side, are responsible for the organiza- 

 tion of perceptive 5) nthesis. Such mechanisms ac- 

 quired b\ experience enrich the primitive repertory 

 of the holokinetic mechanisms; the) pl.iv an es- 

 sentia] role in the orchestration of the idiokinetii 

 melody on the motor cortical kev board. 



Electrical stimulation of these regions effectively 

 produces complex organized movements. Recent 

 experimentation on animals indicates, however, that 

 the results become less striking .is we go up the animal 

 scale. Delgado (26) obtained in the cal rem. 11 k.iUv 

 integrated purposeful movements in the context of 

 ordinary reactions of the animal. Ward (129) ob- 

 served in the monkey badlv .id.iptcd and often un- 

 differentiated moloi effects of such stimulation, and 

 Penfield (95) notes in man thai no stimulation of 

 the motor cortex is able to activate the engram nl 

 organized skilled acts. In the same way, electrical 

 stimulation of the regions for vocalization can only 

 provoke the emission of unarticulated sounds without 

 symbolic significance. (However, the complex struc- 

 tures mediating highly integrated visual and auditory 

 memories are electrically excitable in the temporal 

 regions. I 



These findings lead us to think that we must 

 recognize the presence of an intermediary sv^iem, 

 capable of organizing die play of the motor cortical 

 keyboard but still receiving its excitation from some- 

 where else. The study of the second group of apraxias 

 permits us to glimpse something of the nature and 

 the complexity of these excitatory mechanisms. 



idiokinetic apraxia. This disorder expresses itself 

 by an incapacity on the part of the patient to mobilize 

 the apparatus of action in a manner appropriate to 



