p. BUSER ET A. ROUGEUL 55 1 



interfere!' avec I'elaboratioii volitionnelle; des periodcs de desorientation, 

 d'autre part, rammal devenant transitoirement incapable d'execiiter le 

 niouvenient d'appui. 



La signification de ces rcsultats est discutee, en particulier sous Tangle 

 d'une confrontation avec les donnees neurophysiologiques relatives a la 

 mise en jeu du cortex nioteur, et d'un eventucl role de la voie pyramidale 

 dans la regulation de I'activitc volitionnelle chcz le chat. 



Summary 



A study was performed on cats, of the effects of removing sensorimotor 

 cortex (or other cortical areas) on learning and executing the lever-pressing 

 movement to a signal stiniulus, in an instrumental conditioning situation 

 (alimentary motor). 



After total bilateral removal of sensorimotor cortex (leaving or not a 

 small part of somatic II), normal scores (pattern and latency of gesture) 

 may still be obtained, but most of the observed movenients arc disturbed 

 in several ways which have been analysed. 



Evaluating latencies of pressing movement reveals a first group of 

 significant differences between normal and sensorimotor deprived animals: 

 statistical dispersion of latency values is much larger in the latter case; in 

 time also, individual delays for deprived animals appear mostly variable in 

 course of one session. 



In contrast to this, spontaneous conditioned movement appear less 

 frequent in ablated than in normal animals. 



Two types of qualitative disturbances of movements are further 

 described: 'automatic' hyperactivity on one side, which may interfere 

 with volitional elaboration; desorientation phases, on the other, the animal 

 becoming temporarily iniable to execute the correct secjuence of move- 

 ments to obtain food — though remaining strongly motivated for food 

 reward. 



None of the previously described disturbances are defmitely observed, 

 following other cortical removals (visual area, temporo-occipital cortex, 

 whole neocortex but sensorimotor area, prefrontal cortex). 



These results are discussed in relation to neurophysiological data on 

 afferent projections to and 'integrative' properties of the motor (perisig- 

 moid) cortex in cat. 



DISCUSSION 



Kc:)NORSKi. Since our laboratory has been concerned in recent years with the 

 study oi the effects of scnsori-motor lesions upon instrumental conditioned reflexes 



