p. BUSER ET A. ROUGEUL 553 



After ablations of the motor cortex — second strip — the instrumental reflex is 

 even less impaired than in the previous case, but the animals display a striking 

 symptom of confusing legs, i.e. they perform the trained movement either with 

 the right or with the left foreleg. This almost never occurs either before the opera- 

 tion or after any other cortical lesion. The animals also manifest hyperkinesis of 

 the legs consisting in repeatedly lifting them to various heights — 'pedalling 

 movements' — This symptom is best seen when the animal is lifted into the air 

 (Stcpieii, Stepieii and Konorski, i960). 



While after ablations of sensory or motor cortex the movements ot the animal 

 are more or less awkward and ataxic, after the removal of the third strip — pre- 

 motor area — they are as skilful as before operation, but a striking disintegration 

 of instrumental CRs takes place. The animal is able to perform the trained move- 

 ment without any 'teclinical' difliculty, but he does not 'know' when to perform it. 

 So the movements appear very often in the intervals, sometimes with great 

 frequency, but they often fail to appear to the CS itself. Instead, the animals display 

 either a strong orienting reaction towards the source of the stimulus, or a strong 

 direct alimentary reaction to the bowl, or both. During the experiment the 

 animal displays many irrelevant activities, so that his whole behaviour may be 

 qualified as 'stupid' (Stepien, Stepieii and Konorski, i960). 



To put it briefly one can say that after sensory lesions the animal is ataxic and 

 paretic but his general behaviour is normal. After premotor lesions, on the con- 

 trary, the animal is quite skilful, but his general behaviour is 'senseless'. Lesions of 

 the motor cortex produce intermediary symptoms. The ablation of the whole 

 sensori-motor cortex makes the animal both strongly ataxic-paretic and 'stupid'. 



BusER. I was quite interested by Dr Konorski's remarks. As far as general be- 

 haviour is concerned it is true that cats and dogs behave in similar ways after total 

 ablation of the whole sensorimotor cortex. But we were not led as yet, to con- 

 sider that different divisions of this frontal cortex play different roles. The reason 

 for these discrepancies may be due: (i) to phylogeny, the premotor cortex in cat 

 being smaller and probably less important than in dogs. Actually, a cat deprived of 

 premotor cortex almost behaves — in our pattern of testing — as a normal control 

 animal; (2) to unequal capacity tor diftercntiation between signal and environment, 

 which is normally very clear cut in dogs, and never perfect in cats; thus a slight 

 impairment in the latter case, could be considered as remaining within limits of 

 normal variations. 



Doxyi. I would like Dr Buser to tell us a little more about these very interesting 

 units in the sensorimotor area, on which the auditory and visual systems also seem 

 to converge. What are their firing patterns and latencies for the various sensory 

 stimuli ? 



Buser. hi preparations under chloralosc and in unanaesthetized but curarized 

 preparations, exploration of the cat's motor cortex with macroelectrodes as well as 

 microelectrodes reveals the existence of sensory responses to somatic stimulation. 

 Average latencies are twice (or at most three times) the one on primary cortical 

 fields; microelectrode recordings further show convergencies of all three modalities 

 on the same neurones, finally, facilitation or occlusion occur at this level when two 

 different sensory modalities are applied in combination. 



1 This and further questions refer to a chapter on electrophysiological recordings, which 

 has been, for the sake of simplicity, omitted in this paper. 



