Materials and methods

Results were obtained from 52 chronic cats ( 12 normal cats, 11 totally or partially decorticate, 20 with total or partial brain stem section, 7 with partial coagulation of the brain stem, and 2 which had undergone total ablation of the cerebellum). These animals were implanted with nickel-chrome multipolar sub cortical electrodes and steel cortical electrodes, and were all studied for more than one week. Decortication was carried out in one operation by suction after removal of the skull. An acrylic resin plastic roof was then inserted in place of the bone and the subcortical electrodes were thus kept at that level (Jouvet, Michel and Courjon, 1959a). The brain stem was sectioned by means of a stereotaxically oriented cutting blade, and coagulation was obtained by means of anodal electrolytic lesion. In some cases, the entire part of the encephalon situated in front of the midbrain was removed by aspiration. Poikilotherm, mesencephalic or pontile animals were kept warm and always studied at normal temperatures between 37° and 39°. The cats were placed in soundproof cages and EEG recording was carried out daily for 6 to 12 hours. As a routine measure, together with the EEG, the EMG was recorded by means of a bipolar electrode permanently mounted at the level of the neck muscles. The eye movements were also recorded by electrodes fixed on both sides of the eye balls. The behaviour of the animals (pupils, nictitating membranes, posture, etc.) could also be observed through glass. In all cases, the siting of the electrodes and the topography of the lesions were checked histologically.

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