MICHEL JOUVET 471 



The electrical activity of the brain was recorded and correlated with a 

 number of somatic signs of sleep: sleep posture, aspect of pupils and 

 nictitating membranes, rectal temperature, respiratory rhythms, E.K.G. 

 We found that one of the best signs of sleep was the E.M.G. of the nucchal 

 muscles. 



1. Normal dns (Figs. 1-2). Two opposite E.E.G. patterns were observed 

 during physiological sleep: 



A. The first sta(^c is well known (drowsiness and sleep). Spindles and 

 slow waves were recorded at tlic cortical, diencephalic and, later, at the 

 mesencephalic reticular level. The ventral hippocampus may show a 

 'spike-like' activity. In contrast, the electrical activity at the pontine 

 reticular level remained fast. During this stage, the E.M.G. of nucchal 

 muscles decreased but did not disappear. The threshold of arousal by 

 stimulation of the mesencephalic reticular formation was found to be 

 higher during the slow wave activity than during spindle activity. 



B. The second sra(^c or 'paradoxical staoc' (Fig. i, III, 2, III): It begins 

 suddenly (always after the first stage) and is characterized by a low 

 voltage fast electrical activity at the cortico-diencephalo-mcsencephalic 

 level comparable with the arousal pattern. But the pontine reticular 

 formation usually presents a spindle activity. 



Behaviourally, the cat was soundly asleep and there was a total disap- 

 pearance of any E.M.G. activity. Some very rapid jerks of the vibrissae 

 and movements of the eyes were frequently seen. Spontaneously, or 

 induced by any stimulus, the cat may go back to the first stage of sleep or 

 awaken. 



During the paradoxical stage, the threshold oi arousal (by direct 

 stimulation of the R.F.) was higher than during the slow wave stage. 



2. Ncodccorticatcd Cat (Figs. 3-4). In such preparations, the mesodicn- 

 cephalic activity remained constantly fast with a low voltage. Neither 

 spindles nor slow wave could be recorded, week after week, during the 

 wake-slccping cycle, even after injection of narcotic doses of Nembutal. 



Diiriii<i the paradoxical sta(^e, a 'spindling activity' was recorded at the 

 pontine reticular formation level. Concomitantly the liippocampus 

 showed an arousal type ot activity. 



The same behavioural phenomena as are found in normal cats occurred 

 during this last stage. 



Suhtotally ueodecorticated cats (Fig. 5) : If a very small part of frontal or 

 ten;poral cortex was left intact during the decortication, the patterns ot 



