Neurophysiology of the States of Sleep
Michel Jouvet
Physiological Reviews 47 (2) pp : 117-177 (1967)


Definitions and Abbreviations

State of Sleep Characterized by Slow Cortical Activity Slow Sleep

Behavioral aspect

Electrophysiological aspect

Structures and mechanisms responsible for slow sleep

State of Sleep Characterized by Fast Cortical Activity-Paradoxical Sleep

Behavioral aspects

Electrophysiological aspects

Structures and mechanisms responsible for paradoxical sleep

A synthesis of paradoxical sleep mechanisms

Relationship with oneiric activity in man

Phylogenesis of the States of Sleep

Ontogenesis of the States of Sleep

Relationship Between Slow Sleep and Paradoxical Sleep Unicity or Duality of Sleep Mechanisms

A Possible Monoaminergic Theory of Sleep

Figure 1

Figure 2


Printable version

II. State of sleep chacterized by slow cortical activity slow sleep

A. Behavioral Aspects

This section might seem unnecessary, since anyone can recognize a sleeping cat by its posture (and therefore by the persistence of a certain muscular tonus), by its slow and steady breath, and by the stillness of the eyeballs behind closed eyelids. Yet there is no specific behavioral criterion of slow sleep because the relationship between synchronized or slow cortical activity and sleep behavior is not absolute. Indeed an animal may show spindles or slow cortical waves while standing and showing a waking behavior (l04, 145) or while crouching, lying, or coiled into a ball. However, this dissociation between slow activity and arousal behavior, which often occurs after an atropine injection (438), is normally rather infrequent. But the problem of judging the behavior of the animal is far more difficult in preparations with nervous lesions. Although it is fairly easy to notice the alternation of sleep and arousal in thalamic, hypothalamic, or mesencephalic animals (27, 36, 240, 374, 431, 441), this distinction is less obvious in the posterior mesencephalic or chronic pontine animal in which only two behavioral states appear clearly-a hypertonic state (comparable to arousal) and a state of atony with eye movements (corresponding to PS) (240, 252).

Thus only a few of the behavioral criteria of slow sleep in a normal animal have an absolute value. Ocular signs are useful the myosis [ascribed to a hyper tonus of the neurons of the Edinger-Westphal nucleus (64, 381)] is very marked and the nictitating membranes are relaxed, but these criteria obviously have less value when the peduncular area of the brain stem is destroyed. The study of muscular activity does not yield information of pathognomonic value. There always remains a tonic activity at the level of the neck muscles, which is often but not always lower than in wakefulness (254). A deeper analysis of the motor system does not reveal important shifts at the level of the spinal monosynaptic or polysynaptic reflexes, where amplitude remains the same as in wakefulness (181, 183, 284). The vegetative system does not play an important part in the slow sleep state. There is only a small decrease in blood pressure in this state in the cat compared with the waking state (90, 261). Changes in cardiac and respiratory activity are not sufficient in themselves to confirm the slow sleep state in the cat.

Measurement of the arousal threshold (through stimulation of the mesencephalic tegmentum) is perhaps the best criterion. According to some authors (39, 42, 240) the behavioral arousal threshold rises slightly (30 %) during slow sleep. But others have described a steady and recurrent rise in the reticular arousal threshold in the rat (380) and the rabbit (379) during the phases of slow sleep. The increase reaches its peak during the period preparatory to PS. The study of the arousal threshold in response to auditory stimulation is difficult since habituation to auditory stimuli may occur.

Thus the dissociation that may occur between the cerebral slow activity and behavioral sleep makes the physiologist face an ever-present contradiction (and we cannot avoid it in this review). He will either rely on the EEG criterion alone, thus leading himself to believe in the appearance of sleep in animals showing behavioral arousal with a synchronized activity (104, 159), or he will estimate the criteria of slow sleep without the help of the EEG criterion [as is the case in the chronic pontile animal whose subcortical activity always remains fast (240)]. But such an estimation will be purely subjective-when does arousal and relaxed state end and when does sleep start ?

So the finding of a pathognomonic behavioral criterion of slow sleep good for any type of preparation, as well as the establishment of an electrical subcortical activity (or of a biochemical criterion) that could be the cause or the reflection of this behavioral criterion, remains the major and most urgent aim of the study of the physiology of sleep.

Next page