Telencephalic and rhombencephalic sleep in the cat
Jouvet M.
The Nature of Sleep Ciba Foundation Symposium Churchill (1961)


Materials and methods


Topography of the systems responsible for the two stages of sleep

Mechanisms of the rhombencephalic phase of sleep




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Topography of the systems responsible for the two stages of sleep

(1) First phase of sleep (spindles and slow waves)

Whatever the subcortical structures may be which are responsible for the synchronization phenomena (diffuse thalamic system, Jasper, 1949; or caudal region of the brain stem, Batini et al., 1958) one fact appears to be certain: the spindles and the slow waves which are observed during the first phase of sleep require the presence of the neocortex, since there are no sub cortical spindles or slow waves in the decorticate animal or from behind a section of the brain stem. The study of animals whose brain stem has been partially sectioned enables us to state that the corticifugal inhibitory descending tracts are diffuse within the brain stem R.F., because the slow waves appear behind a section, leaving part of the R.F. intact, however small.

(2) Determination of the cerebral structures responsible for the rapid activity phase (p.p)

a) Structures responsible for the triggering of this phase. Pontile EEG activity and somato-vegetative phenomena which are characteristic of the p.p. continue to appear normally in chronic decorticate, mesencephalic or pontile animals. These phenomena, however, are completely lacking in cats whose brain stems have been sectioned between the pons and the trapezoid bodies. The structures which are responsible for the triggering of such periodic phenomena must, therefore, necessarily be found at the level of the pons (Fig. 7).

The formal proof of this is provided by coagulation experiments limited to this level. These were carried out over a width of 3 to 4 mm. at the level of the pons tegmentum. The nudeus pontis caudalis, the posterior part of the nucleus pontis oralis and the superior central nudeus of Bekhterev were destroyed (Fig. 8). Not one of these animals exhibited a p.p. during sleep.

They all showed, however, a slow cortical activity during the first phase of sleep and were capable of a rapid activity during spontaneous or provoked arousal. The reticular formation of the pons thus appears to be responsible for the rapid activity phase of sleep, which can therefore be described as the rhombencephalic phase of sleep.

(b) Cerebral tracts responslble for rapid cortical activity. These tracts are certainly different from the ascending activating reticular system which is responsible for cortical "arousal" (Moruzzi and Magoun, 1949). Indeed cats whose R.F. is interrupted at the level of the midbrain tegmentum, and which are thus incapable of any rapid cortical activity during nociceptive stimulation or reticular stimulation behind the lesions, continue, however, to exhibit rapid cortical activity during p.p. if the ventral part of the mesencephalon is not damaged at the level of the interpeduncular nucleus and the mammillary bodies (Jouvet and Michel, 1960a). Such structures are known to be passages in a circuit (limbic midbrain circuit-Nauta, 1958) linking certain nuclei situated at the level of the pontile R.F. to limbic and rhinencephalic formations.

It is thus probable that such a circuit is responsible for some cortical electrical aspects of the p.p., particularly for the rhinencephalic rhythmic activity.

c) Structures responsible for somato-vegetative phenomena. The appearance of typical p.p.'s in the cerebellectomized animal having disposed of any possibility of the cerebellum playing a part, the somato-vegetative phenomena associated with this phase may be explained by the active intervention of the bulbar inhibitory R.F. (Magoun, 1950), which is known to exert a general control on muscular tone and acts on the alpha-type as well as on the gamma-type rigidities (decerebellation and decerebration rigidities). Respiratory and cardiovascular centres are also known to exist at the level of the pons and their intervention would explain the characteristic variations in respiratory and cardiac rhythms.

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