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V. Ontogenesis of the States of Sleep
If phylogenesis allows us to dissociate the appearance of the two states
of sleep during evolution, such a dissociation may also be observed during
ontogenesis in the cat. In kittens and newborn rats (84,
86, 236,
422, 423),
PS may be observed immediately after birth, when slow sleep is almost
nonexistent. Paradoxical sleep has a peculiar aspect phasic phenomena
prevail on tonic phenomena, which is why it is called "sleep with
jerks" (422) or "sommeil
agite" (86). It occupies about 50 % of the day and 80-90 % of behavioral
sleep and very often occurs immediately after waking, since there is no
phase of slow sleep between. Progressively, during cortical maturation,
a slow sleep state appears and increases while PS decreases, so that in
the adult, slow sleep constitutes 70 % and PS only 20-25 % of behavioral
sleep. The occurrence of fast cortical activity (423)
and of hippocampal theta rhythm (86)
during PS precedes, by a few days, the waking tonic cortical desynchronization,
which was interpreted in favor of a dissociation of the mechanism respectively
responsible for waking and PS fast cortical activities.
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