Progressive cortical synchronization of ponto-geniculo-occipital potentials during rapid eye movement sleep.
Phasic events, termed ponto-geniculo-occipital potentials, appear in the brainstem, thalamus and cerebral cortex during rapid eye movement sleep. In the cat, the species of choice for ponto-geniculo-occipital studies, these field potentials are usually recorded from the lateral geniculate thalamic nucleus and visual cortex. However, the fact that brainstem cholinergic neurons play a crucial role in the transfer of ponto-geniculo-occipital potentials to the thalamus, coupled with the evidence that mesopontine tegmental neurons project to virtually all thalamic nuclei, together explain why ponto-geniculo-occipital potentials are recorded over widespread territories, beyond the visual thalamocortical system. Here we demonstrate, by means of multi-site unit and field potential recordings from sensory, motor and association cortical areas in behaving cats, that: (i) ponto-geniculo-occipital potentials appear synchronously over the neocortex; and (ii) that their cortical synchronization develops progressively from the period preceding rapid eye movement sleep by 30-90 s (pre-rapid eye movement), to reach the highest degree of intracortical coherence during later epochs of rapid eye movement sleep. We propose that the widespread coherence of cortical ponto-geniculo-occipital potentials underlies the synchronization of fast oscillations (30-40 Hz) during rapid eye movement sleep over many, functionally distinct cortical territories implicated in dreaming, as brainstem-induced ponto-geniculo-occipital-like potentials are consistently followed by such fast oscillations.
Amzica
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F
Laboratoire de Neurophysiologie, Faculté de Médecine, Université Laval, Quebec, Canada.
Steriade
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M
D000818:Animals; D002415:Cats; D004567:Electrodes, Implanted; D005829:Geniculate Bodies / Q000502:physiology*; D009778:Occipital Lobe / Q000502:physiology*; D017286:Polysomnography; D011149:Pons / Q000502:physiology*; D012890:Sleep / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology*