Reversible blockade of PGO waves and concomitant modifications of thalamic unit activity in chronic cats.

The reversible blockade of geniculate PGO waves was carried out by localized cooling of the ponto-geniculate pathways during paradoxical sleep in chronic cats. In parallel, long-term recordings of unit activity were performed in non-specific visuooculomotor thalamic structures where no PGO waves occurred. Blockade of geniculate PGO waves is concomitant with a preferential modification of the phasic discharge of the unit activity (i.e. time-locked with rapid eye movements) when compared to the tonic discharge (i.e. without rapid eye movements). These results suggest that pontine generators of PGO waves could act upon every neuron of the central nervous system. The significance of such an extensive ascending system, the blockade of which does not interrupt paradoxical sleep episodes, still remains puzzling.