PGO Wave Activity and Cortical EEG in the Reserpinized, Anesthetized Cat

We have studied ponto-geniculo-occipital (PGO) spike rhythms and the relation of PGO spikes to degrees of cortical electroencephalographic (EEG) synchrony in the reserpinized, anesthetized cat. Even under reserpine, PGO waves occur with a definite rhythmic character having a basic rhythm of approximately 30-35 min, which is similar to the normal sleep EEG cycle in cats. After peaking in each cycle, PGO activity rates either dropped to zero or fell to very low values. Cortical EEG activity, particularly in the frontal cortex, was clearly related to the density of PGO waves. In periods of dense PGO waves the frontal cortex was most synchronized and the degree of synchrony diminished as the PGO wave rate fell. In most instances during periods of EEG desynchronization, no PGO waves were present. Coherence values between frontal and occipital cortices were greatest during high PGO spike activity. These studies show that even under reserpine, a basic PGO rhythmicity is maintained and that in this preparation there is a clear association of high PGO wave density and cortical EEG synchronization.