An application of long-term frequency analysis in measuring drug-specific alterations in the EEG of the cat.

A method is described for the quantitative measurement of "drug-specific" effects on the EEG of the cat. These effects are dose-related and are independent of the normal sources of EEG variation associated with the sleep-waking cycle. Drug-induced changes are expressed as characteristic alterations in frequency spectra and the time courses of these effects are followed for 5 h following administration of the test compounds. Atropine sulfate (0.5 and 2.0 mg/kg) and physostigmine salicylate (0.05 and 0.20 mg/kg) were administered to three unanesthetized and unrestrained cats and a broad-band frequency analysis was performed on the spontaneous brain electrical activity recorded from the prepyriform cortex, ventral hippocampus, lateral geniculate nucleus and the midbrain reticular formation. The resulting data were used as input to discriminant and canonical statistical analysis programs employed to abstract "drug-specific" patterns of frequency change. It was found that both atropine and physostigmine produce alterations in EEG frequency spectra which are clearly distinct from those patterns associated with the sleep-waking cycle and thus neither compound results in what has been characterized as an "EEG-behavioral dissociation".