HUMAN FLASH-VEP AND QUANTITATIVE EEG ARE INDEPENDENTLY AFFECTED BY ACUTE SCOPOLAMINE

Scopolamine in acute intramuscular doses of 0.25-0.75 mg reduced the P 2-N3 flash-VEP amplitude and, in the quantitative EEG, the 8.5-12.0 Hz power and total power in 8 healthy young mate volunteers. The effects on flash-VEP and EEG total power were dose dependent and were evident 30 min and 90 min respectively after drug administration. regardless of dose. The reduction in 8.5-12.0 Hz power was limited to the 0.50 an d 0.75 mg doses. No systematic effects on the pattern-VEP were observe d. Possible interferences with flash- or pattern-VEP amplitude of the scopolamine-induced EEG changes were identified and removed by regress ion analysis and computation of VEP residuals from the regression func tion. The P2-N3 flash-VEP residuals proved EEG independent and showed relationships with dose and time after drug administration that were s uperimposable on those of the original data, with comparable significa nce levels at the drug/placebo and pre/postdrug statistical comparison s. The results indicate that VEP estimates of drug effects which are i ndependent from EEG changes can be identified in human studies and all ow some inference on the cholinergic specificity of the systems affect ing late flash-VEP components. The statistical approach used in this s tudy is suitable for application in VEP studies when effects of intera cting factors are to be expected.