Effects of phenobarbital on Ripple oscillation. A. Examples of ripple oscillation obtained from one recording session showing that phenobarbital reversibly shortened ripple episode only at 400 μM (asterisks, paired t-tests, P < 0.05). B. Power spectra obtained from different times of a single experiment illustrating the reduction in ripple power only at high drug concentrations (200 and 400 μM). C. Diagrams of collective data for the different measures of the ripple oscillation. Note that the reducing effect of phenobarbital on number, duration and ripple power was statistically significant (asterisks, P < 0.05) only at the highest concentration of 400 μM. Measures of the above variables (except power) at the five drug concentrations were obtained from 2, 3, 7, 5 and 9 slices. Values of power were obtained from 4, 7, 12, 9 and 12 slices.