Fig. 2. Time course of the effect of intracerebroventricular infusion of neostigmine on cross-approximate entropy (C-ApEn) of the electroencephalogram in rats anesthetized with 1.0% isoflurane. Solid curve  shows mean values from seven experiments; dotted lines  show mean ± SD. Neostigmine infusion started at time zero. A maximum effect was reached within 1 h.