“…Gamma, beta, alpha, theta, and delta powers, defined as EEG power between 25 and 100 Hz, 12 and 25 Hz, 8 and 12 Hz, 4 and 8 Hz, and 0 and 4 Hz, respectively, were calculated during wakefulness and normalized by the total power for each animal. We chose the composite theta ratio 9,17,18 -among other quantitative EEG measures for postoperative delirium 9,19 -to assess for power shifts in the frequency spectrum. The theta ratio was calculated as the sum of alpha and beta powers divided by the sum of theta and delta powers: (α + β)/(θ + δ).…”