Wulfsohn, N.L. and Waldron, L. The importance of trains of current producing electrosleep. In Wageneder, F. M. and St. Schuy (Eds.), Electrotherapeutic Sleep and Electroanesthesia. Vol. II, Excerpta Medica, Amsterdam, Pp. 212-216, 1970.
In an early attempt to see what parameters of CES would more likely yield sleep in subjects, 5 cats were implanted subdurally, bitemporally and occipito-frontally. The researchers applied numerous stimulation parameters, and concluded that EEG modulated trains produced better sleep effects than non-modulated trains, and were better than EEG modulated current without trains when compared with controls.