Our previous study showed that theta and alpha electroencephalographic (EEG) activities occurred together during sensory deprivations (SD). The respective activities are expected to manifest different physiological states. In this study, we investigate statistical properties of both types of EEG activities during SD. Wavelet analyses of the original EEG activities during SD and the corresponding surrogation data can distinguish meaningful alpha and theta activities in the original data from accidentally detected ones. As a result, the mean duration of the theta wave is found to be longer than that of the alpha wave. This result could be useful to disclose physiological processes during SD.