Complex sentence: This is called the unihemispherical slow wave sleep (USWS) and here, at any time, the EEG of one hemisphere indicates sleep while that of the other is equivalent to wakefulness.
Split into simpler sentences: This is called the unihemispherical slow wave sleep (USWS). During this, at any time, the EEG of one hemisphere indicates sleep while that of the other is equivalent to wakefulness.