Some researchers have studied the effects of this modality on sleep as well as memory with promising results. One such study demonstrated that by using bilateral tDCS with a pattern of stimulation in the delta frequency range (0-3 Hz) delivered during slow wave sleep, that it is possible to increase delta power during slow wave sleep, as well as improve sleep efficiency. In addition to showing that it is possible to enhance slow waves, it was also demonstrated that this increase was associated with an improvement of a measure of declarative memory consolidation (one of the theorized functions of slow wave sleep). Enhancing memory function in a normal healthy group raises the possibility that it would also be possible to enhance memory in clinical populations who would benefit from such an intervention.