This study will attempt to use a type of non-invasive brain stimulation technology during sleep to improve measures of sleep quality and memory in young healthy students and older adults. The type of brain stimulation is called transcranial direct current stimulation (tDCS), which uses small currents of electricity to increase or decrease the activity of specific areas of the brain.

Transcranial direct current stimulation (tDCS) is a safe, non-invasive, and inexpensive brain stimulation modality that has been shown to have the ability to modulate both cortical and deep brain structure activity. This technique has undergone a significant amount of investigation in varied neuropsychiatric populations and interest in this technique has increased dramatically as of late.

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.

The investigators propose to test this intervention for replication in a similar cohort.

Inclusion Criteria:

• Students
• Adults aged 60 or greater.

Exclusion Criteria:

• If they are taking any prescription or over the counter medications.
• If they have any currently active neurologic, psychiatric, hormonal, metabolic, circulatory, or sleep disturbances. -They must specifically not have a history of seizures, closed head injuries with loss of consciousness for greater than 5 minutes, any known brain tumors or lesions, metal implants or implanted devices above the neck, a history of eczema, or other sensitive conditions, or an allergy to latex.
• They must not smoke cigarettes, use illicit drugs, or meet criteria for alcohol abuse or dependence in their lifetime defined by SCID criteria.
• They must be free of alcohol for at least 48 hours prior to each night of the study
• They must not consume more than the equivalent of 500mg of caffeine daily.