The Effect of tDCS Applied During Sleep on Memory Consolidation

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.