Transcranial Direct Current Stimulation (tDCS) is a safe, non-invasive brain stimulation technology that has demonstrated the ability to temporarily increase or decrease activity in specific regions of the brain. The researchers are investigating the effect of this technology on sleep propensity by applying two different types of stimulation as well as sham (Placebo) stimulation during three different afternoon naps. The researchers are subsequently hoping to recruit healthy volunteers without medical, or sleep problems who have a regular sleep schedule to participate in the study

Recent studies have demonstrated that there are cortical direct current (DC) changes that accompany sleep onset and transitions between sleep states in a stereotyped manner. In these studies it was determined that negative potential shifts occurred prior to and at the transition from wakefulness to sleep and at transitions between Rapid Eye Movement sleep (REM) sleep, and Non-Rapid Eye Movement (NREM) sleep. In a subset of experiments it was demonstrated that the same DC potential shifts occur during the transition from wake to sleep in an afternoon nap. The recorded DC potential shifts occurred predominantly in the pre-frontal cortex (F3, F4), with spread into central areas. No current literature exists that explores whether tDCS could be used to modulate cortical activity prior to sleep, resulting in either increased or decreased sleep propensity.

The application of focal, non-invasive brain stimulation has already led to novel and effective treatments for neuropsychiatric disease with minimal side effects (Most well studied in depression and repetitive Transcranial Magnetic Stimulation or, rTMS). Should the application of tDCS modulate sleep propensity it would represent a novel study paradigm with the potential to lead to a completely novel treatment for sleep disturbance. With this small pilot study, we propose taking the first step in exploring the utility of tDCS in modulating sleep propensity. We propose to recruit 15 healthy non-treatment seeking participants from the community and expose them to three total nap conditions in a randomized counter balanced fashion, with 10 minutes of either, Anodal, Cathodal, or Sham tDCS stimulation occurring prior to each nap opportunity.

Inclusion Criteria:

• age 18-65
• capable of coming in for an initial intake screen, and then again for 2 hours on consecutive Monday, Wednesday, and Friday afternoons

Exclusion Criteria:

• Presence of Neurologic, psychiatric, or sleep disorder.
• Current use of medications affecting the central nervous system.
• Daily consumption of alcohol, or consequences of alcohol use (DUI, occupational, or social dysfunction ect.).
• Tobacco use.
• Consumption of more than the equivalent of 300mg of caffeine daily.
• Habitual sleep duration of less than 6 ½ hours, greater than 8 ½ hours, a difference between weeknight, and weekend sleep of greater than 3 hours, or typical sleep timing more than 3 hours outside of the window of 10pm-6am.
• Score of greater than 5 on the Pittsburgh Sleep Quality Index (PSQ-I), or 10 on the Epworth Sleepiness scale (ESS).
• BMI greater than 30, or Heavy snoring.
• Pregnancy.