Electrodes will be placed in a 4x1 ring configuration over the frontal region in accordance with the International 10-10 EEG system. Stimulation will consist of a ramp up period in which the electrical current is gradually increased, 30 minutes of stimulation at 2 mA, and a ramp down period during which the electrical current is gradually removed. Stimulation will be applied back-to-back over three consecutive days.

Electrodes will be placed in a 4x1 ring configuration over the left temporal region in accordance with the International 10-10 EEG system. Stimulation will consist of a ramp up period in which the electrical current is gradually increased, 30 minutes of stimulation at 2 mA, and a ramp down period during which the electrical current is gradually removed. Stimulation will be applied back-to-back over three consecutive days.

Electrodes will be placed in the same 4x1 ring configuration over the frontal region as the active left frontal condition to ensure a useful control condition. Stimulation will consist of a 30-second ramp up period until reaching 2 mA, followed immediately by a 30-second ramp down, and off for 29 minutes. The same ramp up and down process will be repeated in the final minute of the session to help preserve masking of conditions. Sham stimulation will be applied back-to-back over three consecutive days.

HD-tDCS for this study is not intended to be a treatment, and will be applied continuously for 30 minutes at sham (0 mA) or 2 mA for active conditions across 3 consecutive daily sessions to probe neural circuit integrity. This specific HD-tDCS device is completely computer driven, running on a laptop using specialized software. Circular electrodes (12-mm in diameter) filled with conductive gel will be placed in a 4x1 ring configuration with the central electrode being the anode surrounded by four cathodes.

The RAVLT is a verbal episodic memory test that is sensitive to mesial and lateral verbal episodic memory circuit dysfunction. The primary outcome measure for this task is the total number of items immediately recalled during the learning trials and after the 20 minute delayed recall trial. Changes in scores from baseline to testing immediately following the completion of each condition will be examined.

The DKEFS Trail Making Test is a measure of cognitive flexibility and executive functions. The task requires the subject to as quickly as possible complete five conditions, involving number cancellation, number sequencing, letter sequencing, number-letter switching, and line tracing. The outcome measure for this task is the time to complete each of the five conditions. Changes in scores from baseline to testing immediately following the completion of each condition will be examined.