This study will test the effect of direct current (DC) brain polarization (the application of a very weak electrical current to the brain) on learning and memory. Earlier studies have shown that DC polarization can temporarily improve the ability of healthy people to think of certain words. This study will explore whether it can also temporarily improve learning and memory.

Healthy people 18 years of age and older may be eligible for this study. Subjects participate in two experimental sessions at the NIH Clinical Center. The first session lasts about 1 hour; the second session, on the next day, takes about 10 minutes.

At the beginning of the first session, electrodes are placed on the subject's head and arm for brain stimulation. The current may be turned on for 25 minutes, or only very briefly (sham stimulation). Subjects are not told which type of stimulation they are receiving. No stimulation is applied in the second session.

During the sessions subjects are asked to complete the following tasks that will help elucidate the effects of polarization:

• Read a list of words and remember them. Later they will try to repeat the words from memory.
• Look at a series of designs and remember them. Later they will try to draw the designs from memory.
• Push a button on a keyboard when they see a specific item (for example, when the number 7 appears).
• Generate as many words as they can think of that begin with a particular letter of the alphabet.

Subjects may be videotaped for some or all of the time during the sessions.

OBJECTIVE: The principal objective is to establish whether DC polarization of left lateral prefrontal cortex can enhance verbal memory.

STUDY POPULATION: 75 healthy volunteers over the age of 18 will be enrolled.

DESIGN: The study is a double-blind parallel study with three arms: anodal polarization, cathodal polarization, and sham treatment.

OUTCOME MEASURES: The primary outcome measure is performance on the WMS-III Word Lists test. Secondary outcome measures, testing for effects of DC polarization on basic information processing and non-verbal memory, respectively, are the CalCAP and WMS-III Visual Reproduction Test. The Verbal Fluency Test will be administered prior to stimulation and 24 hours post-stimulation to screen for other residual effects of the polarization on the stimulated region.

• INCLUSION CRITERIA:

Healthy volunteers over age 18. Pregnancy is not an exclusion.

EXCLUSION CRITERIA:

Any history of a central nervous system illness or other behavioral disorder.

Broken skin in the area of the electrodes.

Uncontrolled medical problems, such as diabetes mellitus, hypertension, airway disease, heart failure, coronary artery disease, or any other condition that poses a risk for the subject during participation.

Presence of metal in the cranial cavity.

Holes in the skull made by trauma or surgery.