Objective: The passage of weak DC currents across the head (DC polarization) is a safe and painless means of altering the activity of cortical neurons and their response to exogenous stimulation. This has been demonstrated in the human motor cortex where local anodal polarization increases, and cathodal decreases, the motor evoked potential from TMS. Recent experiments from our lab suggest that polarization may have analogous effects on the prefrontal cortex, where anodal current enhances functions including verbal fluency and psychomotor speed and cathodal current produces slight performance decrements. We are interested in the potential of DC current to enhance function in patients with frontal lobe disorders and to reduce frontal overactivation in conditions such as drug craving. Treatments that alter frontal activity may also have mood altering properties. In order to establish the principle that DC polarization is able to alter frontal lobe activity we propose to combine DC polarization with a variably loaded frontal activation task and measure regional cerebral blood flow (rCBF with H(2)(15)O positron emission tomography (PET) scanning. Study population: Twenty healthy individuals will be studied. Design: On three different days, participants will receive right dorsolateral prefrontal anodal, cathodal, or sham treatment. On each day, rCBF will be measured during rest without and then with treatment. Then subjects will perform the N-back task (a test of working memory) during treatment with the working memory load (N) varied between 0 and 3 items from scan to scan. Outcome measures: Resting rCBF and the relationship between cognitive load and rCBF at the treatment site will be compared between treatments in order to look for effects on task-related activation and performance.
INCLUSION CRITERIA: Participants will be right-handed volunteers, aged 20 to 70, without history of any disorder of the central nervous system. EXCLUSION CRITERIA: Current serious medical or psychiatric condition of any kind. History of any significant trauma or medical condition affecting the brain or skull. History of epileptic seizure. Current use of neuroactive medications, medications affecting the cerebral circulation, or recreational drugs. Presence of metal in the head (other than dental hardware) or body, such as pacemakers, aneurysm clips, metallic prostheses (including heart valves or cochlear implants), patches with metallic foil backing, such as nicotine patches, permanent eyeliner or shrapnel fragments. History of welding or metal work. Broken skin in the area of the stimulating electrodes. Pregnancy/breastfeeding.