Healthy volunteers will be recruited. All subjects will be tested a battery of
neuropsychological tests, then undergo fluorodeoxyglucose-positron emission tomography (PET)
and magnetic resonance imaging (MRI). During the PET and MRI, they will be stimulated with
transcranial direct current stimulation (tDCS) for 15 minutes. A third of subjects will
receive real tDCS on the left prefrontal cortex, a third on the right prefrontal cortex, and
the other third will receive sham tDCS.