A debilitating and common symptom in Gulf War Illnesses (GWI) is the inability to retrieve words. This affects one's conversations, ability to fluidly exchange information verbally and retrieve information from memory. The investigators have discovered 3 brain regions - the PreSupplementary Motor Area (preSMA), caudate nucleus, and the thalamus - that are essential for word retrieval. They have also detected abnormal EEG signals related to these regions in GWI patients who have problems retrieving words. The investigators have used their model of verbal retrieval to design a noninvasive, nonpharmacological treatment that uses High Definition transcranial Direct Current Stimulation (HD tDCS). Using HD tDCS, they deliver small amounts of electric current to areas of the head to stimulate specific brain regions. The objective is to determine if delivery of HD tDCS over the preSMA will improve performance in GWI veterans with a verbal retrieval deficit. The investigators will administer pre-treatment tests of verbal retrieval measures while recording brain electrical activity. They will then administer 10 sessions of HD tDCS over the preSMA (20 minutes a session) in half the veterans. The other half will go through the same procedures, except the current will not be turned on (called the sham condition). The investigators will then compare performance between the active and sham group and assess if the treatment had a significant effect on performing verbal retrieval tasks and if there is a change in the ERP markers to account for how the treatment worked. If the treatment is found to be effective it will be offered to those in the sham group at the study's end. The investigators predict this treatment regimen will lead to positive effects on a person's daily functions, especially improved conversational abilities, with few, if any, side effects. They hope to outline the standard procedures for physicians to perform the treatment by creating a manual on how to apply the treatment in a clinical setting so that it will be quickly available to use in multiple sites if the proposed study demonstrates that it is efficacious. This treatment can be made widely available for Warrior Transition Units, military clinics, and VA medical centers. In addition, if successful, this could potentially lead to development of other targets of stimulation to improve other cognitive deficits in GWI, and help alleviate verbal fluency deficits associated with other disorders.