The neurocognitive manifestations of HIV/AIDS are important for the management, survival, and quality of life of affected patients and their families. Following the advent of Highly Active Anti- Retroviral Therapy (HAART) the incidence of HIV-associated dementia (HAD) has fallen, but the prevalence of the milder forms of HIV-related cognitive disorders has risen. This is important because alterations in cognitive function can have significant impact on work and social activities, mood, and perceived quality of life. The recent NIH-sponsored Consensus Conference on Diagnosis of HIV-Associated Neurocognitive disorders concluded that one major weakness in the field was a lack of a useful neuroimaging marker for HAD and the milder MNCD;although there have been advances in MRI-based measurement of cerebral blood flow and in functional MRI, these methods have limitations. One emerging technology that has not, to date, been applied to HIV/AIDS is magnetoencephalography (MEG). However, before MEG can be used in HIV/AIDS clinical or research settings, it is necessary to establish some prerequisite information. Specifically, it is critical to to determine the reliability (over minutes/hours) and stability (over months) of the MEG signal over time, and to compare and contrast MEG activity relative to fMRI. The purpose of this pilot study is to obtain these critical preliminary data in order to establish the utility of MEG in evaluating HAD and MCMD. PUBLIC HEALTH RELEVANCE The purpose of this research is to understand whether, and by how much the data obtained using a very sensitive brain imaging technology will change simply by repeating the experiment. This is important because without this information it is difficult to know how reliable (reproducible) study results are, and this can have a major impact in terms of the interpretation (understanding) of any future studies.