Sensory-Evoked Cortical Gamma Oscillation

The central hypothesis of the study is that sustained 40Hz gamma oscillatory sensory stimulation therapy will improve cognitive function in patients with AD. The further hypothesis is that the improvement in cognitive function will result from improved connectivity and cortical network function as measured by EEG and ERP. The hypotheses will be tested by the following: 1. \- Elucidate the immediate impact of gamma oscillations on sensory processing and cognitive function by assessing cognitive function and cortical network function prior to the introduction of sensory stimulation and comparing it to post-therapeutic assessments immediately following the acute administration of therapy on visual processing. 2. \- Explore the short and long-term therapeutic benefits of a sub-chronic (8 weeks) treatment by assessing cognitive function and cortical network connectivity immediately after the 8 week sensory stimulation therapy. If significant changes are observed between pre-therapy and post-therapy neurophysiologic data for an individual subject, neurophysiological testing will be repeated 4 weeks following the conclusion of therapy. 3. \- Investigate the correlation between neurophysiology and cognitive function by assessing cognitive function and neurophysiological measures of cortical network activity at multiple time points to determine if therapeutic changes in one domain reflect changes related to the other domain.