New research, published in Nature and reported by NBC news and the Wall Street Journal, shows memory improvement in senior citizens when their brain is stimulated by theta (4 Hz) and Gamma (60 Hz) waves. Here is the NBC story: https://www.nbcnews.com/health/health-news/brain-zapping-cap-appears-boost-memory-least-1-month-early-research-fi-rcna43949, and here is the research publication: https://www.zoundsproductions.com/forum/chapter-10/create-post.