A lack of regular deep sleep allows a toxic protein known as beta-amyloid to increase in the brain, attacking the mind’s memory faculties, research found A lack of regular deep sleep allows a toxic protein known as beta-amyloid to increase in the brain, attacking the mind’s memory faculties. The study by Berkeley, University of California says a “vicious cycle” emerges where the protein build-up not only corrodes memory, but also disrupts sleep further.