As a researcher investigating how electric brain stimulation can improve people's powers of recollection, I'm often asked how memory works – and what we can do to use it more effectively. Happily, decades of research have given us some clear answers to both questions. Memory essentially operates in three stages, with different brain regions contributing to each one . Sensory memory , which can last only milliseconds, registers raw information such as sights, sounds and smells. These are first