This is an easy-to-read, interesting, and informative book about the neurophysiology, purposes, and meanings of sleep and dreaming. The author, Rosalind Cartwright, is a distinguished psychologist and a pioneer in modern sleep research whose work closely follows that conducted by Dement in the early 1960s. Cartwright opened her first sleep laboratory in 1963 and has published 5 books and more than 200 articles.
The Twenty-Four Hour Mind begins by sketching out the findings of the early researchers: sleep occurs in 2 distinct phases, varying in length but not in sequence. During “quiet” (non–rapid eye movement [REM]) sleep, everything in the brain and body slows down. During “active” sleep (called REM sleep, for the rapid eye movements that occur behind the eyelids of the sleeper), the brain wave patterns speed up and change and the sleeper dreams, but the muscles apparently cannot move voluntarily. These original findings prompted many questions, prominent among them the relationships of sleeping and dreaming to learning and memory, still an active and expanding field of inquiry. It is now generally accepted that both REM and non-REM sleep function in the consolidation and conversion of new learning into long-term memory.