This is why you dream What your sleeping brain reveals about your waking life

In this ho-hum study, neurosurgeon Jandial (Life Lessons from a Brain Surgeon) surveys the science of dreams. When preparing to dream, Jandial writes, the brain first paralyzes the body by releasing neurotransmitters that "effectively switch off motor neurons," then the "Executive Network" (which is "responsible for logic, order, and reality testing") turns off, and finally the "Imagination Network" (which is involved in introspection) activates. Discussing evolutionary theories for why humans dream, Jandial notes that some scientists believe dreams keep the brain active so it can more quickly awaken in case of an emergency, while others suggest that dreams allow humans to "rehearse" responses to negative events so they're more prepared to face them in real life. Elsewhere, Jandial covers nightmares, lucid dreaming, and erotic dreams, the frequency of which depends on "how much of our waking life we spend daydreaming about erotic fantasies." There's some stimulating trivia sprinkled throughout (he notes studies from across the world that have repeatedly found falling, "being attacked or pursued," and being in school are the most common dream themes), but Jandial has an unfortunate tendency to make claims without providing evidence, as when he asserts that "dreams follow rules" ("It's extremely rare for objects to turn into people in our dreams," for instance) without mentioning any supporting research. It's a mixed bag. (Jun.)