Following on Musicophilia, with its accounts of patients whose brain injuries caused various sorts of phantom musical experiences, the literary neurologist Oliver Sacks here tells tales of his own youthful Hallucinations (Random House, $26.95). They started when he was a medical resident, and, “seeking a holiday from inner and outer restrictions,” he experimented with a smorgasbord of drugs, including LSD, cannabis, opium, and amphetamines. The resulting head trips were so memorable that he can still describe them in detail. Later, while working in a migraine clinic, Sacks used amphetamines to stimulate his intellectual curiosity. During the last of these trips, he received the revelation that would become his now classic study of migraines—but he had to quit the drugs in order to realize his vision.