Chapter 11: On the Threshold of Sleep and Chapter 12: Narcolepsy and Night Hags Summary and Analysis

In Chapter 11, Sacks explains that many people, on the verge of sleep, have quasi-hallucinations, or hypnagogic hallucinations. These hallucinations are vibrant in color and appear without cognitive thought, and they vary from simple geometric patterns to complex images and scenes. These hallucinations can range from visual, behind closed eyelids, to auditory, including phones ringing, dogs barking, and sentences. Some experience small animals or faces. Some are even lexical in nature. In most cases, these images are highly detailed, with impossible clarity, and in some cases, the images appear other worldly, as something the patient has never seen or imagined. Sacks notes, however, these hypnagogic hallucinations are not real hallucinations, because they are rarely projected into external space. In all...