This article grapples with the notion that insomnia can or should be defined in physiologic terms. It is proposed that insomnia is better understood from a neurobiological perspective. A review of the neurobiology of sleep and wakefulness is provided with a special emphasis on the implications for insomnia. Following the review it is suggested that a complete understanding of insomnia will require that the neurobiologic characterization of insomnia be informed by modern cognitive concepts and methods.
Keywords: ARAS; Homeostasis; Insomnia; Neurobiology; VLPO; inhibition of wakefulness.