This chapter describes the physiological bases of the impact of light on non-image-forming functions before summarizing recent neuroimaging investigations that substantially increased the understanding of the brain mechanisms involved. In accordance with animal research, the neuroimaging results presented in the chapter are compatible with a scenario in which light would influence subcortical structures involved in arousal regulation before significantly affecting the cortical areas involved in the ongoing non-image-forming process. Several factors modulate the effects described in this scenario including light intensity, duration, and wavelength, and possibly task difficulty. The interaction between circadian and sleep homeostasis signals and PERIOD3 (PER3) genotype can amplify or diminish the non-image-forming impact of light on cognitive brain function. For tasks triggering emotional responses, effects within cortical areas specially devoted to decoding the emotional content of a particular type of stimulus appear to be quick and mediated through a network based on hypothalamus and amygdala interactions.

This chapter focuses on two recent studies capitalizing on inter-individual differences in response to increased sleep homeostasis and misalignment between the circadian signal and sleep to better characterize the brain mechanisms involved in the maintenance of wakefulness and associated cognitive processes. Extreme chronotypes are characterized by marked differences in their preferred timing for sleep and wakefulness, as well as optimal times of day to perform cognitively demanding tasks. A study detailed in the chapter used a genetic trait as a means to characterize the regulation of cognitive performance throughout a normal waking day and following total sleep deprivation. A variable-number-of-tandem-repeat (VNTR) polymorphism in the coding region of the clock gene PERIOD3 (PER3) was reported to present a weak association with chronotype. According to a recent model of cognition, the VLPFC plays a key role in higher cognitive control and is involved in complex neurobehavioral processes.

This chapter discusses the organization of human sleep by the brain mechanisms and specific sleep disorders that lead to disturbances in the brain mechanisms. Non-rapid eye movement (NREM) sleep is controlled by brainstem oscillators whose activation leads to the multiple physiological accompaniments of the NREM state. The dream is the unusual mental content that often accompanies REM sleep. As humans transition from wakefulness to sleep, characteristic physiological changes include decreases in respiratory rate, heart rate, and blood pressure. The domain of the insomnias benefits from thoughtful differential diagnosis, as the causation may be both multiple and obscure. The insomnia complaints that are comorbid with medical disorders include both sleep disturbances caused by medical symptoms, and also those sleep disturbances caused by the pathophysiology underlying the medical condition. Restless leg syndrome (RLS) and periodic limb movements of sleep (PLMS) are considered as sleep disorders.

This introduction presents an overview of the concepts discussed in this book The Neuropsychiatry of Epilepsy. In the intervening years, there has been a clear appreciation in biological psychiatry of the neurobiological bases of psychopathologies as major depressive disorder, obsessive-compulsive disorder and other anxiety-related conditions, and there has been further development of psychotropic and anticonvulsant drugs (AEDs). The second edition starts with epidemiology, which has become a prominent discipline in research attempting to disentangle the extent and variety of psychiatric comorbidities in epilepsy. The clinical presentations and the wide spectrum of peri-ictal disorders are then discussed. Depression in epilepsy may not be quite like depression in the absence of epilepsy, the neuroanatomy giving a special stamp on the phenomenology. The book concludes with a discussion on the brain mechanisms of consciousness as may be revealed through investigations of patients with seizure disorders.