With aging, most cognitive functions decline, especially processes concerning memorizing, attention, concentration, organizing, planning and problem solving. Neuropsychology can make an important contribution in early and differential diagnostics. The borderline between normal and pathological cognitive aging is especially important in this respect. The neuropsychologist gains insight in medical, biological, psychological and social factors of the aging person. Has the profile of complaints and deficits a normal background or is a pathological process taking place? It is important to people who are unnecessarily worried about possible dementia.

Neuropsychological assessment also provides information about a patient's disturbed and undisturbed cognitive functions, their personality and their way of coping with problems in every day's life. This is of major importance, because it provides information and possibilities for biological or psychological interventions. Because of the complexity of problems that may occur, it is necessary that the neuropsychologist is experienced and works in a multidisciplinary team in which neurological and psychiatric expertise is present.

Memory complaints and altered states of consciousness with automatic behaviour of narcoleptic patients indicate cognitive dysfunctioning. Although more problems arise while performing attention tasks than memory tasks, the neuropsychological test inquiry doesn't indicate one particular neuropsychological function as consistently impaired. They often perform well because they compensate impaired wakefulness by an increased willingness to respond. Neurophysiological research indicates that the sometimes occurring cognitive dysfunction is associated with a waxing and waning between wakefulness and sleep. The increased psychopathology is partly a reflection of, partly a reaction to the symptoms. The impact of hypersomnia on psychosocial functioning is more important than that of epilepsy in epileptics. In severe cases smoking and driving should better be dissuaded.