Cognitive and memory disorders are characterized of Alzheimer disease. In addition, psychologic and behavioural symptoms, called speak neuropsychiatric symptoms, are frequents and play an important role in prognostic and intervention. These symptoms are noticed before the diagnostic of dementia, their prevalence and their intensity increase with the evolution of disease. Apathy, which is characterized by a decrease of motivation, is the most frequent of this behaviour disrupt. Clinically, a decrease, or a totally, lack of interest, initiative and blunting emotional are noticed. Fundamentally, apathy is considered as a decrease of cognition and behaviour to "go in goal". Assessment of psychological and behavioural symptoms is realised principally with neuropsychiatric scales. These contribute to obtain particular informations about health of patient allowing by patient and caregiver discussions and impressions of clinician. These scales are simples but loss of subjectivity. An alternative of this method is the use of gerontechnology as actigraphy (system out-patient which records locomotive activity with the help of piezo-electrical sensor fixed on a bracelet) and video recording which is associated to an informatic treatment of signal in order event recognition.