Neuropsychiatric symptoms form part of the clinical picture of Alzheimer's disease (AD) and other dementias. Irrespective of the severity of the disease, the most frequently encountered symptom is apathy. Apathy is increasingly diagnosed in patients with neurological and psychiatric conditions. Apathy is a disorder of motivation, defined as "the direction, intensity and persistence of goal-directed behaviour". Most of the current descriptions acknowledge this point and consider apathy in terms of a lack of goal-directed behaviour, cognition or emotion. The classical neuropsychiatric symptom assessments are subjective structured interview-based, using input from the caregiver and/or the patient. New technologies are likely to provide us with a more objective measure. An example is ambulatory actigraphy, consisting of a piezoelectric accelerometer designed to record arm movement in three dimensions.

The aim of the present study is to assess using actigraphy and video recording signal, AD patients with (n = 15) and without (n = 15) apathy and control subjects (n = 5) during an activity of daily living scenario .

Inclusion Criteria:

• male or female, > 65 years ;
• Alzheimer's disease according to the NINCDS-ADRDA criteria (McKhann,Drachman et al. 1984) ;
• Mini Mental Test Examination (MMSE) > 20 ;
• no motor anomaly according to UPDRS III (tremblements, rigidité musculaire) ;
• no depression criteria according to DSM IV-R criteria ;
• patient with a cholinergic treatment at dose stable since 3 months ;
• patient with social insurance ;
• signature of informed consent.

Exclusion Criteria:

• neuropsychologics assessment impossible due to sensorial and disrupt ;
• prescription of psychotrop treatment (hypnotic, anxiolytic, antidepressant, antipsychotic) in the week previous actigraphy recording.