Cognitive symptoms are the core feature of Alzheimer's disease. Besides these problems, behavioural and psychological symptoms (BPSD), and an impairment of activities of daily living (IADL) are frequently encountered and usually show an impact on autonomy maintenance, prognostic and care during the prodromal and early stages of the disease.

Such symptoms are noticeable before the diagnosis of dementia and their occurrences as well as their intensity increase with the evolution of the disease.

Apathy, initially defined as a reduction of motivated behaviours, is the most frequently observed BPSD. Apathy is clinically defined by a significant reduction or complete loss of interest, initiative capacity and emotional blunting. Accordingly, apathy is characterized by diminished goal-directed cognitions and behaviours.

Behavioural and psychological assessment relies essentially on neuropsychiatric scales. These are used to gather precise data regarding patient's clinical state from interviews with the patient, the career or from clinical impressions during the consultation. From their apparent simplicity they have made their way into daily clinical practices, yet neuropsychiatric scales are reportedly biased by the assessors' subjectivity.

However, some tools whose allow simple, fast and objectively valid assessments are not widely used.

Hence, the use of ICT such as actigraphy (wearable device assessing locomotion activities), automatized audio-video recognition and signal analysis from events, may be of interest in addition to current assessment methods.

The aim of this study is to implement an objective assessment of goal directed activities and autonomy in an experimental design including predefined actions. The setting includes video cameras, microphones, actigraphic and Galvanic Skin Response sensors for recording and computer-based recognition of events using audio-video data, locomotion data and sinusal variability respectively as well as extracting biomarkers for supporting detection of dementia at early stages and supporting ongoing tracking of the dementia disease state. The following population will be included: patients with Mild Cognitive Impairment (n=50), patients with Alzheimer's disease (n=50) and control participants (n=50).

This work will provide further objective information for clinical practitioner in order to detect behavioral disturbances such as apathy.

Subjects control Inclusion criteria

• Male or Female ≥ 65 years
• Subjects were not accompanied by an Alzheimer subject recruited for the study;
• Subjects showing no locomotor disability;
• Subjects with no cognitive impairment overall with a score> 27 on the MMSE.

Special cases:

people with no schooling aged 50 to 79 years we take a MMSE> 22/30 and for over 80 years a MMSE> 21/30 - by the standards of Kalafat, 2003) (Folstein, Folstein et al. 1975), or arguments in favor of the following diagnosis: probable Alzheimer's disease according to the criteria of the NINCDS-ADRDA and / or major depressive episode according to DSM-IV-R;

• Subjects receiving a social security system;
• Signature of informed consent.

Exclusion Criteria

• Failure to perform the protocol due to a mobility impairment;
• Prescription of a new psychotropic medication (hypnotic, anxiolytic, antidepressant, antipsychotic) in the week preceding the assessment;
• Patients implanted with a pacemaker;
• Patient Trust under curatorship or judicial protection;
• Detainees (administrative or judicial).

Predementia / MCI Patients Inclusion criteria

• Men or women ≥ 65 years.
• Subjects with a diagnosis of MCI according to the criteria of the National Institute on Ageing and Alzheimer's Association group (Albert MS, 2011, see Appendix B), or Alzheimer's disease stage prédementiel (B. Dubois, 2010; see Appendix C)
• Subjects with a score of 0 to items of "tremors" and "muscle stiffness" of the UPDRS III
• Subjects with no criteria for major depressive episode according to DSM IV-R;
• Subjects receiving a social security system;
• Signature of informed consent. Exclusion Criteria
• Failure to pass neuropsychological testing because of a sensory or motor deficit;
• Prescription of a new psychotropic medication (hypnotic, anxiolytic, antidepressant, antipsychotic) in the week preceding the assessment;
• Patients implanted with a pacemaker;
• Patient Trust under curatorship or judicial protection.

dementia subjects Inclusion criteria

• Men and women older than 65 years
• Subjects with a diagnosis of Alzheimer's disease according to NINCDS-ADRDA (McKhann, Drachman et al. 1984) or Alzheimer's typical or atypical (B. Dubois et al. 2007)
• MMSE score ≥ 16
• Subjects with a score of 0 to items of "tremors" and "muscle stiffness" of the UPDRS III
• Subjects with no criteria for major depressive episode according to DSM IV-R;
• Subjects receiving drug treatment by acetylcholinesterase inhibitor or memantine in standard dose and stable for at least 3 months;
• Subjects receiving a social security system;
• Signature of informed consent.

Exclusion Criteria

• Failure to pass neuropsychological testing because of a sensory or motor deficit;
• Prescription of psychotropic medication (hypnotic, anxiolytic, antidepressant, antipsychotic) in the week preceding the assessment;
• Patients implanted with a pacemaker
• Patient Trust under curatorship or judicial protection.