The diagnosis of neurocognitive disorders such as early Alzheimer's disease (AD) or primary progressive aphasia (PPA) is particularly difficult and constantly evolving, often leading to diagnostic erraticity. However, several studies have shown that graphic parameters are affected in people with moderate to severe Alzheimer's disease. The use of new technologies in the study and analysis of the abilities of people with neurodegenerative diseases is increasingly recommended. The use of a digital tablet with a stylus makes it possible to objectivize the kinematic parameters of writing (pressure, inclination, speed, jerk, time of writing task) and thus would allow a low-cost diffusion of this technology in particular by including it in already existing screening batteries.

The overall objective of the project is to characterize and compare the graphical markers of a writing task, either language-based (writing words, non-words, sentences) or non-language-based (drawing shapes), in patients with PPA, early-stage Alzheimer's disease (i.e., at the stage of minor neurocognitive disorders and major neurocognitive disorders at the beginning of the disease), and in people with no cognitive disorders.

Inclusion Criteria:

• = > 50 years old

For control group :

• not have a diagnosis of minor or major neurocognitive disorder.

For AD :

• Have mild stage Alzheimer's disease: 1/ Be diagnosed according to ICD-10 criteria for the following conditions: Alzheimer's disease and 2/ Have an MMSE score between 20 and 27, corresponding to a major TNC of mild stage or have a diagnosis of minor TNC with an MMSE score between 25 and 30, the validity period of a previously done MMSE is 3 months.

For PPA :

• Have Primary Progressive Aphasia according to the Gorno-Tempini criteria (Gorno-Tempini et al., 2011) and have an MMSE score between 20 and 27, corresponding to major mild TNC or have a diagnosis of minor TNC with an MMSE score between 25 and 30, the validity period of a previously made MMSE is 3 months.

Exclusion Criteria:

• Presence of pathologies of the dominant upper limb(s) (left, right or ambidextrous lateralization) disabling such as osteoarthritis, finger amputation, etc.
• History of stroke.
• Illiterate person.
• Participate in a concurrent experimental clinical study, to avoid interference with our study.
• Not understand oral and written French. The speakers are French-speaking and the language task is performed in French.

Participants will be selected from the patient files of the principal investigator.