Primary progressive aphasia (PPA) is a focal dementia characterized by primary impairment of language abilities and functional disturbances associated with language.

Although PPA is a progressive disorder, new techniques are being proposed to try to activate parts of the brain previously thought to be potentially inactive, due to the possibility of "neuroplasticity". This concept refers to our brain's modularity and learning potential. Transcranial direct current stimulation is a powerful neuromodulatory technique, in which a small current is applied to the participant's scalp through the targeted positioning of an anode and a cathode. The positive or anodal stimulation of tDCS is supposed to increase neuronal activity under the electrode, while cathodal stimulation is supposed to do the opposite.

This project will provide new insights into the nature of the neural activity underlying executive functions in people with primary progressive aphasia compared to those without. The investigators expect to find reduced amplitude of electrophysiological responses and lower accuracy in people with primary progressive aphasia compared with healthy controls. Given the results of previous studies showing the efficacy of tDCS protocols in the treatment of aphasia, the investigators might expect them to improve executive functions. If so, the investigators expect significantly greater electrophysiological responses after stimulation sessions compared with sham conditions. This project is of great clinical relevance. This research will improve current therapeutic protocols used in the treatment of PPA by providing critical findings on whether and how the use of tDCS improves executive functions. Crucially, the research will advance knowledge of executive function decline as a sensitive marker of PPA, informing us about the possibility of early detection of this disorder. At the same time, the investigators will analyze the possibility of controlling symptomatological evolution via the analysis of acoustic and vocal markers. This will enable us to observe the evolution of sensory markers such as acoustic markers according to symptomatological evolution. This will enable us to check whether acoustic markers correlate with the patient's level of symptomatological impairment and/or pathological physiological data.

Inclusion Criteria:

• Be a male or female over the age of 18 with a primary progressive aphasia diagnosis
• Available for treatment and testing sessions
• able to read and speak French
• Be right-handed

Exclusion Criteria:

• Presence of neurodevelopmental disorders or non-degenerative neurological disorders
• Post-stroke aphasia
• Language or cognitive disorders too severe to allow task performance or communication
• Pre-existing psychiatric disorders; severe depression, schizophrenia
• People with pacemakers or metal implants, epilepsy
• Presence of a medical condition that represents a contraindication to tDCS
• Active use of psychotropic drugs
• Treatment with tDCS or TMS in the last 3 months
• Additional language therapy
• Pregnancy or breast-feeding