Apraxia in Neurodegenerative Diseases

From its beginning, at the end of the 19th century, apraxia is associated with neurodegenerative diseases. However, very little work has been done in this area; this is particularly relevant for tool use disorders. This lack of interest might be surprising given that the diagnoses of neurodegenerative diseases also require additional deficits such as apraxia. For example, limb apraxia or conceptual apraxia are quite common in patients with Alzheimer's disease and limb-kinetic, asymmetrical, apraxia is one of the most frequent signs in corticobasal degeneration. Another important issue is that of tool use disorders and its definite impact on patients’ lives, but there are still very few studies in this field. Moreover, several theoretical questions arise regarding the nature of apraxia in these diseases. Does disorders of skilled movement in these pathologies are qualitatively similar to the apraxic syndromes following left parietal damage? Are they due to global deterioration, inability to access knowledge? First, this presentation will provide a synthetic review of works on apraxia in Alzheimer's disease and an analysis of their methodological and theoretical limits. Then, we will present preliminary data from our research on apraxia in patients with mild to moderate Alzheimer's disease. Performances of these patients on our “apraxia and tool use battery” confirm the reality and heterogeneity of tool use disorders in this disease and highlights the importance of individual analysis. In order to explore more precisely the role of conceptual knowledge in object use, we will also provide evidence from semantic dementia. Finally, we discuss relationships between apraxia and movement disorders (Parkinson disease…), ecological implications of apraxia and future research directions.