Dear Colleagues,

Primary progressive aphasia (PPA) is a group of neurodegenerative disorders, characterized by progressive language impairment, as well as cognitive and behavioral changes. By contrast, primary progressive apraxia of speech (PPAOS) is characterized by progressive speech impairment. Our knowledge regarding these disorders has evolved significantly in recent years. Notably, correlations between clinical findings and pathology have improved, and the main clinical, neuroimaging, and genetic features have been described. Furthermore, primary progressive aphasia and apraxia of speech are good models for the study of brain–behavior relationships and have contributed to the knowledge of the neural basis of language and speech functioning. However, many open questions remain. For instance, the classification of PPA into three variants (non-fluent, semantic, and logopenic) is under debate; further data about the epidemiology and natural history of diseases are needed; and, as in other neurodegenerative disorders, successful therapies are lacking.

For this Topic, we invite scholars to submit original research studies and reviews regarding all possible aspects of primary progressive aphasia and apraxia of speech, including basic science, epidemiology, clinical findings, longitudinal course, language and speech features, validation of neuropsychological tools for diagnosis, neuroimaging, blood and cerebrospinal fluid biomarkers, pathology, and treatments. A special focus should be on topics that can advance our assessment, differential diagnosis, and treatment of PPAs and PPAOS.

Dr. Jordi A. Matias-Guiu
Dr. Robert Jr Laforce
Dr. Rene L. Utianski
Collection Editors

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