Neurodegenerative disorders of language and speech: Language-dominant diseases.

Encyclopedia of Behavioural Neuroscience

Deleon, J., Tee, B. L. & García, A. M. (2020). Neurodegenerative disorders of language and speech: Language-dominant diseases. Encyclopedia of Behavioural Neuroscience, segunda edición. Nueva York: Elsevier. Online: https://bit.ly/3lkXMte

Neurodegeneration in speech and language networks can trigger distinct disorders with specific clinical, neuroimaging, and neurophysiological features. This chapter offers a systematic overview such disruptions in four language-dominant neurodegenerative diseases (ldNDs), namely: the non-fluent, semantic, and logopenic variants of primary progressive aphasia as well as primary progressive apraxia of speech. We focus on spared and impaired skills across speech/language levels (phonetics, phonology, lexico-semantics, morphosyntax, discourse-level processing). In addition, we describe each the main neuroimaging and neurophysiological features of each disease (patterns of brain atrophy and tractographic abnormalities, alterations in regional activation, functional connectivity, and oscillatory modulations). We then compare speech and language deficits across the four ldNDs. Finally, we address the current challenges in diagnosis and treatment of these diseases, and outline future directions for the field.