Semantic dementia is a progressive neurodegenerative disease that is characterized by fluent spontaneous speech but with poor information content (“empty speech”) and problems understanding single words. It is commonly accepted that patients with semantic dementia experience a breakdown of semantic abilities (Snowden et al. 1989). According to the Logogen model (a modular neurolinguistic model of speech processing) semantic dementia may mainly be a lexical disorder. By means of a single patient study, an attempt is made to interpret the language disorder within the context of the Logogen model.
Snowden JS, Goulding PJ, Neary D. Semantic dementia: a form of circumscribed cerebral atrophy. Behavioural Neurology 1989; 2: 167-82.