Progressive pure anomia: Insufficient activation of phonology by meaning

Abstract

We report a patient, FM, with progressive fluent aphasia due to selective atrophy of left temporal cortex. The most prominent feature of her neuropsychological profile is a progressive and profound anomia, without the appearance of phonological errors in spontaneous speech or on naming tests. Although FM was originally characterized as a case of early semantic dementia, assessments over three years have revealed only mildly impaired, and stable, performance on a range of tests of semantic knowledge. In terms of cognitive models of speech production, we attribute her profound anomia to reduced communication between the semantic system and the phonological output lexicon. This conclusion is supported by the results of gating experiments in which, when asked to recognize and produce spoken words (concrete nouns) from incremental 50 ms fragments, FM showed minimal additional benefit from simultaneous presentation of the target picture. In addition we demonstrated a rapid loss of phonological information in the face of retained semantic knowledge of the target in immediate and delayed word repetition and wordpicture matching tasks. The syndrome of progressive fluent aphasia is heterogeneous; some patients show disruption at the level of the semantic system (i.e. semantic dementia), whilst others, like FM, have their principal impairment at a post-semantic stage of speech production.