Fractionation of working memory: Neuropsychological evidence for a phonological short-term store

Abstract

A patient with grossly defective short-term memory but fluent speech was studied in order to pinpoint the locus of the deficit. Her immediate memory for consonant sequences showed a clear phonological similarity effect with auditory presentation, but no effect of similarity when presentation was visual. She showed no effect of articulatory suppression and no effect of word length on span, both of which suggest that she was not using subvocal rehearsal. A further test showed that this was not due to her inability to articulate rapidly since her rate of repeating the number sequence 1–10 and of the alphabet was comparable with normal control subjects. These results are interpreted in terms of the articulatory loop component of a working memory model. It is suggested that the loop comprises a phonological store, with obligatory access by auditory spoken material, and optional access through the control process of subvocal rehearsal. Our patient appears to suffer from a defect of the phonological store. This removes the normal advantage gained from using subvocal rehearsal, and induces her to rely instead on visual storage.