Short-term memory processes in patients with apraxia of speech: Implications for the nature and structure of the auditory verbal short-term memory system

Abstract

A series of four experiments examined short-term memory and phonological processing in five patients with apraxia of speech and five control subjects matched for age. Experiments 1 and 2 established that patients' auditory phonological processing skills were intact but they showed an impairment in their ability to abstract sound from print. Experiment 3 established that memory span for digits and high and low frequency words were reduced in all patients compared to control subjects. Experiment 4 established that as a group the patients did not show the normal effects of the phonological similarity and word length on retention of auditorily and visually presented materials. However, the control subjects demonstrated the standard effects of phonological similarity and word length on the retention of auditorily and visually presented lists. It was concluded that a neurogenic disturbance in planning and executing the articulatory code affects performance on span tasks in a way that is broadly consistent with an impairment in articulatory rehearsal. The implications of these conclusions for theories of the structure of the verbal short-term memory system are discussed.