Selective impairment of the “central executive” component of working memory: A single case study

Abstract

We report the case of a head-injured patient (AM) with a specific short-term memory impairment. He did not show any deficit in long-term memory and presented no sign of either intellectual or frontal dysfunction. His spans for verbal and nonverbal material were reduced and he showed a lack of recency effect in free recall for visually presented words. We observed word length and phonological similarity effects as well as the abolition with articulatory suppression of the visual and auditory word length effect and of the visual phonological similarity effect, indicating that both the phonological store and the articulatory rehearsal mechanism were functioning. Furthermore, our investigations did not evidence any structural defect in either the control and planning functions of the central executive, or in its storage functions. The deficit AM presented on a verbal and nonverbal Brown-Peterson task, especially when the distractor tasks were more demanding, suggests that AM's central executive disposed of fewer processing resources. This resource reduction seemed to affect only short-term storage but not processing, and was interpreted as the consequence of strategic adaptation by the patient. Finally, the resource reduction did not cause interference on those divided attention tasks not requiring storage. As such, these results call for a more accurate specification of the allocation of resources in dual tasks.