Phonological short-term memory in logopenic variant primary progressive aphasia and mild Alzheimer's disease

Abstract

It has been argued that individuals with logopenic variant primary progressive aphasia (lvPPA) have an impairment of the phonological loop, which is a component of the short-term memory (STM) system. In contrast, this type of impairment is not thought to be present in mild typical Alzheimer's disease (AD). Thus, one would predict that people with lvPPA would score significantly lower than a matched AD group on tasks that require phonological STM. In the current study, an lvPPA group was compared with a mild AD group that was matched on age, education, and general cognitive functioning. For a subset of the tasks that involved pseudowords, the AD and lvPPA groups were compared to a healthy control group that was matched on age and education. The lvPPA group was more impaired than the AD group on all of the tasks that required phonological STM, including the pseudoword tasks, but there were no significant differences between these groups on tasks that required visuospatial STM. Compared to the healthy controls, the lvPPA group performed significantly worse on the repetition and reading of pseudowords, while the AD group did not differ significantly from the controls on these tasks. These findings are consistent with the hypothesis that phonological STM is impaired in lvPPA.

Keywords: Alzheimer's disease; Phonological processing; Primary progressive aphasia; Short-term memory; Visuospatial processing.

Copyright © 2015 Elsevier Ltd. All rights reserved.

Figures

Figure 1

Mean number of correct items on the forward and backward versions of the digit and spatial span tasks. For this figure and those that follow, the bars represent the standard error.

Figure 2

Mean overall scaled scores for span tasks.

Figure 3

Mean raw scores (left) and mean scaled scores (right) on the block design task.

Figure 4

Mean number of correct items on the BDAE word and sentence repetition subtests.

Figure 5

Mean number of pseudowords repeated correctly at each syllable length.

Figure 6

Mean difference scores for pseudoword and matched real word reading.