A multicomponent exploration of verbal short-term storage deficits in normal aging and Alzheimer's disease

Although many studies have shown diminished performance in verbal short-term memory tasks in normal aging and Alzheimer's disease (AD), the cognitive processes responsible for this verbal short-term storage (STS) impairment are still unclear for both populations. We explored verbal STS functioning in patients with AD, elderly participants, and young participants, by investigating a series of processes that could underlie STS impairments in normal elderly and AD populations. The processes we investigated were (a) the influence of lexical and sublexical language knowledge on short-term storage performance, (b) functioning of the phonological loop component via word length and phonological similarity effects, and (c) executive control processes (coordination and integration). For the AD and elderly groups, the influence of language knowledge on verbal STS performance and the functioning of the phonological loop were preserved. In contrast, the AD group showed deficits for coordination and integration processes. Our results suggest that the verbal STS deficit observed in AD patients is related to impaired executive control processes. On the other hand, language-related processes underlying passive storage capacity seem to be preserved.