Effect of normal aging on the manipulation of information in working memory

Abstract

The goal of this study is to examine the central executive of working memory in normal aging, specifically focusing on its capacities to manipulate or modify the format of the to-be-recalled material. The central executive was measured with the alphabetical span procedure, during which subjects were asked to recall a random series of words in their alphabetical order. The storage demand was equalized across subjects by adjusting the list lengths according to individual span. Experiments 1, 2, and 3 showed that elderly subjects were not impaired in manipulating information, relative to young controls, even when the difficulty of the task was increased. In Experiment 4, validity was tested by asking young subjects to perform the task under the conditions of full or divided attention. Alphabetical recall was more impaired than direct recall during the divided attention condition, which suggests a larger involvement of the central executive component in the former. These results are discussed in relation to the hypothesis of a central executive impairment being associated with normal aging.Working memory (WM) is a short-term memory system involved in tasks that require concurrent retention and processing (Baddeley, 1986;Baddeley & Hitch, 1974, 1994Salthouse, 1994). In Baddeley's theoretical framework, WM is a tripartite system composed of two specialized slave systems-the phonological loop and the visuo spatial sketchpad-and a central executive. The phonological loop contributes to the retention ofverbal information and is subdivided into a passive phonological store and a rehearsal procedure. The visuospatial sketchpad holds images and spatial information. The central executive is an attentional component involved in the control and distribution oflimited resources (Baddeley, 1986(Baddeley, , 1992Baddeley & Hitch, 1974). This study focuses on the manipulation capacities of the central executive in normal aging. Manipulation is defined as the process of actively and consciously modifying the format of the information to be recalled. Within a WM framework, manipulation would require involvement of the central executive component.This work was supported by a grant from the Medical Research Council of Canada (MRC; PG-28) and from Ie Fond de la Recherche en Sante du Quebec (FRSQ) to S,8., by a chercheur-boursier fellowship from the FRSQ to S.8., and by a scholarship from the FCAR to N.R. and N,C. The authors thank Laurent Mottron, Francois Crepeau, Geoffrey R. Loftus, Frank Bellezza, and Leah Light for their helpful comments on an earlier version of the text Thanks to Michel Lamoureux and Jean-Francois Angers for statistical advice, as well as to Fanny Guerin, Sherif Karama, and Sonia Litalien for testing assistance. Special thanks to Rodolphe Sauvage for conducting Experiment 3. Finally, the authors gratefully acknowledge Ronald Dixon for his comments and for editing the text. Correspondence concerning this article should be addressed to Sylvie Belleville, Centre de Recherche de l'Institut Universitaire de Geriatric de...

Brain imaging of the central executive component of working memory

“…This task requires subjects to recall presented verbal information not in serial order (as in a classical span task) but according to the alphabetical order. The processes involved in this type of tasks which can be considered to be dependent upon the central executive include the inhibition of serial order recall, the extraction of alphabetical order from long-term memory and the checking of that order to rearrange the sequence of items before producing the response [14].…”

Effect of manipulation and irrelevant noise on working memory capacity of patients with Alzheimer's dementia.

“…Many studies have provided evidence for a WM impairment in normal aging (Dobbs & Rule, 1989;Foos, 1989;Tun, Wingfield & Stine, 1991;Wright, 1981), which would suggest that DAT and aging lie on a severity continuum. Recent studies suggest that normal aged people are unimpaired on some WM tasks Belleville, Rouleau, & Caza, 1998;Rouleau & Belleville, 1996;Salthouse, Fristoe, Lineweaver, & Coon, 1995). Very few of the above studies have provided data in young subjects that would support the specificity of the impairment, yet finding tasks on which only DAT and not normal aging impairs performance would be very helpful from a clinical perspective.…”

“…Second, it investigates individual differences among DAT patients, which represents crucial information for both clinical and theoretical reasons. Finally, it provides data that can ascertain whether normal aging and DAT lie on a continuum of severity, which is a major issue.EXPERIMENT 1:ALPHABETICAL RECALL Manipulation capacity was measured with the alphabetical span procedure (Belleville et al, 1998;Craik, 1986) whereby subjects are presented with a random series of words, which they have to rearrange mentally and report in alphabetical order. In the procedure, care was taken to control for a phonological storage deficiency.…”

Effect of age on forward and backward span tasks

“…Support for the first assumption is derived primarily from the theoretical model of WM in which the central executive plays a crucial role in manipulation of information from the slave systems (phonological loop and visuospatial sketch pad; Baddeley, 1986Baddeley, , 1996Baddeley, , 2000Baddeley, , 2002. The active and conscious process of manipulating information to be recalled (Belleville et al, 1998) is argued to be required in the reversed reporting of either tapped blocks or spoken digits in the backward span tasks (Baddeley, 1986;Pearson et al, 1999).…”

“…Support for the second assumption is based on the consistent finding that executive skills decline in normal aging (Belleville et al, 1998;Brennan et al, 1997;Fisk & Warr, 1996;Keys & White, 2000;Schretlen et al, 2000;Van der Linden et al, 1998). However some authors have suggested that this decline is not generalized, with some specific components of executive skills being relatively resilient to the effects of aging Greene et al, 1995).…”