Conceptualising and measuring working memory and its relationship to aphasia

Abstract

Background General agreement exists in the literature that individuals with aphasia can exhibit a working memory deficit that contributes to their language processing impairments. Though conceptualized within different working memory frameworks, researchers have suggested that individuals with aphasia have limited working memory capacity, impaired attention-control processes as well as impaired inhibitory mechanisms. However, across studies investigating working memory ability in individuals with aphasia, different measures have been used to quantify their working memory ability and identify the relationship between working memory and language performance. Aims The primary objectives of this article are to (1) review current working memory theoretical frameworks, (2) review tasks used to measure working memory, and (3) discuss findings from studies that have investigated working memory as they relate to language processing in aphasia. Main Contribution Though findings have been consistent across studies investigating working memory ability in individuals with aphasia, discussion of how working memory is conceptualized and defined is often missing, as is discussion of results within a theoretical framework. This is critical, as working memory is conceptualized differently across the different theoretical frameworks. They differ in explaining what limits capacity and the source of individual differences as well as how information is encoded, maintained, and retrieved. When test methods are considered within a theoretical framework, specific hypotheses can be tested and stronger conclusions that are less susceptible to different interpretations can be made. Conclusions Working memory ability has been investigated in numerous studies with individuals with aphasia. To better understand the underlying cognitive constructs that contribute to the language deficits exhibited by individuals with aphasia, future investigations should operationally define the cognitive constructs of interest and discuss findings within theoretical frameworks.

Measuring working memory deficits in aphasia

“…The n-back is a parametric task that requires judging whether a current stimulus matches one that occurred n places back in a stimulus sequence. It is thus considered to have strong construct and face validity in that its structure parallels the definition of WM, i.e., requiring temporary storage and manipulation of information while continuously updating WM contents (Cohen et al, 1997;Salthouse et al, 2003;Wright & Fergadiotis, 2012). Functional neuroimaging studies of healthy adults performing nback tasks consistently report activation of frontal and other cortical areas implicated in the WM network (Cohen et al, 1997), and both imaging and evoked potential investigations have provided evidence that this task engages the central executive component of WM (Smith, Jonides, Marshuetz, & Koeppe, 1998).…”

“…More recently, several researchers have advocated using the n-back task to index WM in aphasia (Baldo & Dronkers, 2006;Christensen & Wright, 2010;Connor & Fucetola, 2011;Friedmann & Gvion, 2003;Wright & Fergadiotis, 2012). The n-back is a parametric task that requires judging whether a current stimulus matches one that occurred n places back in a stimulus sequence.…”

Intentional and Reactive Inhibition During Spoken-Word Stroop Task Performance in People With Aphasia

“…Diminished attention may also point to limited working memory capacity in aphasia (Wright & Fergadiotis, 2012). In the present study, diminished working memory capacity may be evidenced by PWA's apparent inability to integrate contextual information into their responses and potentially diminished moment-by-moment adaptability to the presence and absence of interference and may be underscored by performance on other working memory tasks (described earlier).…”

The contribution of working memory to language comprehension: differential effect of aphasia type

“…Tompkins, Bloise, Timko, and Baumgaertner (1994) conducted a first systematic investigation of WM in aphasia using simplified adaptations of Daneman and Carpenter (1980) complex span tasks. Since then ample empirical evidence has been accumulated demonstrating that individuals with aphasia have reduced WM capacity (for a review, see Murray, Ramage, & Hopper, 2001;Wright & Fergadiotis, 2012;Wright & Shisler, 2005). Numerous studies have shown that participants with aphasia perform worse on WM tasks than control participants who have no neurological, cognitive, or language impairments (Tompkins et al, 1994) and that reduced WM capacity negatively impacts linguistic performance (Caspari, Parkinson, LaPointe, & Katz, 1998;Wright, Newhoff, Downey, & Austermann, 2003), with language comprehension being particularly susceptible to a decreased WM capacity (Sung et al, 2009;Wright, Downey, Gravier, Love, & Shapiro, 2007).…”