Working memory (WM) : capacity / resources / mechanisms for simultaneous

1. Maria V. Ivanova Brooke Hallowell Neurolinguistics Laboratory,School of Hearing, Speech, and Language Sciences, Ohio University, Athens, Ohio, USA Potential Confounding Factors in Studies of Working Memory In Aphasia: Proactive Considerations for Future Research Proactive Considerations for Future Research • Working memory (WM): capacity / resources / mechanisms for simultaneous • storage and processing of information • Related to various higher-level cognitive abilities (Miyake & Shah, 1999) • WM deficits are an important subset of nonlinguistic impairments in aphasia (Murray, 2004; Wright & Shisler, 2005) • Reduced WM capacity in individuals with LHD (Tompkins et al., 1994) • Relationship between WM capacity and general language abilities in • aphasia (Caspari et al, 1998; Friedmann & Gvion, 2003; Wright et al., 2003; Wright et al., 2007) • Important areas of control for developing appropriate WM tasks and measures: • Dependence on comprehension of complex task instructions; • Difficulty of the processing component; • Degree of linguistic processing demand in WM and language tasks; • Degree of specific linguistic deficits in participants; • Dependence on metalinguisticskills; • Separation of processing and storage components of WM tasks; • Distinction of WM processing scores from WM storage scores; • Response requirements; • Reliability and validity of new or modified tasks or measures based • on people with and without aphasia; and • Standardization of procedures and scoring methods. Key Questions about WM Deficits and the Nature of Aphasia • Are WM limitations domain-specific or domain-general? • If domain-specific, are they specific to certain information types? • What is the relationship between WM and linguistic processing? • Can improvement in WM capacity lead to improvement in language abilities? • What are the sub-mechanisms of and constraints on WM? • For example, what is the role of short-term memory, allocation of attention • and speed of processing? • How might we most validly and reliably measure WM in aphasia? Tasks and Measures of Working Memory in Aphasia Research Next Steps for Proactively Addressing Confounding Factors • Complex span tasks – modified reading/listening span with short and simple sentences and recognition instead of recall (Caspari et al., 1998; Friedmann & Gvion, 2003;Tompkins et al., 1994; Wright et al., 2003) • Confounds associated with the processing component: • True/false judgments rely on metalinguistic skills; • Comprehension questions are disruptive or provide a limited processing score; • Use of linguistic stimuli leads to potential overlap with language measures; • The difficulty of the task depends on a person’s receptive language abilities; • Length and complexity of sentences may differentially impact performance. • Scoring methods are inconsistent across studies; span scores are used most commonly; processing is often not take into account. • The validity and reliability of modified span tasks have not been established. • N-back tasks(Friedmann & Gvion, 2003; Wright et al., 2007) • Concurrent validity and construct validity are problematic; associated measures are not correlated with complex span measures in individuals without language or cognitive impairments (Kane et al., 2007; Kwong See & Rayn, 1995; Roberts & Gibson, 2002). • Additional confounds include the unknown impacts of rate of stimulus presentation and of number of items back on performance measures. • Backward span tasks(Francis et al., 2003; Ronnberg et al., 1996) • Construct validity of the WM factor is not consistently assured (Engle et al., 1999). • Additional confounds include a lack of control for the difficulty of the processing component, and a required verbal response, as in the original standardized version of the task (Wechsler, 1997). • Further modification of reading/listening span task: • Selectively modify length/complexity of the linguistic stimuli • Control for participants’ linguistic abilities • Minimize metalinguistic demands • Control for potential motor/verbal response confounds • Use alternative verbal span tasks, such as operation and counting • span • Use spatial span tasks • Memory for ignored speech task (Cowan et al., 2005) • Implement eye-tracking methods Acknowledgements This work was supported in part by, an Ohio University Graduate Fellowship in the School of Hearing, Speech and Language Sciences, International Graduate Student Award from the ASHA Foundation, and a CHHS Student Research and Scholarly Activity Award. References available upon request