The effective operation of auditory verbal working memory processes is essential to both understanding and communicating in everyday life. These processes are particularly vulnerable to disruption in a wide range of clinical conditions that affect brain functioning. Problems with working memory are frequently the primary reason why people with brain dysfunction are referred for neuropsychological assessment; consequently, verbal memory has been ranked as the second most frequently assessed cognitive ability. However, current psychometric approaches, predominantly serial recall, paired-associate- and list-learning tasks have been designed mainly to detect the presence (and severity) or absence of memory impairment rather than identifying intact or impaired processes. Performance is usually measured by scores of free recall and recognition, with testing procedures that are often lengthy and time-consuming for both patients and clinicians. When assessing working memory, the span tasks have been viewed as “a complete assessment of the function of phonological short-term memory” (Vallar & Papagno, 2002). Digit span, in particular, has come to be regarded as the principal neuropsychological methodology for evaluating the capacity of auditory working memory (Andrewes, 2001), despite doubts about its lack of sensitivity (Lezak, Howieson, & Loring, 2004) and potential to overestimate capacity (Andrewes, 2001). Theoretical advances regarding the underlying component processes of encoding and retrieval have only slowly been incorporated into clinical practice but have not been applied in any systematic or coherent manner. Concepts of working memory have been extended to include semantic, phonological and temporal aspects. One potentially useful approach examined the role of phonological and semantic codes and cues and their susceptibility and immunity to interference effects (Tehan & Humphreys, 1995). Alternatively, another study investigated patients’ ability to accurately retrieve visual information by keeping track of the current episode, differentiating it from previous similar episodes that had the potential to reduce effective performance because of interference effects or poor discrimination (Parkin, Leng, & Hunkin, 1990). The aim of the research reported in this thesis was to develop a more compact cuedretrieval procedure to directly measure the phonological, semantic and temporal aspects of working memory and to examine its clinical usefulness by administering the task to brain injury rehabilitation patients. The conceptual section of the introductory chapter commences with a discussion on memory systems, particularly working memory, and is followed by an examination of some of the core processes involved in successful and unsuccessful remembering (forgetting). The applied section examines traditional and current approaches to memory assessment in clinical practice and their limitations in addressing the clinical needs of patients with memory impairments. Finally, an alternative approach that focuses on specific encoding and cueing processes rather than overall recall, is proposed. Empirical studies are reported in the following four chapters; Chapter 2 described the development and implementation of the initial studies with non-clinical participants, while Chapter 3 described the refinement of the procedure. Semantic and phonological coding and cueing effects were examined within a temporal context. The findings clearly demonstrated that semantic and phonological processes acted in quite distinct and consistent ways, irrespective of the degree of prior exposure to the word stimuli. Participants had more difficulty keeping track of the current episode when the codes and cues were phonological. Following refinements to the stimuli and procedure, replication of the previous results confirmed that cued-retrieval using semantic, phonological and temporal cues was a legitimate approach to memory assessment. Furthermore, differential effects were still found even after significantly shortening the procedure, thus adding support for its potential usefulness in clinical settings. The next two chapters examined the clinical application of this alternative approach in brain injury rehabilitation patients. The ability of non-clinical participants and brain injury rehabilitation patients to effectively use codes and cues to retrieve verbal information was compared. Quite distinct profiles indicated that the cued-retrieval procedure clearly differentiated clinical and non-clinical participants. Brain injury patients obviously performed more poorly on both semantic and phonological tasks but they also demonstrated a reduced ability to effectively use phonological codes and cues in retrieving information, as their performance declined across successive episodes due to increasing interference effects. Finally, the cued-retrieval procedure was administered to brain injury patients in the context of routine, post-injury, comprehensive neuropsychological assessment to examine the comparative value of this process approach in relation to other currently used clinical tests of verbal and working memory. The results clearly indicated that cued-retrieval was more sensitive in detecting memory impairments than most of the other tests in current use and, due to its brevity, was able to provide this information relatively quickly. The closing chapter summarized and integrated the empirical findings of these research studies and highlighted the implications for future clinical practice and further research. The preliminary evidence clearly indicated that this brief and sensitive method of examining the underlying processes of verbal working memory has clinical and theoretical potential.
| Identifer | oai:union.ndltd.org:ADTP/279320 |
| Creators | Dale Fogarty |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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