Jan Egil Nordvik

SUMMARY

Cognitive impairment following acquired brain injury (ABI) may have a lifelong negative effect on activities of daily life functioning, social life and occupational prospects. A key aspect of performing daily activities is the ability to monitor ongoing cognitive processes and to remember what one just did and the next action to take. To solve this kind of challenges we depend heavily on working memory (WM), which has been found to be frequently impaired following the most common types of ABI, i.e. stroke and traumatic brain injury (TBI).

Rehabilitation approaches to the cognitive sequelea of ABI have mostly focused on finding compensatory strategies for coping with the cognitive deficits. Errorless learning (EL) is an example of a compensatory approach that aims to achieve more efficient learning by reducing or eliminating the chance for error making during information acquisition. The concept of EL became known in the field of cognitive rehabilitation of ABI through the work of Barbara Wilson and Alan Baddeley from the early 1990s and onwards. The two first papers of this thesis build on this work. Previous research on EL has mainly related the beneficial effect of EL to mechanisms of long-term memory (LTM). In this thesis a supplementary explanation of the advantages of EL is introduced, i.e. the role of working memory.

Concurrent with EL being recognized as a promising compensatory approach to memory impairment, new knowledge about microbiological brain processes, generated by novel neuroimaging techniques such as MRI and PET, has given rise to a more optimistic view on brain plasticity. Could it be that the brain’s ability to regain lost functioning through systematic stimulation is greater than previously assumed?

This thesis is a blend of clinical and basic research. Clinical neuropsychology has a long tradition for gaining knowledge relevant for our understanding normal cognitive functions through the study of impaired cognitive processes. In line with this practice, the clinical interventions, EL and CCT, investigated in this thesis may offer interesting knowledge about normal cognitive processes. Equally important, methodology from basic research is in this thesis applied to shed light on clinical research questions, previously investigated with traditional methods such as neuropsychological tests. The effect of CCT has, to our knowledge, not previously been examined with the use of quantitative structural MRI.

In Paper I, an experimental, laboratory-based design was applied to investigate how errors may impair encoding of new information in a sample of cognitively well-functioning healthy adults.  The purpose of this experiment was to learn more about the expected negative effect of errors in information processing, and to examine if errorless learning – a learning principle mostly associated with clinical populations – would be beneficial also to healthy adults when their working memory capacity was challenged. In Paper II the participants were patients with ABI, and the study is in part a clinical replication of Paper I. In addition to addressing some of the same hypotheses as in Paper I, Paper II was extended with two new features, i.e. stimuli targeting the visuospatial sketchpad of Alan Baddeley’s WM model to attend both verbal and visual qualities of WM, and an experimental condition involving self-generated errors inspired by Alan Baddeley and Barbara Wilson’s classic errorless learning paradigm from 1994.

While the first and the second paper are concerned with optimizing learning outcome within a limited working memory capacity, Paper III focuses on the possibility of extending cognitive capacity through computerized cognitive training. In this paper quantitative structural MRI and fractional anisotropy (FA), currently applied in basic research, are used to search for microstructural markers for treatment effect. This may also provide more knowledge about the plasticity of working memory in general

Publisert 19. okt. 2011 12:34