Abnormal Inhibition of Return in Mild Cognitive Impairment: Is it Specific to the Presence of Prodromal Dementia?

Article type: Research Article

Authors: Bayer, Antony^a | Phillips, Michelle^b | Porter, Gillian^c | Leonards, Ute^c | Bompas, Aline^d | Tales, Andrea^{c; e; *}

Affiliations: [a] School of Medicine, Cardiff University, University Hospital Llandough, Penarth, Wales, UK | [b] Centre for Mental Health, Addiction and Suicide Research, University of Bristol, Oakfield House, Oakfield Grove, Bristol, UK | [c] School of Experimental Psychology, University of Bristol, Bristol, UK | [d] Lyon Neuroscience Research Center, Centre Hospitalier Vinatier, Bron, Cedex, France | [e] Department of Psychology, College of Human and Health Sciences, University of Swansea, Singleton Park, Swansea, Wales, UK

Correspondence: [*] Correspondence to: Andrea Tales, Department of Psychology, College of Human and Health Sciences, University of Swansea, Singleton Park, Swansea, Wales, UK. Tel.: +44 (0) 1792 295586; E-mail: A.Tales@swansea.ac.uk.

Abstract: Although there is some evidence that amnestic mild cognitive impairment (aMCI) can be characterized by significant deficits in visuospatial function, the cross-sectional design of the majority of these studies renders it impossible to determine whether such deficits occur in aMCI as a result of, or accompany, amnestic dysfunction per se or whether they are the result of disproportionately poorer performance in a sub-group of patients for whom aMCI represents prodromal dementia. Similarly, whether the absence of aMCI-related functional deficit stems from the masking of dementia-specific abnormality by the preserved performance of those with a different cause of aMCI cannot be ascertained. Here we report the outcome of a cross-sectional and 2.5-year longitudinal evaluation follow-up, computer-based study of visuospatial attention, specifically attentional disengagement and inhibition of return and the mean (RTSPEED) and intra-individual variability (IIVRT) of their component reaction times, in 45 patients with aMCI and 31 cognitively healthy older adults. Reduced inhibition of return (p = 0.01 and p = 0.037 in response to 400 and 800 ms cue to target interval conditions), slowed RTSPEED (p = 0.038 and p = 0.03 in response to 400 and 800 ms cue), and raised IIVRT at baseline testing (p = 0.003, p = 0.026, p = 0.013 in response to 200, 400 and 800 ms cue) were associated with the development of dementia within the 2.5-year follow-up period, whereas the performance of patients with aMCI who did not develop dementia did not differ significantly from that of the cognitively healthy controls. Attentional disengagement appeared insensitive to the presence of prodromal dementia or amnestic dysfunction per se. The results indicate that those patients for whom aMCI represents prodromal dementia may experience, in addition to amnestic dysfunction, a decline in the functional integrity of some fundamental aspects of visual information processing, an effect potentially capable of increasing disease burden and reducing quality of life.

Keywords: Aging, attentional disengagement, inhibition of return, mild cognitive impairment, methodology, reaction time, visual attention

DOI: 10.3233/JAD-131934

Journal: Journal of Alzheimer's Disease, vol. 40, no. 1, pp. 177-189, 2014