Intra-Individual Reaction Time Variability in Amnestic Mild Cognitive Impairment: A Precursor to Dementia?

Article type: Research Article

Authors: Tales, Andrea^{a; *} | Leonards, Ute^a | Bompas, Aline^b | Snowden, Robert J.^c | Philips, Michelle^a | Porter, Gillian^a | Haworth, Judy^d | Wilcock, Gordon^e | Bayer, Antony^f

Affiliations: [a] School of Experimental Psychology, Bristol University, Clifton, Bristol, UK | [b] CUBRIC – School of Psychology, Cardiff University, Park Place, Cardiff, Wales, UK | [c] School of Psychology, Cardiff University, Park Place, Cardiff, Wales, UK | [d] Memory Disorders Clinic, Frenchay Hospital, Frenchay, Bristol, UK | [e] Nuffield Department of Medicine, John Radcliffe Hospital, University of Oxford, Headington, Oxford, UK | [f] School of Medicine, Cardiff University, University Hospital, Llandough, Penarth, Wales, UK

Correspondence: [*] Correspondence to: Andrea Tales, School of Experimental Psychology, Bristol University, Clifton, Bristol, UK. Tel.: +44 117 928 8450; Fax: +44 117 928 8588; E-mail: Andrea.Tales@bristol.ac.uk.

Abstract: We used an exogenous target detection cueing paradigm to examine whether intra-individual reaction time variability (IIV) or phasic alerting varied significantly between patients with amnestic mild cognitive impairment (aMCI) (n = 45) and healthy older adult controls (n = 31) or between those with aMCI who, within a 2.5 year follow-up period, developed dementia (n = 13) and those who did not (n = 26). Neither IIV, nor simple reaction time, differentiated aMCI from healthy aging, indicating that raised IIV and overall response slowing are not general characteristics of aMCI. However, within the aMCI group, IIV did differentiate between those who converted to dementia and those who remained with a diagnosis of aMCI (non-converters), being significantly more variable in those who later developed dementia. Furthermore, there was no difference in IIV between non-converters and healthy controls. High IIV appears related to an increased probability that an individual with aMCI will become demented within 2.5 years, rather than to amnestic dysfunction per se. In contrast, phasic alerting performance significantly differentiated aMCI from healthy aging, but failed to discriminate those with aMCI who developed dementia from those who did not. In addition, those patients with aMCI who did not develop dementia still showed a significantly poorer phasic alerting effect compared to healthy aging. The phasic alerting abnormality in aMCI compared to healthy aging does not appear specifically related to the performance of those patients for whom aMCI represents the prodromal stages of dementia.

Keywords: Aging, dementia, mild cognitive impairment, reaction time, visual attention

DOI: 10.3233/JAD-2012-120505

Journal: Journal of Alzheimer's Disease, vol. 32, no. 2, pp. 457-466, 2012