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

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.

A Systematic Review of Longitudinal Associations Between Reaction Time Intraindividual Variability and Age-Related Cognitive Decline or Impairment, Dementia, and Mortality

“…Although we identified 22 studies that met our inclusion criteria, several of these involved samples drawn from the same study population. Specifically, the PATH Through Life Study Das et al, 2014), Project MIND (Bielak, Hultsch, Strauss, MacDonald, & Hunter, 2010a, 2010bGrand, Stawski, & MacDonald, 2016;Yao, Stawski, Hultsch, & MacDonald, 2016), the Victoria Longitudinal Study (Bielak, Hughes, Small, & Dixon, 2007;MacDonald, Hultsch, & Dixon, 2003, 2008Whitehead, Dixon, Hultsch, & MacDonald, 2011), the West of Scotland Twenty-07 Study (Deary & Der, 2005a, 2005b, while two further studies used identical participants (Bayer et al, 2014;Tales et al, 2012).…”

“…One such study assessed 1. (Bayer et al, 2014;Tales et al, 2012). However, as converters were also more cognitively impaired at baseline, it is unclear whether these results would remain if absolute baseline differences in cognition were controlled for.…”

Spatial inhibition of return is impaired in mild cognitive impairment and mild Alzheimer’s disease

“…Early studies suggest that spatial IOR is relatively preserved in AD [8][9][10] . By contrast, more recent studies suggest that spatial IOR may be impaired in individuals with MCI or AD [11][12][13] , and IOR deficits in individuals with MCI may be predictive of conversion to dementia 13 . Most previous studies employed the classic single cuetarget paradigm 2 .…”

Anxiety in old age and dementia - implications for clinical and research practice

“…As some of these functions or component processes have been found to be abnormal in AD and/or MCI [94][95][96][97], generally in studies in Research Andrea Tales which participants with anxiety disorders have been excluded, the detrimental effect may be exacerbated further in individuals with various forms of anxiety. It is possible that everyday environmental interpretation and response, highly dependent upon vision and attentionrelated function, may be significant poorer in MCI and dementia compared to cognitively healthy ageing, as a result, at least in part, of concomitant anxiety in these disorders.…”

“…In addition to the traditional aspects of cognitive function explored in older adulthood, SCI, MCI and dementia, particularly in relation to diagnosis and progression, research has revealed that many other components and levels of information processing, particularly those related to attention [94][95][96][97], can also be abnormal in these conditions. However, the potential impact of anxiety upon such function remains a relative unknown and in the following section we highlight evidence related to the possibility that anxiety may directly or indirectly influence the results of both clinical and research tests of attention-related function.…”