Functional neural correlates of attentional deficits in amnestic mild cognitive impairment.

Nicholas T Van Dam,Jin Fan,Yunsoo Park,Xiaosi Gu,Patrick R Hof,Effie M Mitsis,Hillel T Grossman,Mary Sano,Stephen D. Ginsberg

doi:10.1371/journal.pone.0054035

Abstract

Although amnestic mild cognitive impairment (aMCI; often considered a prodromal phase of Alzheimer’s disease, AD) is most recognized by its implications for decline in memory function, research suggests that deficits in attention are present early in aMCI and may be predictive of progression to AD. The present study used functional magnetic resonance imaging to examine differences in the brain during the attention network test between 8 individuals with aMCI and 8 neurologically healthy, demographically matched controls. While there were no significant behavioral differences between groups for the alerting and orienting functions, patients with aMCI showed more activity in neural regions typically associated with the networks subserving these functions (e.g., temporoparietal junction and posterior parietal regions, respectively). More importantly, there were both behavioral (i.e., greater conflict effect) and corresponding neural deficits in executive control (e.g., less activation in the prefrontal and anterior cingulate cortices). Although based on a small number of patients, our findings suggest that deficits of attention, especially the executive control of attention, may significantly contribute to the behavioral and cognitive deficits of aMCI.

Highlights

Alzheimer’s disease (AD) first presents as mild cognitive impairment (MCI) in terms of memory loss or decline in other cognitive functions
healthy controls (HC) were not excluded for a Clinical Dementia Rating scale (CDR) = 0.5, since those with ‘mild’ dementia are not necessarily representative of individuals who are likely to progress to AD, and some minimal dementia might be anticipated in a normal geriatric sample
1.05# 0.33 0.06 0.31 activation in the alerting and orienting networks, one might argue that compensatory activity contributed to behavioral performance among the Amnestic MCI (aMCI) group comparable to HC

Summary

Introduction

Alzheimer’s disease (AD) first presents as mild cognitive impairment (MCI) in terms of memory loss or decline in other cognitive functions (e.g., attention). Studies suggest that the conversion rate of MCI to AD is 41% over a 1-year period and 64% over a 2-year period [1]. Global projections suggest that delaying the progression and onset of AD by as little as one year could have a massive impact on the global economic burden of the disease [5]. AD is primarily characterized by memory impairments [6], there is accumulating evidence that attentional deficits occur during relatively early stages of the disease [7,8,9,10,11]. Other studies have shown that attentional impairment is a predictor of cognitive decline in early stages of probable AD [13]. Alterations in attentional function may be a useful diagnostic marker, prognostic indicator, and potential point of intervention, among those with prodromal AD

Methods

Results

Conclusion