Neural correlates of saccadic inhibition in healthy elderly and patients with amnestic mild cognitive impairment

Abstract

Performance on tasks that require saccadic inhibition declines with age and altered inhibitory functioning has also been reported in patients with Alzheimer's disease. Although mild cognitive impairment (MCI) is assumed to be a high-risk factor for conversion to AD, little is known about changes in saccadic inhibition and its neural correlates in this condition. Our study determined whether the neural activation associated with saccadic inhibition is altered in persons with amnestic mild cognitive impairment (aMCI). Functional magnetic resonance imaging (fMRI) revealed decreased activation in parietal lobe in healthy elderly persons compared to young persons and decreased activation in frontal eye fields in aMCI patients compared to healthy elderly persons during the execution of anti-saccades. These results illustrate that the decline in inhibitory functions is associated with impaired frontal activation in aMCI. This alteration in function might reflect early manifestations of AD and provide new insights in the neural activation changes that occur in pathological ageing.

Keywords: Alzheimer's disease (AD); ageing; anti-saccades; fMRI; inhibition functions; mild cognitive impairment.

Figure 1

Brain areas showing significant activation associated with pro-saccades and anti-saccades in all subject groups (contrasts: pro-saccades > baseline, anti-saccades > baseline). (Panels A,C,E) present the results for the pro-saccade condition, whereas (Panels B,D,F) display the results for the anti-saccade condition. Abbreviations: YHC, young healthy controls; EHC, elderly healthy controls; aMCI, patients with mild cognitive impairment; LH, left hemisphere; RH, right hemisphere; FEF, frontal eye fields; SEF, supplementary eye fields; PEF, parietal eye fields. Color insets present the T-values for the contrast saccade condition vs. baseline.