The reduced fidelity of selective sensory information processing in the elderly with mild cognitive impairment

Abstract

Mild cognitive impairment (MCI) is a neurocognitive disorder found in ~30% of the elderly population. Declines in visuospatial and executive functions are common in MCI populations. However, it is unclear if these deficits are due to a general decline in sensory processing or dysfunction in selective attention. Here, we compared neural processes that indicate both sensory and selective information processing across the elderly subjects with and without MCI (60-72 years old, age-matched). We measured behavioral and EEG responses from the volunteers while they performed the attention-cueing Eriksen Flanker task. In this task, they discriminated shapes of a cued target surrounded by the distractors (i.e. flankers) whose shapes could be congruent or incongruent to the target shape. When task difficulty was matched, the elderly with MCI had slower response times than the healthy control, and this was observed in both congruent and incongruent conditions. The amplitudes of the target-evoked event-related potentials (ERPs), particularly the P1 and P3 components, were reduced in these MCI individuals. This suggested declines in early sensory and post-sensory decision-related processes, reflecting their behavioral responses. Furthermore, to quantify the spatial precision and timing of attentional focus, we employed inverted encoding models to reconstruct the spatially selective representations of the attentional focus centered at the cue onset and the target locations based on their alpha-band activity (~8-12Hz) in the EEG data. The healthy control exhibited more precise alpha-based spatial representations with an earlier onset. On the other hand, the MCI patients showed significantly broader spatial representations with a slower onset. Together, our findings provide strong neural evidence suggesting that declines in visuospatial and executive functions in MCI is contributed by the diminishing fidelity of selective sensory information processing.