Neural correlates of selective attention in cognitively normal older adults, patients with mild cognitive impairment and patients with mild Alzheimer's disease

Abstract

It is well established that people experience a decline in cognitive functions, such as selective attention (SA), as they get older. SA is the ability to focus on task-relevant information and suppress task-irrelevant information. The Stroop task has been used to assess SA. In the current study, the neural correlates of SA were investigated using functional MRI-Stroop task with cognitively normal older adults (NC), patients with amnestic Mild Cognitive Impairment (aMCI) and patients with mild Alzheimer’s disease (AD). The current study reanalyzed previous master student’s data, due to the disagreement in analyzing the data. In the fMRI data analysis, the contrast of correct responses in the naming incongruent color (SC) condition minus correct responses in the reading incongruent word (RW) condition (SC-RW) in series 2a and 2b was reanalyzed using an event-related analysis. The current Stroop experiment was in a block design with four series: series 0, series 1, series 2a and 2b. In behavioral analysis, the performance of the word-reading task was expected to be significantly better than the color-naming task in series 1, series 2a and 2b because the belief that reading incongruent color word was always an easier task than the color-naming task. The results from behavioral analysis showed that significant more errors were made in reading incongruent color words in series 2a and 2b than in series 1. In the functional MRI data analysis, although brain activation associated with inhibition was expected in the contrast of SC-RW of series 2a & 2b, the results did not show any brain activation. The unexpected results could be due to the RSE that was elicited by the task switching paradigm of series 2a and 2b. The results suggest that the current Stroop task adapted from the Stroop Neuropsychological Screening Test may not yield a Stroop interference effect of sufficient magnitude to be detected with fMRI in the contrast of SC-RW of series 2a and 2b.