Attentional control in amnestic MCI subtypes: insights from a Simon task

Our aim was to compare attentional control abilities in healthy older subjects and amnestic mild cognitive impairment (aMCI) subtypes. We also analyzed group differences in dynamic changes in performance across the entire reaction time (RT) distribution.

Thirty-one multiple domain (mda-MCI), 31 single domain (sda-MCI), and 41 healthy control adults (HC) participated in the study. Participants performed a spatial stimulus-response consistency task in which relevant and irrelevant stimulus dimensions overlapped in the spatial response dimension. We analyzed reaction times (RTs), number of errors (NEs), and omitted responses (ORs), and implemented statistical procedures to neutralize age and processing speed effects.

There were no significant RT group differences across consistency conditions. Accuracy (NE) was lower in the mda-MCI group than in HC for inconsistent trials. Distributional analysis revealed increased RT-Simon effect in longer RTs and increased NE-Simon effect in the faster quintiles in a similar way for all groups. NE-Simon effect was greater in the mda-MCI group than in the other groups in the faster quintiles.

All groups displayed difficulty in suppression of automatic response pathway and in enacting the deliberate pathway to intentionally control the responses. The greater impairment in the mda-MCI group relative to the other groups is basically quantitative in nature and involves stronger activation of the pathway of automatic response.