Event-Related Potentials Reveal Altered Executive Control Activity in Healthy Elderly With Subjective Memory Complaints

Abstract

Several studies reported that healthy elderly with subjective memory complaints (SMC) evolve to Alzheimer's disease (AD) more frequently than elderly without subjective memory decline. In the present study, we investigated event-related potentials (ERPs) associated to executive control processes taking place during the performance of a Simon task with two irrelevant dimensions (stimulus position and direction pointed by an arrow) in healthy elderly divided in low and high SMC (LSMC, HSMC) groups. P300 was studied as a correlate of working memory. Medial frontal negativity (MFN) was studied as a correlate of conflict monitoring. Whereas the LSMC group showed interference from the stimulus position, participants with HSMC showed interference from both irrelevant dimensions. P300 latency was longer and P300 amplitude was lower when the stimulus position was incompatible with the required response but differences between both groups were not observed. MFN was not modulated in the LSMC group; however, the HSMC group showed larger MFN when the stimulus position and/or the direction pointed by the arrow were incompatible with the required response. These results suggest that participants with HSMC deployed greater conflict monitoring activity to maintain the performance when the target stimulus contained conflictive spatial information.

Keywords: aging; event-related potentials; executive functions; simon task; subjective memory complaints.

Figure 1

Schematic representation of the eight types of stimuli, which gave rise to the following experimental conditions: Compatible Direction-Compatible Position (CDCP), In CDCP (IDCP), Compatible Direction-Incompatible Position (CDIP), InCDIP (IDIP). Eighty trials per experimental condition were presented, giving rise to 320 trials in total. The response buttons assigned to each color were counterbalanced among participants.

Figure 2

Distributional analyses of the reaction times (RTs) in the three experimental conditions in which a spatial conflict was present. Interference from the spatial position was significant in all the quintiles for both groups. Interference from the direction pointed by the arrow was significant in q3 for the high subjective memory complaints (HSMC) group.

Figure 3

Stimulus-locked averages. P300 was measured as the maximum positive peak observed between 300 ms and 600 ms for each participant and its amplitude in a time window of 100 ms around peak latency. P300 latency was longer and P300 amplitude was smaller in those conditions where the target stimulus position was incompatible with the required response.

Figure 4

Response-locked averages. Medial Frontal Negativity (MFN) was measured in a pool of fronto-central electrodes. In the HSMC group, MFN amplitude was larger in those conditions where the stimulus position and/or the direction pointed by the arrow were spatially incompatible with the required response.