Age-Related Differences in Inhibitory Function: Investigation of Simon and Flanker Conflicts in Erps

It is unclear whether or not older adults experience more difficulty managing cognitive conflict by inhibiting distracting stimuli and/or ignoring irrelevant information than younger adults. A common procedure used to measure inhibitory function is through the use of congruent and incongruent stimuli. Specifically, past literature that used tasks like the Simon and flanker have found differing effects on reaction times and various event-related potential (ERP) amplitudes and latencies, suggesting that either inhibitory function is a unitary mechanism or multifaceted. Moreover, research exhibits uncertainty for whether or not age influences deficits to inhibitory function. Another way to measure inhibitory deficits with these two tasks is through the use and measurements of conflict adaptation. Previous literature that have used such tasks support the notion that higher-conflict trials that precede lower-conflict trials result in smaller congruency effects, or what is known as conflict adaptation. While conflict processing has been associated with activity in the medial prefrontal cortex, it is typically considered a measure of the lateral prefrontal cortex and cognitive control. To date, no study has investigated age-related conflict processing and conflict adaptation effects between the Simon and Flanker tasks simultaneously. Therefore, the present study utilized an original combined Simon and flanker task to measure age-related inhibitory differences by measuring reaction time, accuracy, and various ERP (P1, N1, N2, P3) amplitudes to determine if older adults experience inhibitory deficits during the Simon and flanker tasks and whether inhibitory function is a unitary mechanism. Results of the present study indicate that older adults experience greater inhibitory deficits during cognitive conflict as compared to younger adults. Additionally, it was found that the combination of Simon and flanker effects significantly modulated inhibitory deficits for both age groups, but especially for older adults, as seen through both behavioral and electrophysiological means. Specifically, such deficits were most prominent during later processing (i.e. N2 and P3) as compared to early processing. Therefore, the study provides support for age-related changes in inhibitory function and conclude that inhibitory function is comprised of a unitary mechanism. Although these findings deem promising, future research should be conducted to provide conclusive evidence. Regardless, these findings are an important step towards better understanding how inhibitory function manifests and how older adults experience inhibitory deficits. Further, these results provide an initial framework into the identification and understanding of age-related changes during the normal aging process for the field of cognitive neuroscience