Abstract

The current thesis investigated the cognitive mechanisms that contribute to age-related declines in pre-potent response suppression, and the interaction between those mechanisms and motor control processes that support response production. To achieve this goal, participants were visually cued to perform repeated pairs of key presses that established a pre-potent response. This was contrasted with responses that conflicted with the pre-potent pair. Cognitive and motor processes were delineated through kinematic analyses that decomposed reaction time into movement planning and execution phases. The goal of Study 1 was to explore whether there are age differences in conflict adaptation effects during pre-potent response suppression. In this study, conflicts were presented once, twice, or three times in each sequence. Older adults performed the first conflicting response in a series as well as young adults, but at a cost to pre-potent response performance. Younger adults improved performance with increased conflict frequency, whereas older adults did not. Older adults spent less time planning, but more time executing their conflicting responses compared to younger adults. This study revealed that conflict adaptation effects are diminished in the elderly, and that flexible adjustments in motor control by younger adults contribute to age-related differences in pre-potent response suppression. In Study 2, the neurophysiological correlates of conflict monitoring, and their relation to adjustments in motor control were investigated with concurrent acquisition of motion capture and event-related potential (ERP) data. Context effects were also explored through manipulation of the proportion of conflicting responses across conditions. The movement patterns, and ERP data revealed larger conflict-related interference effects for both groups when the proportion of conflicting responses was low. This context effect was exaggerated in the elderly. Moreover, only younger adults showed a robust conflict-related N2 component over fronto-central electrode sites. The magnitude of this N2 was related to shorter execution time in the younger, but not older participants, indicating that conflict detection facilitated within-trial adjustments in movement control. These findings are discussed in terms of current models of cognitive control and aging. These data contribute to current knowledge about the mechanisms by which conflict monitoring and cognitive control processes influence motor performance.