This study tested the postulation that change in the ability to modulate corticospinal excitability and inhibitory processes underlie age-related differences in response preparation and generation during tasks requiring either rapid execution of a motor action or actively withholding that same action. Younger (n = 13, mean age = 26.0 years) and older adults (n = 13, mean age = 65.5 years) performed an RT task in which a warning signal (WS) was followed by an imperative signal (IS) to which participants were required to respond with a rapid flexion of the right thumb (go condition) or withhold their response (no-go condition). We explored the neural correlates of response preparation, generation, and inhibition using single- and paired-pulse TMS, which was administered at various times between WS and IS (response preparation phase) and between IS and onset of response-related muscle activity in the right thumb (response generation phase). Both groups exhibited increases in motorevoked potential amplitudes (relative to WS onset) during response generation; however, this increase began earlier and was more pronounced for the younger adults in the go condition. Moreover, younger adults showed a general decrease in shortinterval intracortical inhibition during response preparation in both the go and no-go conditions, which was not observed in older adults. Importantly, correlation analysis suggested that for older adults the task-related increases of corticospinal excitability and intracortical inhibition were associated with faster RT. We propose that the declined ability to functionally modulate corticospinal activity with advancing age may underlie response slowing in older adults.
Funding
Australian Research Council
History
Publication title
Journal of Cognitive Neuroscience
Volume
24
Issue
5
Pagination
1253-1263
ISSN
0898-929X
Department/School
School of Psychological Sciences
Publisher
M I T Press
Place of publication
55 Hayward St, Cambridge, MA 02142, USA
Rights statement
Copyright 2012 Massachusetts Institute of Technology