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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.

Item Type:	Refereed Article
Keywords:	Aging, reaction time, sensorimotor, transcranial magnetic stimulation
Research Division:	Psychology and Cognitive Sciences
Research Group:	Psychology
Research Field:	Developmental Psychology and Ageing
Objective Division:	Health
Objective Group:	Specific Population Health (excl. Indigenous Health)
Objective Field:	Health Related to Ageing
Author:	Fujiyama, H (Dr Hakuei Fujiyama)
Author:	Hinder, MR (Dr Mark Hinder)
Author:	Schmidt, MW (Mr Matthew Schmidt)
Author:	Garry, MI (Dr Michael Garry)
Author:	Summers, JJ (Professor Jeffery Summers)
ID Code:	77431
Year Published:	2012
Funding Support:	Australian Research Council (DP1094440)
Web of Science® Times Cited:	24
Deposited By:	Psychology
Deposited On:	2012-04-13
Last Modified:	2014-12-05
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