The ability to coordinate upper and lower limbs—a prerequisite for many everyday activities—is known to decline with age. Here we report 2 experiments in which transcranial magnetic stimulation (TMS) was used to assess corticospinal excitatory and inhibitory processes in younger and older adults during cyclical hand-foot movements. In experiment 1, motor evoked potentials (MEP) and silent period (SP) durations were measured from the active right extensor carpi radialis (ECR) muscle while it executed rhythmic oscillations in conjunction with the right or left foot. Younger adults exhibited increased SP with ipsilateral limb combinations and decreased SP with contralateral limb combinations, relative to a baseline hand only condition. Strikingly, older adults exhibited a reduced SP when ipsilateral limbs moved in opposite directions. This effect was found to be most pronounced in those older adults who exhibited poor coordination performance, suggesting that the inability to regulate inhibitory processes may underlie age-related degradation of task performance. Experiment 2 examined motor evoked potentials and SP duration in the left extensor carpi radialis which maintained a tonic contraction while the coordination task was undertaken by the right arm and right or left foot. For younger adults, coordination of ipsilateral limbs was accompanied by increased inhibition in the ipsilateral motor cortex than during the coordination of contralateral limbs. No differences in SP between conditions were noted for the older adults. In summary, older adults’ reduced ability to coordinate upper and lower limbs may be related to the capacity to regulate inhibitory function in both hemispheres. This study suggests for the first time a direct link between age-related differences in interlimb coordination and the control of corticospinal inhibitory processes.

Item Type:	Refereed Article
Keywords:	aging, motor control, transcranial magnetic stimulation
Research Division:	Psychology and Cognitive Sciences
Research Group:	Psychology
Research Field:	Sensory Processes, Perception and Performance
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in Psychology and Cognitive Sciences
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:	75842
Year Published:	2012
Deposited By:	Psychology
Deposited On:	2012-02-17
Last Modified:	2017-11-05
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