Impairments of the response preparation process in the elderly.
In 20 young adults (23.1 +/- 1.64 yrs) and 20 old adults (68.5 +/- 5.53 yrs), H-reflexes were evoked simultaneously in the right soleus muscle that was preparing to respond to a reaction time stimulus and in the left soleus muscle that was uninvolved in the impending reaction time response. In the one-second period preceding the presentation of the response stimulus, the right H-reflex was inhibited as compared to the left H-reflex in the young adults; whereas, in the old adults, the response preparation profiles for the left and right H-reflexes were similar. Following the presentation of the response stimulus, H-reflex facilitation in the young adults reflected a non-specific tuning response and a specific, movement-related response. The nonspecific H-reflex enhancement was not observed in our older adults. These results indicate that the generalized tuning sequence necessary for movement planning is impaired in the elderly.
Burke
J R
JR
University of South Carolina, Department of Exercise Science, Columbia 29210, USA.
Kamen
G
G
D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D004576:Electromyography; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D009068:Movement; D018482:Muscle, Skeletal / Q000502:physiology; D011930:Reaction Time; D013569:Synapses / Q000502:physiology