Impairments of the Response Preparation Process in the Elderly

Abstract

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.

Key Words:

• H-reflex
• soleus muscle
• aging
• reaction lime
• voluntary movement
• humans