INITIATION AND INHIBITION OF SACCADIC EYE-MOVEMENTS IN YOUNGER AND OLDER ADULTS - AN ANALYSIS OF THE GAP EFFECT

Previous research with young adults has shown that the latency to init iate a saccadic eye movement is typically reduced when the visual fixa tion stimulus is removed prior to the appearance of a peripheral targe t stimulus (the ''gap effect''). The present study sought to determine whether such fixation offsets would produce similar reductions in rea ction time in both younger and older adults. The results indicated tha t older adults have longer overall latencies to initiate saccadic eye movements and that they exhibit the gap effect. However, the reduction in reaction time due to the fixation offset was approximately equal b etween younger and older adults relative to the overall saccadic laten cies. These findings, along with some other recent evidence, suggest t hat some of the mechanisms involved in the production of saccadic eye movements may not reveal the changes often found in the skeletal motor system with increasing age. The implications of the findings to age-r elated differences in inhibitory function are discussed.