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 initiate a saccadic eye movement is typically reduced when the visual fixation stimulus is removed prior to the appearance of a peripheral target stimulus (the "gap effect"). The present study sought to determine whether such fixation offsets would produce similar reductions in reaction time in both younger and older adults. The results indicated that 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 between younger and older adults relative to the overall saccadic latencies. These findings, along with some other recent evidence, suggest that 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-related differences in inhibitory function are discussed.