Age dependence of sensory and motor components in saccades

Abstract

Humans usually perform about 3-4 saccades per second; hence, precision as well as latency and velocity of these fast eye movements are of crucial importance for analyzing complex and fast changing visual scenes, for example in traffic. Since visual performance is known to slowly decline with age, we investigated the effect of age on the most important characteristics of visually guided saccades. This investigation on age dependence of visually guided saccades included, for the first time, the gap condition, where the old fixation point disappears before the new one appears, allowing subjects to prepare for a saccade. Saccadic latencies and intersaccadic intervals increased with age, while their peak velocities and gains decreased, especially for threshold-adjusted luminance of the targets. The gap condition, however, improved reaction times (latencies) most pronounced in the older age groups, bringing performance for these groups close to the performance level of the young groups. This indicates that the slowing down of saccadic reaction times with age is not predominantly a motor problem, but, according to a common interpretation of the gap effect, a problem of disengaging attention from the old fixation spot.