Smooth pursuit in senescence. Effects of target acceleration and velocity.

Smooth pursuit responses to sinusoidal and triangular waveform targets were investigated in elderly and middle-aged subjects. The middle-aged pursued triangular targets with significantly lower gain than sinusoidal targets. In the elderly, pursuit gain was significantly lower than in the middle-aged under all target conditions. When all smooth eye movements at a constant frequency were correlated with varying target velocity, pursuit gain was uniformly reduced in the elderly, irrespective of target velocity up to 63 degrees/s or accelerations up to 395 degrees/s2. Within these limits, the steady-state gain of pursuit was depressed. At higher target accelerations having the same velocity range, smooth pursuit velocities were further reduced in the elderly. Senescent tracking is depressed by involvement of the steady-state gain element of the pursuit system at low target accelerations and by acceleration saturation at higher demands.