The mechanics of human smooth pursuit eye movement.

Dodge, in 1903, was among the first to draw a distinction between saccadic and smooth pursuit human eye movements. Saccadic movements have attracted much attention because they reflect the most rapid activity of a very fast mammalian skeletal muscle. Smooth pursuit movements, however, constitute a large portion of ocular activity and while some descriptions of them exist (Rashbass, 1961; Westheimer, 1954) and some theories have been proposed on their integration into ocular targetfollowing (Young & Stark, 1963), a more thorough examination of them and their concomitant muscular activity seems desirable as a preface to further investigations into the oculomotor system. The experiments reported here elucidate the nature of the net active state tension in the horizontal recti that accelerates the eye in smooth pursuit movements from one velocity to another in about 130 msec. These experiments also indicate that the sampled data system analogy of eye movements proposed by Young & Stark (1963), while quite successful for saccadic movements, seems not pertinent to the smooth pursuit system for which the stimulus-response relation appears to be continuous in nature.