COMPARISON OF HORIZONTAL, VERTICAL AND DIAGONAL SMOOTH-PURSUIT EYE-MOVEMENTS IN NORMAL HUMAN-SUBJECTS

We compared horizontal and vertical smooth pursuit eye movements in fi ve healthy human subjects. When maintenance of pursuit was tested usin g predictable waveforms (sinusoidal or triangular target motion), the gain of horizontal pursuit was greater, in all subjects, than that of vertical pursuit; this was also the case for the horizontal and vertic al components of diagonal and circular tracking. When initiation of pu rsuit was tested, four subjects tended to show larger eye acceleration s for vertical as opposed to horizontal pursuit; this trend became a c onsistent finding during diagonal tracking. These findings support the view that different mechanisms govern the onset of smooth pursuit, an d its subsequent maintenance when the target moves in a predictable wa veform. Since the properties of these two aspects of pursuit differ fo r horizontal and vertical movements, our findings also point to separa te control of horizontal and vertical pursuit. Copyright (C) 1996 Else vier Science Ltd.