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Abstract:
Although many studies have been devoted to
motion perception during smooth pursuit eye movements,
relatively little attention has been paid to the
question of whether the compensation for the effects of
these eye movements is the same across different stimulus
directions. The few studies that have addressed this
issue provide conflicting conclusions. We measured the
perceived motion direction of a stimulus dot during
horizontal ocular pursuit for stimulus directions spanning
the entire range of 360. The stimulus moved at
either 3 or 8/s. Constancy of the degree of compensation
was assessed by fitting the classical linear model of
motion perception during pursuit. According to this
model, the perceived velocity is the result of adding an
eye movement signal that estimates the eye velocity to
the retinal signal that estimates the retinal image velocity
for a given stimulus object. The perceived direction depends
on the gain ratio of the two signals, which is assumed
to be constant across stimulus directions. The
model provided a good fit to the data, suggesting that
compensation is indeed constant across stimulus direction.
Moreover, the gain ratio was lower for the higher
stimulus speed, explaining differences in results in the
literature.
