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Monday July 2nd,
2007
Location: Salle de séminaire Harvey +1, UCL
Brussels
Time:
12:30 ”Different mechanisms of motion processing
for perception and pursuit eye movements”
Abstract: The
analysis of visual motion serves many different functions ranging from
object motion perception to the control of self-motion. The perception of
visual motion and the oculomotor tracking of a moving object are known to
be closely related and are assumed to be controlled by shared brain areas.
I will report results from experiments in which we compared perceived
velocity and the velocity of smooth pursuit eye movements in human observers
in a paradigm requiring the segmentation of target object motion from
context motion. In each trial, a pursuit target and a visual context were
independently perturbed simultaneously to briefly increase or decrease in
speed. Observers had to accurately track the target and estimate target
speed during the perturbation interval. Results show that the same motion
signals are processed in fundamentally different ways for perception and
smooth pursuit eye movements. For the computation of perceived velocity, motion
of the context was subtracted from target motion (motion contrast), whereas
pursuit velocity was determined by the motion average (motion
assimilation). I will conclude that the human motion system uses these
computations to optimally accomplish different functions: image
segmentation for object motion perception and velocity estimation for the
control of smooth pursuit eye movements.
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