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Thursday November
22nd, 2007
Location: Auditoire Maisin, UCL Brussels
Time: 17:00
Visual
sensitivity during smooth pursuit eye movements
Abstract: When
we view the world around us, we constantly move our eyes. Between periods
of fixation rapid eye movements, called saccades, bring objects of interest
into the region of highest acuity, the fovea. Slow voluntary tracking
movements, called smooth pursuit, are performed to keep moving target
objects in the fovea. The execution of these eye movements requires the
allocation of spatial attention and induces shifts of the retinal image.
Both factors have been shown to deteriorate visual performance during eye movements
when compared to fixation. Here we show that sensitivity for some types of
visual stimuli is improved during smooth pursuit eye movements. Detection
thresholds for briefly flashed coloured stimuli
were 15% lower during pursuit compared to fixation. Similarly, detection
thresholds for luminance-defined stimuli of high spatial frequency were
lowered. These findings indicate that the pursuit-induced sensitivity
increase may originate in the parvocellular retino-thalamic system. This implies that the visual
system not only can use feedback-connections to improve processing for
certain attended locations and objects, but that a whole processing
subsystem can be boosted when necessary. During smooth pursuit,
facilitation of the parvocellular system may aim
at improving object recognition and increasing sensitivity to small retinal
speed errors while tracking objects.
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