Visual input guides the development of visual system in which distinct critical periods are connected with separate functions. Monocular deprivation during critical period leads to acuity defi cits, while binocular deprivation impairs more specifi c visual functions. Children with later onset of binocular cataract have normal global motion perception, while patients with congenital cataract show a defi cit (Lewis and Maurer 2005). Similarly global motion detection is impaired in cats binocularly deprived for 6 months (Burnat et al. 2002). The exact time-frame for global motion perception critical period still needs to be established. Two experimental groups of cats: congenital (2BD) binocularly deprived for fi rst 2 months of life and developmental (2N2BD) with 2 months of normal vision followed by 2 months of deprivation were used. Controls had normal visual input. Animals were trained in two-choice apparatus for a food reward. Visual discrimination tasks with random dot patterns differing in velocity and, or direction were used. In 2N2BD group we found signifi cant impairment as compared to 2BD group in velocity discrimination tasks. Moreover, we found in 2N2BD group that the detection of global motion signal at low contrast is impaired by the addition of dark noise. Surprisingly, visual experience for fi rst 2 months limited to the moving shadows may facilitate global motion perception as the 2BD group learned motion tasks faster than control group. Supported by MNiSW grant N40132/1002.
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