• Donald E Mitchell, Jan Kennie, and Diane Kung.
• Psychology Department, Dalhousie University, Halifax, NS, Canada. d.e.mitchell@dal.ca
• Curr. Biol. 2009 Apr 28;19(8):645-9.

AbstractThe accurate representation of the motion of external objects is one of the more important tasks of the visual areas of the brain because motion by itself can provide sufficient information for discriminating visual forms and hence breaking camouflage. Whereas the analysis of the motion of single small elements can occur in primary visual cortex (V1), the perception of a common direction of global motion of some visual elements among many is supported by extrastriate cortical areas [1, 2]. Humans treated for binocular congenital cataracts afterward exhibit extreme deficits of global motion, but after monocular cataracts, the deficits are minimal [3]. These observations suggest a need for normal early patterned visual experience through at least one eye for global motion perception to develop in a typical fashion. We investigated this role for early experience and its timing on kittens that were deprived of light or patterned light at different ages. Such deprivation in the first 6 weeks resulted in long-lasting (>2 yr) profound deficits of perception of global motion but no apparent effects on the perception of simple unidirectional motion. Contrary to current opinion, sensitive periods to visual deprivation in primary and extrastriate cortex may be of similar duration.

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