10 Days of Darkness Does Not Restore Neural or Visual Plasticity in Adult Cats

Abstract

Recently it was demonstrated that 10-days of darkness could restore visual plasticity and promote fast and complete recovery from amblyopia in juvenile kittens (Duffy and Mitchell, 2013). To test whether 10-days of darkness could restore plasticity and promote recovery from amblyopia in adult cats (≥1year), two sets of studies were conducted. First, the effect of darkness on promoting recovery from monocular deprivation was tested behaviourally by examining the visual acuity of amblyopic adult cats placed in darkness, and examined histologically by measurement of soma size and neurofilament-H (NF-H) label density in the dorsal lateral geniculate nucleus (dLGN). Second, the capacity of darkness to induce plasticity in normal adult cats was tested through examining the effect of a subsequent period of monocular deprivation on visual acuity and on soma size and NF-H label density in the dLGN. In all conditions examined, darkness was wholly unable to promote visual or anatomical plasticity.