Fig. 4.

The effect of MD is reduced in animals with a history of MD. Control conditions (shaded area) demonstrate that the effect of an early and brief MD is erased with provision of binocular vision. An early period of MD reduces the size of neurons in deprived-eye layers of the dLGN, producing an imbalance of cell sizes between layers serving the right and left eye (A). This imbalance was restored to normal by opening the deprived eye and providing 8 days of binocular vision. A subsequent period of MD of the fellow eye elicited a small reduction of deprived cell size. Importantly, animals that were not subjected to a prior MD exhibited a reduction of deprived-eye cell size that was larger than the effect observed in animals with a prior MD. A similar pattern of results was observed when the same animals were examined for neurofilament labeling (B). Early MD reduced neurofilament-positive cell density within deprived layers of the dLGN by almost 50%, but this recovered and appeared normal within 8 days of providing binocular vision. Animals subjected to this early period of MD that at 8 weeks of age had their fellow eye deprived exhibited an effect on neurofilament labeling that was about half the size of the effect measured from age-matched animals that did not have a history of MD.