Layer differences in the effect of monocular vision in light- and dark-reared kittens.
We compared the effect of 2 days of monocular vision on the ocular dominance of cells in the visual cortex of light-reared kittens with the effect in dark-reared kittens at 6, 9, and 14 weeks of age, and analyzed the results by layer. The size of the ocular-dominance shift declined with age in all layers in light-reared animals. There was not a large change in the ocular-dominance shift with age in dark-reared animals in any layer, suggesting that dark rearing largely keeps the cortex in the immature 6-week state until 14 weeks or longer, although there was a slight decrease in layers II, III, and IV, and a slight increase in layers V and VI. At 14 weeks, the difference between light- and dark-reared animals was smallest in layer IV, larger in layers II/III, and largest in layers V/VI, suggesting that dark rearing has a large effect on intracortical synapses and a small effect on geniculocortical synapses. There was a significant ocular-dominance shift in layer IV at 14 weeks of age in both light- animals and dark-reared animals, showing that the critical period for ocular-dominance plasticity is not ended at this age. While the ocular-dominance shift after 26 h of monocular deprivation in 6-week animals was similar in light- and dark-reared animals, after 14 h it was smaller in dark-reared animals, showing that ocular-dominance changes occur more slowly in dark-reared animals at this age, in agreement with Mower (1991). Increases in selectivity for axis of movement after 26 h of monocular vision were seen in dark-reared animals at 6 weeks of age, but not at 9 or 14 weeks of age, showing that the critical period for axial selectivity ends earlier than the critical period for ocular dominance in dark-reared animals, as it does in light-reared animals.
Beaver
C J
CJ
Department of Ophthalmology and Visual Science, Yale University School of Medicine, New Haven, CT 06520-8061, USA.
Ji
Q
Q
Daw
N W
NW
D000375:Aging / Q000502:physiology; D000818:Animals; D002415:Cats; D003623:Dark Adaptation / Q000502:physiology*; D023882:Dominance, Ocular / Q000502:physiology*; D004594:Electrophysiology; D009473:Neuronal Plasticity / Q000502:physiology; D012683:Sensory Deprivation; D013569:Synapses / Q000502:physiology; D015349:Vision, Monocular / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology*