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S. V. Aydin, V. Manahilov, N. C. Strang, U. Shahani; Perceptual Rivalry in Aging and Amblyopic Eyes. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1841.
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Excitatory and inhibitory neural mechanisms develop during childhood, approach an optimal balance in adolescence and young adulthood and weaken in old age. Amblyopic eyes often fail to reach optimal levels and exhibit similar neural characteristics to the older eye. To test this, we compared changes of perceptual suppression and facilitation during perceptual rivalry using the Rubin Vase-Faces image in older and amblyopic individuals.
18 young (22-34 years) and 16 older (61-83 years) adults were tested in experiment 1 and 6 anisometropic amblyopes (19-30 years) and 6 controls (19-30 years) took part in experiment 2. In experiment 1 viewing was binocular and in experiment 2 subjects viewed the image with each eye and then binocularly. Mini-Mental-State-Examination was performed to screen for possible dementia and other cognitive impairment. All subjects performed both passive rivalry tasks and those requiring voluntary control by either holding or switching the dominant percept using external and internal cues. External cues (black dots) were superimposed either on the faces or the vase; internal cues were initiated by verbal instructions. Dominance duration of each percept was measured in each condition.
Experiment 1: Dominance durations of older subjects were 50% longer in the passive condition (p<0.01) and 78% in the switch with external cues condition (p<0.005) when compared with those of young subjects. Experiment 2: In binocular viewing amblyopes showed longer dominance durations in both the passive condition (83%, p<0.05) and the hold condition with internal cueing (84%, p<0.05). Interocular differences were not found in the amblyopes during monocular viewing.
Older and amblyopic eyes show similar prolonged dominance durations in the passive condition. This result may reflect impaired balance of suppressive and facilitatory perceptual mechanisms. The balance of these mechanisms under voluntary control is also different from that of controls. Older adults show reduced ability to voluntarily increase the rate of reversals between the percepts using external cues, while amblyopes are able to hold internally the dominant percept longer than controls.
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