Abstract
Cognition is very important in our daily life. However, amblyopia has abnormal visual cognition. Physiological changes of the brain during processes of cognition could be reflected with ERPs. So the purpose of this study was to investigate the speed and the capacity of resource allocation in visual cognitive processing in orientation discrimination task during monocular and binocular viewing conditions of amblyopia and normal control as well as the corresponding eyes of the two groups with ERPs. We also sought to investigate whether the speed and the capacity of resource allocation in visual cognitive processing vary with target stimuli at different spatial frequencies (3, 6 and 9 cpd) in amblyopia and normal control as well as between the corresponding eyes of the two groups. Fifteen mild to moderate anisometropic amblyopes and ten normal controls were recruited. Three-stimulus oddball paradigms of three different spatial frequency orientation discrimination tasks were used in monocular and binocular conditions in amblyopes and normal controls to elicit event-related potentials (ERPs). Accuracy (ACC), reaction time (RT), the latency of novelty P300 and P3b, and the amplitude of novelty P300 and P3b were measured. Results showed that RT was longer in the amblyopic eye than in both eyes of amblyopia and non-dominant eye in control. Novelty P300 amplitude was largest in the amblyopic eye, followed by the fellow eye, and smallest in both eyes of amblyopia. Novelty P300 amplitude was larger in the amblyopic eye than non-dominant eye and was larger in fellow eye than dominant eye. P3b latency was longer in the amblyopic eye than in the fellow eye, both eyes of amblyopia and non-dominant eye of control. P3b latency was not associated with RT in amblyopia. Neural responses of the amblyopic eye are abnormal at the middle and late stages of cognitive processing, indicating that the amblyopic eye needs to spend more time or integrate more resources to process the same visual task. Fellow eye and both eyes in amblyopia are slightly different from the dominant eye and both eyes in normal control at the middle and late stages of cognitive processing. Meanwhile, abnormal extents of amblyopic eye do not vary with three different spatial frequencies used in our study.
Highlights
Amblyopia is a neural-developmental visual disorder without obvious organic deficits caused by inadequate early visual experience
In anisometropic amblyopes and normal controls, a 3 × 3 univariate repeated measures ANOVA was conducted for ACC and reaction time (RT)
Compared with the corresponding eyes of two groups, a 2× 3 univariate repeated measures ANOVA was conducted for ACC and RT
Summary
Amblyopia is a neural-developmental visual disorder without obvious organic deficits caused by inadequate early visual experience. It is always accompanied by one or more known factors, such as anisometropia (anisometropic amblyopia), strabismus (strabismic amblyopia), high refractive error (refractive error amblyopia), ptosis and cataract (form-deprivation amblyopia) [1, 2]. Previous psychophysical and neuroimaging studies have suggested that amblyopia leads to abnormal responses in the primary and secondary visual areas and deficits at higher levels of visual pathways [10]. Some studies have observed abnormal neural responses in subjects with amblyopia using electrophysiological techniques [11,12,13,14].
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