Amblyopia And Liver Degeneration In Patients With Visual Cognitive Impairment In The Mechanism Of Noise And Model Analysis

Currently, external noise is frequently used by psychologists to measure the properties of a wide range of perceptual process. The basic idea of this methos is to estimate the amount of internal noise and characteristics of the perceptual processes by studying how performance in some task is affected by experimenter-manipulated external noise. In this paper, we apply the external noise method and a Perceptucal Template Model (PTM) to identify the mechanism of the visual deficit in amblyopia and Wilson's Disease patients. In addition, we also studied the detection threshold of second-order motion signal in amblyopia and the relationship of perceptual learning and category learning in Wilson's Disease patients.Amblyopia is a developmental visual disorder characterized by reduced vision in the absence of any detectable structural or pathological abnormalities that does not improve with refractive correction. In our experiment, amblyopic observers performed a Gabor orientation identification task in fovea with 8 level white external noises (contrast 0-0.33) added. Threshold versus external noise contrast (TvC) functions were measured at two performance criterion levels (d'=1.09 and d'=1.63). For a subset of observers, we also manipulated the center spatial frequency of the Gabor from spatial frequency 1.5-4.6 c/d. With PTM model analysis, we found that two independent factors contributed to amblyopic deficits: (1) increased additive internal noise, and (2) deficient perceptual templates. Whereas increased additive noise underlay performance deficits in all spatial frequencies, the degree of perceptual template deterioration increased with the center spatial frequency of the Gabor. In addition, we found that amblyopia did not affect the non-linear transducer and multiplicative noise.In the first-order and second-order motion detection experiments, we measured the sensitivity of first-order and second-order motion of sinusoidal grating signal in eight anisometropic amblyopes and ten normal observers. The measurement of second-order motion was performed in two conditions: with non-equated visible carrier and with equated visible carrier. The amblyopic eyes of amblyopes showed deficit in both perceptions of first-order and second-order motion with non-equated carrier, relative to their fellow eyes and to normal eyes. But with the equated carrier, we revealed the second order motion perception was normal for the amblyopic eyes, which means the deficit of second-order motion in amblyopic eye could be a sequence of its first-order detection loss.Wilson's disease (WD), hepatolenticular degeneration, is an autosomal recessively inherited disorder of copper metabolism. In this suty, we evaluated explicit and implicit category learning and perceptual learning in subjects with treated Wilson's disease and normal controls. The WD subjects exhibited deficits in both forms of category learning as well as perceptual learning in high external noise. However, their perceptual learning in low external noise was relatively spared. Furthermore, there were significant correlations between perceptual learning in high external noise and both forms of category learning, but perceptual learning in low external noise was not significantly correlated with either form of category learning. The results suggest that damages to brain structures in Wilson's disease that are important for category learning may lead to poor perceptual learning in high external noise, but may spare perceptual learning in low external noise; perceptual learning in high and low external noise environments may be served by different brain structures.With the method of systematic variations of environmental noise in signal detection task and quantification in a model analysis, increasing information can be acquired in our research experiments and new mechanisms of visual processing can be revealed in future.