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H. K. Falkenberg, G. N. Dutton, W. A. Simpson; Does Motion Discrimination Sensitivity in Children Aged 5-14 Years Improve After 1 Year?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1839.
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We have previously shown that motion detection and discrimination in human observers are limited by internal noise and poor sampling efficiency. We have also reported that the development of motion discrimination is immature in school-aged children due to reduced sampling efficiency and not increased internal noise. However, not all children were able to perform all tasks, and a 1-year follow up study was performed on a group of children to ensure that the development of motion discrimination sensitivity is due to improvement in sampling efficiency and not internal noise.
14 child observers aged 5-14 years who performed all three experiments at the initial visit returned for testing 12 ± 2 months later. All participated with informed consent. Contrast detection and discrimination thresholds were measured as a function of two external dynamic noise levels in three tasks; detection of a drifting grating; detection of the sum of two oppositely drifting gratings and direction discrimination of oppositely drifting gratings. The sinusoidal grating (2 c/deg) were drifting at either 1 or 6 Hz. An ideal observer paradigm was used to investigate the underlying changes in sampling efficiency and internal noise with age and task.
For direction discrimination a repeated measures ANOVA showed a significant main effect for speed (F(1,13) = 34.9, p<0,01), and age (F(1,13) = 30.3, p<0,01), and a significant interaction between age and speed (F(1,13) = 14, p<0,01). There was also a significant difference between visit 1 and visit 2 (F(1,13) = 31.8, p = p0.25). The sampling efficiency for detection and summation or the internal noise did not change with age, speed or between visits (all p>0.08).
This study confirms that development of motion direction discrimination in children can be attributed to improvement in sampling efficiency and not reduced levels of internal noise in individual observers. The results also support the suggestion that motion detection and discrimination develop at different rates and are processed by different mechanisms.
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