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Francesca Pei, Chuan Hou, Anthony M Norcia; Texture thresholds in aults and infants. Journal of Vision 2003;3(9):617. doi: 10.1167/3.9.617.
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© ARVO (1962-2015); The Authors (2016-present)
Textures are defined by regularities in spatial scale and orientation. In previous experiments, we have studied brain responses elicited by a sub-class of textures that have a single spatial scale. These textures are made up of Gabor patches that are either randomly arranged or are comprised of a single orientation across the image. In order to discriminate the two stimuli, observers have to be able to compare the relative orientations of multiple patches, a “global” task. Using these textures, we have identified a texture-specific component in the VEP that is present as early as 8 weeks of age in human infants.
In the present study, we wanted to quantify the relative maturity of this response by measuring the minimum amount of organization required to elicit the texture-specific component in infants and adults. Thresholds were measured by varying the percentage of patches that were of the same orientation vs of a random orientation (percent coherence). The exchange of random and organized images leads to a texture-specific component at the first harmonic of the exchange rate and thresholds were measured by extrapolating the first harmonic amplitude vs. percent coherence function to zero amplitude. Adult texture-specific responses were robust and their thresholds were around 20%. Infant texture-specific responses were weaker and thresholds were not measurable in most individual infants. However thresholds of around 50% could be estimated from group average data. Infants are capable of detecting the global structure of our textures, but their sensitivity is quite low. Our results are broadly consistent with two previous behavioral studies that have found successful detection of highly coherent line textures in 3–4 month old (Atkinson and Braddick, 1992), but a long developmental period before adult thresholds are reached (Sireteanu and Rieth 1992).
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