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Yasmine El-Shamayleh, Lynne Kiorpes, J. Anthony Movshon; Different aspects of form perception develop at diffierent rates. Journal of Vision 2005;5(8):220. doi: 10.1167/5.8.220.
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© ARVO (1962-2015); The Authors (2016-present)
Newborn macaques can detect the presence of luminance gratings. However, they are unable to process more complex cues, such as dots pairs that define a global form percept in Glass patterns, until about 11 wks. This difference may be due to the late development of ventral extrastriate areas, known to be important for mature form vision, or may be attributed to differences in the extent of spatial integration required to extract the form cues present in simpler and more complex stimuli. To address this question, we compared the performance of macaques on a texture-defined form task, which did not require extensive integration over space, to detection of Glass patterns. The texture cue was defined by differences in the orientation of carrier patterns whose spatial form was determined by a separate modulator pattern (Landy & Oruc, 2002).
We trained young monkeys to discriminate orientation. We presented two modulators; one vertical, the other horizontal. The animal's task was to indicate the vertical target. We varied texture modulation depth and modulator spatial frequency, and used either horizontal/vertical or oblique carrier patterns whose orientation differed by 90 deg. For comparison, we tested the same animals on a Glass pattern detection task using concentric or linear form cues.
Infant monkeys can detect texture-defined boundaries as early as 4 wks and are able to use this cue for orientation discrimination as early as 6 wks. Sensitivity is higher for textures defined by horizontal/vertical carriers than for those based on oblique carriers. All animals performed the texture discrimination at earlier ages than Glass pattern detection. Our results suggest that different aspects of form perception develop over different time courses, reflecting a developmental cascade of visual functions. Thus, mechanisms underlying the integration of form cues on a local spatial scale mature earlier than those implicated in global spatial integration.
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