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Eric Seemiller, T. Candy; Vergence responses to changing disparity in 5 to 10 week old human infants.. Journal of Vision 2017;17(10):444. doi: https://doi.org/10.1167/17.10.444.
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Numerous studies have suggested that young infants do not respond to binocular cues such as retinal disparity until approximately 3 to 5 months of age (e.g., Petrig et. al, 1981; Thorn et. al, 1994). However, full-cue vergence responses have been observed in newborns (Slater and Findlay, 1975) and examined quantitatively in 2-month-olds, who responded to a 2 deg. stimulus in depth (Seemiller et. al, 2016). In adults, small errors in vergence responses are corrected using the disparity cue. Is it possible that vergence responses can be driven by disparity at younger ages than the classically documented onset of disparity sensitivity? 22 full-term, typically developing infants were tested between 5 and 10 weeks postpartum. Subjects viewed a large field (44 x 66 deg.) dynamic random noise stimulus that oscillated in disparity sinusoidally (0.1 Hz, amplitude = 2 degrees) for 30 seconds. Horizontal eye position was measured using a Purkinje image eye tracker (PlusOptix) at 50 Hz. Fast Fourier Transforms were then used to compare the amplitude of their vergence response at the frequency of the stimulus to an estimate of background vergence noise. Usable data were collected from 16 of 22 infants (mean age = 56.2 +/- 10.0 days) and 10 adult controls. Across the group, responses at the frequency of the stimulus were significantly larger than at the adjacent frequencies for both infants (paired t-test: t = 6.374, p < 0.00001) and adults (t = 10.602, p < 0.000001). These results suggest that infants in this age group are capable of processing disparity at a younger age than previously believed; responses were observed in the youngest infants tested (35 days). Furthermore, because the noise fields were temporally uncorrelated, there was no static feature for independent monocular alignment or "bifoveal fixation" (e.g., Held, 1993).
Meeting abstract presented at VSS 2017
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