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Karen Dobkins, Emily Blumenthal, Melissa McIntire, Suzanne McDonald, Holly Bergen; Effects of External Noise on Contrast Sensitivity for Intact and Scrambled Faces in Infants. Journal of Vision 2014;14(10):224. doi: 10.1167/14.10.224.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction: Previous EEG studies in infants have shown that intrinsic noise levels are much higher in neonates than in adults, demonstrated by the finding that the amount of external noise needed to affect grating contrast sensitivity (measured by sweep VEPs to gratings) is significantly greater in infants (Skoczenski and Norcia, 1997). Here, we addressed the question of intrinsic noise and face contrast sensitivity using a behavioral paradigm, and compared effects between intact vs. scrambled faces. Methods: Using forced-choice preferential looking (FPL) in 3-month-olds (n = 12) and 6-month-olds (n = 14), two measures were obtained for each subject, for either intact or scrambled faces. (1) Contrast Sensitivity (CS): We first obtained CS to intact or scrambled faces, using stimuli that were 17 by 22째, centered 16.5째 from center. Across trials, contrast varied between 1 and 22 RMS contrast. (2) Noise Sensitivity (NS): In the second stage, we measured the amount of noise needed to bring subject performance for detecting the "target" stimulus (intact or scrambled faces) down to 75% correct. For each subject, the target stimulus was presented at 4-fold their contrast threshold from part (1) so that visibility was equated across all subjects. Noise consisted of randomly positioned light and dark squares (0.6째 square) added to the target stimuli (noise contrast varied from 1 and 30 RMS contrast). Results: For part (1), CS increased between 3- and 6-months for intact (p <0.01) but not scrambled faces (p = 0.49, ns). For part (2): NS was roughly constant between 3- and 6-months for both intact (p = 0.21, ns) and scrambled faces (p = 0.94, ns). Conclusions: These preliminary results suggest that the increase in contrast sensitivity to faces in the first six months of life is not a result of age-related decreases in intrinsic noise within face detection mechanisms.
Meeting abstract presented at VSS 2014
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