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Asymmetrical cortical processing of radial expansion / contraction in infants and adults |
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| Authors: | Nobu Shirai Deirdre Birtles John Wattam‐Bell Masami K Yamaguchi So Kanazawa Janette Atkinson Oliver Braddick |
| Institution: | 1. Department of Psychology, Faculty of Humanities, Niigata University, Japan;2. Visual Development Unit, Department of Psychology, University College London, UK;3. Department of Experimental Psychology, University of Oxford, UK;4. Department of Psychology, Chuo University, Japan;5. Japan Science and Technology Agency, Japan;6. Department of Psychology, Faculty of Integrated Art and Social Sciences, Japan Women's University, Japan;7. Department of Experimental Psychology, University of Oxford, UK |
| Abstract: | We report asymmetrical cortical responses (steady‐state visual evoked potentials) to radial expansion and contraction in human infants and adults. Forty‐four infants (22 3‐month‐olds and 22 4‐month‐olds) and nine adults viewed dynamic dot patterns which cyclically (2.1 Hz) alternate between radial expansion (or contraction) and random directional motion. The first harmonic (F1) response in the steady‐state VEP response must arise from mechanisms sensitive to the global radial motion structure. We compared F1 amplitudes between expansion‐random and contraction‐random motion alternations. F1 amplitudes for contraction were significantly larger than those for expansion for the older infants and adults but not for the younger infants. These results suggest that the human cortical motion mechanisms have asymmetrical sensitivity for radial expansion vs. contraction, which develops at around 4 months of age. The relation between development of sensitivity to radial motion and cortical motion mechanisms is discussed. |
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