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| Research article summary (published 29 Apr 2003): |
Motion coherence thresholds in infants--different tasks identify at least two distinct motion systems.
Full Abstract
Optokinetic nystagmus (OKN) can be demonstrated from birth, but behavioural discrimination tasks such as habituation and preferential looking do not reveal any sensitivity to motion direction until a few weeks of age. This study compared coherence threshold for motion direction for OKN and preferential looking responses using closely comparable stimuli, in infants between 6 and 27 weeks of age. Infants were tested with two random dot motion displays, a uniform area of moving dots for OKN responses and a display in which a region was segmented on one side by differential motion direction for preferential looking responses. Coherence thresholds for each response were determined by a staircase method. For OKN responses, mean coherence thresholds were between 20% and 25%, with no significant improvement in OKN performance throughout the age range. Preferential looking thresholds were significantly higher than OKN thresholds. Preferential looking thresholds improved significantly with age, but remained higher than OKN thresholds throughout the age range tested. Experiments varying direction reversal frequency and stimulus area indicated that these differences were not simply a consequence of the spatial and temporal non-uniformity of the preferential looking stimulus.The differences in sensitivity levels and age trends for OKN and preferential looking responses we have found suggest that different directional mechanisms are involved in the two responses. We discuss the possibility that, in early infancy, OKN and preferential looking reflect the performance of subcortical and cortical directional mechanisms respectively.
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Author information
Author/s: Mason, A J S (AJ); Braddick, O J (OJ); Wattam-Bell, J (J);
Affiliation: Department of Psychology, Visual Development Unit, University College London, Gower Street, London WC1E 6BT, UK. alexandra.mason(-atsign-)ucl.ac.uk
Journal and publication information
Publication Type: Journal Article
Journal: Vision research (Vision Res), published in England. (Language: eng)
Reference: 2003-May; vol 43 (issue 10) : pp 1149-57
Dates: Created 2003/04/22; Completed 2003/07/21; Revised 2004/11/17;
PMID: 12705955, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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