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Visuomotor control in normal infants and children with Williams Syndrome

King, John Andrew; (1998) Visuomotor control in normal infants and children with Williams Syndrome. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Young infants show clear preferences in preferential looking which are dependent on the eccentricity, contrast, size and shape of objects. Functional onset and increasing sensitivity of specifically tuned neurones within visual cortical streams are postulated as the neurological underpinnings for these preferences. The first part of this thesis is a report of experiments comparing preferential looking (PL) and preferential reaching (PR) in 5 to 15-month-old normal infants for pairs of small objects (red, high contrast 6-cm-long cylinders, diameter 1–6 cm), using the ELITE motion capture system to record the detailed kinematics of reaching. All PR studies found a strong bias toward reaching on the ipsilateral side to the reaching hand. This bias lessens with age and is significantly reduced when the object on the contralateral side is of graspable size. In PL, where the objects were 2-D renderings of the cylinders displayed on either side of the fixation point on a monitor, there was a strong effect of retinal eccentricity, with more first looks to objects with inner edges nearer the central fixation point. When retinal eccentricity was controlled for different sized objects, there were size-related effects, with more first looks to smaller, graspable objects. The preferences of looking and reaching are discussed in relation to current neurobiological models of visual processing in the dorsal and ventral streams. In the second part of this thesis, kinematic analysis techniques are used in a study of impairment of visuospatial processing in Williams Syndrome (WS), a genetically-based condition resulting in a number of cognitive and behavioural problems. Posting and visual matching tasks are used to investigate differential impairment of the dorsal and ventral cortical visual streams. Two subjects out of 11 were found to perform well at matching but very poorly at posting, and were postulated to be impaired in dorsal processing compared to ventral processing. Others exhibited general impairment at both tasks, with often more marked impairment on the posting task than the matching task. The variability of the results lead to the proposal that WS may not be a unitary homogeneous group, but rather a number of associated impairments resulting from a shared but variable genetic mutation.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Visuomotor control in normal infants and children with Williams Syndrome
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Biological sciences; Infants; Visuomotor control; Williams Syndrome
URI: https://discovery.ucl.ac.uk/id/eprint/10103151
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