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A. R. O'Connor, P. Knox, D. Newsham, V. Wong, D. Clark; Spatial Localisation in Very Low Birth Weight Children. Invest. Ophthalmol. Vis. Sci. 2007;48(13):905.
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© ARVO (1962-2015); The Authors (2016-present)
Very low birth weight (VLBW) children, without serious neurological deficits, have an increased prevalence of visual and visuomotor disorders which should impact on visually guided behaviour. We have examined the accuracy of pointing to visual targets with and without a memory delay.
Subjects (10 full term controls; mean age 12±4y; 11 VLBWs; 13±3y) binocularly viewed a touchscreen monitor. Single targets (1°x1° black squares on a grey background) were presented at one of 25 randomly chosen positions in a 5 X 5 grid. They were presented with a minimum of five sets of five targets in each of two tasks. In Task 1 (T1), the subject touched the monitor at the target position as soon as the target appeared. In T2, 5 targets appeared in sequence, at 5 randomly assigned positions; after a 5s delay, the subject touched each of the remembered target positions in sequence. For both tasks we analysed the distance of the touch position (in pixels) from the centre of each target. For T2, we calculated the error for those responses in which the 5-target sequence was correctly remembered (2A), and compared this with pointing error averaged over all sequences (2B).
For T1 and T2A, the two groups exhibited similar pointing error magnitudes, although the responses of the VLBWs were more variable (see Fig); there was no significant group difference in the number of correctly remembered sequences (t-test, p=0.3). However, the VLBWs’ pointing errors were markedly greater for T2B. After removal of the VLBWs with IQ<70, this same pattern remained. When these data (10 controls vs 6 VLBWs, IQ>70) were tested with ANOVA (factors - task, T1,T2A, T2B, within subjects; group, between subjects), both task (p<0.001) and group (p<0.001) were statistically significant.
While the VLBW group had little problem with online spatial localisation in visually closed-loop conditions, the significant decline in their performance when they had both to remember a sequence and the spatial positions of targets within sequences suggests problems with visual memory which could impact on visually guided behaviour.
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