Papers by Oliver Braddick
Develop Med Child Neurol, 2007
In Investigative Opthalmology and Visual Science, 2002
Vision research, 2016
Advances in potential treatments for rod and cone dystrophies have increased the need to understa... more Advances in potential treatments for rod and cone dystrophies have increased the need to understand the contributions of rods and cones to higher-level cortical vision. We measured form, motion and biological motion coherence thresholds and EEG steady-state visual evoked potentials (SSVEP) responses under light conditions ranging from photopic to scotopic. Low light increased thresholds for all three kinds of stimuli; however, global form thresholds were relatively more impaired than those for global motion or biological motion. SSVEP responses to coherent global form and motion were reduced in low light, and motion responses showed a shift in topography from the midline to more lateral locations. Contrast sensitivity measures confirmed that basic visual processing was also affected by low light. However, comparison with contrast sensitivity function (CSF) reductions achieved by optical blur indicated that these were insufficient to explain the pattern of results, although the tempo...
Investigative ophthalmology & visual science, 2016
While basic visual functions have been described in subjects with congenital achromatopsia (ACHM)... more While basic visual functions have been described in subjects with congenital achromatopsia (ACHM), little is known about their mid- or high-level cortical visual processing. We compared midlevel cortical visual processing in ACHM subjects (n = 11) and controls (n = 20). Abilities to detect global form, global motion, and biological motion embedded in noise were tested across a range of light levels, including scotopic, in which both ACHM subjects and controls must rely on rods. Contrast sensitivity functions (CSFs) were also measured. Achromatopsia subjects showed differential impairments across tests. In scotopic conditions, global form was most impaired, while biological motion was normal. In a subset of three ACHM subjects with normal scotopic CSFs, two of the three showed global form perception worse than controls; all showed global motion comparable to controls; and strikingly, two of the three showed biological motion perception superior to controls. The cone signal appears to...
Investigative Ophthalmology and Visual Science 919 919, 1997
Developmental Neuropsychology 23 Pp 139 172, 2002
We examine hypotheses for the neural basis of the profile of visual cognition in young children w... more We examine hypotheses for the neural basis of the profile of visual cognition in young children with Williams syndrome (WS). These are: (a) that it is a consequence of anomalies in sensory visual processing; (b) that it is a deficit of the dorsal relative to the ventral cortical stream; (c) that it reflects deficit of frontal function, in particular of fronto-parietal interaction; (d) that it is related to impaired function in the right hemisphere relative to the left. The tests reported here are particularly relevant to (b) and (c). They form part of a more extensive programme of investigating visual, visuospatial, and cognitive function in large group of children with WS children, aged 8 months to 15 years. To compare performance across tests, Neurobiological models of visuo-spatial cognition in children with WS p.28
Strabismus 12 223 241, 2004
The Second Cambridge Population Infant Vision Screening Programme using the VPR-1 videorefractor ... more The Second Cambridge Population Infant Vision Screening Programme using the VPR-1 videorefractor without cycloplegia was undertaken in order to identify those infants with refractive errors who were potentially amblyogenic or strabismogenic. Infants identified at eight months were entered into a control trial of treatment with partial spectacle correction and underwent a long-term follow-up that monitored a wide range of visual, visuoperceptual, visuocognitive, visuomotor, linguistic and social development. In the present paper, the authors report on the outcome measures of visual acuity and strabismus. Poor acuity was defined as a best-corrected acuity of 6/12 or worse on crowded letters or 6/9 or worse on single letters, at age 4 years. Acuity was measured in 79 infants who were significantly hyperopic and/or anisometropic at 11-12 months of age, 23 who showed hyperopia of +3D but less than +3.5D, 196 control subjects, 14 controls with refractive errors, and 126 others who showed an accommodative lag on screening but were not significantly hyperopic on first retinoscopy. There was a poorer acuity outcome in the untreated group of hyperopes compared to controls (p < 0.0001) and to the children who were compliant in spectacle wear (p < 0.001) or who were prescribed spectacles (p < 0.05). Children who were significantly hyperopic at eight months were also more likely to be strabismic by 5.5 years compared to the emmetropic control group (p < 0.001). However, the present study did not find a significant difference in the incidence of strabismus between corrected and uncorrected hyperopic infants. Children who were not refractively corrected for significant hyperopia were four times more likely to have poor acuity at 5.5 years than infants who wore their hyperopic correction, supporting the findings of the First Cambridge Population Infant Vision Screening Programme.
American Journal of Optometry and Physiological Optics, Oct 1, 1985
An optical analysis of a photographic technique, "eccentric photorefraction," d... more An optical analysis of a photographic technique, "eccentric photorefraction," designed to measure refraction and accommodative states along a single meridian of the eye, is presented. Empirical measures taken from a model eye support the theoretical derivation. The application of the technique for use with human infants is discussed with reference to measurements taken from human eyes.
PloS one, 2015
This study measured changes in switches of attention between 1 and 9 months of age in 67 typicall... more This study measured changes in switches of attention between 1 and 9 months of age in 67 typically developing infants. Remote eye-tracking (Tobii X120) was used to measure saccadic latencies, related to switches of fixation, as a measure of shifts of attention, from a central stimulus to a peripheral visual target, measured in the Fixation Shift Paradigm. Fixation shifts occur later if the central fixation stimulus stays visible when the peripheral target appears (competition condition), than if the central stimulus disappears as the peripheral target appears (non-competition condition). This difference decreases with age. Our results show significantly faster disengagement in infants over 4 months than in the younger group, and provide more precise measures of fixation shifts, than behavioural observation with the same paradigm. Reduced saccadic latencies in the course of a test session indicate a novel learning effect. The Fixation Shift Paradigm combined with remote eye-tracking ...
Vision Res, 1977
Abstract 1. Studied 16 414 wk old infants' detection of spatial detail by observing fix... more Abstract 1. Studied 16 414 wk old infants' detection of spatial detail by observing fixation preferences when Ss were presented simultaneously with 2 pictures of the same face, one of which was defocused. Ss were also tested with gratings. There was a high correlation ...
Documenta Ophthalmologica Proceedings 45 107 115, 1986
Investigative Ophthalmology Visual Science 44 U327 U327, May 1, 2003
Brain and Development 20 336 336, 1998
It has been suggested that learning an object's location relative to (1) intramaze landmarks and ... more It has been suggested that learning an object's location relative to (1) intramaze landmarks and (2) local boundaries is supported by parallel striatal and hippocampal systems, both of which rely upon input from a third system for orientation. However, little is known about the developmental trajectories of these systems' contributions to spatial learning. The present study tested 5-and 7-year-old children and adults on a water maze-like task in which all three types of cue were available. Participants had to remember the location of an object hidden in a circular bounded environment containing a moveable intramaze landmark and surrounded by distal cues. Children performed less accurately than adults, and showed a different pattern of error. While adults relied most on the stable cue provided by the boundary, children relied on both landmark and boundary cues similarly, suggesting a developmental increase in the weighting given to boundary cues. Further, adults were most accurate in coding angular information (dependent on distal cues), whereas children were most accurate in coding distance, suggesting a developing ability to use distal cues to orient. These results indicate that children as young as 5 years use boundary, intramaze landmark, and distal visual cues in parallel, but that the basic accuracy and relative weighting of these cues changes during subsequent development.
In Child Vision Research Society Mumeum of Natural History Paris France, 2001
Perception Ecvp Abstract, Oct 10, 2014
Background Aims: 1. Investigate effects of eye-movements (potentially non-verbal task) compared t... more Background Aims: 1. Investigate effects of eye-movements (potentially non-verbal task) compared to manual responses (instructions required) on ERPs 2. Apply this measure to investigate brain mechanisms of attention shifts using eye-tracking in combinations with EEG Random inter-trial interval [0.5; 2.5] sec + fixation Fixation Shift Task 3 Instead of fixation dot: competing target disengagement necessary Discussion • Slower saccadic latencies under competition and with two targets • Similar ERP components can be found under competition as in study 1 • Difference waves show similar effects as in study 1 • Hemispheric differences are bigger under competition, though insignificantly
Experimental Brain Research, Apr 1, 2010
Stepping down at a change of height is a fundamental part of human locomotion. At a novel step, t... more Stepping down at a change of height is a fundamental part of human locomotion. At a novel step, this requires the transformation of visual information about a depth change into a stepping movement of appropriate size. However, little is known about this process or its development. We studied adults, 3-and 4-year-old children stepping down a single stair of variable height. We assessed how well stepping down was scaled to stair height using several kinematic measures. Of these, 'kneedrop' and 'toedrop' describe how far the leg has descended by the time it begins to 'swing in' in preparation for landing; and 'toeheight (speedpeak)' describes where the toe begins to decelerate. If visually controlled, their values should scale to the height of the stair. Under normal visual conditions, children scaled these movements to stair height as well as adults. In a second condition, participants closed their eyes just before stepping down to remove visual feedback during the step. Adults' steps were barely affected. For 4-year olds, only toeheight (speedpeak) decreased. For 3-year olds, both toedrop and toeheight (speedpeak) scaled less well to stair height than normal. The results suggest that visuomotor processes for fine-tuned stepping control develop remarkably early, but are initially dependent on visual feedback.
Exp Brain Res 217 237 249, Mar 1, 2012
It has been shown that infants over the age of 6 months will reach for an object in complete dark... more It has been shown that infants over the age of 6 months will reach for an object in complete darkness. This experiment measured the reaching movements of 9-to 16-month-old infants and adults under several diVerent conditions of illumination to investigate the role of vision and stored visual representations in reach control. In one condition, participants reached for an object with the lights on. In a second condition, participants reached for an object glowing in the dark (glowing condition). This allowed us to measure the eVects of vision of the arm and vision of the reach space. We also looked at the eVect of removing vision of the object on reach control: in the Wnal two conditions, participants reached for an object in complete darkness (0-s dark) and in complete darkness after a 4-s delay (4-s dark). We compared the kinematics of a reach (e.g. average speed, reach straightness) between the four illumination conditions. The results showed that infants reached faster and decelerated for a shorter period of time in the dark (0-and 4-s dark) than in the light. By comparison, adults reached slower and decelerated for a longer period of time in the dark (0-and 4-s dark) than in the light. We did not Wnd any eVect of the glowing condition compared to full vision on infant reaching movements. These results suggest that infant reaching movements only become compromised when the target is not visible, whereas vision of the hand and the reach space are less signiWcant. Without online visual feedback, an infant reach in the dark appears to be driven by feedforward mechanisms and control may be aVected by an immature ability to form and/or retain visual spatial memory.
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Papers by Oliver Braddick