The functional selectivity of human primary visual cortex (V1) for orientation and motion direction is established by around 3 months of age
1–3, but there have been few studies of the development of ...extrastriate visual areas that integrate outputs from V1
4–8. We investigated sensitivity and topographical organization for global form and motion with high-density visual event-related potentials (VERPs) in 4- to 5-month-old infants and adults. Responses were measured to transitions between concentrically organized elements (short arc segments for form, dot trajectories for motion) and random arrangements. Adults showed topographically separate responses, with midline motion and more lateral form responses. Of 26 infants, 25 showed significant motion responses but only 13 showed form responses, suggesting more advanced development for extrastriate motion areas than form. Infants' form and motion responses were topographically distinct but contrasted with the corresponding adult topographies, with infants' motion responses more lateral than form responses. These results imply distinct neural sources at both ages and raise the possibility of substantial reorganization of extrastriate networks between infancy and adulthood. We speculate that global motion responses arise from area V5 in infants but are dominated by more medial areas such as V3/V3A and V6 in adults.
► ERPs to global visual form and motion stimuli have distinct scalp topographies ► This implies that the form and motion stimuli activate different cortical areas ► 5-month-olds and adults have markedly different ERP topographies ► The cortical networks processing form and motion are reorganized during development
Attentional problems are commonly reported as a feature of the behavioural profile in both Williams syndrome (WS) and Down's syndrome (DS). Recent studies have begun to investigate these impairments ...empirically, acknowledging the need for an approach that considers cross‐syndrome comparisons and developmental changes across the different component functions of attention. The present study assessed children with WS and DS using a new preschool attention battery (ECAB: early childhood attention battery), designed to be suitable for mental age 3–6 years including groups with developmental disorders. The ECAB has the advantage of giving an individual profile of attentional abilities for each child, covering different components of attention. In relation to test norms for their mental age, both groups showed a profile of strengths and weaknesses in the attention domain. Both syndrome groups performed relatively well on tests of sustained attention and poorly on aspects of selective attention and attentional control (executive function). The DS group showed a specific strength in auditory sustained attention, whilst the WS group showed a particular deficit in visuo‐spatial response control. There was also evidence for considerable differences in the developmental trajectory of these abilities across the two groups. The results provide evidence for syndrome‐specific patterns of impairment, and distinct profiles of strengths and weaknesses that may be useful in understanding the nature of everyday attention difficulties in these groups and tailoring interventions to meet these needs.
To report on two population screening programs designed to detect significant refractive errors in 8308 8- to 9-month-old infants, examine the sequelae of infant hyperopia, and test whether early ...partial spectacle correction improved visual outcome (strabismus and acuity). The second program also examined whether infant hyperopia was associated with developmental differences across various domains such as language, cognition, attention, and visuomotor competences up to age 7 years. Linked programs in six European countries assessed costs of infant refractive screening.
In the first program, screening included an orthoptic examination and isotropic photorefraction, with cycloplegia. In the second program we carried out the same screening procedure without cycloplegia. Hyperopic infants (> or = +4 D) were followed up alongside an emmetropic control group, with visual and developmental measures up to age 7 years, and entered a controlled trial of partial spectacle correction.
The second program showed that accommodative lag during photorefraction with a target at 75 cm (focus > or = +1.5 D) was a marker for significant hyperopia. In each program, prevalence of significant hyperopia at 9 to 11 months was around 5%; manifest strabismus was 0.3% at 9 months and 1.5 to 2.0% by school age. Infant hyperopia was associated with increased strabismus and poor acuity at 4 years. Spectacle wear by infant hyperopes produced better visual outcome than in uncorrected infants, although an improvement in strabismus was found in the first program only. The corrections did not affect emmetropization to 3.5 years; however, both corrected and uncorrected groups remained more hyperopic than controls in the preschool years. The hyperopic group showed poorer overall performance than controls between 1 and 7 years on visuoperceptual, cognitive, motor, and attention tests, but showed no consistent differences in early language or phonological awareness. Relative cost estimates suggest that refractive screening programs can detect visual problems in infancy at lower overall cost than surveillance in primary care.
Photo/videorefraction can successfully screen infants for refractive errors, with visual outcomes improved through early refractive correction. Infant hyperopia is associated with mild delays across many aspects of visuocognitive and visuomotor development. These studies raise the possibility that infant refractive screening can identify not only visual problems, but also potential developmental and learning difficulties.
Age differences in goal-directed bimanual coordination were studied in typically developing infants aged 9–29 months, compared to a group of children aged 4–6 years and a group of adults, using an ...object retrieval task. This task required one hand to open and hold the lid of a transparent box, while the second hand retrieved a small toy from inside the box. Well-coordinated retrieval strategies with differentiated use of the two hands were not established in the majority of infants until 18 months of age. Temporal analysis of the hand actions revealed that, unlike adults who perform the task with close synchronization of the hands at the start, the infants performed the task sequentially and did not activate the second hand until the first hand had started to lift the lid. The children’s hand preferences for the two-hand actions also contrasted with those of adults. In children aged 27–29 months and 4–6 years, there was a preference for using the right-hand to lift the lid while in right-handed adults, the reverse pattern was observed. The results suggest that although bimanual coordination starts to develop in the second year of life, the adult pattern of performance on this task is not observed before 6 years of age. It is likely that further maturation of the brain networks involved in bimanual coordination, and in particular functional interhemispheric transfer via the corpus callosum, is required before automatization of bimanual hand actions is achieved.
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 frontoparietal interaction, and (d) that it is related to impaired function in the right hemisphere relative to the left. The tests reported here are particularly relevant to hypotheses 2 and 3. They form part of a more extensive program 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, avoiding floor and ceiling effects, we have measured performance in children with WS in terms of the "age equivalence" for typically developing children. In this article the relation between dorsal and ventral function is tested by motion and form coherence thresholds, respectively. We confirm the presence of a subgroup of children with WS who perform particularly poorly on the motion (dorsal) task. However, such performance is also characteristic of normally developing children up to 5 years; thus the WS performance may reflect an overall persisting immaturity of visuospatial processing that is particularly evident in the dorsal stream. Looking at the performance on the global coherence tasks of the entire WS group, we find that there is also a subgroup who have both high form and motion coherence thresholds, relative to the performance of children of the same chronological age and verbal age on the British Picture Vocabulary Scale, suggesting a more general global processing deficit.
The distribution of cortical activity to radial expansion or contraction motion with adults and infants (3 to 4 months and 4 to 5 months of age) was examined by measuring steady-state visual evoked ...potentials with a high-density electrode array. A motion pattern which was either radial expansion or contraction was alternately presented with a pattern of random motion, and the mean amplitude of the fundamental harmonic component (F1) corresponding to the pattern alternation frequency (2Hz) was measured. The results indicated the adults showed greater activity to contraction than to expansion in the right parietal area. Although the older (but not the younger) infants also showed contraction bias, the bias was spread over the whole occipitoparietal area. These results suggest that in adults radial motion processing may be achieved by different neural mechanisms to those in infants.
This study investigated the relation between sensory visual problems and the severity of visuospatial difficulties in a large group of young children with Williams’syndrome (WS). A questionnaire ...describing visual and associated problems was completed by the families of 108 children with WS and detailed follow‐up assessments were conducted, including visual, spatial, motor, visuocognitive, and linguistic tests of 73 of these children (mean age 7 years 3 months; 40 males, 73 females). Children with WS showed a much higher incidence of common paediatric sensory vision problems (strabismus, visual acuity loss, amblyopia, reduced stereopsis) than normally developing children. It was found that delays with respect to age normative values increased with age on all tests. No significant correlation was found between the presence of a visual deficit and the severity of the visuospatial problems, suggesting that the difficulties children with WS have in understanding spatial arrangements are not simply a result of their earlier sensory visual problems. Results confirm the dissociation between visuospatial and language abilities in children with WS, and support the neurobiological model of a split between ventral and dorsal stream processing of visual information with a generalized deficit in dorsal stream processing in young children with WS.
Williams' syndrome (WS) is a rare, genetically based disorder of cognitive development. Affected individuals show a severe deficit of spatial cognition but a relative sparing of language and face ...recognition. To examine the possible neural basis of the spatial deficit, we tested a group of WS children, aged 4-14 years, on two measures specific to dorsal cortical stream function: global motion coherence thresholds, in comparison with an analogous form-coherence test, and visuo-manual accuracy in posting a card through a slot, compared with matching the slot orientation. Deficits in these tasks provide the first evidence of specific involvement in WS of the dorsal stream, the cortical system believed to encode information about spatial relationships and the visual control of action.
This study investigated the relation between sensory visual problems and the severity of visuospatial difficulties in a large group of young children with Williams' syndrome (WS). A questionnaire ...describing visual and associated problems was completed by the families of 108 children with WS and detailed follow-up assessments were conducted, including visual, spatial, motor, visuocognitive, and linguistic tests of 73 of these children (mean age 7 years 3 months; 40 males, 73 females). Children with WS showed a much higher incidence of common paediatric sensory vision problems (strabismus, visual acuity loss, amblyopia, reduced stereopsis) than normally developing children. It was found that delays with respect to age normative values increased with age on all tests. No significant correlation was found between the presence of a visual deficit and the severity of the visuospatial problems, suggesting that the difficulties children with WS have in understanding spatial arrangements are not simply a result of their earlier sensory visual problems. Results confirm the dissociation between visuospatial and language abilities in children with WS, and support the neurobiological model of a split between ventral and dorsal stream processing of visual information with a generalized deficit in dorsal stream processing in young children with WS.
We have previously reported that significant hyperopia at 9 months predicts mild deficits on visuocognitive and visuomotor measures between 2 years and 5 years 6 months. Here we compare the motor ...skills of children who had been hyperopic in infancy (hyperopic group) with those who had been emmetropic (control group), using the Movement Assessment Battery for Children (Movement ABC). Children were tested at 3 years 6 months (hyperopic group: 47 males, 63 females, mean age 3y 7mo, SD 1.6mo; control group: 61 males, 70 females, mean age 3y 7mo, SD 1.2mo) and at 5 years 6 months (hyperopic group: 43 males, 56 females, mean age 5y 4mo, SD 1.7mo; control group: 51 males, 62 females, mean age 5y 3mo, SD 1.6mo). The hyperopic group performed significantly worse at both ages, overall and on at least one test from each category of motor skill (manual dexterity, balance, and ball skills). Distributions of scores showed that these differences were not due to poor performance by a minority but to a widespread mild deficit in the hyperopic group. This study also provides the first normative data on the Movement ABC for children below 4 years of age, and shows that it provides a useful measure of motor development at this young age.
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