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Every year millions of children are exposed to general anesthesia while undergoing surgical and diagnostic procedures. In the field of ophthalmology, 44,000 children are exposed to general anesthesia annually for strabismus surgery alone. While it is clear that general anesthesia is necessary for sedation and pain minimization during surgical procedures, the possibility of neurotoxic impairments from its exposure is of concern. In animals there is strong evidence linking early anesthesia exposure to abnormal neural development. but in humans the effects of anesthesia are debated. In humans many aspects of vision develop within the first year of life, making the visual system vulnerable to early adverse experiences and potentially vulnerable to early exposure to general anesthesia. We attempt to address whether the visual system is affected by early postnatal exposure to general anesthesia. We first summarize key mechanisms that could account for the neurotoxic effects of general anesthesia on the developing brain and review existing literature on the effects of early anesthesia exposure on the visual system in both animals and humans and on neurocognitive development in humans. Finally, we conclude by proposing future directions for research that could address unanswered questions regarding the impact of general anesthesia on visual development. [ABSTRACT FROM AUTHOR]

The trisomy of chromosome 21, the smallest autosome, is associated with significant systemic manifestations in addition to intellectual disability. The triplication of this chromosome, known as Down syndrome (DS) is also associated with several manifestations in the eye, and ocular adnexae. People with DS have a variety of ophthalmic conditions, some of which require intervention. The variable systemic and ophthalmic presentations in DS can make the delivery of eye care challenging. We highlight common ophthalmic presentations in people with DS, as well as the practical implications of delivering eye examinations for this complex needs population. We aim to aid clinicians involved in the ophthalmic care of people with DS in both clinical and research settings. [ABSTRACT FROM AUTHOR]

Overarching theories such as the interactive specialization and maturational frameworks have been proposed to describe human functional brain development. However, these frameworks have not yet been systematically examined across the fMRI literature. Visual processing is one of the most well-studied fields in neuroimaging, and research in this area has recently expanded to include naturalistic paradigms that facilitate study in younger age ranges, allowing for an in-depth critical appraisal of these frameworks across childhood. To this end, we conducted a scoping review of 94 developmental visual fMRI studies, including both traditional experimental task and naturalistic studies, across multiple sub-domains (early visual processing, category-specific higher order processing, naturalistic visual processing). We found that across domains, many studies reported progressive development, but few studies describe regressive or emergent changes necessary to fit the maturational or interactive specialization frameworks. Our findings suggest a need for the expansion of developmental frameworks and clearer reporting of both progressive and regressive changes, along with well-powered, longitudinal studies. • 94 studies on the functional brain development of visual processing from infancy to adulthood were reviewed. • No clear consensus supporting either the interactive specialization or maturational frameworks of development. • Implications and suggestions for future research in the field of developmental neuroimaging are discussed. [ABSTRACT FROM AUTHOR]

We examined development of 5- and 10.5-month-old infants' face representations, focusing on infants' discrimination and categorization of female and male faces. We tested for gender-based preferences and categorization of female and male faces by presenting infants with pairs of faces and then habituating them to a series of majority female or male face ensembles. We then tested for gender preferences with new face pairs (one female and one male; Study 1) or new face ensembles (majority female and majority male; Study 2). We found that both 5- and 10.5-month-old infants discriminated female from male faces in face pairs, and both age groups looked more at female faces during habituation. Neither age group, however, provided evidence of gender-based categorization. We interpret these findings within a theoretical framework that stresses environmental exposure to different social categories, and infants' ability to detect commonalities of features within categories. We conclude that infants' gender-based categorization of faces is constrained by the set of features available in the input. [ABSTRACT FROM AUTHOR]

New digital approaches allow stereovision to be assessed with greater precision than current clinical stereo tests. Those current tests present a relatively narrow range of stimulus disparities in coarsely quantized steps. With dichoptic treatments for amblyopia emerging, more accurate assessment of especially coarse stereopsis becomes increasingly important for verifying their aim to improve 3D vision. We used digital testing in subjects of a large age range (4–59 years), with groups having both normal (n = 34) and impaired binocular vision due to unilateral amblyopia, with or without strabismus (n = 27). Random-dot stimuli were presented on a 3D monitor with shutter glasses. The test applies adaptive procedures to measure psychometric functions and provides thresholds with associated confidence intervals. Digital thresholds for controls (range 11–160 arcsec) and stereodeficient subjects (range 43–911 arcsec) were compared to the TNO, a standard clinical test which uses similar random-dot targets presented with anaglyph glasses. Agreement between digital and TNO thresholds varied with the level of stereopsis. Stereoacuity was measurable in several subjects who failed on the TNO. With the digital test we found good repeatability for both groups, with the indication of a small learning effect for subjects with coarse stereopsis. Thus, assessment of all target groups for new tests is important, and repeated testing before therapy may avoid confusing learning and treatment effects. Our digital approach supplies a large range of accurate stereo data in children and adults; together with its associated measure of variability, it will be useful in longitudinal treatment studies. [ABSTRACT FROM AUTHOR]

Metacontrast masking is one of the most widely studied types of visual masking, in which a visual stimulus is rendered invisible by a subsequent mask that does not spatially overlap with the target. Metacontrast has been used for many decades as a tool to study visual processing and conscious perception in adults. However, there are so far no infant studies on metacontrast and it remains unknown even whether it occurs in infants. The present study examined metacontrast masking in 3- to 8-month-old infants (N = 168) using a habituation paradigm. We found that metacontrast is ineffective for infants under 7 months and that younger infants can perceive a masked stimulus that older infants cannot. Our results suggest that metacontrast is distinct from other simple types of masking that occur in early infancy, and would be consistent with the idea that metacontrast results from the disruption of recurrent processing. [ABSTRACT FROM AUTHOR]

Cerebral Palsy (CP) is developmental brain abnormalities which is prior to birth or during birth and after delivery. Cerebral brain damage cells which leads to other health issues such as vision, hearing, and motor activities and so on. The major health issues for the cerebral palsy children such as vision problem. The proposed approach is used to measure and quantify the performance evaluation of Functional Vision Assessments for the disabled children examination with CP. Analyzed the Improvement of Vision of CP children by Visually Evoked Potential (VEP) device used for before and after the therapy Process in CP Rehabilitation. This method is performed with ophthalmological device together with Functional Vision Questionnaire and evaluate the assessment were completely regarding Twenty Five children (20 males,5 females, age range between 1-11years; motor disability activity classification function system (GMFCS) level V; Manual disability activity classification function system level V)who have been recognized with CP(80% spastic quadriplegia,7%athetoid quadriplegia,10%mixed type,3% hemiplegic). All CP children had motor and intellectual incapacity and failure to impart reliably through either visual or verbal correspondence. As the Results, the significant difference is found in the VEP for the CP children and controls analyzed with the parameter measurement of mean latency and mean amplitudes between them. Abnormal VEP in children with CP exhibited a connection with the nearness of direct to extreme delayed developmental Growth. The Major of the Visual Functional Assessment of CP children which were assessed in Rehabilitation Center, activities of CP children are performed in rehabilitation center and found the good response from item given to the CP children. The proposed one which achieve the diagnostic performance by Functional Questionnaire routine vision assessment of children with CP and also the utilizing of ophthalmological device VEP for evaluating the performance of Vision development. The neurophysiologic investigations of VEP they can serve as essential tool in the clinical work up of CP children. So, conclude that the VEP device is used as a clinical purpose for quantitative evaluation of visual acuity in children with neurological or visual impairment. The VEP measurement is showed good improvement in amplitude and latency of the waveform in two children with CP. [ABSTRACT FROM AUTHOR]

Infancy is a complex period of human life, in which environmental experiences have a fundamental role for neurodevelopment. Although conditions of social and sensory deprivation are uncommon in high income countries, the Covid-19 pandemic abruptly modified this condition, by depriving people of their social stimuli of daily life. To understand the impact of this deprivation on infants' behaviour, we investigated the short-term effects of isolation and use of individual protective systems by mothers during the first two weeks of life. The study included 11 mother-infant dyads with mothers tested positive to SARS-CoV-2 at the time of delivery (Covid group) and 11 dyads with a SARS-CoV-2 negative mother as controls. Neurobehavioral, visual, and sensory processing assessments were performed from birth to 3 months of age. Findings showed the effect of deprivation on some neurobehavioral abilities of infants in the Covid group; in addition, differences in sensory maturation trends were observed, although they tended to gradually decrease until disappearance at 3 months of age. These findings suggest the significant effects of early sensory and social deprivation during the first two weeks of life, but also provide several insights on the ability of the brain to restore its aptitudes by deleting or reducing the effects of early deprivation before the critical periods' closure. • Early deprivation influences adaptation of infants born from COVID-19 positive mothers. • Isolated neonates showed more signs of neurological immaturity and increased stress. • Impoverished environment impacts developmental trajectory of sensory processing. • Enrichment protocols for children at risk of social impoverishment are necessary. [ABSTRACT FROM AUTHOR]

Face exposure during development determines adults' abilities to recognize faces and the information they use to process them. Individual differences in the face categories represented in the visual environment can lead to category-specific deficits for recognizing faces that are atypical of observer's experience (e.g. the other-race effect). But what happens when observers have limited opportunities to learn about faces in general? In previous work, we found that observers from depopulated areas have poorer face recognition performance than observers from larger communities, suggesting that impoverished face experience limits face processing broadly. Here, we further investigate this phenomenon by examining how hometown size impacts the ability to assess appearance variability in natural images of faces and bodies. We asked individuals from small and large communities to complete (1) an unconstrained card-sorting task designed to test observers' ability to categorize within-person and between-person appearance variability properly, and (2) the Cambridge Face Memory Test. For both tasks, we examined the direct comparison between groups as well as the relationship between CFMT scores and sorting performance as a function of face experience. We find that small-town observers perform more poorly on the CFMT, but exhibit both better and worse performance than large-town observers on different aspects of the card-sorting task. Further, we also examine the relationship between CFMT performance and card-sorting errors. Our results suggest that individual differences in lifetime face exposure induce important variation in face processing abilities. [ABSTRACT FROM AUTHOR]

Three studies examined young infants' ability to distinguish between expected and unexpected motion of objects based on their shape. Using a preferential-looking paradigm, 8- and 12-month-old infants' looking time towards expected and unexpected motion displays of familiar, everyday objects (e.g., balls and cubes) was examined. Experiment 1 demonstrated that two factors drive infants' preferential fixations of object motion displays. Both 8- and 12-month-olds displayed a tendency to look at rotating information over non-rotating, stationary visual information. In contrast, only 12-month-olds showed a tendency to look at object motions that were inconsistent or "unexpected" based on shape. After controlling for the preference for more complex (rolling) by adding rolling motion to both displays (Experiment 2), 12-month-olds' ability to distinguish between expected and unexpected motion displays was facilitated. Experiment 3 provided a control by demonstrating that the preference for the unexpected object motion was not due to any other motion properties of the objects. Overall, these results indicate that 12-month-old infants have the ability to recognize the role that object shape plays in constraining object motion, which has important theoretical implications for the development of object perception. [ABSTRACT FROM AUTHOR]

In our previous study, we found that the normalized levels of the synaptosomal filament actin (F-actin) to monomeric global actin (G-actin) ratio in the primary visual cortex (V1) of rats was significantly lower on postnatal day (P) 45 compared with P30, however, the synaptic density in the monocular area of primary visual cortex (V1M) maintained a stable high level from P30 to P45. The mechanisms underlying the different patterned of change in synaptic density and actin rearrangements from P30 to P45 are unclear. During visual development, there is a synaptic pruning process in the binocular segment of primates’ visual cortex (V1B) and we suppose the pruning activity may contribute to the decreased synaptosomal F-actin to G-actin ratio. To address this issue, first, samples were derived from the region of V1B for TEM analysis but no significant difference was demonstrated between the P30 and P45 groups. In addition, the expression of PSD-95 detected by immunobloting in the synaptosomes of V1 at P30 and P45 also showed no significant difference. Combined with the previous results of actin dynamics in the V1 and synaptic density in the V1M, we conclude that the synaptic density and actin dynamics in the rats’ primary visual cortex are inter-related but not absolutely identical. This study suggests actin cytoskeleton not only provides the structural basis but also regulates a various array of cellular activities underlying synaptic function. Besides, it highlights a further research of synaptic pruning. [ABSTRACT FROM AUTHOR]

There are discrepancies with respect to the age at which adult-like performance is reached on tasks assessing global motion perception. This is in part because performance in children depends on stimulus parameters. We recently showed that five-year-olds demonstrated adult-like performance over a range of speeds when the speed ratio was comprised of longer spatial and temporal displacements; but displayed immature performance when the speed ratio was comprised of shorter displacements. The goal of the current study was to assess the effect of these global motion stimulus parameters across a broader age range in order to estimate the age at which mature performance is reached. Motion coherence thresholds were assessed in 182 children and adults aged 7-30years. Dot displacement (Δx) was 1, 5, or 30min of arc; frame duration (Δt) was 17 or 50ms. This created a total of six conditions. Consistent with our previous results, coherence thresholds in the youngest children assessed were adult-like at the two conditions with the largest Δx. Maturity was reached around age 12 for the medium Δx, and by age 16 for the smallest Δx. Performance did not appear to be affected by Δt. This late maturation may reflect a long developmental period for cortical networks underlying global motion perception. These findings resolve many of the discrepancies across previous studies, and should be considered when using global motion tasks to assess children with atypical development. [ABSTRACT FROM AUTHOR]

Contrast sensitivity is regulated by neural mechanisms that flexibly adjust responsiveness to optimize stimulus encoding across different environments. Here we studied the developmental status of gain control mechanisms in school-age children (5-17years) and adults using a visual masking paradigm. A variable contrast, spatially random 2-D noise test pattern was masked by the presence of a superimposed independent noise pattern presented at 0, 12 and 40% contrast. Frequency-tagged steady state visual evoked potentials were used to separately record responses to the test (5.14Hz) and the mask (7.2Hz). By incrementally increasing the test contrast we measured contrast response functions for each mask contrast. The unmasked contrast response functions were largely similar in shape across age, but peak amplitude was higher in the children. Masking shifted the contrast response function rightward on the contrast axis in both the adults and older children, elevating contrast thresholds by a similar factor across age. However, in younger children, masking resulted in a change in the slope of the contrast response function. These findings suggest that immaturity in the contrast normalization process persists until approximately 11years of age. [ABSTRACT FROM AUTHOR]

Background: Infants born prematurely or with low birth weight are at increased risk of visual perceptual impairment. Face recognition is a high-order visual ability important for social development, which has been rarely assessed in premature or low birth weight children.Aims: To evaluate the influence of prematurity and low birth weight on face recognition skills.Methods: Seventy-seven children were evaluated as part of a prospective cohort study. They were divided into premature and term birth cohorts. Children with a birth weight below the 10th centile were considered small for gestational age. All children underwent a full ophthalmologic assessment and evaluation of face recognition skills using the Facial Memory subtest from the Test of Memory and Learning.Results: Premature infants scored worse on immediate face recognition compared to term infants. However, after adjusting for birth weight, prematurity was not associated with worse outcomes. Independent of gestational age, outcomes of low birth weight children were worse than those of appropriate birth weight children, for immediate face recognition (odds ratio [OR], 5.14; 95% confidence interval [CI], 1.32-21.74) and for face memory (OR, 4.48; 95% CI, 1.14-16.95).Conclusions: Being born small for gestational age is associated with suboptimal face recognition skills, even in children without major neurodevelopmental problems. [ABSTRACT FROM AUTHOR]

Global motion sensitivity in typically developing children depends on the spatial (Δx) and temporal (Δt) displacement parameters of the motion stimulus. Specifically, sensitivity for small Δx values matures at a later age, suggesting it may be the most vulnerable to damage by amblyopia. To explore this possibility, we compared motion coherence thresholds of children with amblyopia (7-14years old) to age-matched controls. Three Δx values were used with two Δt values, yielding six conditions covering a range of speeds (0.3-30deg/s). We predicted children with amblyopia would show normal coherence thresholds for the same parameters on which 5-year-olds previously demonstrated mature performance, and elevated coherence thresholds for parameters on which 5-year-olds demonstrated immaturities. Consistent with this, we found that children with amblyopia showed deficits with amblyopic eye viewing compared to controls for small and medium Δx values, regardless of Δt value. The fellow eye showed similar results at the smaller Δt. These results confirm that global motion perception in children with amblyopia is particularly deficient at the finer spatial scales that typically mature later in development. An additional implication is that carefully designed stimuli that are adequately sensitive must be used to assess global motion function in developmental disorders. Stimulus parameters for which performance matures early in life may not reveal global motion perception deficits. [ABSTRACT FROM AUTHOR]

Global motion processing depends on a network of brain regions that includes extrastriate area V5 in the dorsal visual stream. For this reason, psychophysical measures of global motion perception have been used to provide a behavioral measure of dorsal stream function. This approach assumes that global motion is relatively independent of visual functions that arise earlier in the visual processing hierarchy such as contrast sensitivity and visual acuity. We tested this assumption by assessing the relationships between global motion perception, contrast sensitivity for coherent motion direction discrimination (henceforth referred to as contrast sensitivity) and habitual visual acuity in a large group of 4.5-year-old children (n=117). The children were born at risk of abnormal neurodevelopment because of prenatal drug exposure or risk factors for neonatal hypoglycemia. Motion coherence thresholds, a measure of global motion perception, were assessed using random dot kinematograms. The contrast of the stimuli was fixed at 100% and coherence was varied. Contrast sensitivity was measured using the same stimuli by fixing motion coherence at 100% and varying dot contrast. Stereoacuity was also measured. Motion coherence thresholds were not correlated with contrast sensitivity or visual acuity. However, lower (better) motion coherence thresholds were correlated with finer stereoacuity (ρ=0.38, p=0.004). Contrast sensitivity and visual acuity were also correlated (ρ=-0.26, p=0.004) with each other. These results indicate that global motion perception for high contrast stimuli is independent of contrast sensitivity and visual acuity and can be used to assess motion integration mechanisms in children. [ABSTRACT FROM AUTHOR]

There is growing evidence for deficits in motion perception in amblyopia, but these are rarely assessed clinically. In this prospective study we examined the effect of occlusion therapy on motion-defined form perception and multiple-object tracking. Participants included children (3–10 years old) with unilateral anisometropic and/or strabismic amblyopia who were currently undergoing occlusion therapy and age-matched control children with normal vision. At the start of the study, deficits in motion-defined form perception were present in at least one eye in 69% of the children with amblyopia. These deficits were still present at the end of the study in 55% of the amblyopia group. For multiple-object tracking, deficits were present initially in 64% and finally in 55% of the children with amblyopia, even after completion of occlusion therapy. Many of these deficits persisted in spite of an improvement in amblyopic eye visual acuity in response to occlusion therapy. The prevalence of motion perception deficits in amblyopia as well as their resistance to occlusion therapy, support the need for new approaches to amblyopia treatment. [ABSTRACT FROM AUTHOR]

To date, very little is known about the normal development trajectory of visual texture segregation, or how it is affected by preterm birth. The goal of this study was to characterize the development of visual texture segregation using texture segregation visual evoked potentials (tsVEPs) in children born full-term and children born preterm without major neurological impairment. Forty-five full-term and 43 preterm children were tested at either 12, 24 or 36 months of age (corrected age for prematurity at 12 and 24 months old). VEPs were obtained using two lower-level stimuli defined by orientation (oriVEP) and two higher-level stimuli defined by texture (texVEP). TsVEP was obtained by dividing by two the subtraction of oriVEP from texVEP. Results show a clear maturation of the processes underlying visual texture segregation in the full-term group, with a significant N2 latency reduction between 12 and 36 months of age for all conditions. Significant N2 amplitude reduction was observed for oriVEP between 12 and 24 months, as well as for texVEP between 12 and 24 months, and 12 and 36 months. Comparison between full-term and preterm children indicated significantly lower N2 amplitude for the preterm group at 12 months for oriVEP and texVEP. These differences were no longer apparent at 24 months of age, suggesting that children born preterm catch up with their full-term counterparts somewhere between 12 and 24 months of age. Our results appear to reflect a maturational delay in preterm children in both lower-level and higher-level visual processing during, at least, early childhood. [ABSTRACT FROM AUTHOR]

Very low birth weight (VLBW) premature born infants have a high risk to develop visual perceptual and learning deficits as well as widespread functional and structural brain abnormalities during infancy and childhood. Whether and how prematurity alters neural specialization within visual neural networks is still unknown. We used functional and structural brain imaging to examine the visual semantic system of VLBW born (<1250 g, gestational age 25–32 weeks) adolescents (13–15 years, n =11, 3 males) and matched term born control participants (13–15 years, n =11, 3 males). Neurocognitive assessment revealed no group differences except for lower scores on an adaptive visuomotor integration test. All adolescents were scanned while viewing pictures of animals and tools and scrambled versions of these pictures. Both groups demonstrated animal and tool category related neural networks. Term born adolescents showed tool category related neural activity, i.e. tool pictures elicited more activity than animal pictures, in temporal and parietal brain areas. Animal category related activity was found in the occipital, temporal and frontal cortex. VLBW born adolescents showed reduced tool category related activity in the dorsal visual stream compared with controls, specifically the left anterior intraparietal sulcus, and enhanced animal category related activity in the left middle occipital gyrus and right lingual gyrus. Lower birth weight of VLBW adolescents correlated with larger thickness of the pericalcarine gyrus in the occipital cortex and smaller surface area of the superior temporal gyrus in the lateral temporal cortex. Moreover, larger thickness of the pericalcarine gyrus and smaller surface area of the superior temporal gyrus correlated with reduced tool category related activity in the parietal cortex. Together, our data suggest that very low birth weight predicts alterations of higher order visual semantic networks, particularly in the dorsal stream. The differences in neural specialization may be associated with aberrant cortical development of areas in the visual system that develop early in childhood. [ABSTRACT FROM AUTHOR]

Background Visual cognitive integrative functions need to be evaluated by a behavioral assessment, which requires an experienced evaluator. The Preverbal Visual Assessment (PreViAs) questionnaire was designed to evaluate these functions, both in general pediatric population or in children with high risk of visual cognitive problems, through primary caregivers' answers. Aim We aimed to validate the PreViAs questionnaire by comparing caregiver reports with results from a comprehensive clinical protocol. Study design A total of 220 infants (< 2 years old) were divided into two groups according to visual development, as determined by the clinical protocol. Their primary caregivers completed the PreViAs questionnaire, which consists of 30 questions related to one or more visual domains: visual attention, visual communication, visual–motor coordination, and visual processing. Questionnaire answers were compared with results of behavioral assessments performed by three pediatric ophthalmologists. Results Results of the clinical protocol classified 128 infants as having normal visual maturation, and 92 as having abnormal visual maturation. The specificity of PreViAs questionnaire was > 80%, and sensitivity was 64%–79%. More than 80% of the infants were correctly classified, and test–retest reliability exceeded 0.9 for all domains. Conclusions The PreViAs questionnaire is useful to detect abnormal visual maturation in infants from birth to 24 months of age. It improves the anamnesis process in infants at risk of visual dysfunctions. [ABSTRACT FROM AUTHOR]

While the close link between eye movements and visual attention has often been demonstrated, recently distinct attentional modes have been associated with specific eye movement patterns. The ambient mode—serving the localization of objects and dominating early scene inspection—is expressed by short fixations and large saccade amplitudes. The focal mode—associated with the identification of object details and dominating later stages of scene exploration—is indicated by longer fixations embedded in short saccades. The relationship between these processing modes and eye movement characteristics has so far only been examined in adults. While studies in children revealed a maturation of oculomotor behavior up to adolescence, developmental aspects of the processing modes are still unknown. Here we explored these mechanisms by comparing eye movements during the inspection of naturalistic scenes. Therefore, gaze behavior from adults and children in four different age groups (2, 4–6, 6–8, 8–10 years old) was examined. We found a general effect of age, revealing that with age fixation durations decrease and saccade amplitudes increase. However, in all age groups fixations were shorter and saccades were longer at the beginning of scene inspection but fixations became longer and saccades became shorter over time. While saliency influenced eye guidance in the two youngest groups over the full inspection period, for the older groups this influence was found only at the beginning of scene inspection. The results reveal indications for ambient and focal processing strategies for as early as 2 years of age. [ABSTRACT FROM AUTHOR]

The development of motion processing is a critical part of visual development, allowing children to interact with moving objects and navigate within a dynamic environment. However, global motion processing, which requires pooling motion information across space, develops late, reaching adult-like levels only by mid-to-late childhood. The reasons underlying this protracted development are not yet fully understood. In this study, we sought to determine whether the development of motion coherence sensitivity is limited by internal noise (i.e., imprecision in estimating the directions of individual elements) and/or global pooling across local estimates. To this end, we presented equivalent noise direction discrimination tasks and motion coherence tasks at both slow (1.5°/s) and fast (6°/s) speeds to children aged 5, 7, 9 and 11 years, and adults. We show that, as children get older, their levels of internal noise reduce, and they are able to average across more local motion estimates. Regression analyses indicated, however, that age-related improvements in coherent motion perception are driven solely by improvements in averaging and not by reductions in internal noise. Our results suggest that the development of coherent motion sensitivity is primarily limited by developmental changes within brain regions involved in integrating motion signals (e.g., MT/V5). [ABSTRACT FROM AUTHOR]

Highlights: [•] This study reports the first data from a pseudoisochromatic plate test modified for infants. [•] 95% of infants completed the test, with all detecting the plate representing a blue/yellow confusion axis. [•] Most older (16–23 mo) but not younger babies could detect the plate representing a red/green axis. [•] The failure rate among male infants was significantly higher than that for females. [•] The test shows good validity in both color-normal and color-deficient adults. [ABSTRACT FROM AUTHOR]

Abstract: Background: Visual cognitive functions of preverbal infants are evaluated by means of a behavioral assessment. Parents or primary caregivers may be appropriate to certify the acquisition of certain abilities. Aims: To develop the PreViAs (Preverbal Visual Assessment) questionnaire to assess visual behavior of infants under 24months of age and to assess the normative outcomes for each item at each age. Study design: The process was divided into three phases: scale development (items and domains generation), pilot testing, and exploratory analysis. Results: The final version of the PreViAs questionnaire consisted of 30 items, each related to one or more of four domains (visual attention, visual communication, visual–motor coordination, and visual processing). For the exploratory analysis, 298 children (159 boys and 139 girls) were recruited. Their ages ranged from 0.1 to 24months (mean, 11.2months). Internal consistency of the questionnaire was high for all domains (Cronbach's α coefficients of 0.85–0.94). Conclusions: The PreViAs questionnaire is a useful scale for assessing visual cognitive abilities of infants under 24months of age. It is easy and feasible to complete by primary caregivers. [Copyright &y& Elsevier]

Highlights: [•] Global motion maturity in 5-year olds depended on spatial and temporal offsets. [•] Children showed more mature performance when larger spatial and temporal offsets used. [•] Stimulus parameters must be considered when comparing across developmental studies. [Copyright &y& Elsevier]

Highlights: [•] Early short-lasting pattern deprivation does not affect motion perception. [•] Delayed onset of deprivation impairs velocity and low contrast motion perception. [•] Motion perception is sensitive to deprivation after second month of life. [Copyright &y& Elsevier]

Abstract: This review aims to disentangle cause and effect in the relationship between anisometropia and amblyopia. Specifically, we examine the literature for evidence to support different possible developmental sequences that could ultimately lead to the presentation of both conditions. The prevalence of anisometropia is around 20% for an inter-ocular difference of 0.5D or greater in spherical equivalent refraction, falling to 2–3%, for an inter-ocular difference of 3D or above. Anisometropia prevalence is relatively high in the weeks following birth, in the teenage years coinciding with the onset of myopia and, most notably, in older adults starting after the onset of presbyopia. It has about one-third the prevalence of bilateral refractive errors of the same magnitude. Importantly, the prevalence of anisometropia is higher in highly ametropic groups, suggesting that emmetropization failures underlying ametropia and anisometropia may be similar. Amblyopia is present in 1–3% of humans and around one-half to two-thirds of amblyopes have anisometropia either alone or in combination with strabismus. The frequent co-existence of amblyopia and anisometropia at a child's first clinical examination promotes the belief that the anisometropia has caused the amblyopia, as has been demonstrated in animal models of the condition. In reviewing the human and monkey literature however it is clear that there are additional paths beyond this classic hypothesis to the co-occurrence of anisometropia and amblyopia. For example, after the emergence of amblyopia secondary to either deprivation or strabismus, anisometropia often follows. In cases of anisometropia with no apparent deprivation or strabismus, questions remain about the failure of the emmetropization mechanism that routinely eliminates infantile anisometropia. Also, the chronology of amblyopia development is poorly documented in cases of ‘pure’ anisometropic amblyopia. Although indirect, the therapeutic impact of refractive correction on anisometropic amblyopia provides strong support for the hypothesis that the anisometropia caused the amblyopia. Direct evidence for the aetiology of anisometropic amblyopia will require longitudinal tracking of at-risk infants, which poses numerous methodological and ethical challenges. However, if we are to prevent this condition, we must understand the factors that cause it to develop. [Copyright &y& Elsevier]

Highlights: [•] The juvenile PBT suffers high mortality through contact or collision with tank walls. [•] Fish mortality, bone injuries, and stress responses decrease in patterned wall tanks. [•] Survival rates of fish in lattice and polka-dot pattern walled tanks did not differ. [•] Mass death in juvenile PBT is failure to see the tank wall. [ABSTRACT FROM AUTHOR]

Highlights: [•] Maturation on a stereo depth order task varied as a function of disparity. [•] Performance was similar to that of adults at the youngest age tested (4years) for large disparities that produced double vision. [•] Performance was immature for the smallest disparities in the fusable range even at 14years of age. [Copyright &y& Elsevier]

Abstract: The processing of speed is a critical part of a child’s visual development, allowing children to track and interact with moving objects. Despite such importance, no study has investigated the developmental trajectory of speed discrimination abilities or precisely when these abilities become adult-like. Here, we measured speed discrimination thresholds in 5-, 7-, 9-, 11-year-olds and adults using random dot stimuli with two different reference speeds (slow: 1.5deg/s; fast: 6deg/s). Sensitivity for both reference speeds improved exponentially with age and, at all ages, participants were more sensitive to the faster reference speed. However, sensitivity to slow speeds followed a more protracted developmental trajectory than that for faster speeds. Furthermore, sensitivity to the faster reference speed reached adult-like levels by 11years, whereas sensitivity to the slower reference speed was not yet adult-like by this age. Different developmental trajectories may reflect distinct systems for processing fast and slow speeds. The reasonably late development of speed processing abilities may be due to inherent limits in the integration of neuronal responses in motion-sensitive areas in early childhood. [Copyright &y& Elsevier]

Abstract: Neuronal plasticity deficits underlie many of the cognitive problems seen in fetal alcohol spectrum disorders (FASD). We have developed a ferret model showing that early alcohol exposure leads to a persistent disruption in ocular dominance (OD) plasticity. Recently, we showed that this deficit could be reversed by overexpression of serum response factor (SRF) in the primary visual cortex during the period of monocular deprivation (MD). Surprisingly, this restoration was observed throughout the extent of visual cortex and most of the cells transfected by the virus were positive for the astrocytic marker GFAP rather than the neuronal marker NeuN. Here we test whether overexpression of SRF exclusively in astrocytes is sufficient to restore OD plasticity in alcohol-exposed ferrets. To accomplish that, first we exposed cultured astrocytes to Sindbis viruses carrying either a constitutively active form of SRF (SRF+), a dominant negative (SRF−) or control Green Fluorescent Protein (GFP). After 24h, these astrocytes were implanted in the visual cortex of alcohol-exposed animals or saline controls one day before MD. Optical imaging of intrinsic signals showed that alcohol-exposed animals that were implanted with astrocytes expressing SRF, but not SRF− or GFP, showed robust restoration of OD plasticity in all visual cortex. These findings suggest that overexpression of SRF exclusively in astrocytes can improve neuronal plasticity in FASD. [Copyright &y& Elsevier]

Abstract: The adult visual system is optimally tuned to process the spatial properties of natural scenes, which is demonstrated by sensitivity to changes in the 1/fα amplitude spectrum. It is also well documented that different aspects of spatial vision, including those likely responsible for the perception of natural scenes (e.g., spatial frequency discrimination), do not become mature until late childhood. This led us to hypothesise that the developing visual system is not optimally tuned to process the spatial properties of real-world scenes. The present study investigated how sensitivity to the statistical properties of natural images changes during development. Thresholds for discriminating a change in the slope of the amplitude spectrum of a natural scene with a reference α of 0.7, 1.0, or 1.3 where measured in children aged 6, 8, and 10years (n =16 per age) and in adults (mean age=23). Consistent with previous studies, adults were least sensitive for the shallowest α (i.e., 0.7) and most sensitive for the steepest α (i.e., 1.3). Six- and 8-year-olds had significantly higher discrimination thresholds compared to the 10-year-olds and adults for α’s of 1.0 and 1.3, and 10-year-olds did not differ significantly from adults for any of the α’s tested. These data suggest that sensitivity to detecting a change in the spatial characteristics of natural scenes during childhood may not be optimally tuned to the statistics of natural images until about 10years of age. Rather, is seems that perception of natural images could be limited by the known immaturities in spatial vision (). The question remains as to whether the adult’s exquisite sensitivity to the spatial properties of the natural world is experience driven or whether it is part of our genetic programming that only fully expresses itself in late childhood. [Copyright &y& Elsevier]

Abstract: The peak latency of pattern-reversal (PR)-VEP has been found to develop rapidly, reaching the adult level around 15weeks of age. However, the development of orientation-reversal (OR)-VEP, reflecting the specific spatial organization of cortical receptive fields, still remains unknown. OR-VEP was tested in 81 adults at 1–12reversals/sec (r/s) and 94 infants (age 4–79weeks) at 2–8r/s. OR data at 4r/s from an additional 123 infants (age 4.0–20.3weeks) studied previously were also analyzed. In addition to peak transient latencies at 1–4r/s, latency values derived from the gradient of phase against temporal frequency in steady-state recording were also calculated. For both adults and infants, no significant latency differences in the initial positive peaks were found among the low reversal rates. The calculated latency was statistically longer than the transient latency in both groups. While the transient latency asymptoted to adult value of 102ms at around 50weeks of age, the calculated latency, unlike that for PR-VEP, showed little variation across the age span. The data suggest a dominant effect of transmission delay on the initial peak in infancy, which reduces with age. However, the overall timing of the cortical response to orientation change remains slower than for pattern reversal in the fully developed visual cortex. Upon reaching maturity, the latencies of the initial positive peak in both pattern and orientation VEPs may arise from the same level of cortical processing in V1, but the overall time course reflected in the steady-state phase continues to show a much more prolonged response to orientation change than the transmission delay seen in the transient VEPs. [Copyright &y& Elsevier]

Abstract: To explore the relative development of the dorsal and ventral extrastriate processing streams, we studied the development of sensitivity to form and motion in macaque monkeys (Macaca nemestrina). We used Glass patterns and random dot kinematograms (RDK) to assay ventral and dorsal stream function, respectively. We tested 24 animals, longitudinally or cross-sectionally, between the ages of 5weeks and 3years. Each animal was tested with Glass patterns and RDK stimuli with each of two pattern types – circular and linear – at each age using a two alternative forced-choice task. We measured coherence threshold for discrimination of the global form or motion pattern from an incoherent control stimulus. Sensitivity to global motion appeared earlier than to global form and was higher at all ages, but performance approached adult levels at similar ages. Infants were most sensitive to large spatial scale (Δx) and fast speeds; sensitivity to fine scale and slow speeds developed more slowly independently of pattern type. Within the motion domain, pattern type had little effect on overall performance. However, within the form domain, sensitivity for linear Glass patterns was substantially poorer than that for concentric patterns. Our data show comparatively early onset for global motion integration ability, perhaps reflecting early development of the dorsal stream. However, both pathways mature over long time courses reaching adult levels between 2 and 3years after birth. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to investigate the effect of dot speed and dot density on the development of global motion perception by comparing the performance of adults and children (5–6years old) on a direction-discrimination task. Motion coherence thresholds were measured at two dot speeds (1 and 4deg/s) and three dot densities (1, 15, 30dots/deg2). Adult coherence thresholds were constant at approximately 9%, regardless of speed or density. Child coherence thresholds were significantly higher across conditions, and were most immature at the slow speed and at the sparse density. Thus, the development of global motion perception depends heavily on stimulus parameters. This finding can account for some of the discrepancy in the current developmental literature. Our results, however, caution against making general claims about motion deficits in clinical populations based on only a single measurement at a specific combination of speed and density. [Copyright &y& Elsevier]

Abstract: Methylisothiazolinone (MIT) is a commonly used biocide known to be neurotoxic in vitro. Brief exposure of cortical neurons in culture to MIT results in increased neurodegeneration, whereas chronic exposure of developing neurons in culture to low concentrations of MIT has been shown to interfere with normal neurite outgrowth. However, the effects of chronic MIT exposure on the developing nervous system have not been tested in vivo. Here we expose Xenopus laevis tadpoles to sub-lethal concentrations of MIT during a critical period in neural development. We find that MIT exposure results in deficits in visually mediated avoidance behavior and increased susceptibility to seizures, as well electrophysiological abnormalities in optic tectal function, without any effects on overall morphology, gross anatomy of the visual projections, overall visual function, and swimming ability. These effects indicate that chronic exposure to low levels of MIT results in neural circuit-level deficits that result in abnormal neurological function without causing increased mortality or even gross anatomical defects. Our findings, combined with the fact that the long-term neurological impacts of environmental exposure to MIT have not been determined, suggest a need for a closer evaluation of the safety of MIT in commercial and industrial products. [Copyright &y& Elsevier]

Abstract: By 1985 newly devised behavioural and electrophysiological techniques had been used to track development of infants’ acuity, contrast sensitivity and binocularity, and for clinical evaluation of developing visual function. This review focusses on advances in the development and assessment of infant vision in the following 25years. Infants’ visual cortical function has been studied through selectivity for orientation, directional motion and binocular disparity, and the control of subcortical oculomotor mechanisms in fixation shifts and optokinetic nystagmus, leading to a model of increasing cortical dominance over subcortical pathways. Neonatal face processing remains a challenge for this model. Recent research has focussed on development of integrative processing (hyperacuity, texture segmentation, and sensitivity to global form and motion coherence) in extra-striate visual areas, including signatures of dorsal and ventral stream processing. Asynchronies in development of these two streams may be related to their differential vulnerability in both acquired and genetic disorders. New methods and approaches to clinical disorders are reviewed, in particular the increasing focus on paediatric neurology as well as ophthalmology. Visual measures in early infancy in high-risk children are allowing measures not only of existing deficits in infancy but prediction of later visual and cognitive outcome. Work with early cataract and later recovery from blinding disorders has thrown new light on the plasticity of the visual system and its limitations. The review concludes with a forward look to future opportunities provided by studies of development post infancy, new imaging and eye tracking methods, and sampling infants’ visual ecology. [Copyright &y& Elsevier]

Abstract: Mutations in the human cone-rod homeobox (Crx) gene are associated with retinal dystrophies such as Leber Congenital Amaurosis (LCA), characterized by complete or near complete absence of vision from birth. The photoreceptors of Crx−/− mice lack outer segments, and therefore cannot capture light signals through rods and cones, thus resulting in a lack of normal retinal ganglion cell activity from birth. Using specific antibodies to subsets of neurons and markers of activity, we examined the impact of this absence of sensory input on the development of the primary visual cortex (V1) in early postnatal Crx−/− mice, before wiring of the visual system is complete, and in adulthood. We revealed that Crx−/− mice did not exhibit gross anatomical differences in V1; however, they exhibited significantly fewer calcium-binding protein (parvalbumin and calbindin-D28k) expressing interneurons, as well as reduced nonphosphorylated neurofilament expression in V1. These results reveal that the Crx mutation and lack of light stimulation through the photoreceptor pathway regulate the development and phenotype of different neuronal populations in V1 but not its general morphology. We conclude, therefore, that photoreceptor-mediated visual input during development is crucial for the normal postnatal development and maturation of subsets of cortical neurons. [Copyright &y& Elsevier]

Abstract: Motion cues provide a rich source of information about translations of the observer through the environment as well as the movements of objects and surfaces. While the direction of motion can be extracted locally these local measurements are, in general, insufficient for determining object and surface motions. To study the development of local and global motion processing mechanisms, we recorded Visual Evoked Potentials (VEPs) in response to dynamic random dot displays that alternated between coherent rotational motion and random motion at 0.8Hz. We compared the spatio-temporal tuning of the evoked response in 4–6months old infants to that of adults by recording over a range of dot displacements and temporal update rates. Responses recorded at the frequency of the coherent motion modulation were tuned for displacement at the occipital midline in both adults in infants. Responses at lateral electrodes were tuned for speed in adults, but not in infants. Infant responses were maximal at a larger range of spatial displacement than that of adults. In contrast, responses recorded at the dot-update rate showed a more similar parametric displacement tuning and scalp topography in infants and adults. Taken together, our results suggest that while local motion processing is relatively mature at 4–6months, global integration mechanisms exhibit significant immaturities at this age. [Copyright &y& Elsevier]

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Preterm birth is associated with an increased risk of visual impairment. However, not all visual deficits can be fully explained by the typical prematurity morbidity factors. In addition, children born preterm often exhibit transient hypothroxinemia of prematurity (THOP) due to premature severing of the maternal supply of thyroid hormones. Because thyroid hormone is critically needed for multiple facets of early brain development, including the structures needed for visual processing, and because the maternal thyroid supply is essential throughout pregnancy, it is possible that THOP contributes to the visual impairments seen in preterm children. To test this hypothesis, we used both clinical tests and visual-evoked potential techniques to assess visual abilities in two cohorts of preterm infants whose thyroid hormone levels were measured in the perinatal period. In the first cohort born 30 to 35 weeks gestation, we found associations between low thyroid hormone levels and reduced visual attention at 3 months corrected age (Study 1) and poor visuomotor abilities at 12 and 18 months corrected age (Study 2). In the second cohort born 23 to 35 weeks gestation, THOP severity was negatively correlated with attention at 3 months corrected age (Study 3) and contrast sensitivity and color vision at 6 months corrected age (Study 4). These findings therefore suggest that thyroid hormone is necessary for the development of early visual abilities and that THOP may partially explain the visual deficits of preterm infants. [Copyright &y& Elsevier]

The development of the visual system is the most studied of the sensory systems. The advances in technology have made it possible to study the neuroprocesses at the cellular and circuit level. The physical structure of the eye develops early in fetal life, whereas the neurocomponents and connections develop in later fetal and early neonatal life. The development of the visual system involves genetic coding, endogenous brain activity, exogenous visual stimulation after birth at term, and protected sleep cycles, particularly rapid eye movement sleep. Before birth at term, the fetus requires no outside visual stimulation or light. The critical element in development of the visual system before birth at term is protection of rapid eye movement sleep and sleep cycles. Sleep deprivation or disruption in utero and early months of neonatal life causes significant interference with visual development resulting in loss of the topographic relationships between the retina, the lateral geniculate nucleus, and the primary visual cortex in the infant. [Copyright &y& Elsevier]

Abstract: Purpose: Strabismus in human infants is linked strongly to nasotemporal asymmetries of smooth pursuit, but many features of this co-morbidity are unknown. The purpose of this study was to determine how the duration of early-onset strabismus (or timeliness of repair) affects the severity of pursuit asymmetries in a primate model. Methods: Binocular image decorrelation was imposed on infant macaques by fitting them with prism goggles on day 1 of life. The goggles were removed after 3 weeks (n=2), 12 weeks (n=2) or 24 weeks (n=3), emulating surgical repair of strabismus in humans at 3, 12, and 24 months of age, respectively. Two control monkeys wore plano lenses. Several months after the goggles were removed, horizontal smooth pursuit was recorded using binocular search coils and a nasal-bias index (NBI) was calculated. Results: Each animal in the 12- and 24-week groups developed a constant, alternating esotropic strabismus and a nasotemporal asymmetry of pursuit when viewing with either eye. Spatial vision was normal (no amblyopia). The 3-week duration monkeys were indistinguishable from control animals; they had normal eye alignment and symmetric pursuit. In the 12- and 24-week monkeys, the longer the duration of binocular decorrelation, the greater the pursuit asymmetry: for 15°/s target motion, the NBI in the 12-week and 24-week animals was 16× and 22× greater respectively, than that in the 3-week animals (ANOVA, P=0.03). Conclusions: Binocular decorrelation in primates during an early period of fusion development causes permanent smooth pursuit asymmetries when the duration exceeds the equivalent of 3 months in human. These findings support the conclusion that early correction of infantile strabismus promotes normal development of cerebral gaze pathways. [Copyright &y& Elsevier]

Abstract: We measured the developmental time course for temporal contrast sensitivity in macaque monkeys. The animals, aged 5 weeks to 4 years, detected an unpatterned field of light sinusoidally modulated over time at frequencies ranging from 1 to 40Hz. Young infants showed reduced sensitivity for all frequencies, and a reduced range of detectable frequencies. Sensitivity to high and low frequencies developed at different rates, but the shape of the temporal contrast sensitivity function did not change significantly with age. Temporal contrast sensitivity matures earlier than spatial contrast sensitivity. The development of high, but not low, frequency sensitivity may be limited by maturation of the magnocellular pathway. [Copyright &y& Elsevier]

Abstract: Previous research has indicated that the ability to integrate individual elements in the presence of noise is immature in 3-month-old infants. The present study extended the developmental timeline by investigating 6-month-olds’ ability to integrate individual elements into whole contours through an assessment of their capability to discriminate circle and square contours constructed from oriented Gabor patches via a newly designed cueing paradigm for infants. If infants discriminate the centrally-presented contour cues, then their eye movements would correctly anticipate subsequent target presentation at a rate greater than chance. The results indicated that infants integrated the contours and discriminated the different shapes, but, consistent with past research, this ability is still fairly immature at this age, tolerating limited amount of noise. [Copyright &y& Elsevier]

Abstract: Disorders of visual function are common findings in children with neonatal brain lesions of antenatal and perinatal onset. In the last few years the development of age appropriate batteries for assessing visual function in the first years and the combined use of neuroimaging and neurophysiological techniques have allowed to achieve better understanding of the mechanisms underlying development of vision in low risk infants and in those with brain lesions. We will review the main models of visual development and the tests available to assess visual function in infancy, focusing on the recently described battery of tests for assessing early visual abilities in preterm and full term infants. [Copyright &y& Elsevier]

Abstract: Higher visual functions were investigated in patients treated for bilateral congenital cataracts in two experiments. Participants were asked to detect either real or illusory contours (Kanizsa squares in Experiment 1 or one of four different Kanizsa contours in Experiment 2) among distractor items. Compared to normally sighted participants matched for age, gender and education, cataract patients treated after the age of 5–6 months took relatively longer to detect Kanizsa figures (Experiments 1 and 2) and they had higher miss rates (Experiment 2). The present results suggest that the ability of visual feature binding depends on early visual input and is permanently impaired if patterned vision is prevented in early infancy for 5 months or more. [Copyright &y& Elsevier]

Abstract: High-density EEG was used to investigate the cortical processing of a rotating visual pattern in 2-, 3-, and 5-month-old infants and in adults. Motion induced ERP in the parietal and the temporal–occipital border regions (OT) was elicited at all ages. The ERP was discernable in the 2-months-olds, significant and unilateral in the 3-month-olds and significantly bilateral in the 5-month-olds and adults. The motion induced ERP in the primary visual area was absent in the 2-month-olds and later than in the OT area for the 3-month-olds indicating that information to OT may be supplied by the V1 bypass at these ages. The results are in agreement with behavioural and psychophysical data in infants. [Copyright &y& Elsevier]

Abstract: Extreme natural ambient light reduction, in both energy and range of wavelength spectrum, occurs during the winter season at very high latitudes (above the Arctic Circle or 66°32′ North) that in turn results in increased exposure to artificial lighting. In contrast, during the summer months, the sun remains above the horizon and there is no darkness or night. Little is known about these extreme changes in light exposure on human visual perception. Measuring color discriminations with the FM100 Test revealed that Norwegians born above the Arctic Circle were less sensitive to yellow-green, green, and green-blue spectrum differences whereas they were more sensitive to hue variations in the purple range than individuals born below the Arctic Circle. Additionally, it was found that the Norwegian individuals born above the Arctic Circle and during autumn showed an overall decrease in color sensitivity, whereas those born in the summer showed a relative increase. All participants were adults and their color vision was tested in the same location (i.e., in Tromsø at 69.7° North). These findings are consistent with the idea that there is a measurable impact on colour vision as adults of the photic environment that individuals born above the Arctic Circle and in the autumn experienced during infancy, namely a reduction in exposure to direct sunlight and an increase in exposure to twilight and artificial lighting. [Copyright &y& Elsevier]

Abstract: Any object may contain at least two spatio-temporal components referred to as first- and second-order, respectively, defined by spatial-temporal luminance modulation or by contrast, texture or depth modulation. This study investigates form sensitivity of infants, normals, premature or strabismic. A two-alternative forced-choice preferential looking procedure was used in monocular and binocular condition. Maturation profile for both stimuli was similar in the control group. Strabismic infants showed a vertical offset in maturation, which affected the second-order more severely. The pre-term group showed a lag of second-order sensitivity. Our results underline differences between first- and second-order processing. [Copyright &y& Elsevier]