Central and peripheral vision in early infancy

Sensory hypersensitivity predicts enhanced attention capture by faces in the early development of ASD

Sensory sensitivity is prevalent among young children with ASD, but its relation to social communication impairment is unclear. Recently, increased sensory hypersensitivity has been linked to greater activity of the neural salience network (Green et al., 2016). Increased neural sensitivity to stimuli, especially social stimuli, could provide greater opportunity for social learning and improved outcomes. Consistent with this framework, in Experiment 1 we found that parent report of greater sensory hypersensitivity at 2 years in toddlers with ASD (N=27) was predictive of increased neural responsiveness to social stimuli (larger amplitude event-related potential/ERP responses to faces at P1, P400 and Nc) at 4 years, and this in turn was related to parent report of increased social approach at 4 years. In Experiment 2, parent report of increased perceptual sensitivity at 6 months in infants at low and high familial risk for ASD (N=35) predicted larger ERP P1 amplitude to faces at 18 months. Increased sensory hypersensitivity in early development thus predicted greater attention capture by faces in later development, and this related to more optimal social behavioral development. Sensory hypersensitivity may index a child's ability to benefit from supportive environments during development. Early sensory symptoms may not always be developmentally problematic for individuals with ASD.

Face Orientation and Motion Differently Affect the Deployment of Visual Attention in Newborns and 4-Month-Old Infants

Orienting visual attention allows us to properly select relevant visual information from a noisy environment. Despite extensive investigation of the orienting of visual attention in infancy, it is unknown whether and how stimulus characteristics modulate the deployment of attention from birth to 4 months of age, a period in which the efficiency in orienting of attention improves dramatically. The aim of the present study was to compare 4-month-old infants' and newborns' ability to orient attention from central to peripheral stimuli that have the same or different attributes. In Experiment 1, all the stimuli were dynamic and the only attribute of the central and peripheral stimuli to be manipulated was face orientation. In Experiment 2, both face orientation and motion of the central and peripheral stimuli were contrasted. The number of valid trials and saccadic latency were measured at both ages. Our results demonstrated that the deployment of attention is mainly influenced by motion at birth, while it is also influenced by face orientation at 4-month of age. These findings provide insight into the development of the orienting visual attention in the first few months of life and suggest that maturation may be not the only factor that determines the developmental change in orienting visual attention from birth to 4 months.

A new system for quantitative evaluation of infant gaze capabilities in a wide visual field

BACKGROUND

The visual assessment of infants poses specific challenges: many techniques that are used on adults are based on the patient's response, and are not suitable for infants. Significant advances in the eye-tracking have made this assessment of infant visual capabilities easier, however, eye-tracking still requires the subject's collaboration, in most cases and thus limiting the application in infant research. Moreover, there is a lack of transferability to clinical practice, and thus it emerges the need for a new tool to measure the paradigms and explore the most common visual competences in a wide visual field. This work presents the design, development and preliminary testing of a new system for measuring infant's gaze in the wide visual field called CareToy C: CareToy for Clinics.

METHODS

The system is based on a commercial eye tracker (SmartEye) with six cameras running at 60 Hz, suitable for measuring an infant's gaze. In order to stimulate the infant visually and audibly, a mechanical structure has been designed to support five speakers and five screens at a specific distance (60 cm) and angle: one in the centre, two on the right-hand side and two on the left (at 30° and 60° respectively). Different tasks have been designed in order to evaluate the system capability to assess the infant's gaze movements during different conditions (such as gap, overlap or audio-visual paradigms). Nine healthy infants aged 4-10 months were assessed as they performed the visual tasks at random.

RESULTS

We developed a system able to measure infant's gaze in a wide visual field covering a total visual range of ±60° from the centre with an intermediate evaluation at ±30°. Moreover, the same system, thanks to different integrated software, was able to provide different visual paradigms (as gap, overlap and audio-visual) assessing and comparing different visual and multisensory sub-competencies. The proposed system endowed the integration of a commercial eye-tracker into a purposive setup in a smart and innovative way.

CONCLUSIONS

The proposed system is suitable for measuring and evaluating infant's gaze capabilities in a wide visual field, in order to provide quantitative data that can enrich the clinical assessment.

The early development of visual attention and its implications for social and cognitive development

Looking behavior plays a crucial role in the daily life of an infant and forms the basis for cognitive and social development. The infant's visual attentional systems undergo rapid development during the first few months of life. During the last decennia, the study of visual attentional development in infants has received increasing interest. Several reliable measures to investigate the early development of attentional processes have been developed, and currently a number of new methods are giving fresh impetus to the field. Research on overt and covert as well as exogenously and endogenously controlled attention shifts is presented. The development of gaze shifts to peripheral targets, covert attention, and visual scanning behavior is treated. Whereas most attentional mechanisms in very young infants are thought to be mediated mainly by subcortical structures, cortical mechanisms become increasingly more functional throughout the first months. Different accounts of the neurophysiological underpinnings of attentional processes and their developmental changes are discussed. Finally, a number of studies investigating the implications of attentional development for early cognitive and social development are presented.

Measured visual field extent varies with peripheral stimulus flicker rate in very young children

PURPOSE

The purpose of this article is to describe measured visual field extent in very young children in response to variation in peripheral stimulus flicker rate.

METHODS

Binocular visual field extent was measured using a black, double-arc perimeter and an LED static perimetry procedure in 120 11-month-old, 120 17-month-old, and 120 30-month-old children and 40 adults. Each subject was tested with one of four flicker rates: 1 Hz, 10 Hz, 20 Hz, or 40 Hz. An interpolated estimate of the eccentricity at which 50% of subjects detected the peripheral stimulus and the mean of the farthest eccentricity at which subjects detected the peripheral stimulus were calculated for each flicker rate for each age group.

RESULTS

In 11-, 17-, and 30-month-old children, but not in adults, measured visual field extent (eccentricity at which the stimulus was detected) varied significantly with rate of stimulus flicker. The largest measured visual field extent was produced by a 10-Hz stimulus and the smallest was produced by 1-Hz and 40-Hz stimuli. Measured visual field extent in children was similar to that of adults for 10-Hz flicker, but smaller than that of adults for 1-Hz, 20-Hz, and 40-Hz flicker.

CONCLUSIONS

These results underscore the importance of standardizing stimulus parameters when developing tests for clinical assessment of visual fields in children. Furthermore, for longitudinal assessment of young patients, use of a 10-Hz flicker rate, in combination with the other parameters used in the present study, would help to avoid difficulties in interpretation that could arise from an interaction between age-related and disease-related changes that might occur if other stimulus flicker rates were used.

The effect of flicker rate on measured visual field extent in very young children

PURPOSE

To investigate the effect of flicker rate on measured visual field extent in toddlers.

METHODS

A total of 270 full-term children (90 each at 11-, 17-, and 30-months of age) and 36 adults were tested binocularly with an LED static perimetry procedure using a black double-arc perimeter. Each subject was tested with one of three flicker rates: 0, 3, or 10 Hz. The median farthest location seen and an interpolated estimate of the location at which 50% of the subjects detected the peripheral stimulus were calculated for each age group for each flicker rate.

RESULTS

For 11-, 17-, and 30-month-old subjects, but not adults, flickering stimuli produced a larger measured visual field extent than nonflickering stimuli. For the 10-Hz stimuli, measured visual field extent in children did not differ from that of adults.

CONCLUSIONS

In infants and young children, binocular measured visual field extent is enhanced by peripheral stimulus flicker. Maturity of the measured visual field depends on the stimulus parameters used during testing.

Visual field extent in children 3.5-30 months of age tested with a double-arc LED perimeter

Visual field extent along the four diagonal meridia was measured cross-sectionally in 180 normal children (infants and toddlers), and 22 adults. Infants were tested monocularly at 3.5, 7, or 9 months, and toddlers were tested binocularly at 11, 17, or 30 months. Adult control data were obtained under monocular viewing. Three testing methods were investigated: static and hybrid static-kinetic perimetry, using LED arrays under computer control, and kinetic perimetry, using white styrofoam spheres manipulated by hand. Data analysis included corrections for false positives in the method of constant stimuli and for errors of anticipation in the ascending method of limits. Across all data sets from children, kinetic perimetry yielded larger, more adult-like fields, which approached adult levels around 17 months, whereas static and hybrid static-kinetic perimetry yielded smaller visual fields, approaching adult levels only at 30 months.

Peripheral stimulus localization by infants with eye and head movements during visual attention

The effect of attention to a focal stimulus on 14, 20 and 26-week-old infant's peripheral stimulus localization with eye and head movements was examined in this study. Fixation was engaged on a stimulus in the central visual field and a stimulus was presented in the periphery immediately or after a delay. Peripheral stimulus localization occurred less frequently near the beginning of fixation and when a significant heart rate deceleration had occurred (sustained attention), compared with when no focal stimulus was present or after heart rate had returned to prestimulus level (attention termination). Localization was accompanied by head movements on more than two-thirds of the trials, and the likelihood of head movements was positively associated with stimulus eccentricity. The saccades to localize the peripheral stimulus had unusually high velocities in the attention conditions for the two older aged groups relative to their saccades in inattentive conditions. There were unusual "localizing head movements" in the attention conditions in the absence of localizing saccades or changes in fixation for the two older age groups. Infant attention modulates eye movement characteristics of infants. These data also support the hypothesis that eye and head movement systems are relatively independent in the infant, and that eye-head relations during infant attention may be different from during inattention.

The development of the temporal and nasal visual fields during infancy

We used static perimetry to measure the development of the monocular visual field during infancy. Infants from birth to 6 months of age, and adults, were shown a 3 or 6 degrees flashing light at various locations between 15 and 120 degrees in the temporal and nasal visual fields. We assumed that subjects could see a light if they moved their eyes toward it more often than they looked in the same direction on blank control trials. For both the 3 and 6 degrees lights, the visual field expanded with age from the center out, and development in the nasal visual field lagged behind development in the temporal visual field. Possible reasons for these findings are discussed.

Visual fields in 4- to 10-year-old children using Goldmann and double-arc perimeters

We report the comparison of field extent measured using two kinetic perimeters: 1) a double-arc perimeter developed by van Hof-van Duin for use in infants and young children, and 2) the standard Goldmann apparatus. Targets used were the V-4-e target on the Goldmann and both 2- and 6-degree targets on the double-arc perimeter. Visual fields were measured by assessing looking responses toward targets presented in a pseudorandom order at 45 degrees, 135 degrees, 225 degrees, and 315 degrees. Fifty-six children (mean age: 6.8 years, range: 4 to 10 years) were tested, with retests undertaken in 20%. The extent of total field size was highly correlated among the three tests (P less than .001) and test-retest reliability was high for all three targets (P less than .001). Our previous observation of continued growth with age in visual field extent using the 6-degree target in 4- to 10-year-old children was confirmed and also seen with the 2-degree target in arc perimetry and with the V-4-e in the Goldmann apparatus. Kinetic perimetry using a double-arc perimeter with 2- and 6-degree target sizes appears reliable and comparable, in the four meridia tested, to conventional kinetic perimetry techniques in 4- to 10-year-old children.

Sensory visual loss and cognitive deficits in the selective attentional system of normal infants and neurologically impaired children

The ability of infants to shift their gaze laterally from a central target (fixation shift) was investigated in normal one- and three-month-old infants in two visual tasks; competition (central fixating stimulus remained visible while peripheral target was presented) and non-competition (central fixating stimulus replaced by peripheral target). The younger infants were significantly more disrupted by the competition condition, in terms of latency to refixate and direction of first eye movement. An immature attention system is proposed to explain this affect. In addition, visually evoked potentials in response to comparable stimuli were easier to elicit in older infants, suggesting that the one-month-olds possessed more immature sensory and perceptual visual systems, as well as poorer neural systems for controlling selective attention. Both techniques have been applied to a group of neurologically impaired children, and the results indicate that the tests may be useful in distinguishing sensory loss from attentional impairments in these patients.

Intermodal enhancement of stimulus localisation in infants born prematurely

The interaction of auditory and visual modalities in the enhancement of orientation was examined in premature and near-term infants by presenting them auditory or visual stimuli or auditory-visual stimulus combinations at various positions in sensory space. In 4.5--15-mo-olds, brisk orienting responses could be elicited to very peripheral stimulus positions but only when the stimulus consisted of a spatially coherent auditory-visual combination (i.e., where a sound and a light occurred at the same point in space). This occurred for all infants, irrespective of age or gestational age at birth. First, the result shows that infants can respond to visual stimuli at eccentric positions, beyond the supposed limits of their effective visual fields as measured by standard perimetry. Second, the result extends earlier studies showing that intersensory integration and stimulus localisation develop relatively normally in prematurely born infants. The auditory-visual enhancement test as used here may have a number of further uses and applications in the clinic and laboratory.

Kinetic perimetry assessment of binocular visual field shape and size in young infants

Kinetic perimetry was used to measure the extent of the binocular visual field in 8 directions in 77 full-term infants tested as neonates, 4-week-olds, or 8-week-olds. The apparatus consisted of a black, 4-arm arc perimeter, a centrally-located 6-deg stationary white sphere, and an identical sphere that served as the peripheral target. Neonates showed larger visual fields than did 4- and 8-week-olds, perhaps due to the strength of the older infants' fixation of the central target. Infants at all ages showed significantly smaller fields than did adults. However, visual field shape was similar in infants and adults.

Perception of symmetry in infancy: the salience of vertical symmetry and the perception of pattern wholes

Four experiments were conducted to assess converging aspects of 4-month-old infants' perception of symmetry in visual patterns. Experiments 1 and 2 manipulated the structure and orientation of comparable patterns in order to evaluate the specialty of vertical symmetry. Infants showed no preference among vertically symmetrical, vertically repeated, and obliquely symmetrical patterns, but they processed vertically symmetrical patterns more efficiently than either vertically repeated patterns or obliquely symmetrical patterns. Experiment 3 manipulated the spatial separation of pattern components in order to determine the ability of young infants to integrate and coalesce information in visual patterns that is distributed in space. Infants processed vertically symmetrical patterns whose components were contiguous or nearly contiguous about the vertical axis (0 to 2.5 degrees separations) more efficiently than discontiguous patterns (5 and 10 degrees separations). Thus, extreme spatial separation about the vertical meridian caused infants to lose the advantage for vertical symmetry, and by inference their holistic perception of the visual pattern. Experiment 4 manipulated the organization of individual components of a vertical pattern in order to examine further infants' sensitivity to perceptual organization and synthesis of pattern form. Infants discriminated vertically symmetrical patterns from asymmetrical patterns with a vertical organization, thereby demonstrating sensitivity to the symmetrical organization of the pattern above their perception of components in the pattern. The results of these four experiments together corroborate and extend previous findings that vertical symmetry has a special status in early perceptual development and that infants can perceive pattern wholes.

The development of young infants' ability to detect stimuli in the nasal visual field

We compared infants' ability to detect single lines of varying width in the temporal and nasal visual fields. The smallest lines detected by 1-month-olds at 20 degrees in the nasal visual field were more than eight times wider than those detected at 30 degrees in the temporal visual field. In contrast, 2-month-olds detected smaller lines at 20 degrees in the nasal visual field than at 30 degrees in the temporal visual field. Converging evidence suggests that the observed improvement between 1 and 2 months in detection in the nasal visual field reflects the maturation of a projection from the retina through the visual cortex to the superior colliculus.

Area-threshold relations at controlled retinal locations in 1-month-old infants

A fixation-and-flash technique has been developed to provide control over the retinal eccentricities of stimuli presented to infant subjects, to within a few degrees of visual angle. The technique is a variant of forced-choice preferential looking (FPL). An adult observer triggers presentation of the test stimulus when she judges that the infant is fixating a centrally located fixation target. The stimuli are short in relation to the infant's refixation latency. Auxiliary experiments confirmed that on most trials the stimuli fell within +/- 4 degrees of the designated eccentricity. Test fields of two sizes, 3.1 and 17 degrees, were presented to 1-month-old infants at one of four retinal locations, 9, 18, 27 and 36 degrees eccentric. The infants' data show a perfect area-intensity tradeoff at all four locations. Adult control subjects showed summation over areas of only 1-2 degrees. The results are discussed in relation to other evidence of coarse spatial processing in human infants and other immature mammalian systems.

Peripheral vision and optokinetic nystagmus in children with unilateral congenital cataract

The vision of cats which were monocularly deprived during early infancy, of kittens, and of young human infants shares two limitations: detection in the nasal visual field is far poorer than detection in the temporal visual field, and optokinetic nystagmus (OKN) is difficult to elicit when a pattern moves nasally to temporally. Here we report similar limitations on the vision of children who had a dense central cataract in one eye during early infancy. Extensive static perimetry with one of these children whose visual acuity was good in both eyes revealed that her threshold for detection all along the horizontal meridian was higher in her aphakic than in her normal eye, with this difference much more pronounced in the nasal visual field than in the temporal visual field. Three children who developed cataracts after 6 months of age showed no such discrepancy between thresholds in the temporal and nasal fields. We tested the symmetry of OKN in 12 children treated for unilateral congenital cataract. In every test of an aphakic (n = 4) or normal eye (n = 12), OKN occurred significantly more often when stripes moved temporally to nasally than when they moved nasally to temporally. In contrast, no asymmetry was observed in any of 13 children treated for traumatic cataracts incurred after 3 years of age. We conclude that children treated for unilateral congenital cataract, like young human infants and monocularly deprived cats, show asymmetric OKN and relatively poor detection in the nasal visual field.

Development of fixation and pursuit eye movements in human infants

Visual fixation and pursuit abilities of human infants were tested during their first year of life. Eye as well as head position was measured. Results show that the fixation of visual targets is accomplished by a head rotation accompanied by a series of small eye saccades. The number of these saccades increases with target eccentricity but progressively decreases with age. Pursuit of a moving visual target is performed by a smooth eye and head movement only if the target velocity is low. The maximum speed of pursuit progressively increases with age. The results are compatible with the relatively late development of the fovea.

Detection of moving stimuli in the binocular and nasal visual fields by infants three and four months old

A technique of monocular eye patching was used to measure the response of infants three and four months old to nasally and temporally placed stimuli at various eccentricities in the visual field. The results indicated a field of field of binocular overlap of approximately 60 deg in infants three months old and 80 deg in infants four months old. These figures compare with visual field widths obtained under binocular viewing conditions of at least 140 deg in infants three months old and of at least 150 deg in infants four months old.

The development of the kitten's visual field

We tested the monocular visual field of 16 kittens aged 13-56 days, by observing their unreinforced visual orienting. At 13-14 days the kittens oriented toward stimuli out of 45 degrees in the nasal field. Until 7-8 weeks, performance was significantly poorer in the nasal field than in the temporal field. This delayed development of the nasal field may be related to the relatively slow development of the uncrossed retino-geniculate projection and of the pathway through the visual cortex to the superior colliculus.

Ophthalmological examination of the infant. Developmental aspects

In recent years, the ophthalmic examination of infants has been of increasing interest to both clinicians and vision researchers. Clinicians have documented a greater risk of retinopathy, strabismus and amblyopia in premature infants, especially those of low birthweight. In addition to the external and retinal examination of the infant eye, a number of clinical tests can help the ophthalmologist to detect visual dysfunction through the evaluation of pupillary responses and ocular motility. Recently, the development of objective techniques (optokinetic nystagmus, forced choice preferential looking, and visually evoked potentials) have not only aided in the detection of ophthalmic disorders in infants; they have contributed to useful definitions of "normal" vision at various ages and to the understanding of factors that influence the pre- and post-gestational development of visual function.

Effect of peripheral visual field size upon visual search in children and adults

Twenty observers in each of the age groups, three, four, five, and twenty-one years, were asked to identify pictures displayed through five different sizes of peephole. Recognition latency changes as a cube-root power function of aperture area. It was found that latency decreased as age and area increased. However, the exponent of the power function showed little age-related change. Effectiveness of the peripheral visual field size was discussed in terms of magnitude of the exponent.

Central and peripheral object distances as determinants of the effective visual field in early infancy

While visually fixating on a central, coloured object, thirty-six infants aged between two and five months were presented with a peripheral target to the right or to the left of midline. Both objects were presented at two distances: either 30 or 90 cm from the infant. The extent of the effective visual field was measured by the presence and the latency of saccadic shifts of gaze from the fixation object toward the target object placed at varying degrees of eccentricity. The effective visual field expanded between two and four months. Near peripheral targets were detected at greater angles of eccentricity than those more distant, but this effect was modified both by age and by the distance of central fixation. For two- and three-month infants the effective visual field was most reduced when the central fixation object was placed at 30 cm and the target object at 90 cm. The ability to respond to peripheral objects more distant than the fixation object develops after three months.

Discrimination by young infants of stimuli presented discontinuously

Four experiments are reported showing that young infants can pick up visual information from very brief displays. Pattern, edge orientation, and form can be discriminated when stimuli are presented for repeated exposures of only 300 ms.