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M S Banks

Publications and source records attributed to M S Banks.

At least 55 records · Page 3Linked to original sources
PubMed1988

Optical and photoreceptor immaturities limit the spatial and chromatic vision of human neonates.

We examine the contributions of preneural mechanisms, i.e., the optics of the eye and the aperture, spacing, and efficiency of foveal cones, to poor spatial and chromatic vision in human neonates. We do so by comparing the performances of ideal observers incorporating the characteristics of the optics and the foveal cones of adults and neonates. Our analyses show that many, but not all, of the differences between neonatal and adult contrast sensitivities and grating acuities can be explained by age-related changes in these factors. The analyses also predict differing growth curves for vernier and grating acuities. Finally, we demonstrate that preneural mechanisms constrain chromatic discrimination in human neonates and that discrimination failures may reflect poor visual efficiency rather than immature chromatic mechanisms per se.

Aging↗
PubMed1987

The physical limits of grating visibility.

We examined the extent to which pre-neural factors constrain the detectability of sinusoidal gratings of different spatial frequencies and luminances. Contrast sensitivity functions were measured in two observers for foveally-presented grating patches. Spatial extent of the patches was inversely proportional to grating frequency. The observers' contrast sensitivity functions were then compared to the performance of an ideal discriminator (Geisler, 1984) which incorporated the effects of quantal fluctuations, optical transfer, ocular media transmittance, and the aperture, quantum efficiency, and spatial distribution of foveal photoreceptors. The sensitivity of the ideal discriminator was roughly 20-fold greater than that of the human observers, but the shapes of the ideal and human CSFs were quite similar from 5 to 40 c/deg and from 3.4 to 340 cd/m2. The similarity of shapes demonstrates that the high-frequency rolloff of the foveal CSF for gratings with a fixed number of cycles can be explained by the operation of pre-neural factors alone. Previous research has shown that grating summation area is inversely proportional to the square of spatial frequency. Thus, for gratings with fixed spatial extent the high-frequency rolloff can be explained by the pre-neural factors plus variations in grating summation area. These conclusions imply in turn that the neural transfer function is much flatter than previously thought and that private line connections from foveal photoreceptors to higher visual centers are common.

Eye Movements↗
PubMed1987

Contrast discrimination in human infants.

The ability to detect differences in spatial contrast is crucial to object recognition and identification. This ability is generally examined by measuring the contrast discrimination function. This function represents, for a variety of conditions, the smallest contrast difference required to discriminate otherwise identical patterns. We examined human infants' ability to discriminate patterns on the basis of differences in spatial contrast. The forced-choice preferential looking procedure was used to estimate contrast increment thresholds at a number of background contrasts. The Weber fractions of 6- and 12-week-old infants were about 1 log unit higher than adult values for background contrasts ranging from 0.14 to 0.55. Furthermore, the slopes of infants' discrimination functions were much shallower than those of adults. These age differences in contrast discrimination imply certain changes in the neural mechanisms that underlie contrast encoding. They also aid our understanding of the anomalies observed in early pattern vision.

Attention↗
PubMed1987

Stimulus energy does not account for 2-month-olds' face preferences.

We examined the determinants of 2-month-olds' preferences among facelike and abstract patterns. Observed preferences were compared with the predictions of two preference models--one based on stimulus energy (as measured by the amplitude spectrum) and the other based on stimulus structure (as measured by the phase spectrum). It is known that the phase spectrum is the primary determinant of perceived identity to adults. Twenty-five 2-month-olds saw six pairings of four patterns: a schematic face, a lattice, a pattern composed of the amplitude spectrum of the lattice and the phase spectrum of the face, and a pattern composed of the amplitude spectrum of the face and the phase spectrum of the lattice. Only patterns with the face's phase spectrum look facelike to adults. Unlike the preferences of newborns (Kleiner, 1987), 2-month-olds' preferences could be predicted from the phase spectrum but not from the amplitude spectrum. In other words, the 2-month-olds preferred the patterns that looked facelike to adults. These results offer clear evidence that 2-month-olds' preferences for facelike patterns are not governed by stimulus energy.

Attention↗
PubMed1985

The development of basic mechanisms of pattern vision: spatial frequency channels.

The mature visual system possesses mechanisms that analyze visual inputs into bands of spatial frequency. This analysis appears to be important to several visual capabilities. We have investigated the development of these spatial-frequency channels in young infants. Experiment 1 used a masking paradigm to test 6-week-olds, 12-week-olds, and adults. The detectability of sine wave gratings of different spatial frequencies was measured in the presence and the absence of a narrowband noise masker. The 12-week data showed that at least two spatial-frequency channels with adultlike specificity are present at 12 weeks. The 6-week data did not reveal the presence of narrowband spatial-frequency channels. Experiment 2 used a different paradigm to investigate the same issue. The detectability of gratings composed of two sine wave components was measured in 6-week-olds and adults. The results were entirely consistent with those of experiment 1. The 12-week and adult data indicated the presence of narrowband spatial-frequency channels. The 6-week data did not. The results of these experiments suggest that the manner in which pattern information is processed changes fundamentally between 6 and 12 weeks of age.

Adult↗
PubMed1985

The development of contrast constancy.

The mature visual system possesses mechanisms that enable invariant perception of the contrast of an object and its features as the object undergoes changes in distance. This phenomenon, which has been called contrast constancy, obtains at suprathreshold contrasts only. Some models of contrast constancy assume the presence of narrowband spatial-frequency channels. An implication of M.S. Banks, B.R. Stephens, and E.E. Hartmann (1985, Journal of Experimental Child Psychology, 40, 501-527) is that contrast constancy should not be observed at 6 weeks but may be observed at 12 weeks. We examined this implication by investigating the development of contrast constancy in 6- and 12-week-old infants. Two sine wave gratings, differing in spatial frequency by a factor of 3, were presented side-by-side. The contrast of one grating was varied in order to estimate the contrast at which preference for the two gratings was equal. The equal preference points for 6-week-olds were predictable from their contrast thresholds. The 12-week-olds' equal preference points for low-contrast stimuli were predictable from their contrast thresholds, but those for intermediate and high-contrast stimuli were not. Thus, if one accepts the assumption that equal preference in infants is analogous to apparent contrast matches in adults, these data imply that contrast constancy is observed at 12 weeks but not 6 weeks. The perceptual consequences of this developmental transition are discussed.

Adult↗
PubMed1983

Photorefraction of normal and astigmatic infants during viewing of patterned stimuli.

Photorefraction was used to assess the state of accommodation of 3-month old infants with and without astigmatism while they viewed stimuli in an apparatus commonly used to test infant visual acuity. The stimuli were a 1.6 c/deg vertical grating, a 1.6 c/deg horizontal grating and a cross composed of orthogonal 19 min lines, which were presented 55 cm from the infants. Most infants' accommodation was appropriate for the vertical grating. Astigmatic infants did not change their focus when the orientation of the grating was changed.

Accommodation, Ocular↗
PubMed1983

The development of light adaptation in human infants.

Increment threshold functions were measured from -4.0 to 1.2 log cd/m2 in 7-12-week-old infants using a behavioral forced-choice paradigm. The slopes of the infant functions were considerably shallower than the slopes of adult functions over the same luminance range. The value of the infant slope increased rapidly between 7 and 12 weeks postnatally. A number of explanations for this developmental shift are considered. It is concluded that changes with age in either spatial summation or intensity-response function gain could cause the increase in slope.

Adaptation, Ocular↗
PubMed1982

The contrast sensitivity of human infants to gratings differing in duty cycle.

Human infants' contrast thresholds for rectangular wave gratings differing in duty cycle were measured. The forced-choice preferential looking technique was used to estimate thresholds in fifteen 8- to 10-week old infants. The results indicated that contrast threshold varied systematically with duty cycle. Our findings were consistent with the predictions of a linear, multiple channel model and one version of a linear, single channel model but were inconsistent with the predictions of a contour density and another version of a single channel model.

Form Perception↗
PubMed1982

A failure to observe negative preference in infant acuity testing.

Held et al. (1979) Vision Res. 19, 1377-1379, reported that infants' psychometric functions in preferential looking experiments exhibit a region of below chance performance or "negative preference". They argued from this that previous preferential looking experiments may have systematically underestimated acuity because they ignored this negative preference. We present data from an experiment designed to reveal negative preference in the version of the preferential looking paradigm used in our laboratory. The results do not exhibit negative preference apart from random variations about 50%. Gwiazda et al. (1980) Am. J. Optom. physiol. Opt. 57, 420-427; 428-432, developed a psychophysical procedure for infant testing that is designed to yield accurate threshold estimates in a short period of time. We present the results of computer simulations of more conventional psychophysical procedures. The simulations demonstrate that an up-down staircase procedure is more efficient than the Gwiazda et al. procedure.

Computers↗
PubMed1980

Infant refraction and accommodation.

A reasonable amount of information concerning early refraction and accommodation has been accumulated. The measurements of refraction appear to be reliable and concurrently valid, although more attention should be devoted to both of those issues. There is also some evidence that the measurements can be developmentally significant since adults with histories of early spherical or cylindrical errors exhibit nonreversible visual deficits. The retrospective findings [11, 43] that evidenced this point do not necessarily imply that large refractive errors during infancy invariably yield visual deficits later on. To determine the significance of early errors, their predictive validity must be better estimated. Some evidence indicates that neonatal refractions predict refractions later in infancy. But the actual magnitude of the relationship between early and school aged or adult refractions is uncertain. Longitudinal studies of refraction from birth to at least the elementary school years would yield appropriate data. It is hoped that with the increasing interest in early visual function and the development of accurate, yet rapid techniques of measurement (such as photorefraction), such information will soon be forthcoming. It will be of special interest to unveil the mechanisms that control the development of refraction, in particular, to reveal the developmental relationship between refraction and accommodation.

Accommodation, Ocular↗
PubMed1980

The development of visual accommodation during early infancy.

4 experiments were conducted concerning the development of visual accommodation in 1- to 3-month-old infants. In experiments 1 and 2 dynamic retinoscopy was used to measure accomodation responses at 3 stimulus distances. The results of experiment 1 revealed better accommodative capability from 1 to 3 months than reported originally. The procedure of experiment 2 was somewhat different but the results confirmed those of experiment 1. In experiment 3, accommodative responses at 7 stimulus distances were carefully measured in a small number of infants. These data provided estimates of the shape of infants' accommodation functions. In experiment 4, we used infrared photography to measure infants' pupil diameters while they viewed the stimuli of experiments 1 and 2. 2 simple hypotheses of the developmental mechanisms which underlie early accommodative development were considered. First, development of the motor component of the accommodative system might determine accommodative development. Second, development of the sensory component of the accommodative system might determine the observed development. The first hypothesis was tentatively rejected because it is inconsistent with some clinical findings. Evaluation of the second hypothesis involved calculating infants' depth of focus. We used those depth-of-focus values to predict how well infants of different ages should accommodate if their only limitation were in the sensory component of the accommodative system. The agreement between those predictions and observed accommodation was excellent, suggesting that changes in depth of focus in the first 3 months are largely responsible for growth in accommodation. The theoretical implications of this finding are discussed.

Accommodation, Ocular↗
PubMed1978

Acuity and contrast sensitivity in 1-, 2-, and 3-month-old human infants.

The importance of assessing infant visual function is indicated by recent demonstrations that early visual experience in part determines the eventual state of adult visual function. It is argued that the contrast sensitivity function (CSF) could be a valuable index in the assessment of infant vision because it provides information concerning several aspects of vision. CSF's were measured in 1-, 2-, and 3-month-old infants. The "cut-off" spatial frequencies, which are estimates of visual acuity, were 2.4 cy/deg for 1-month-olds, 2.8 cy/deg for 2-month-olds, and 4.0 cy/deg for 3-month-olds. Sensitivity to contrast was shown to increase between 1 and 3 months of age. The CSF's measured also provide evidence for the presence of a low-frequency fall-off at 2 and 3 months.

Age Factors↗