Contrast sensitivity function of sine-wave gratings in children with acute malnutrition.

Santos, Natanael Antônio dos; Alencar, Caroline Costa Gomes; Dias, Yuri Henrique Nunes

doi:10.3922/j.psns.2009.1.003

Cited by 5 publications

(7 citation statements)

References 16 publications

(18 reference statements)

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“…A major part of our initial knowledge of the visual system is based on the findings of the investigations conducted using sine-wave gratings (Campbell and Green 1965;Campbell and Robson 1968;Blakemore and Campbell 1969;Field and Tolhurst 1986;Ringach et al 2002). Measurement of contrast sensitivity to sine-wave gratings is widely used for the investigation and treatment of visual impairments (Arden 1978;Arundale 1978;Adams and Courage 2002;Hertle and Reese 2007;Santos et al 2009). Studies show (Howell and Hess 1978) that variation of contrast sensitivity to simple sine-wave grating with stimulus area unveils the properties of the underlying mechanism called spatial integration, which also depends on area.…”

Section: Introductionmentioning

confidence: 99%

Stochastic resonance in visual sensitivity

Kundu

Sarkar

2014

Biol Cybern

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It is well known from psychophysical studies that stochastic resonance, in its simplest threshold paradigm, can be used as a tool to measure the detection sensitivity to fine details in noise contaminated stimuli. In the present manuscript, we report simulation studies conducted in the similar threshold paradigm of stochastic resonance. We have estimated the contrast sensitivity in detecting noisy sine-wave stimuli, with varying area and spatial frequency, as a function of noise strength. In all the cases, the measured sensitivity attained a peak at intermediate noise strength, which indicate the occurrence of stochastic resonance. The peak sensitivity exhibited a strong dependence on area and spatial frequency of the stimulus. We show that the peak contrast sensitivity varies with spatial frequency in a nonmonotonic fashion and the qualitative nature of the sensitivity variation is in good agreement with human contrast sensitivity function. We also demonstrate that the peak sensitivity first increases and then saturates with increasing area, and this result is in line with the results of psychophysical experiments. Additionally, we also show that critical area, denoting the saturation of contrast sensitivity, decreases with spatial frequency and the associated maximum contrast sensitivity varies with spatial frequency in a manner that is consistent with the results of psychophysical experiments. In all the studies, the sensitivities were elevated via a nonlinear filtering operation called stochastic resonance. Because of this nonlinear effect, it was not guaranteed that the sensitivities, estimated at each frequency, would be in agreement with the corresponding results of psychophysical experiments; on the contrary, close agreements were observed between our results and the findings of psychophysical investigations. These observations indicate the utility of stochastic resonance in human vision and suggest that this paradigm can be useful in psychophysical studies.

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Section: Introductionmentioning

confidence: 99%

Stochastic resonance in visual sensitivity

Kundu

Sarkar

2014

Biol Cybern

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“…Consistent with this hypothesis, visual neuroscience research uses visual CS to evaluate and diagnose changes in optic and neural structures related to diseases that are not directly related to visual changes, such as depression (Wesner & Tan, 2006), schizophrenia (Slaghuis & Thompson, 2003), and malnutrition (Santos, Alencar, & Dias, 2009;Santos & Alencar, 2010), among others.…”

Section: Discussionmentioning

confidence: 99%

Visual contrast sensitivity in tonic-clonic epileptic patients.

Bezerra¹,

Alencar²,

Mousinho³

et al. 2011

Psychology & Neuroscience

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We measured the effects of epilepsy on visual contrast sensitivity to linear and vertical sine-wave gratings. Sixteen female adults, aged 21 to 50 years, comprised the sample in this study, including eight adults with generalized tonic-clonic seizure-type epilepsy and eight age-matched controls without epilepsy. Contrast threshold was measured using a temporal two-alternative forced-choice binocular psychophysical method at a distance of 150 cm from the stimuli, with a mean luminance of 40.1 cd/m 2 . A one-way analysis of variance (ANOVA) applied to the linear contrast threshold showed significant differences between groups (F[3,188] = 14.829; p < .05). Adults with epilepsy had higher contrast thresholds (1.45, 1.04, and 1.18 times for frequencies of 0.25, 2.0, and 8.0 cycles per degree of visual angle, respectively). The Tukey Honestly Significant Difference post hoc test showed significant differences (p < .05) for all of the tested spatial frequencies. The largest difference between groups was in the lowest spatial frequency. Therefore, epilepsy may cause more damage to the neural pathways that process low spatial frequencies. However, epilepsy probably alters both the magnocellular visual pathway, which processes low spatial frequencies, and the parvocellular visual pathway, which processes high spatial frequencies. The experimental group had lower visual contrast sensitivity to all tested spatial frequencies.

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“…The central idea of this study related to predictable responses of the visual system in children who were malnourished for at least 6 months, from birth to 2 years of age. In previous studies we measured CS to linear gratings in children with acute (Santos et al, 2009) and early (Santos & Alencar, 2010) malnutrition. We found that acute malnourished children (AM group) with normal height according to age but underweight according to height were 1.34-, 1.27-, 1.50-, and 1.36-fold less sensitive to the detection of linear sinewave gratings with spatial frequencies of .25, 1.0, 2.0, and 8.0 cpd, respectively, than children in the E group.…”

Section: Discussionmentioning

confidence: 99%

“…Based on prior research indicating that nonCartesian gratings are processed with increasing selectivity in visual centers beyond V1, such as V2 and V4 (Gallant et al, 1996;Merigan, 1996;, we sought to extend our prior results that examined the effects of early malnutrition in children using Cartesian sinewave gratings (Santos et al, 2009;Santos & Alencar, 2010) by examining contrast sensitivity (CS) to non-Cartesian gratings in children who experienced malnutrition.…”

Section: Introductionmentioning

confidence: 99%

“…Both behavioral (Santos, Alencar, & Dias, 2009;Santos & Alencar, 2010) and electrophysiological Uauy et al, 1990;Morale et al, 2005) evidence indicate that inadequate nutrition during development leads to losses in sensitivity to traditional Cartesian sinewave luminance gratings. Does malnutrition affect all of the visual centers in the cortex?…”

Section: Introductionmentioning

confidence: 99%

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Early malnutrition decreases contrast sensitivity to circular concentric gratings.

Alencar¹,

Santos²

2012

Psychology & Neuroscience

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Early malnutrition refers to inadequate nutrition during the critical period of nervous system development followed by nutritional recovery, resulting in a short stature according to age but normal weight according to short stature. We measured the effects of early malnutrition on contrast sensitivity (CS) to concentric circular gratings in 18 children of both sexes, aged 8 to 11 years (mean = 9.2 years, standard deviation = .99 years). Nine of the children were eutrophic (E group), and nine experienced early malnutrition (EM group) based on state healthcare records and Waterlow's anthropometric parameters. Contrast sensitivity to four spatial frequencies (.25, 1.0, 2.0, and 8.0 cycles per degree [cpd]) was measured using a temporal two-alternative forced-choice psychophysical method with mean luminance of 40.1 cd/m 2 . Statistical analyses showed significant differences between groups and a group × frequency interaction. EM group was significantly less sensitive than the E group to the 8.0 cpd frequency and needed 1.49-times more contrast to detect the gratings. These results suggest that early malnutrition impairs CS to high-spatialfrequency concentric circular gratings in children. Therefore, early malnutrition, which is known to affect primary visual cortical areas, may also affect higher visual cortical areas such as V4 and the inferotemporal cortex.

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Contrast sensitivity function of sine-wave gratings in children with acute malnutrition.

Cited by 5 publications

References 16 publications

Stochastic resonance in visual sensitivity

Stochastic resonance in visual sensitivity

Visual contrast sensitivity in tonic-clonic epileptic patients.

Early malnutrition decreases contrast sensitivity to circular concentric gratings.

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