Motion Contrast Sensitivity Research Articles

Vision Impairment and On-Road Driving.

Good vision is important for safe driving. The impact of vision impairment associated with common eye diseases on driving performance, and the association between vision measures and driving performance, are discussed. Studies include those where participants drove a real vehicle on a closed road or on public roads. Closed-road studies include evaluation of both simulated and true vision impairment and day- and night-time driving. Collectively, the findings provide important insights into the impact of refractive conditions, cataracts, glaucoma, age-related macular degeneration, and hemianopic field loss on driving; however, study results show varying impacts on driving performance and are often limited by small sample sizes. Vision measures including motion sensitivity, contrast sensitivity, and useful field of view have stronger associations with driving performance than do visual acuity or visual fields, with studies suggesting that some drivers with field loss can compensate for their field defects through increased eye and head movements.

White matter deficits correlate with visual motion perception impairments in dyslexic carriers of the DCDC2 genetic risk variant

Motion perception deficits in dyslexia show a large intersubjective variability, partly reflecting genetic factors influencing brain architecture development. In previous work, we have demonstrated that dyslexic carriers of a mutation of the DCDC2 gene have a very strong impairment in motion perception. In the present study, we investigated structural white matter alterations associated with the poor motion perception in a cohort of twenty dyslexics with a subgroup carrying the DCDC2 gene deletion (DCDC2d+) and a subgroup without the risk variant (DCDC2d–). We observed significant deficits in motion contrast sensitivity and in motion direction discrimination accuracy at high contrast, stronger in the DCDC2d+ group. Both motion perception impairments correlated significantly with the fractional anisotropy in posterior ventral and dorsal tracts, including early visual pathways both along the optic radiation and in proximity of occipital cortex, MT and VWFA. However, the DCDC2d+ group showed stronger correlations between FA and motion perception impairments than the DCDC2d– group in early visual white matter bundles, including the optic radiations, and in ventral pathways located in the left inferior temporal cortex. Our results suggest that the DCDC2d+ group experiences higher vulnerability in visual motion processing even at early stages of visual analysis, which might represent a specific feature associated with the genotype and provide further neurobiological support to the visual-motion deficit account of dyslexia in a specific subpopulation.

Expert opinion on classification for footballers with vision impairment: Towards evidence-based minimum impairment criteria

ABSTRACT In Para sport, the aim of classification is to minimize the impact of impairment on the outcome of competition. Despite requirements of the International Paralympic Committee Athlete Classification Code for classification to be evidence-based and sport-specific, sports for athletes with VI, including football, use the same generic classes across almost all sports. The aim of this study was to consult with experts to establish the needs and challenges for developing a code-compliant system of classification for VI football. A panel of 18 experts with international experience in VI football (16.8 ± 10.2 years) took part in a three-round Delphi study using online surveys. Results showed that the panel did not think that the current system completely fulfils the aim of classification. The panel identified measures of visual function they considered to be relevant but are not currently measured during classification including dynamic acuity, depth and motion perception, and contrast and light sensitivity. Moreover, they identified technical skills such as ball control, dribbling and passing, as well as perceptual-cognitive skills, as most likely to be affected by vision impairment. Findings outline the need for change and offer a framework for future research to develop an evidence-based classification for VI football.

Age-related decline in motion contrast sensitivity due to lower absorption rate of cones and calculation efficiency

Motion perception is affected by healthy aging, which impairs the ability of older adults to perform some daily activities such as driving. The current study investigated the underlying causes of age-related motion contrast sensitivity losses by using an equivalent noise paradigm to decompose motion contrast sensitivity into calculation efficiency, the temporal modulation transfer function (i.e., temporal blur) and 3 sources of internal noise: stochastic absorption of photons by photoreceptors (i.e., photon noise), neural noise occurring at the retinal level (i.e., early noise) and at the cortical level (i.e., late noise). These sources of internal noise can be disentangled because there impacts on motion contrast sensitivity vary differently as a function of luminance intensity. The impact of healthy aging on these factors was evaluated by measuring motion contrast sensitivity of young and older healthy adults at different luminance intensities, temporal frequencies and with/without external noise. The older adults were found to have higher photon noise, which suggests a lower photon absorption rate of cones. When roughly equating the amount of photons being absorbed by the photoreceptors, older adults had lower calculation efficiencies, but no significant aging effect was found on temporal modulation transfer function, early noise and late noise.

A New Approach to Assess Early Progressive Loss Across Multiple Visual Channels In the Natural History of Glaucoma.

We aimed to evaluate the ability of new psychophysical discrimination tests, based on readily available hardware, to probe motion, achromatic, and chromatic contrast sensitivity, across the natural history of glaucoma. We assessed the sensitivity of these tests to detect functional damage at ocular hypertension stage, using receiver operating characteristic analysis. We also explored whether eccentricity-related patterns of damage change with disease progression. We studied a cohort of 43 participants, who were divided between different groups: ocular hypertension (n=16 eyes), glaucoma suspects (n=15), and primary open-angle glaucoma (n=12). These patients were compared with an age-matched control group (n=15 eyes). We tested distinct subsets of retinal ganglion cell populations using 3 novel 2-alternative forced choice psychophysical discrimination tests (independent variables: motion, achromatic, and chromatic L, M, and S-cone contrasts) between 2 separated peripheral, small moving single dots at 4 distinct meridians. Notably these tests were implemented in relatively standard hardware. All tests showed significant correlation with disease progression (mean ρ±SD=0.708±0.075; P<0.0001) and had sufficient power to discriminate glaucoma subgroups. Most tests using this design had large sensitivity (above 90% for 80% specificity) to detect functional damage at the ocular hypertensive stage. Disease-related eccentricity patterns of damage were also found, matching the expected pattern of progression. Our new psychophysical discrimination tests are capable of probing disease progression and to detect functional damage at ocular hypertension stage. It is therefore possible to customize psychophysical test software to detect early changes and monitor disease progression, including progressive loss of functional reserve, using relatively simple hardware.

The effects of aging on perception and cognition

The developed world is aging faster than ever before. Even in the absence of neurodegenerative disease, aging affects all kinds of human functions including perception and cognition. In most perceptual studies, one paradigm is tested and it is usually found that older participants perform worse than younger participants. Implicitly, these results are taken as evidence that there is one aging factor for each individual determining his/her overall performance levels. Here, we show that visual and cognitive functions age differently. We tested 131 older participants (mean age 70 years old) and 108 younger participants (mean age 22 years old) in 14 perceptual tests (including motion perception, contrast and orientation sensitivity, biological motion perception) and in 3 cognitive tasks (WCST, verbal fluency and digit span). Young participants performed better than older participants in almost all of the tests. However, within the older participants group, age did not predict performance, i.e., a participant could have good results in biological motion perception but poor results in orientation discrimination. It seems that there is not a single “aging” factor but many.

Changes of spatial and temporal frequency tuning properties of neurons in the middle temporal area of aged rhesus monkeys

Aged humans exhibit severe deficits in visual motion perception and contrast sensitivity under various levels of spatial and temporal modulation. Previous studies indicated that many of these deficits are probably mediated by the neural degradation of the central visual system. To clarify the neuronal response mechanisms underlying the visual degradation during aging, we examined the spatial and temporal frequency tuning properties of neurons from anesthetised and paralysed aged monkeys at the middle temporal area (area MT), which is downstream of the primary visual cortex in the visual processing pathway and thought to be critical for motion perception. We found that the preferred spatial and temporal frequencies, spatial resolution and high temporal frequency cutoff of area MT neurons were reduced in aged monkeys, and were accompanied by the broadened tuning width of spatial frequency, elevated spontaneous activity, and decreased signal-to-noise ratio. These results showed that, for neurons in area MT, aging significantly changed both the spatial and temporal frequency response tuning properties. Such evidence provides new insight into the changes occurring at the electrophysiological level that may be related to the aging-related visual deficits, especially in processing spatial and temporal information.

Driving under low-contrast visibility conditions in Parkinson disease

To assess driving performance in Parkinson disease (PD) under low-contrast visibility conditions. Licensed, active drivers with mild to moderate PD (n = 67, aged 66.2 +/- 9.0 years, median Hoehn-Yahr stage = 2) and controls (n = 51, aged 64.0 +/- 7.2 years) drove in a driving simulator under high- (clear sky) and low-contrast visibility (fog) conditions, leading up to an intersection where an incurring vehicle posed a crash risk in fog. Drivers with PD had higher SD of lateral position (SDLP) and lane violation counts (LVC) than controls during fog (p < 0.001). Transition from high- to low-contrast visibility condition increased SDLP and LVC more in PD than in controls (p < 0.01). A larger proportion of drivers with PD crashed at the intersection in fog (76.1% vs 37.3%, p < 0.0001). The time to first reaction in response to incursion was longer in drivers with PD compared with controls (median 2.5 vs 2.0 seconds, p < 0.0001). Within the PD group, the strongest predictors of poor driving outcomes under low-contrast visibility conditions were worse scores on measures of visual processing speed and attention, motion perception, contrast sensitivity, visuospatial construction, motor speed, and activities of daily living score. During driving simulation under low-contrast visibility conditions, drivers with Parkinson disease (PD) had poorer vehicle control and were at higher risk for crashes, which were primarily predicted by decreased visual perception and cognition; motor dysfunction also contributed. Our results suggest that drivers with PD may be at risk for unsafe driving in low-contrast visibility conditions such as during fog or twilight.

Characteristics of dynamic processing in the visual field of patients with age-related maculopathy

PurposeTo investigate the characteristics of dynamic processing in the visual field of patients with age-related maculopathy (ARM) by measuring motion sensitivity, double-pulse resolution (DPR), and critical flicker fusion.MethodsFourteen subjects with ARM (18 eyes), 14 age-matched controls (19 eyes), and 7 young controls (8 eyes) served as subjects. Motion contrast thresholds were determined by a four-alternative forced-choice (4 afc) staircase procedure with a modification by Kernbach for presenting a plaid (size = 3.8°) moving within a stationary spatial and temporal Gaussian envelope in one of four directions. Measurements were performed on the horizontal meridian at 10°, 20°, 30°, 40°, and 60° eccentricity. DPR was defined as the minimal temporal gap detectable by the subject using a 9-fold interleaved adaptive procedure, with stimuli positioned on concentric rings at 5°, 10°, and 20° eccentricity on the principal and oblique meridians. Critical flicker fusion thresholds (CFF) and the Lanthony D-15 color vision test were applied foveally, and the subjects were free to use their fovea or whatever retinal area they needed to use instead, due to their retinal lesions caused by ARM. All measurements were performed under photopic conditions.ResultsMotion contrast sensitivity in subjects with ARM was pronouncedly reduced (0.23–0.66 log units, p < 0.01), not only in the macula but in a region up to 20° eccentricity. In the two control groups, motion contrast sensitivity systematically declined with retinal eccentricity (0.009–0.032 log units/degree) and with age (0.01 log units/year). Double-pulse thresholds in healthy subjects were approximately constant in the central visual field and increased outside a radius of 10° (1.73 ms/degree). DPR thresholds were elevated in subjects with ARM (by 23–32 ms, p < 0.01) up to 20° eccentricity, and their foveal CFFs were increased by 5.5 Hz or 14% (p < 0.01) as compared with age-matched controls.ConclusionsDynamic processing properties in subjects with ARM are severely impaired in the central visual field up to 20° eccentricity, which is clearly beyond the borders of the macula.

Directional motion contrast sensitivity in developmental dyslexia

The present study compared the perception of visual motion in two dyslexia classification schemes; the [Boder, E. (1973). Developmental dyslexia: a diagnostic approach based on three atypical reading-spelling patterns. Developmental Medicine and Child Neurology, 15, 663–687.] dyseidetic, dysphonetic and mixed subgroups and [Williams, M. J., Stuart, G. W., Castles, A., & McAnally, K. I. (2003). Contrast sensitivity in subgroups of developmental dyslexia. Vision Research, 43, 467–477.] surface, phonological and mixed subgroups by measuring the contrast sensitivity for drifting gratings at three spatial frequencies (1.0, 4.0, and 8.0 c/deg) and five drift velocities (0.75, 3.0, 6.0, 12.0, and 18.0 cyc/s) in a sample of 32 children with dyslexia and 32 matched normal readers. The findings show that there were no differences in motion direction perception between normal readers and the group with dyslexia when dyslexia was taken as a homogeneous group. Motion direction perception was found to be intact in the dyseidetic and surface dyslexia subgroups and significantly lowered in both mixed dyslexia subgroups. The one inconsistency in the findings was that motion direction perception was significantly lowered in the [Boder, E. (1973). Developmental dyslexia: a diagnostic approach based on three atypical reading-spelling patterns. Developmental Medicine and Child Neurology, 15, 663–687.] dysphonetic subgroup and intact in the [Williams, M. J., Stuart, G. W., Castles, A., & McAnally, K. I. (2003). Contrast sensitivity in subgroups of developmental dyslexia. Vision Research, 43, 467–477.] phonological subgroup. The findings also provide evidence for the presence of a disorder in sequential and temporal order processing that appears to reflect a difficulty in retaining sequences of non-meaningful auditory and visual stimuli in short-term working memory in children with dyslexia.

Smooth-pursuit eye movement and directional motion-contrast sensitivity in schizophrenia

Although the occurrence of visual processing and eye-movement disorders in schizophrenia have been widely recognized, their relationship with the symptoms of schizophrenia is less well understood. In two experiments the relationship between directional-motion processing and smooth-pursuit eye movement was investigated in normal observers and in groups with positive and negative symptoms in schizophrenia. The first experiment measured linear smooth-pursuit eye movement at six target velocities from 5.0 to 30.0 degrees s(-1) and the second experiment measured directional motion-contrast sensitivity at three spatial (1.0, 4.0 and 8.0 c/deg) and five temporal (0.75, 3.0, 6.0, 12.0 and 18.0 Hz) frequencies in the same groups of observers. No significant differences were found between the control and positive-symptom group in directional motion-contrast sensitivity and smooth-pursuit eye movements. In comparison, a relationship was found between a significant reduction in directional motion-contrast sensitivity and significantly reduced smooth-pursuit eye movement in the negative-symptom group and serves to further cleave the distinction between positive and negative symptoms in schizophrenia. The relationship between visual motion processing and pursuit eye movement in the negative-symptom group was explained by a disorder in directional motion processing that fails to fully engage the pursuit eye movement system and reduces smooth pursuit eye-velocity gain.

Motion-contrast computation without directionally selective motion sensors

The detection of relative motion, i.e., motion contrast, has been reported for motion-sensitive neurons in several vertebrate systems, yet the mechanism underlying motion-contrast sensitivity remains unknown. An algorithm for computing motion contrast directly from the moving intensity distribution is proposed. In this algorithm, the time-dependent intensity distribution of the visual space is convolved with a periodic function. For coherent motion, the resulting convolution integral reduces to a traveling wave of fixed amplitude, while incoherent motion causes the amplitude to oscillate. The frequency of the amplitude oscillation provides a measure of motion contrast. The algorithm is successful in reproducing tuning curves derived from measurements of motion-contrast sensitivity in avian tectum and primate middle temporal area.

Psychophysical Indexes of Temporal Processing Abnormalities in Children With Developmental Dyslexia

Children with dyslexia and children progressing normally in reading performed several perceptual tasks to determine (a) the psychophysical measures that best differentiate children with dyslexia from children with average reading abilities; (b) the extent of temporal processing deficits in a single, well-defined group of children with dyslexia; and (c) the co-occurrence of visual and auditory temporal processing deficits in children with dyslexia. 4 of our 12 psychophysical tasks indicated differences in temporal processing ability between children with dyslexia and children with good reading skills. These included 2 auditory tasks (dichotic pitch perception and FM tone discrimination) and 2 visual tasks (global motion perception and contrast sensitivity). The battery of 12 tasks successfully classified 80% of the children into their respective reading-level groups. Within the group of children with dyslexia who had temporal processing deficits, most were affected in either audition or vision; few children were affected in both modalities. The observed deficits suggest that impaired temporal processing in dyslexia is most evident on tasks that require the ability to synthesize local, temporally modulated inputs into a global percept and the ability to extract the resultant global percept from a noisy environment.

Functional analysis of human MT and related visual cortical areas using magnetic resonance imaging

Using noninvasive functional magnetic resonance imaging (fMRI) technique, we analyzed the responses in human area MT with regard to visual motion, color, and luminance contrast sensitivity, and retinotopy. As in previous PET studies, we found that area MT responded selectively to moving (compared to stationary) stimuli. The location of human MT in the present fMRI results is consistent with that of MT in earlier PET and anatomical studies. In addition we found that area MT has a much higher contrast sensitivity than that in several other areas, including primary visual cortex (V1). Functional MRI half-amplitudes in V1 and MT occurred at approximately 15% and 1% luminance contrast, respectively. High sensitivity to contrast and motion in MT have been closely associated with magnocellular stream specialization in nonhuman primates. Human psychophysics indicates that visual motion appears to diminish when moving color-varying stimuli are equated in luminance. Electrophysiological results from macaque MT suggest that the human percept could be due to decreases in firing of area MT cells at equiluminance. We show here that fMRI activity in human MT does in fact decrease at and near individually measured equiluminance. Tests with visuotopically restricted stimuli in each hemifield produced spatial variations in fMRI activity consistent with retinotopy in human homologs of macaque areas V1, V2, V3, and VP. Such activity in area MT appeared much less retinotopic, as in macaque. However, it was possible to measure the interhemispheric spread of fMRI activity in human MT (half amplitude activation across the vertical meridian = approximately 15 degrees).

Motion-contrast sensitivity: visibility of motion gradients of various spatial frequencies

The purpose of our experiments was to estimate basic sensitivity to motion gradients and to evaluate the evidence for second-order integration and differentiation of motion signals. We measured sensitivity to spatially sinusoidal contrast modulation between two oppositely moving bandpass-filtered noise images. The motion-contrast sensitivity function, defined as the inverse of threshold modulation amplitude as a function of modulation spatial frequency, was bandpass in shape with declines at both highest and lowest frequencies. The functions for three noise spatial frequencies had approximately the same shape when modulation frequency was expressed as a fraction of noise frequency. We compared the data with a model in which linear motion filters, whose outputs are squared or rectified, are followed by a second stage of excitatory or inhibitory pooling. The data are consistent with a model in which (1) all excitatory pooling occurs at the linear stage and (2) the second stage contains a large inhibitory pooling area, with a radius approximately eight times that of the linear receptive field.

Selective effects of low doses of apomorphine on spatiotemporal contrast sensitivity in healthy volunteers: a double‐blind placebo‐ controlled study.

1. Apomorphine (1 and 5 micrograms kg-1) and placebo were given to nine normal volunteers, using a Latin-square design and double-blind procedures. The visual perception of static and moving patterns (static and motion contrast sensitivity) was evaluated before and 15 min after the dose administration. 2. Apomorphine (1 and 5 micrograms kg-1), as compared with placebo, led to a significant overall reduction of the visual perception of movement. This effect was dose-related, and apomorphine (5 micrograms kg-1) induced a more pronounced decrease in the visual perception of movement than apomorphine (1 microgram kg-1). With apomorphine (5 micrograms kg-1), the reduction was more pronounced for low spatial frequencies, and was linearly inversely correlated to the spatial frequency for a temporal frequency of 3 Hz. Finally, no significant effect of apomorphine was observed for sensitivity to static patterns. 3. Several non exclusive hypotheses may be suggested: The effects of apomorphine may result from stimulation of retinal D1- and/or D2-dopaminergic receptors. Apomorphine may increase the surround inhibition of ganglion cells' receptive-fields. This modification of the centre-surround balance may explain the decrease in contrast sensitivity for low spatial frequencies. The specific effects of apomorphine on the visual perception of movement support the hypothesis that apomorphine preferentially affects the magnocellular pathway which mediates sensitivity to moving patterns.

Spatiotemporal contrast sensitivity differs in normal aging and Parkinson's disease

We measured contrast sensitivity for static and laterally drifting vertical gratings in 12 young adults, 7 normal elderly adults, and 8 patients with Parkinson's disease (PD). We compared static and motion contrast sensitivity for spatial frequencies of 0.25, 1, and 4 cycles per degree (cpd), and temporal frequencies of 1, 3, and 9 Hz. Results show that normal aging leads to a reduction of motion sensitivity for the spatial frequency of 0.25 cpd. Compared with elderly controls, PD patients do not present specific abnormalities in this domain. However, for spatial frequencies of 1 and 4 cpd and temporal frequencies of 1 and 3 Hz, motion sensitivity is worse than static sensitivity in PD patients and not in elderly controls. These findings suggest a specific deficit of motion perception in PD, and possible dopaminergic involvement in the control of visuospatial behavior.