scholarly journals Age- and frequency-dependent changes in dynamic contrast perception in visual snow syndrome

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Ozan E. Eren ◽  
Andreas Straube ◽  
Florian Schöberl ◽  
Ruth Ruscheweyh ◽  
Thomas Eggert ◽  
...  
Keyword(s):  
Contrast Sensitivity ◽  
Visual Disturbance ◽  
Contrast Threshold ◽  
Frequency Dependent ◽  
Contrast Detection ◽  
Choice Procedure ◽  
Visual Contrast ◽  
Age Related ◽  
Forced Choice Procedure ◽  
Contrast Perception

Abstract Objective Patients with visual snow syndrome (VSS) suffer from a debilitating continuous (“TV noise-like”) visual disturbance. They report problems with vision at night and palinopsia despite normal visual acuity. The underlying pathophysiology of VSS is largely unknown. Currently, it is a clinical diagnosis based on the patient’s history, an objective test is not available. Here, we tested the hypothesis that patients with VSS have an increased threshold for detecting visual contrasts at particular temporal frequencies by measuring dynamic contrast detection-thresholds. Methods Twenty patients with VSS were compared to age-, gender-, migraine- and aura-matched controls in this case-control study. Subjects were shown bars randomly tilted to the left or right, flickering at six different frequencies (15 Hz, 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz). The contrast threshold (CT) for detection of left or right tilt was measured in a two-alternative adaptive forced-choice procedure (QUEST). The threshold was defined as the Michelson contrast necessary to achieve the correct response in 75% of the cases. Results The CT increased for higher flicker frequencies (ANOVA: main effect frequency: F (5,180) = 942; p < 0.001), with an additional significant frequency*diagnosis interaction (ANOVA: F (5,180) = 5.00; p < 0.001). This interaction effect was due to an increased CT at a flicker frequency of 15 Hz in the VSS cohort (VSS: MC = 1.17%; controls: MC = 0.77%). At the other frequencies, group comparisons revealed no differences. Furthermore, in the VSS cohort we observed an increase of CT with higher age (r = 0.69; p < 0.001), which was not seen in controls (r = 0.30; p = 0.20). Conclusions This study demonstrates a lower visual contrast sensitivity exclusively at 15 Hz in VSS patients and demonstrates frequency-dependent differences in dynamic contrast vision. The peak sensitivities of both parvo- and magnocellular visual pathways are close to a frequency of about 10 Hz. Therefore, this frequency seems to be of crucial importance in everyday life. Thus, it seems plausible that the impairment of contrast sensitivity at 15 Hz might be an important pathophysiological correlate of VSS. Furthermore, the overall age-related decrease in contrast sensitivity only in VSS patients underscores the vulnerability of dynamic contrast detection in VSS patients. Dynamic CT detection seems to be a promising neurophysiological test that may contribute to the diagnosis of VSS.

Validation of an On-line Implementation of the Imitative Test of Speech Pattern Contrast Perception (IMSPAC)

2003 ◽  
Vol 14 (02) ◽  
pp. 072-083 ◽  
Author(s):  
Christine Kosky ◽  
Arthur Boothroyd
Keyword(s):  
Training Study ◽  
Auditory Speech ◽  
Auditory Models ◽  
Choice Procedure ◽  
On Line ◽  
Forced Choice Procedure ◽  
Phonetic Contrasts ◽  
Contrast Perception ◽  
Changes Over Time ◽  
Over Time

The imitations of syllables by six children with sensorineural hearing loss were evaluated in a forced-choice procedure, providing information on the production and perception of ten phonetic contrasts. One listener responded on-line. Four listeners responded off-line, to recordings. When all listeners were unfamiliar with the talkers, on- and off-line scores were not significantly different. After a training study, in which the on-line listener was the teacher, on-line scores were 9% pts higher than off-line. There were also task-related improvements in the children's performance. The children's performance increased considerably when text was presented with the auditory models. It is concluded that: children's imitations can provide a measure of auditory speech perception that is not necessarily limited by speech production; imitations can be evaluated on-line without affecting validity - provided that listener is not intimately familiar with the child's speech. Task-related learning on the part of the child should be taken into account when assessing changes over time.

An Assessment of Decision-Making as a Possible Factor in the Age-Related Loss of Contrast Sensitivity

Perception ◽  
1986 ◽  
Vol 15 (5) ◽  
pp. 541-552 ◽  
Author(s):  
James D Morrison ◽  
James Reilly
Keyword(s):  
Decision Making ◽  
Contrast Sensitivity ◽  
Contrast Threshold ◽  
Sinusoidal Grating ◽  
Hit Rate ◽  
Grating Pattern ◽  
Age Related ◽  
Spatial Frequencies ◽  
Young Subjects ◽  
Contrast Thresholds

The possibility that changes in decision-making may contribute to the age-related decline in contrast sensitivity has been investigated in nineteen young subjects (ages 21–38 years) and twenty-seven old subjects (ages 55–92 years). A signal detection paradigm was employed in which the detection of stationary sinusoidal grating patterns was measured at 3 and 15 cycles deg−1 for a range of contrasts which were psychophysically equivalent for each subject. A decline in contrast sensitivity with age at the spatial frequencies studied was confirmed for contrast thresholds obtained both by the ascending method and from the 50% hit rate for detection of the grating pattern. The criterion adopted for decision-making, expressed as both β and percentage bias, did not change significantly between young and old subjects at 15 cycles deg−1. At 3 cycles deg−1, criterion β did not change significantly at x0.8, x1.0, or x1.2 contrast threshold, but at contrast giving 50% hit rate there was a significant increase with age. The percentage bias increased significantly at contrast threshold but not at 50% hit rate. It is inferred from the results that the loss of contrast sensitivity was not accountable in terms of the adoption of a more conservative criterion by older subjects. Hence visual loss in ageing is attributed to changes within the visual pathway rather than within higher decision-making centres.

scholarly journals Contrast Detection Learning Improves Visual Contrast Sensitivity of Cat

2010 ◽  
Vol 31 (2) ◽  
pp. 155-162
Author(s):  
Tian-Miao HUA ◽  
Zhen-Hua WANG ◽  
Jin-Wang XU ◽  
Jian-Gang DIAO
Keyword(s):  
Contrast Sensitivity ◽  
Contrast Detection ◽  
Visual Contrast ◽  
Visual Contrast Sensitivity

scholarly journals Contrast Threshold of a Brisk-Transient Ganglion Cell In Vitro

2003 ◽  
Vol 89 (5) ◽  
pp. 2360-2369 ◽  
Author(s):  
Narender K. Dhingra ◽  
Yen-Hong Kao ◽  
Peter Sterling ◽  
Robert G. Smith
Keyword(s):  
Ganglion Cells ◽  
Probability Distributions ◽  
Linear Interpolation ◽  
Ideal Observer ◽  
In Vivo Studies ◽  
Contrast Threshold ◽  
Choice Procedure ◽  
Forced Choice Procedure

We measured the contrast threshold for mammalian brisk-transient ganglion cells in vitro. Spikes were recorded extracellularly in the intact retina (guinea pig) in response to a spot with sharp onset, flashed for 100 ms over the receptive field center. Probability density functions were constructed from spike responses to stimulus contrasts that bracketed threshold. Then an “ideal observer” (IO) compared additional trials to these probability distributions and decided, using a single-interval, two-alternative forced-choice procedure, which contrasts had most likely been presented. From these decisions we constructed neurometric functions that yielded the threshold contrast by linear interpolation. Based on the number of spikes in a response, the IO detected contrasts as low as 1% [4.2 ± 0.4% (SE); n = 35]; based on the temporal pattern of spikes, the IO detected contrasts as low as 0.8% (2.8 ± 0.2%). Contrast increments above a very low “basal contrast” were discriminated with greater sensitivity than they were detected against the background. Performance was optimal near 37°C and declined with a Q 10 of about 2, similar to that of retinal metabolism. By the method used by previous in vivo studies of brisk-transient cells, our most sensitive cells had similar thresholds. The in vitro measurements thus provide an important benchmark for comparing sensitivity of neurons upstream (cone and bipolar cell) and downstream to assess efficiency of retinal and central circuits.

Pharmacological separation of mechanisms contributing to human contrast sensitivity

1993 ◽  
Vol 10 (6) ◽  
pp. 1073-1079 ◽  
Author(s):  
A. T. Smith ◽  
C. M. Baker-Short
Keyword(s):  
Contrast Sensitivity ◽  
Cholinergic Receptor ◽  
Sensitivity Functions ◽  
Choice Procedure ◽  
Spatial Frequencies ◽  
Arousal System ◽  
Buccal Absorption ◽  
Human Volunteers ◽  
Forced Choice Procedure ◽  
Spatiotemporal Filters

AbstractTwo basic types of cholinergic receptor have been identified in nervous systems: nicotinic and muscarinic. In the mammalian visual system, the balance of evidence suggests that nicotinic activity is associated primarily with transmission and processing of information while muscarinic activity reflects modulatory influences arising in the brainstem and basal forebrain. We have measured contrast sensitivity functions using a two-alternative forced-choice procedure in young human volunteers with and without administration of nicotine (1.5 mg by buccal absorption) or the muscarinic antagonist scopolamine (1.2 mg orally). Scopolamine elevates contrast-detection thresholds uniformly at all spatial frequencies, consistent with blocking of a nonspecific arousal system. Nicotine, in contrast, improves sensitivity at low spatial frequencies (below about 4 cycle/deg); at higher spatial frequencies sensitivity is, if anything, impaired. Using counterphase gratings, we find that scopolamine elevates thresholds uniformly at all temporal frequencies. Nicotine lowers thresholds at high but not low temporal frequencies. The results obtained with nicotine suggest that contrast sensitivity reflects the activity of two mechanisms, or sets of spatiotemporal filters, that are pharmacologically distinct, the contrast sensitivity function reflecting the envelope of their sensitivities.

scholarly journals High Ripple-Density Resolution for Discriminating Between Rippled and Nonrippled Signals: Effect of Temporal Processing or Combination Products?

2021 ◽  
Vol 25 ◽  
pp. 233121652110101
Author(s):  
Dmitry I. Nechaev ◽  
Olga N. Milekhina ◽  
Marina S. Tomozova ◽  
Alexander Y. Supin
Keyword(s):  
Low Frequency ◽  
Noise Signal ◽  
Density Variation ◽  
Choice Procedure ◽  
Masker Level ◽  
Reference Signals ◽  
Forced Choice Procedure ◽  
The Mean ◽  
Density Resolution

The goal of the study was to investigate the role of combination products in the higher ripple-density resolution estimates obtained by discrimination between a spectrally rippled and a nonrippled noise signal than that obtained by discrimination between two rippled signals. To attain this goal, a noise band was used to mask the frequency band of expected low-frequency combination products. A three-alternative forced-choice procedure with adaptive ripple-density variation was used. The mean background (unmasked) ripple-density resolution was 9.8 ripples/oct for rippled reference signals and 21.8 ripples/oct for nonrippled reference signals. Low-frequency maskers reduced the ripple-density resolution. For masker levels from −10 to 10 dB re. signal, the ripple-density resolution for nonrippled reference signals was approximately twice as high as that for rippled reference signals. At a masker level as high as 20 dB re. signal, the ripple-density resolution decreased in both discrimination tasks. This result leads to the conclusion that low-frequency combination products are not responsible for the task-dependent difference in ripple-density resolution estimates.

scholarly journals Visual Contrast Sensitivity in Early-Stage Parkinson's Disease

2016 ◽  
Vol 57 (13) ◽  
pp. 5696 ◽  
Author(s):  
Wendy Ming ◽  
Dimitrios J. Palidis ◽  
Miriam Spering ◽  
Martin J. McKeown
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Contrast Sensitivity ◽  
Early Stage ◽  
Visual Contrast ◽  
Visual Contrast Sensitivity

FUNCTIONAL METHODS OF EARLY DIAGNOSTICS OF AGE MACULAR DEGENERATION.(LITERATURE REVIEW)

2021 ◽  
Vol Special issue (2) ◽  
pp. 61-67
Author(s):  
Azamat Yusupov ◽  
◽  
Mukhiddin Ziyoviddinov ◽  
Shavkat Mukhanov ◽  
O.O. Sobirov
Keyword(s):  
Literature Review ◽  
Macular Degeneration ◽  
Contrast Sensitivity ◽  
Morphological Changes ◽  
Pigment Epithelium ◽  
Sensitivity Study ◽  
Age Related Macular Degeneration ◽  
Functional Diagnostics ◽  
Advantages And Disadvantages ◽  
Age Related

This article provides an unsystematic literature review devoted to analyzing the currently existing methods of functional diagnostics for age-related macular degeneration.The essence, advantages and disadvantages, and literature data on the use of such methods asphotostresstest, electrooculography, dark adaptation study, contrast sensitivity function assessment, light and color sensitivity study,electroretinographyand critical flicker fusion frequencyare described.Based on the analysis of literature data, itis shownthat currently, there is a need to searchfor informative and accessible methods of functional diagnostics in age-related macular degeneration, especially for its early diagnosis. The analysis has shown that the existing methods are mainly aimed either at fixing secondary morphological changes in the layer of pigment epithelial cells, at identifying the pathology of the pigment epithelium in conjunction with determining the function of photoreceptor elements, or at a comprehensive assessment of the structures of several layers of the retina. Keywords:age-related macular degeneration; methods of functional diagnostics; photostress test; electrooculography; contrast sensitivity

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