Monophasic Temporal Modulation Increases Apparent Spatial Frequency

Perception ◽  
1974 ◽  
Vol 3 (3) ◽  
pp. 337-353 ◽  
Author(s):  
V Virsu ◽  
G Nyman
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Spatial Effect ◽  
Phase Changes ◽  
Human Vision ◽  
Maximum Effect ◽  
Temporal Modulation ◽  
Flicker Fusion Frequency ◽  
Spatial Phase ◽  
Spatial Frequencies

There are three different types of flicker—monophasic, diphasic, and polyphasic—and they have different spatial consequences with gratings. Monophasic flicker does not alter the spatial phase in time, but spatial phase changes are caused by the other two types. The effects of sinusoidal monophasic flicker on the apparent spatial frequency of sinusoidal gratings were studied in the present experiments by simultaneous spatial-frequency matches. Monophasic temporal modulation increased apparent spatial frequency. The stimulus conditions for producing a maximum effect were (a) a relatively low spatial frequency, (b) a relatively high level of light adaptation, (c) an intermediate temporal frequency (4–8 Hz), and (d) an intermediate contrast. The largest apparent increases exceeded 30%. The magnitude of the spatial effect was correlated with data on temporal resolution and contrast sensitivity collected under the same conditions. The spatial effect had a high correlation with the critical flicker-fusion frequency, and the contrast-sensitivity enhancements caused by the flicker followed functions similar to those of the spatial effect when the spatial frequency and the level of adaptation were varied. We interpret the spatial effect of low-frequency monophasic flicker as evidence that there are channels for spatial frequency in human vision whose spatial tuning depends on the spatial distribution of sensitivity in the receptive fields of single neurones. Flicker at intermediate temporal frequencies decreases the functional effectiveness of centre—surround antagonism, and makes channels otherwise responsive to high spatial frequencies responsive to low spatial frequencies. As the central decoding of channel outputs can be assumed invariant, an increase in the apparent spatial frequency follows from the change of tuning properties if the channels mediate the perception of spatial frequency. An analysis of the variability of spatial frequency matches indicated that spatial frequency discrimination, if considered in relative terms, is independent of the spatial frequency, the mean luminance, and the contrast of gratings within broad ranges of variation.

scholarly journals Neuronal basis of perceptual learning in striate cortex

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Zhen Ren ◽  
Jiawei Zhou ◽  
Zhimo Yao ◽  
Zhengchun Wang ◽  
Nini Yuan ◽  
...  
Keyword(s):  
Spatial Frequency ◽  
Perceptual Learning ◽  
Contrast Sensitivity ◽  
Striate Cortex ◽  
Signal To Noise Ratio ◽  
High Spatial Frequency ◽  
Sensitivity Training ◽  
Spatial Frequencies ◽  
Cortex Area ◽  
Adult Cats

Abstract It is well known that, in humans, contrast sensitivity training at high spatial frequency (SF) not only leads to contrast sensitivity improvement, but also results in an improvement in visual acuity as assessed with gratings (direct effect) or letters (transfer effect). However, the underlying neural mechanisms of this high spatial frequency training improvement remain to be elucidated. In the present study, we examined four properties of neurons in primary visual cortex (area 17) of adult cats that exhibited significantly improved acuity after contrast sensitivity training with a high spatial frequency grating and those of untrained control cats. We found no difference in neuronal contrast sensitivity or tuning width (Width) between the trained and untrained cats. However, the trained cats showed a displacement of the cells’ optimal spatial frequency (OSF) to higher spatial frequencies as well as a larger neuronal signal-to-noise ratio (SNR). Furthermore, both the neuronal differences in OSF and SNR were significantly correlated with the improvement of acuity measured behaviorally. These results suggest that striate neurons might mediate the perceptual learning-induced improvement for high spatial frequency stimuli by an alteration in their spatial frequency representation and by an increased SNR.

Orientation Specificity and Spatial Selectivity in Human Vision

Perception ◽  
1973 ◽  
Vol 2 (1) ◽  
pp. 53-60 ◽  
Author(s):  
J A Movshon ◽  
C Blakemore
Keyword(s):  
Spatial Frequency ◽  
Human Visual System ◽  
Human Vision ◽  
Orientation Tuning ◽  
High Contrast ◽  
Vertical Grating ◽  
Spatial Frequencies ◽  
High Contrast Grating ◽  
Orientation Specificity ◽  
Adaptation Method

An adaptation method is used to determine the orientation specificity of channels sensitive to different spatial frequencies in the human visual system. Comparison between different frequencies is made possible by a data transformation in which orientational effects are expressed in terms of equivalent contrast (the contrast of a vertical grating producing the same adaptational effect as a high-contrast grating of a given orientation). It is shown that, despite great variances in the range of orientations affected by adaptation at different spatial frequencies (±10° to ±50°), the half-width at half-amplitude of the orientation channels does not vary systematically as a function of spatial frequency over the range tested (2·5 to 20 cycles deg−1). Two subjects were used and they showed significantly different orientation tuning across the range of spatial frequencies. The results are discussed with reference to previous determinations of orientation specificity, and to related psychophysical and neurophysiological phenomena.

Spatial Integration of Objectively Equiluminous Chromatic Gratings

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 200-200
Author(s):  
M I Kankaanpää ◽  
J Rovamo ◽  
H T Kukkonen ◽  
J Hallikainen
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Spatial Integration ◽  
Chromatic Contrast ◽  
Shape Difference ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Low Pass ◽  
Chromatic Aberrations ◽  
Chromatic Contrast Sensitivity

Contrast sensitivity functions for achromatic and chromatic gratings tend to be band-pass and low-pass in shape, respectively. Our aim was to test whether spatial integration contributes to the shape difference found at low spatial frequencies. We measured binocular chromatic contrast sensitivity as a function of grating area for objectively equiluminous red - green and blue - yellow chromatic gratings. Chromatic contrast refers to the Michelson contrast of either of the two chromatic component gratings presented in counterphase against the combined background. Grating area ( A) varied from 1 to 256 square cycles ( Af2) at spatial frequencies ( f) of 0.125 – 4.0 cycles deg−1. We used only horizontal gratings at low and medium spatial frequencies to minimise the transverse and longitudinal chromatic aberrations due to ocular optics. At all spatial frequencies studied, chromatic contrast sensitivity increased with grating area. Ac was found to be constant at low spatial frequencies (0.125 – 0.5 cycles deg−1) but decreased in inverse proportion to increasing spatial frequency at 1 – 4 cycles deg−1. Thus, spatial integration depends similarly on spatial frequency for achromatic (Luntinen et al, 1995 Vision Research35 2339 – 2346) and chromatic gratings, and differences in spatial integration do not contribute to the shape difference of the respective contrast sensitivity functions.

Spatio-Chromatic Information Content of Natural Scenes

Perception ◽  
1996 ◽  
Vol 25 (1_suppl) ◽  
pp. 162-162 ◽  
Author(s):  
T Troscianko ◽  
C A Parraga ◽  
G Brelstaff ◽  
D Carr ◽  
K Nelson
Keyword(s):  
Spatial Frequency ◽  
Human Vision ◽  
Natural Scenes ◽  
Data Set ◽  
Frequency Space ◽  
Sensitivity Functions ◽  
Visual Encoding ◽  
Spatial Frequencies ◽  
Hyper Spectral ◽  
Fourier Spectra

A common assumption in the study of the relationship between human vision and the visual environment is that human vision has developed in order to encode the incident information in an optimal manner. Such arguments have been used to support the 1/f dependence of scene content as a function of spatial frequency. In keeping with this assumption, we ask whether there are any important differences between the luminance and (r/g) chrominance Fourier spectra of natural scenes, the simple expectation being that the chrominance spectrum should be relatively richer in low spatial frequencies than the luminance spectrum, to correspond with the different shape of luminance and chrominance contrast sensitivity functions. We analysed a data set of 29 images of natural scenes (predominantly of vegetation at different distances) which were obtained with a hyper-spectral camera (measuring the scene through a set of 31 wavelength bands in the range 400 – 700 nm). The images were transformed to the three Smith — Pokorny cone fundamentals, and further transformed into ‘luminance’ (r+g) and ‘chrominance’ (r-g) images, with various assumptions being made about the relative weighting of the r and g components, and the form of the chrominance response. We then analysed the Fourier spectra of these images using logarithmic intervals in spatial frequency space. This allowed a determination of the total energy within each Fourier band for each of the luminance and chrominance representations. The results strongly indicate that, for the set of scenes studied here, there was no evidence of a predominance of low-spatial-frequency chrominance information. Two classes of explanation are possible: (a) that raw Fourier content may not be the main organising principle determining visual encoding of colour, and/or (b) that our scenes were atypical of what may have driven visual evolution. We present arguments in favour of both of these propositions.

Does L/M Cone Opponency Disappear in Human Periphery?

Perception ◽  
10.1068/p5374 ◽  
2005 ◽  
Vol 34 (8) ◽  
pp. 951-959 ◽  
Author(s):  
Kathy T Mullen ◽  
Masato Sakurai ◽  
William Chu
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Sine Wave ◽  
Human Vision ◽  
Peripheral Retina ◽  
Contrast Detection ◽  
Colour Contrast

We have assessed the optimal cone contrast sensitivity across eccentricity in human vision of the two cone-opponent mechanisms [L/M or red-green, and S/(L + M) or blue-yellow] and the luminance mechanism. We have used a novel stimulus, termed a ‘sinring’, that is a radially modulated sine-wave arc, Gaussian enveloped in both angular and radial directions. This stimulus overcomes the problem inherent in Gabor stimuli of confounding stimulus spatial frequency, size, and eccentricity and so allows contrast sensitivity to be tracked accurately into the periphery. Our results show that L/M cone opponency declines steeply across the human periphery and becomes behaviourally absent by 25–30 deg (in the nasal field). This result suggests that any L/M cone-opponent neurons found in primate peripheral retina beyond this limit are unlikely to be significant for colour contrast detection measured behaviourally.

scholarly journals Training for object recognition with increasing spatial frequency: A comparison of deep learning with human vision

2021 ◽  
Author(s):  
Lev Kiar Avberšek ◽  
Astrid Zeman ◽  
Hans P. Op de Beeck
Keyword(s):  
Spatial Frequency ◽  
Poor Performance ◽  
Visual Input ◽  
Human Vision ◽  
Striking Similarity ◽  
Deep Convolutional Neural Networks ◽  
Frequency Information ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Coarse To Fine

AbstractThe ontogenetic development of human vision, and the real-time neural processing of visual input, both exhibit a striking similarity – a sensitivity towards spatial frequencies that progress in a coarse-to-fine manner. During early human development, sensitivity for higher spatial frequencies increases with age. In adulthood, when humans receive new visual input, low spatial frequencies are typically processed first before subsequently guiding the processing of higher spatial frequencies. We investigated to what extent this coarse-to-fine progression might impact visual representations in artificial vision and compared this to adult human representations. We simulated the coarse-to-fine progression of image processing in deep convolutional neural networks (CNNs) by gradually increasing spatial frequency information during training. We compared CNN performance, after standard and coarse-to-fine training, with a wide range of datasets from behavioural and neuroimaging experiments. In contrast to humans, CNNs that are trained using the standard protocol are very insensitive to low spatial frequency information, showing very poor performance in being able to classify such object images. By training CNNs using our coarse-to-fine method, we improved the classification accuracy of CNNs from 0% to 32% on low-pass filtered images taken from the ImageNet dataset. When comparing differently trained networks on images containing full spatial frequency information, we saw no representational differences. Overall, this integration of computational, neural, and behavioural findings shows the relevance of the exposure to and processing of input with a variation in spatial frequency content for some aspects of high-level object representations.

scholarly journals Comparison of CSV-1000 and Metrovision contrast sensitivity tests in normal eyes

2021 ◽  
Vol 2 (2) ◽  
pp. 63-70
Author(s):  
Abolfazl Tahkor ◽  
Javad Heravian Shandiz ◽  
Abbas Azimi Khorasani ◽  
Alireza Ansari Moghadam
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Measurement Methods ◽  
Slit Lamp ◽  
Limits Of Agreement ◽  
Cross Sectional ◽  
Spatial Frequencies ◽  
Sensitivity Tests ◽  
Movement Assessment ◽  
Visual Screening

Background: Measuring contrast sensitivity (CS) allows a better understanding of the visual performance of the human eye. This study aimed to examine the correlation and agreement between the results of two sinewave grating-based CS measurement methods, Metrovision and CSV-1000, in normal eyes. Methods: This cross-sectional, comparative study was performed between December 2018 and April 2019, at an optometry clinic. Subjects underwent comprehensive ocular examinations, which included pupil reflexes, subjective refraction, external eye examinations, smooth pursuit eye movement assessment, the cover–uncover test, and detailed slit-lamp examination of the anterior and posterior segments. Metrovision and CSV-1000 were employed to assess CS under photopic conditions. The correlation and agreement of the results of the two tests were evaluated. Results: CS was measured for 104 normal eyes for 3, 6, 12, and 18 cycles per degree (cpd) spatial frequencies (participants’ mean age ± standard deviation: 37.3 ± 26.4 years). The CSV-1000 measurements were significantly higher for the 3 and 6 cpd spatial frequencies (both P = 0.01); however, at higher spatial frequencies, CS scores were similar. The highest and lowest differences between the two tests were recorded for the 3 cpd spatial frequency and 18 cpd spatial frequency, respectively. Except for the 3 cpd spatial frequency, in both eyes, the findings correlated significantly between the CSV-1000 and Metrovision (P < 0.05). The narrowest and widest limits of agreement between the two tests were found for the 12 and 3 cpd spatial frequencies, respectively. Conclusions: The CSV-1000 method estimated CS higher than the Metrovision method, mostly at lower spatial frequencies. Furthermore, the agreement between the two methods was greater at higher spatial frequencies than at lower frequencies. This should be kept in mind when using the two methods interchangeably in visual screening.

A Comparative Study of the Spatial-Frequency Spectrum of Different Letter Optotypes and its Role in Target Recognition

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 214-214 ◽  
Author(s):  
S A Koskin ◽  
V F Danilichev ◽  
Y E Shelepin
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Frequency Spectrum ◽  
Brain Diseases ◽  
Sinusoidal Grating ◽  
Sensitivity Functions ◽  
Spatial Frequencies ◽  
Wide Range ◽  
Narrow Frequency Band ◽  
Spatial Frequency Spectrum

We studied the contrast sensitivity functions (CSFs) in patients with different eye and brain diseases using a computerised sinusoidal grating test with a wide range of frequencies (0.4 – 19.0 cycles deg−1), the Pelli - Robson chart and a new chart with frequency-filtered Snellen optotypes. The patients had different CSF curves with a decrease of contrast sensitivity in the low, middle, or high frequencies depending on their main disease (refraction anomalies, cataract, glaucoma, neuritis of optic nerve, brain tumours, etc). Analysis showed that optotypes in the Pelli - Robson chart have a wide-range spatial-frequency spectrum, and optotype recognition is determined not only by low spatial frequencies. We find that the recognition of standard Sloan's optotypes is determined mostly by sensitivity in the range of 9.4 – 14.0 cycles deg−1. At the same time we measured contrast sensitivity using the new filtered Snellen optotypes. Our calculations support our earlier suggestions that the new filtered optotypes have a narrow-band spatial-frequency spectrum, thus enabling selective measurement of contrast sensitivity in each narrow frequency band.

scholarly journals Is the DeVries-Rose to Weber Transition Empirically Possible with Sine-Wave Gratings?

2005 ◽  
Vol 8 (2) ◽  
pp. 113-118
Author(s):  
Miguel A. García-Pérez
Keyword(s):  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Light Level ◽  
Sine Wave ◽  
Retinal Illuminance ◽  
Visual Functioning ◽  
Photopic Vision ◽  
Spatial Frequencies ◽  
Grating Acuity ◽  
Sine Wave Gratings

Visual functioning at various retinal illuminance levels is usually measured either by determining grating acuity as a function of light level or by determining how sensitivity to sine-wave gratings changes with retinal illuminance. The former line of research has shown that grating acuity follows a two-branch relationship with retinal illuminance, with the point of discontinuity occurring at the transition from scotopic to photopic vision. Results of the latter line of research have summarily been described as a transition from the DeVries-Rose law to Weber's law, according to which log sensitivity increases linearly with log illuminance with a slope of 0.5 over a range of low illuminances (the DeVries-Rose range) and then levels off and does not increase with further increases of illuminance (the Weber range). This paper aims at determining the compatibility of the results of these two lines of research. We consider empirical constraints from data bearing on the shape of the surface describing contrast sensitivity to sine-wave gratings as a function of spatial frequency and illuminance simultaneously, in order to determine whether they are consistent with a summary description in terms of DeVries-Rose and Weber's laws. Our analysis indicates that, with sine-wave gratings, the DeVries-Rose law can only hold empirically at low spatial frequencies.

Evidence of a Global Oblique Effect in Human Extrafoveal Vision

Perception ◽  
1996 ◽  
Vol 25 (5) ◽  
pp. 523-530 ◽  
Author(s):  
Jonathan S Pointer
Keyword(s):  
Visual Field ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Oblique Effect ◽  
Spatial Summation ◽  
Single Subject ◽  
Frequency Dependency ◽  
Spatial Frequencies ◽  
Sensitivity Data

Analysis of recently published human contrast-sensitivity data obtained along the cardinal and major oblique visual-field meridians of a single subject has demonstrated a consistently greater sensitivity at a given eccentricity to horizontally oriented as compared with obliquely oriented gratings. This difference was evident not only at foveal but also at several eccentric loci over a range of low to medium spatial frequencies. This observation is to be distinguished in extrafoveal fixation from the well-documented oblique effect, which describes the variation in sensitivity with orientation at a single visual-field locus. With periodic stimuli which were well localised in space and frequency, and had comparable spatial-summation properties, a spatial-frequency dependency of what could be termed the global oblique effect could be demonstrated along isoeccentric contours centred on the fovea (eccentricity 0 deg) out to an eccentricity of at least 40 deg.

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