An estimation and application of the human cortical magnification factor

Rovamo, Jyrki; Virsu, Veijo

doi:10.1007/bf00236819

Cited by 721 publications

(426 citation statements)

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“…These results confirm the findings of Koenderink et ul. (1978a,b) and Rovamo and Virsu (1979). The pilot experin~ent shows that the same scaling factors apply to both stationary gratings and flickering gratings (for both detection criteria).…”

Section: For An Em-gratingmentioning

confidence: 80%

“…1977, Koenderink ef rrl., 1978a. It has also been found ta hold for measurements of spatial contrast sensitivity functions (Koenderink et al, 1978a;Rovamo et al, X978;Virsu and Rovamo, 1979;Rovamo and Virsu, 1979), of colour discrimination (Noorlander,198t), fetter ~denti~~ation (Anstis. f974), criticaf size for spatiai summation in measuring contrast thresholds for round spots of light (Wilson, 1970) [see Virsu and Rovamo (1979) who plotted the data of Anstis and Wilson against M] and displacement detection (Westheimer, 1979).…”

Section: Introductionmentioning

confidence: 89%

“…Figure 2 shows that the scaling factors (stimulus sizes) determined in the pilot experiment are in accordance with previous estimates of the cortical n~agnificat~on factor. The figure shows the dependence on eccentricity of the cortical magnification factor M [according to the equation of Rovamo and Virsu (1979) for the nasal visual field: dashed linef and the stimulus sizes used in Experiment 1 (squares). The figure further shows how (grating) acuity (so&d circles) and optimum spatial frequency (the spatial frequency for which the contrast threshold is lowest; open symbols) vary with eccentricity.…”

Section: For An Em-gratingmentioning

confidence: 99%

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The sensitivity of the peripheral visual system to amplitude-modulation and frequency-modulation of sine-wave patterns

1984

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Abstract-The det~tabi~~ty ofamp~itud~ modulation and spat% frequency modulation ofsuprat~resh~~ld sine-wave gratings was measured at retinal eccentricities ranging from 0 to 30 deg. The main conclusions to be drawn from the experimental results are: (I) for this visual task it is not possible to bring peripherai sensitivity to the same level as fovea1 sensitivity by scaling the stimuli with the inverse of the cortical magnification factor M. (2) Increasing the number of cycles in the carrier grating improves modulation detectability. For gratings in the periphery this holds up to the largest stimulus size used (6-l cyclrs). In earlier investigations it has been shown that for central vision the improvement ends at about I6 cycles.

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Section: For An Em-gratingmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 89%

Section: For An Em-gratingmentioning

confidence: 99%

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The sensitivity of the peripheral visual system to amplitude-modulation and frequency-modulation of sine-wave patterns

1984

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“…The Virsu and Rovamo model does not necessarily contradict Koenderink and van Doorn's model, in that the cortical representation of a given stimulus is proportional to the square root of RF density of retinal ganglion cells being activated (Rovamo and Virsu, 1979). In an earlier study, however, found that CS is proportional to the square root of the number of stimulated ganglion cells.…”

Section: Models To Predict the Maximum Height Of A Csfmentioning

confidence: 86%

Spatial contrast sensitivity of birds

2006

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Contrast sensitivity (CS) is the ability of the observer to discriminate between adjacent stimuli on the basis of their differences in relative luminosity (contrast) rather than their absolute luminances. Prior to this study, birds had been thought to have low contrast detection thresholds relative to mammals and fishes. This was a surprising phenomenon because birds had been traditionally attributed with superior vision. In addition, the low CS of birds could not be explained by retinal or optical factors, or secondary stimulus characteristics. Unfortunately, avian contrast sensitivity functions (CSFs) were sparse in the literature, so it was unknown whether low contrast sensitivity was a general phenomenon in birds. This study measured CS in six species of birds The quail and pigeon data obtained in this experiment fit well with existing CS data for these species. The kestrel data were not similar to kestrel data in the literature; however the data in the literature were collected from a single subject. All of the birds studied had contrast sensitivities that were consistent with their retinal or optical morphologies relative to other birds (in species for which such data exists) and seem well suited for their natural environments. In addition, all of these birds exhibited low CS relative to humans and most mammals, which suggests that low CS is a general phenomenon of birds.Explanations for this avian low CS phenomenon include a possible trade-off between contrast mechanisms and UV mechanisms in cone systems, and lateral inhibitory mechanisms that are perhaps categorically different from mammals. Lateral inhibition affects contrast gain, and has been shown to differ according to ganglion cell types, which in turn will differ in vertebrate species.

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“…This extension seems plausible, given evidence in the vision literature of a strong degree of invariance in spatial contrast sensitivity with variation in retinal eccentricity when the sensitivity functions are scaled by the so-called cortical magnification factor (Rovamo & Virsu, 1979;Virsu & Rovamo, 1979). However, when it comes to visual character recognition, there are systematic differences between foveal and eccentric viewing that go beyond differences in spatial resolution (Bouma, 197 1;Loomis, 1978).…”

Section: Discussionmentioning

confidence: 99%

A model of character recognition and legibility.

Loomis¹

1990

Journal of Experimental Psychology: Human Perception and Perfor

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This article presents a model of character recognition and the experiments used to develop and test it. The model applies to foveal viewing of blurred or unblurred characters and to tactile sensing of raised characters using the fingerpad. The primary goal of the model is to account for variations in legibility across character sets; a secondary goal is to account for variations in the cell entries of the confusion matrix for a given character set. The model consists of two distinct processing stages. The first involves transformation of each stimulus into an internal representation; this transformation consists of linear low-pass spatial filtering followed by nonlinear compression of stimulus intensity. The second stage involves both template matching of the transformed test stimulus with each of the stored internal representations of the characters within the set and response selection, which is assumed to conform to the unbiased choice model of Luce (1963). Though purely stimulus driven, the model accounts quite well for differences in the legibility of character sets differing in character type, size of character, and number of characters within the set; it is somewhat less successful in accounting for the details of each confusion matrix.Over the years much effort has been devoted to the study of character recognition and legibility in perceptual psychology. Many of the experimental studies in vision have been motivated by applied concerns, such as determining optimal character types for print and computer displays (e.g., Berger, 1944;Maddox, Burnette, & Gutmann, 1977;S. L. Smith, 1978S. L. Smith, , 1979Tinker, 1963) and assessing how various factorssuch as achromatic and chromatic contrast, character size, and display resolution-influence character legibility (e.g., Arps, Erdmann, Neal, & Schlaepfer, 1969; Pastoor, Schwarz, & Beldie, 1983; S. L. Smith, 1979;Snyder & Taylor, 1979;Tinker, 1963;Van Nes & Bouma, 1980). Similarly, many tactile studies, especially in earlier years, have been concerned with optimizing raised print and graphics symbols (Biirklen, 1932;Gill & James, 1973;Nolan & Kederis, 1969; Nolan & Moms, 1971; Uniform Type Committee of the American Association of Workers for the Blind, 19 13, 19 15). In recent years there has been a shift, in both vision and touch research, toward more basic research concerned with understanding This research was supported by Grant 15 129 from NINCDS and by a grant from the Academic Senate of the University of California, Santa Barbara. The model was presented at the 1985 meetings of the Psychonomic Society and of the Psychological Society of Ribeirlo Preto, Slo Paulo, Brazil. The author is grateful to Gregory Ashby, Naofumi Fujita, Dominic Massaro, and James Townsend for helpful comments.On request, the author will provide an IBM 1.2 MB floppy disk containing the following: (a) a program for editing character sets, (b) the seven character sets of Experiment 1, (c) a C program implementing the model, and (d) the empirical and theoretical confusion matrices deal...

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An estimation and application of the human cortical magnification factor

Cited by 721 publications

References 32 publications

The sensitivity of the peripheral visual system to amplitude-modulation and frequency-modulation of sine-wave patterns

The sensitivity of the peripheral visual system to amplitude-modulation and frequency-modulation of sine-wave patterns

Spatial contrast sensitivity of birds

A model of character recognition and legibility.

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