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Fovea-periphery axis symmetry of surround modulation in the human visual system.

Nurminen L, Kilpeläinen M, Vanni S - PLoS ONE (2013)

Bottom Line: We measured surround modulation of blood-oxygenation-level-dependent signal and perceived contrast with surrounds that extended either towards the periphery or the fovea from a center stimulus, centered at 6° eccentricity.This design compares the effects of two surrounds which are identical in visual field size, but differ in the sizes of their cortical representations.Although the fovea-periphery anisotropy affects nearly all aspects of spatial vision, our results suggest that in surround modulation the visual system compensates for it.

View Article: PubMed Central - PubMed

Affiliation: Brain Research Unit, O.V. Lounasmaa Laboratory, Aalto University, Espoo, Finland. lnurmin@neuro.hut.fi

ABSTRACT
A visual stimulus activates different sized cortical area depending on eccentricity of the stimulus. Here, our aim is to understand whether the visual field size of a stimulus or cortical size of the corresponding representation determines how strongly it interacts with other stimuli. We measured surround modulation of blood-oxygenation-level-dependent signal and perceived contrast with surrounds that extended either towards the periphery or the fovea from a center stimulus, centered at 6° eccentricity. This design compares the effects of two surrounds which are identical in visual field size, but differ in the sizes of their cortical representations. The surrounds produced equally strong suppression, which suggests that visual field size of the surround determines suppression strength. A modeled population of neuronal responses, in which all the parameters were experimentally fixed, captured the pattern of results both in psychophysics and functional magnetic resonance imaging. Although the fovea-periphery anisotropy affects nearly all aspects of spatial vision, our results suggest that in surround modulation the visual system compensates for it.

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Related in: MedlinePlus

The stimuli and their corresponding cortical representations.Upper row illustrates the two surrounds types and the center used in this study. The lower row depicts canonical cortical surface representations of the same stimuli computed using the Schwarz [47] formula. The red color indicates here and below the outward surround and black the inward surround.
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pone-0057906-g001: The stimuli and their corresponding cortical representations.Upper row illustrates the two surrounds types and the center used in this study. The lower row depicts canonical cortical surface representations of the same stimuli computed using the Schwarz [47] formula. The red color indicates here and below the outward surround and black the inward surround.

Mentions: In the surround modulation experiment, the test stimuli consisted of gratings in center-surround configuration (Figure 1). Diameter of the center was 1.8°. The outer radius of the surround hemi-annulus was always 5 degrees. Five gap sizes between the center and surround were used (0.1, 0.35, 0.6, 1.1 and 2.1°). Sharp edges of the stimuli were smoothed with a Gaussian filter (SD 6 pixels). We adopt terminology from Petrov et al. [37] and term the surround extending towards the fovea inward surround and the one extending towards the periphery the outward surround. The comparison stimulus was identical with the test center, except for the contrast which was varied.


Fovea-periphery axis symmetry of surround modulation in the human visual system.

Nurminen L, Kilpeläinen M, Vanni S - PLoS ONE (2013)

The stimuli and their corresponding cortical representations.Upper row illustrates the two surrounds types and the center used in this study. The lower row depicts canonical cortical surface representations of the same stimuli computed using the Schwarz [47] formula. The red color indicates here and below the outward surround and black the inward surround.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585267&req=5

pone-0057906-g001: The stimuli and their corresponding cortical representations.Upper row illustrates the two surrounds types and the center used in this study. The lower row depicts canonical cortical surface representations of the same stimuli computed using the Schwarz [47] formula. The red color indicates here and below the outward surround and black the inward surround.
Mentions: In the surround modulation experiment, the test stimuli consisted of gratings in center-surround configuration (Figure 1). Diameter of the center was 1.8°. The outer radius of the surround hemi-annulus was always 5 degrees. Five gap sizes between the center and surround were used (0.1, 0.35, 0.6, 1.1 and 2.1°). Sharp edges of the stimuli were smoothed with a Gaussian filter (SD 6 pixels). We adopt terminology from Petrov et al. [37] and term the surround extending towards the fovea inward surround and the one extending towards the periphery the outward surround. The comparison stimulus was identical with the test center, except for the contrast which was varied.

Bottom Line: We measured surround modulation of blood-oxygenation-level-dependent signal and perceived contrast with surrounds that extended either towards the periphery or the fovea from a center stimulus, centered at 6° eccentricity.This design compares the effects of two surrounds which are identical in visual field size, but differ in the sizes of their cortical representations.Although the fovea-periphery anisotropy affects nearly all aspects of spatial vision, our results suggest that in surround modulation the visual system compensates for it.

View Article: PubMed Central - PubMed

Affiliation: Brain Research Unit, O.V. Lounasmaa Laboratory, Aalto University, Espoo, Finland. lnurmin@neuro.hut.fi

ABSTRACT
A visual stimulus activates different sized cortical area depending on eccentricity of the stimulus. Here, our aim is to understand whether the visual field size of a stimulus or cortical size of the corresponding representation determines how strongly it interacts with other stimuli. We measured surround modulation of blood-oxygenation-level-dependent signal and perceived contrast with surrounds that extended either towards the periphery or the fovea from a center stimulus, centered at 6° eccentricity. This design compares the effects of two surrounds which are identical in visual field size, but differ in the sizes of their cortical representations. The surrounds produced equally strong suppression, which suggests that visual field size of the surround determines suppression strength. A modeled population of neuronal responses, in which all the parameters were experimentally fixed, captured the pattern of results both in psychophysics and functional magnetic resonance imaging. Although the fovea-periphery anisotropy affects nearly all aspects of spatial vision, our results suggest that in surround modulation the visual system compensates for it.

Show MeSH
Related in: MedlinePlus