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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

Area summation functions.Each panel depicts the data of one subject. Smooth lines represent the fitted difference-of-integrals of Gaussians function. Vertical dashed lines mark the summation and surround field sizes. Errorbars depict the s.e.m.
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pone-0057906-g002: Area summation functions.Each panel depicts the data of one subject. Smooth lines represent the fitted difference-of-integrals of Gaussians function. Vertical dashed lines mark the summation and surround field sizes. Errorbars depict the s.e.m.

Mentions: For each subject, threshold versus pedestal diameter functions were measured and fitted with difference-of-integrals of Gaussians functions (Figure 2). Three quantities were extracted from the fitted functions; summation field size is the pedestal diameter in which the function peaks, surround field size is the smallest pedestal diameter with which the threshold is within 5% of the threshold at the largest pedestal diameter, and suppression strength is the percentage reduction in threshold from the peak to the value at the largest pedestal diameter. Averaged over the subjects, summation field size was 1.71±0.12° (mean ± s.e.m), surround field size was 3.87±0.47° and the suppression strength was 64±5%.


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

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

Area summation functions.Each panel depicts the data of one subject. Smooth lines represent the fitted difference-of-integrals of Gaussians function. Vertical dashed lines mark the summation and surround field sizes. Errorbars depict the s.e.m.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0057906-g002: Area summation functions.Each panel depicts the data of one subject. Smooth lines represent the fitted difference-of-integrals of Gaussians function. Vertical dashed lines mark the summation and surround field sizes. Errorbars depict the s.e.m.
Mentions: For each subject, threshold versus pedestal diameter functions were measured and fitted with difference-of-integrals of Gaussians functions (Figure 2). Three quantities were extracted from the fitted functions; summation field size is the pedestal diameter in which the function peaks, surround field size is the smallest pedestal diameter with which the threshold is within 5% of the threshold at the largest pedestal diameter, and suppression strength is the percentage reduction in threshold from the peak to the value at the largest pedestal diameter. Averaged over the subjects, summation field size was 1.71±0.12° (mean ± s.e.m), surround field size was 3.87±0.47° and the suppression strength was 64±5%.

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