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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

Responses in the center region-of-interest.a) The mean ± s.e.m. of the BOLD signal changes averaged over 10 subjects. b) Outward surround alone signals for one subject projected to the unfolded surface of primary visual cortex. The white continuous curve marks the area activated by the center alone localizer with 100% contrast. c) Same as b but for the inward surround. d) Number of significantly activated voxels in the surround only conditions.
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pone-0057906-g005: Responses in the center region-of-interest.a) The mean ± s.e.m. of the BOLD signal changes averaged over 10 subjects. b) Outward surround alone signals for one subject projected to the unfolded surface of primary visual cortex. The white continuous curve marks the area activated by the center alone localizer with 100% contrast. c) Same as b but for the inward surround. d) Number of significantly activated voxels in the surround only conditions.

Mentions: Figure 5a shows the BOLD signals that the center, the inward and the outward surrounds alone and combined with the center produced in the center region-of-interest. All of these stimuli evoked signals in the center region-of-interest that deviated statistically significantly from zero (one-sample t-test). The BOLD signal changes were 0.88±0.07% (t(9) = 12.9, p<0.001) for the center, 0.33±0.09% (t (9) = 3.58, p<0.01) for the inward surround alone and 0.46±0.12% (t(9) = 3.78, p<0.01) for the outward surround alone. The inward surround combined with the center produced 0.77±0.09% (t(9) = 9.02, p<0.001) BOLD signal change and the outward surround combined with the center 0.70±0.10% (t(9) = 7.07, p<0.001). The BOLD signal change was significantly lower when the outward surround was combined with the center, compared to the center presented alone (paired one tailed t-test, t(9) = 2.01, p<0.05). The same test for the center alone versus inward surround combined with the center was not statistically significant (paired one tailed t-test, t(9) = 1.23, p = 0.13). The BOLD signal change difference between the inward and outward surrounds was not significant neither when the surrounds were combined with the center (paired two-tailed t-test, t(9) = 0.98, p = 0.35) nor when they were presented alone (paired two-tailed t-test, t(9) = 0.87, p = 0.41).


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

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

Responses in the center region-of-interest.a) The mean ± s.e.m. of the BOLD signal changes averaged over 10 subjects. b) Outward surround alone signals for one subject projected to the unfolded surface of primary visual cortex. The white continuous curve marks the area activated by the center alone localizer with 100% contrast. c) Same as b but for the inward surround. d) Number of significantly activated voxels in the surround only conditions.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585267&req=5

pone-0057906-g005: Responses in the center region-of-interest.a) The mean ± s.e.m. of the BOLD signal changes averaged over 10 subjects. b) Outward surround alone signals for one subject projected to the unfolded surface of primary visual cortex. The white continuous curve marks the area activated by the center alone localizer with 100% contrast. c) Same as b but for the inward surround. d) Number of significantly activated voxels in the surround only conditions.
Mentions: Figure 5a shows the BOLD signals that the center, the inward and the outward surrounds alone and combined with the center produced in the center region-of-interest. All of these stimuli evoked signals in the center region-of-interest that deviated statistically significantly from zero (one-sample t-test). The BOLD signal changes were 0.88±0.07% (t(9) = 12.9, p<0.001) for the center, 0.33±0.09% (t (9) = 3.58, p<0.01) for the inward surround alone and 0.46±0.12% (t(9) = 3.78, p<0.01) for the outward surround alone. The inward surround combined with the center produced 0.77±0.09% (t(9) = 9.02, p<0.001) BOLD signal change and the outward surround combined with the center 0.70±0.10% (t(9) = 7.07, p<0.001). The BOLD signal change was significantly lower when the outward surround was combined with the center, compared to the center presented alone (paired one tailed t-test, t(9) = 2.01, p<0.05). The same test for the center alone versus inward surround combined with the center was not statistically significant (paired one tailed t-test, t(9) = 1.23, p = 0.13). The BOLD signal change difference between the inward and outward surrounds was not significant neither when the surrounds were combined with the center (paired two-tailed t-test, t(9) = 0.98, p = 0.35) nor when they were presented alone (paired two-tailed t-test, t(9) = 0.87, p = 0.41).

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