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Visual Contextual Effects of Orientation, Contrast, Flicker, and Luminance: All Are Affected by Normal Aging.

Nguyen BN, McKendrick AM - Front Aging Neurosci (2016)

Bottom Line: The perception of a visual stimulus can be markedly altered by spatial interactions between the stimulus and its surround.Such center-surround interactions in visual perception are numerous and arise from both cortical and pre-cortical neural circuitry.Here, we compare the perception of older and younger observers on a battery of tasks designed to assess such visual contextual effects.

View Article: PubMed Central - PubMed

Affiliation: Department of Optometry and Vision Sciences, University of Melbourne, Parkville VIC, Australia.

ABSTRACT
The perception of a visual stimulus can be markedly altered by spatial interactions between the stimulus and its surround. For example, a grating stimulus appears lower in contrast when surrounded by a similar pattern of higher contrast: a phenomenon known as surround suppression of perceived contrast. Such center-surround interactions in visual perception are numerous and arise from both cortical and pre-cortical neural circuitry. For example, perceptual surround suppression of luminance and flicker are predominantly mediated pre-cortically, whereas contrast and orientation suppression have strong cortical contributions. Here, we compare the perception of older and younger observers on a battery of tasks designed to assess such visual contextual effects. For all visual dimensions tested (luminance, flicker, contrast, and orientation), on average the older adults showed greater suppression of central targets than the younger adult group. The increase in suppression was consistent in magnitude across all tasks, suggesting that normal aging produces a generalized, non-specific alteration to contextual processing in vision.

No MeSH data available.


Related in: MedlinePlus

The magnitude of contextual effects across different tasks in older observers.Z-scores were calculated relative to the younger group performance. The shaded area is where 95% of the younger participants’ data lies (1.96 standard deviations from the mean). Positive z-scores indicate stronger suppression relative to the younger group mean, taking into account task variability. Error bars are the 95% confidence limits of the mean. There was no group difference in Z-scores across all tasks, F(3,98.15) = 0.23, p = 0.87.
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Figure 4: The magnitude of contextual effects across different tasks in older observers.Z-scores were calculated relative to the younger group performance. The shaded area is where 95% of the younger participants’ data lies (1.96 standard deviations from the mean). Positive z-scores indicate stronger suppression relative to the younger group mean, taking into account task variability. Error bars are the 95% confidence limits of the mean. There was no group difference in Z-scores across all tasks, F(3,98.15) = 0.23, p = 0.87.

Mentions: and μ1 and μ2 are the mean suppression indices for the younger and older groups, respectively, and σ1 and σ2 are the standard deviations. Effect sizes were medium-large (Cohen’s d > 0.5) for all stimuli tested (luminance: d = 1.30, flicker: d = 0.73, contrast: d = 1.22, orientation: d = 0.72). To take into account differences in task variability, suppression indices were normalized against the performance of the control group (z-scores; Figure 4). The relative increase in surround suppression in older adults (increased positive z-score) was not stimulus-dependent [group × stimulus interaction: F(3,98.15) = 0.23, p = 0.87]. Thus, differences in contextual effects between older and younger observers appear to be widespread and of similar magnitude (medium–large effect size) across different visual dimensions.


Visual Contextual Effects of Orientation, Contrast, Flicker, and Luminance: All Are Affected by Normal Aging.

Nguyen BN, McKendrick AM - Front Aging Neurosci (2016)

The magnitude of contextual effects across different tasks in older observers.Z-scores were calculated relative to the younger group performance. The shaded area is where 95% of the younger participants’ data lies (1.96 standard deviations from the mean). Positive z-scores indicate stronger suppression relative to the younger group mean, taking into account task variability. Error bars are the 95% confidence limits of the mean. There was no group difference in Z-scores across all tasks, F(3,98.15) = 0.23, p = 0.87.
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Related In: Results  -  Collection

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Figure 4: The magnitude of contextual effects across different tasks in older observers.Z-scores were calculated relative to the younger group performance. The shaded area is where 95% of the younger participants’ data lies (1.96 standard deviations from the mean). Positive z-scores indicate stronger suppression relative to the younger group mean, taking into account task variability. Error bars are the 95% confidence limits of the mean. There was no group difference in Z-scores across all tasks, F(3,98.15) = 0.23, p = 0.87.
Mentions: and μ1 and μ2 are the mean suppression indices for the younger and older groups, respectively, and σ1 and σ2 are the standard deviations. Effect sizes were medium-large (Cohen’s d > 0.5) for all stimuli tested (luminance: d = 1.30, flicker: d = 0.73, contrast: d = 1.22, orientation: d = 0.72). To take into account differences in task variability, suppression indices were normalized against the performance of the control group (z-scores; Figure 4). The relative increase in surround suppression in older adults (increased positive z-score) was not stimulus-dependent [group × stimulus interaction: F(3,98.15) = 0.23, p = 0.87]. Thus, differences in contextual effects between older and younger observers appear to be widespread and of similar magnitude (medium–large effect size) across different visual dimensions.

Bottom Line: The perception of a visual stimulus can be markedly altered by spatial interactions between the stimulus and its surround.Such center-surround interactions in visual perception are numerous and arise from both cortical and pre-cortical neural circuitry.Here, we compare the perception of older and younger observers on a battery of tasks designed to assess such visual contextual effects.

View Article: PubMed Central - PubMed

Affiliation: Department of Optometry and Vision Sciences, University of Melbourne, Parkville VIC, Australia.

ABSTRACT
The perception of a visual stimulus can be markedly altered by spatial interactions between the stimulus and its surround. For example, a grating stimulus appears lower in contrast when surrounded by a similar pattern of higher contrast: a phenomenon known as surround suppression of perceived contrast. Such center-surround interactions in visual perception are numerous and arise from both cortical and pre-cortical neural circuitry. For example, perceptual surround suppression of luminance and flicker are predominantly mediated pre-cortically, whereas contrast and orientation suppression have strong cortical contributions. Here, we compare the perception of older and younger observers on a battery of tasks designed to assess such visual contextual effects. For all visual dimensions tested (luminance, flicker, contrast, and orientation), on average the older adults showed greater suppression of central targets than the younger adult group. The increase in suppression was consistent in magnitude across all tasks, suggesting that normal aging produces a generalized, non-specific alteration to contextual processing in vision.

No MeSH data available.


Related in: MedlinePlus