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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

(A) Schematic of the two-interval forced choice (2IFC) procedure used throughout the testing. The first interval (500 ms) contained the variable target (0.67° radius) with no surround. The second interval (500 ms) contained the fixed, reference target that was either presented without a surround (‘no surround’ condition), or with a surround as depicted here (‘surround’ condition, 4° radius annulus). The interstimulus interval was 500 ms. Four white nonius lines appeared before and after each trial to assist with central fixation. The stimulus shown here is an example of the luminance task. Example ‘surround’ stimuli for the (B) contrast task and (C) orientation task.
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Figure 1: (A) Schematic of the two-interval forced choice (2IFC) procedure used throughout the testing. The first interval (500 ms) contained the variable target (0.67° radius) with no surround. The second interval (500 ms) contained the fixed, reference target that was either presented without a surround (‘no surround’ condition), or with a surround as depicted here (‘surround’ condition, 4° radius annulus). The interstimulus interval was 500 ms. Four white nonius lines appeared before and after each trial to assist with central fixation. The stimulus shown here is an example of the luminance task. Example ‘surround’ stimuli for the (B) contrast task and (C) orientation task.

Mentions: Participants typically required 2 h to complete all of the tasks including regular rest breaks. There were eight tasks in total: four stimuli (luminance, flicker, contrast, and orientation) and two conditions (‘surround’ and ‘no surround’). The ‘no surround’ condition (0.67° radius center stimulus only) was tested first, followed by the ‘surround’ condition (center + 4° radius surround). The inclusion of a ‘no surround’ condition was important to establish that participants were able to accurately judge the stimuli (the specific judgments required are described below) and to account for any baseline biases. The order of the four stimuli was randomized for every participant and counterbalanced between older and younger groups to avoid order-dependent effects of learning or fatigue. Each task was tested twice using a Method of Constant Stimuli (MOCS) consisting of seven stimulus levels of 10 repeats (total 140 presentations per condition). For training purposes and to decide which stimulus levels to formally test for the ‘surround’ conditions, an initial abbreviated MOCS was performed (10 levels, two trials each). On each trial, participants viewed two stimuli (500 ms duration each) that were presented one after the other (two-interval forced choice, 2IFC) separated by a 500 ms interstimulus interval (Figure 1A). All stimuli shown were supra-threshold. Fixation was assisted by four white nonius lines, which appeared after each trial and disappeared during stimulus presentations.


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

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

(A) Schematic of the two-interval forced choice (2IFC) procedure used throughout the testing. The first interval (500 ms) contained the variable target (0.67° radius) with no surround. The second interval (500 ms) contained the fixed, reference target that was either presented without a surround (‘no surround’ condition), or with a surround as depicted here (‘surround’ condition, 4° radius annulus). The interstimulus interval was 500 ms. Four white nonius lines appeared before and after each trial to assist with central fixation. The stimulus shown here is an example of the luminance task. Example ‘surround’ stimuli for the (B) contrast task and (C) orientation task.
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Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834301&req=5

Figure 1: (A) Schematic of the two-interval forced choice (2IFC) procedure used throughout the testing. The first interval (500 ms) contained the variable target (0.67° radius) with no surround. The second interval (500 ms) contained the fixed, reference target that was either presented without a surround (‘no surround’ condition), or with a surround as depicted here (‘surround’ condition, 4° radius annulus). The interstimulus interval was 500 ms. Four white nonius lines appeared before and after each trial to assist with central fixation. The stimulus shown here is an example of the luminance task. Example ‘surround’ stimuli for the (B) contrast task and (C) orientation task.
Mentions: Participants typically required 2 h to complete all of the tasks including regular rest breaks. There were eight tasks in total: four stimuli (luminance, flicker, contrast, and orientation) and two conditions (‘surround’ and ‘no surround’). The ‘no surround’ condition (0.67° radius center stimulus only) was tested first, followed by the ‘surround’ condition (center + 4° radius surround). The inclusion of a ‘no surround’ condition was important to establish that participants were able to accurately judge the stimuli (the specific judgments required are described below) and to account for any baseline biases. The order of the four stimuli was randomized for every participant and counterbalanced between older and younger groups to avoid order-dependent effects of learning or fatigue. Each task was tested twice using a Method of Constant Stimuli (MOCS) consisting of seven stimulus levels of 10 repeats (total 140 presentations per condition). For training purposes and to decide which stimulus levels to formally test for the ‘surround’ conditions, an initial abbreviated MOCS was performed (10 levels, two trials each). On each trial, participants viewed two stimuli (500 ms duration each) that were presented one after the other (two-interval forced choice, 2IFC) separated by a 500 ms interstimulus interval (Figure 1A). All stimuli shown were supra-threshold. Fixation was assisted by four white nonius lines, which appeared after each trial and disappeared during stimulus presentations.

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