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The ups and downs of global motion perception: a paradoxical advantage for smaller stimuli in the aging visual system.

Hutchinson CV, Ledgeway T, Allen HA - Front Aging Neurosci (2014)

Bottom Line: We found that older adults' performance was relatively unaffected by changes in aperture size, the number and density of local elements in the display.These findings suggest that the normal (disease-free) aging process does not lead to a general decline in perceptual ability and in some cases may be visually advantageous.These include age-related changes in spatial summation, reduced cortical inhibition, neural blur and attentional resource allocation.

View Article: PubMed Central - PubMed

Affiliation: College of Medicine, Biological Sciences and Psychology, School of Psychology, University of Leicester Leicester, UK.

ABSTRACT
Recent evidence suggests that normal aging is typically accompanied by impairment in the ability to perceive the global (overall) motion of visual objects in the world. The purpose of this study was to examine the interplay between age-related changes in the ability to perceive translational global motion (up vs. down) and important factors such as the spatial extent (size) over which movement occurs and how cluttered the moving elements are (density). We used random dot kinematograms (RDKs) and measured motion coherence thresholds (% signal elements required to reliably discriminate global direction) for young and older adults. We did so as a function of the number and density of local signal elements, and the aperture area in which they were displayed. We found that older adults' performance was relatively unaffected by changes in aperture size, the number and density of local elements in the display. In young adults, performance was also insensitive to element number and density but was modulated markedly by display size, such that motion coherence thresholds decreased as aperture area increased (participants required fewer local elements to move coherently to determine the overall image direction). With the smallest apertures tested, young participants' motion coherence thresholds were considerably higher (~1.5 times worse) than those of their older counterparts. Therefore, when RDK size is relatively small, older participants were actually better than young participants at processing global motion. These findings suggest that the normal (disease-free) aging process does not lead to a general decline in perceptual ability and in some cases may be visually advantageous. The results have important implications for the understanding of the consequences of aging on visual function and a number of potential explanations are explored. These include age-related changes in spatial summation, reduced cortical inhibition, neural blur and attentional resource allocation.

No MeSH data available.


Related in: MedlinePlus

Experiment 2: Mean global motion coherence thresholds for “young” and “old” participants as a function of aperture area. Dot density remained constant (1.13 dots/deg2) across conditions such that a two-fold increase in aperture area (in the range 14–227 deg2) corresponded to an equivalent increase in dot number (in the range 16–256 dots). Error bars = ±1 S.E.M.
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Figure 3: Experiment 2: Mean global motion coherence thresholds for “young” and “old” participants as a function of aperture area. Dot density remained constant (1.13 dots/deg2) across conditions such that a two-fold increase in aperture area (in the range 14–227 deg2) corresponded to an equivalent increase in dot number (in the range 16–256 dots). Error bars = ±1 S.E.M.

Mentions: To separate the effects of aperture size and dot density, in Experiment 2, dot number increased with increasing aperture area such that dot density remained constant across conditions at 1.13 dots/deg2. Mean global motion coherence for younger and older participants as a function of aperture size are shown in Figure 3. Even when dot density remained constant the findings were comparable to those in Experiment 1. A 2 (age) × 5 (aperture size) mixed ANOVA again showed a significant interaction between age and aperture size [F(4,88) = 7.945, p < 0.0001]. For younger participants, motion coherence thresholds decreased significantly as aperture size increased [F(4,64) = 6.042, p < 0.0001]. For older participants performance remained relatively consistent irrespective of the spatial extent of the image [F(4,54) = 1.956, ns]. For large apertures (≥~113 deg2), there was no significant difference between younger and older participants’ performance, but for smaller aperture sizes younger participants motion coherence thresholds were higher than older participants (see Table 2 for further details).


The ups and downs of global motion perception: a paradoxical advantage for smaller stimuli in the aging visual system.

Hutchinson CV, Ledgeway T, Allen HA - Front Aging Neurosci (2014)

Experiment 2: Mean global motion coherence thresholds for “young” and “old” participants as a function of aperture area. Dot density remained constant (1.13 dots/deg2) across conditions such that a two-fold increase in aperture area (in the range 14–227 deg2) corresponded to an equivalent increase in dot number (in the range 16–256 dots). Error bars = ±1 S.E.M.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126366&req=5

Figure 3: Experiment 2: Mean global motion coherence thresholds for “young” and “old” participants as a function of aperture area. Dot density remained constant (1.13 dots/deg2) across conditions such that a two-fold increase in aperture area (in the range 14–227 deg2) corresponded to an equivalent increase in dot number (in the range 16–256 dots). Error bars = ±1 S.E.M.
Mentions: To separate the effects of aperture size and dot density, in Experiment 2, dot number increased with increasing aperture area such that dot density remained constant across conditions at 1.13 dots/deg2. Mean global motion coherence for younger and older participants as a function of aperture size are shown in Figure 3. Even when dot density remained constant the findings were comparable to those in Experiment 1. A 2 (age) × 5 (aperture size) mixed ANOVA again showed a significant interaction between age and aperture size [F(4,88) = 7.945, p < 0.0001]. For younger participants, motion coherence thresholds decreased significantly as aperture size increased [F(4,64) = 6.042, p < 0.0001]. For older participants performance remained relatively consistent irrespective of the spatial extent of the image [F(4,54) = 1.956, ns]. For large apertures (≥~113 deg2), there was no significant difference between younger and older participants’ performance, but for smaller aperture sizes younger participants motion coherence thresholds were higher than older participants (see Table 2 for further details).

Bottom Line: We found that older adults' performance was relatively unaffected by changes in aperture size, the number and density of local elements in the display.These findings suggest that the normal (disease-free) aging process does not lead to a general decline in perceptual ability and in some cases may be visually advantageous.These include age-related changes in spatial summation, reduced cortical inhibition, neural blur and attentional resource allocation.

View Article: PubMed Central - PubMed

Affiliation: College of Medicine, Biological Sciences and Psychology, School of Psychology, University of Leicester Leicester, UK.

ABSTRACT
Recent evidence suggests that normal aging is typically accompanied by impairment in the ability to perceive the global (overall) motion of visual objects in the world. The purpose of this study was to examine the interplay between age-related changes in the ability to perceive translational global motion (up vs. down) and important factors such as the spatial extent (size) over which movement occurs and how cluttered the moving elements are (density). We used random dot kinematograms (RDKs) and measured motion coherence thresholds (% signal elements required to reliably discriminate global direction) for young and older adults. We did so as a function of the number and density of local signal elements, and the aperture area in which they were displayed. We found that older adults' performance was relatively unaffected by changes in aperture size, the number and density of local elements in the display. In young adults, performance was also insensitive to element number and density but was modulated markedly by display size, such that motion coherence thresholds decreased as aperture area increased (participants required fewer local elements to move coherently to determine the overall image direction). With the smallest apertures tested, young participants' motion coherence thresholds were considerably higher (~1.5 times worse) than those of their older counterparts. Therefore, when RDK size is relatively small, older participants were actually better than young participants at processing global motion. These findings suggest that the normal (disease-free) aging process does not lead to a general decline in perceptual ability and in some cases may be visually advantageous. The results have important implications for the understanding of the consequences of aging on visual function and a number of potential explanations are explored. These include age-related changes in spatial summation, reduced cortical inhibition, neural blur and attentional resource allocation.

No MeSH data available.


Related in: MedlinePlus