Limits...
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 1: Mean global motion coherence thresholds (% signal dots supporting 79% correct direction discrimination performance) for “young” and “old” participants as a function of aperture area. Dot number remained constant (64 dots) such that a two-fold increase in aperture area (in the range 28–227 deg2) corresponded to a two-fold decrease in dot density (in the range 2.26–0.28 dots/deg2). Error bars = ±1 S.E.M.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4126366&req=5

Figure 2: Experiment 1: Mean global motion coherence thresholds (% signal dots supporting 79% correct direction discrimination performance) for “young” and “old” participants as a function of aperture area. Dot number remained constant (64 dots) such that a two-fold increase in aperture area (in the range 28–227 deg2) corresponded to a two-fold decrease in dot density (in the range 2.26–0.28 dots/deg2). Error bars = ±1 S.E.M.

Mentions: In Experiment 1, dot number remained constant at 64 dots such that dot density decreased as aperture size increased. Findings are presented in Figure 2 which shows mean global motion coherence thresholds (% of signal dots required for 79% correct direction discrimination performance) for younger and older participants as a function of aperture size. Younger participants’ performance was more markedly affected by changes in aperture size/dot density than that of older participants. A 2 (age) × 4 (aperture size) mixed analysis of variance (ANOVA) showed that there was a significant interaction between age and aperture size [F(1.535, 30.709) = 4.568, p < 0.05]. Closer inspection of the data using one-way ANOVA, performed separately for each age group, confirmed that younger participants’ motion coherence thresholds decreased significantly as aperture size increased [F(3, 47) = 5.401, p < 0.005] whereas older participants’ performance remained relatively immune to changes in the spatial aperture [F(3,39) = 1.019, ns]. Furthermore, for conditions in which the aperture size was relatively large (≥~113 deg2), there was no significant difference between younger and older participants’ performance. However at smaller aperture sizes (≤~57 deg2), younger participants exhibited higher motion coherence thresholds (performance was worse) than older participants (see Table 1 for further details of t-test pairwise comparisons).


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 1: Mean global motion coherence thresholds (% signal dots supporting 79% correct direction discrimination performance) for “young” and “old” participants as a function of aperture area. Dot number remained constant (64 dots) such that a two-fold increase in aperture area (in the range 28–227 deg2) corresponded to a two-fold decrease in dot density (in the range 2.26–0.28 dots/deg2). 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 2: Experiment 1: Mean global motion coherence thresholds (% signal dots supporting 79% correct direction discrimination performance) for “young” and “old” participants as a function of aperture area. Dot number remained constant (64 dots) such that a two-fold increase in aperture area (in the range 28–227 deg2) corresponded to a two-fold decrease in dot density (in the range 2.26–0.28 dots/deg2). Error bars = ±1 S.E.M.
Mentions: In Experiment 1, dot number remained constant at 64 dots such that dot density decreased as aperture size increased. Findings are presented in Figure 2 which shows mean global motion coherence thresholds (% of signal dots required for 79% correct direction discrimination performance) for younger and older participants as a function of aperture size. Younger participants’ performance was more markedly affected by changes in aperture size/dot density than that of older participants. A 2 (age) × 4 (aperture size) mixed analysis of variance (ANOVA) showed that there was a significant interaction between age and aperture size [F(1.535, 30.709) = 4.568, p < 0.05]. Closer inspection of the data using one-way ANOVA, performed separately for each age group, confirmed that younger participants’ motion coherence thresholds decreased significantly as aperture size increased [F(3, 47) = 5.401, p < 0.005] whereas older participants’ performance remained relatively immune to changes in the spatial aperture [F(3,39) = 1.019, ns]. Furthermore, for conditions in which the aperture size was relatively large (≥~113 deg2), there was no significant difference between younger and older participants’ performance. However at smaller aperture sizes (≤~57 deg2), younger participants exhibited higher motion coherence thresholds (performance was worse) than older participants (see Table 1 for further details of t-test pairwise comparisons).

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