| Abstract No.: | B-D2157 |
| Country: | Canada |
| | |
| Title: | THE EFFECTS OF AGING ON THE BANDWIDTHS OF DIRECTIONALLY-SELECTIVE MECHANISMS. |
| | |
| Authors/Affiliations: | 2 Lia E. Tsotsos*; 2 Allison B. Sekuler; 1 Patrick J. Bennett;
1 McMaster Univerity, Hamilton, ON, Canada
|
| | |
| Content: | Objectives: Psychophysical studies show that motion detection thresholds are elevated, and the accuracy of perceived direction is diminished, in older human subjects (Bennett et al., 2007, Vision Res, 47, 799-809). This result is consistent with the hypothesis that the bandwidth of directionally-selective channels widens with age. The current experiment examined this hypothesis directly by estimating directional selectivity in groups of young (n=10; mean age = 21) junior senior (n=10; mean age = 65.36) and senior senior (n=13; mean age = 73.46) subjects using a notched-noise masking technique.
Materials and Methods: The stimuli were presentations of random dot kinematograms that drifted coherently to the right (0 deg) or left (180 deg) at 5 deg/sec and were displayed for 500ms. The subject's task was to identify the direction of motion, and thresholds were estimated by varying dot contrast. The dots were embedded within a mask comprised of high-contrast dots that moved in random directions on each frame. The direction of each mask dot was drawn from a random distribution spanning 360 deg, with the restriction that the direction could not fall within the ranges of 0±n and 180±n deg. The width of the noise notch, 2n, was varied from 0 to 179 deg in separate blocks.
Results: Initial analyses found main effects of age and notch width. Additionally, it appears that thresholds decreased more slowly as a function of notch width in older subjects, a result that is consistent with the hypothesis that the bandwidth of directional-selective channels increases with age.
Conclusion: Our preliminary results are consistent with the claim that directionally-selective channels are more broadly tuned in older subjects. We currently are conducting more in-depth analyses and extending this result to other dot speeds and mask contrasts.
|
| | |
| Back |
|
