Abstract
Age-related declines in contrast sensitivity have real-world implications for safety among older adults in situations like driving. Such aging effects could be ameliorated by perceptual learning, which improves perceptual performance through repeated exposure or practice with a perceptual task. In this study, older adults completed three days of perceptual learning training in one of three different tasks: binocular orientation discrimination (Group 1), stereoscopic slant in depth (rotation toward vs. away) for Group 2 and Group 3. A 2D Gabor pattern was used in all three tasks. In Group 1 the same patch was presented to both eyes, while in Group 2, the orientation difference appeared in the right eye. In Group 3, the orientation difference could appear in either eye. CSF thresholds were estimated monocularly at five orientations (45 to 135 degrees) before and after training for all participants. Training always occurred at 45 degrees orientation. If improvements on low-level perceptual tasks are found across all groups in both the trained and untrained eyes and orientations, then perceptual learning would be occurring at at later processing stages. This is because binocular information would not be integrated until later stages of visual processing (e.g., V2, IPS, etc.). If improvement occurs for only the trained eye and orientation, then there would be evidence in favor of an early, low-level mechanism (i.e., at V1) since these neurons are limited to monocular visual input at specific orientations. The results showed unique effects of training on eye and orientation for each group on the CSF bandwidth and peak frequency, while all groups improved sensitivity to binocular orientation discrimination. These results suggest that perceptual learning of different features of a stimulus can occur concurrently at both early and later stages of processing.
Acknowledgement: National Institute of Health (Grant #P20GM113109)