Abstract
Previous research has shown that sensitivity to basic aspects of foveally-viewed motion, such as direction and speed, declines with age (e.g., Norman et al., 2003; Snowden & Kavanagh, 2006; Bennett et al., 2007). Although sensitivity to peripheral motion has been studied extensively in younger observers, relatively little is known about the effects of aging on peripheral motion perception, despite its importance for navigation and balance. The current experiment tested peripheral direction discrimination in three groups of 8 observers: younger (70, mean age=74). Stimuli were 500 ms presentations of random dot kinematograms that drifted coherently to the right or left at 5 deg/sec, displayed within a 3 deg wide annulus with its inner radius at an eccentricity of 5.5 deg. The subject's task was to identify the direction of motion of 25 target dots while fixating centrally, and thresholds were estimated by varying target contrast across trials. Target dots were embedded within a mask comprising 475 dots that moved in random directions on each frame. The contrast of the mask dots was varied across blocks. A 3 (Group) × 4 (Contrast) ANOVA found significant main effects of Group and Contrast, and a significant Group × Contrast interaction. Post-hoc tests showed that, at each mask contrast, younger subjects had lower thresholds than seniors, but the two senior groups did not differ. Our preliminary analyses suggest that the effects of aging on peripheral motion sensitivity do not differ significantly from the effects found with similar foveally-viewed stimuli (Tsotsos et al., 2008). We are expanding this result by examining the effects of attention and varying the eccentricity of our stimuli.
NSERC, CIHR Training Grant: Communication & Social Interaction in Healthy Aging.