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

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.

Basic activity of Neurons in the dark during Somnolence induced by Anesthesia

“…In line with previous research, our findings confirm implication of orientation in the discharge of cells. [11,12], and showed that stimuli missing orientation; does not change significantly the responses of interneurons after the second stimulus. Discharge depends strongly of the influence of the second grating with an orientation.…”

Testing the generality of the zoom-lens model: Evidence for visual-pathway specific effects of attended-region size on perception

“…In the absence of a direct experimental manipulation of attended-region size, one would simply be measuring participants' default or current attendedregion size and comparing the effect of an induced region size to this state. There indeed are demonstrable differences in default or preferred attended-region size across different groups, such as for people of different ethnicities, personality, and age groups (Elahipanah, Christensen, & Reingold, 2011;Greenwood & Parasuraman, 2004;Hutchinson, Ledgeway, & Allen, 2014;Kramer, Ellenberg, Leonard, & Share, 1996;McKone et al, 2010;Roalf, Lowery, & Turetsky, 2006;Wilson, Lowe, Ruppel, Pratt, & Ferber, 2016). Such default differences are not an issue here, because all of our key manipulations are manipulated within-subjects rather than between-subjects.…”

Motion perception as a model for perceptual aging

“…Moreover, speed discrimination (Genova & Bocheva, 2013;Norman, Ross, Hawkes, & Long, 2003) as well as motion direction discrimination (Ball & Sekuler, 1986;Bennett et al, 2007;Bocheva, Angelova, & Stefanova, 2013;Bogfjellmo et al, 2013) have been found to decline with increasing age. However, results seem to vary largely depending on stimulus parameters such motion direction (Ball & Sekuler, 1986;Pilz, Miller, & Agnew, 2017), stimulus size (Hutchinson, Ledgeway, & Allen, 2014), contrast (Allen et al, 2010), stimulus duration (Bennett et al, 2007;Conlon, Power, Hine, & Rahaley, 2017), or location (Wojciechowski et al, 1995). Indeed, the mechanisms that modulate age effects are often not well understood, but call for caution when trying to derive overall conclusions on functional changes.…”