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Lindsay E. Farber, Allison B. Sekuler, Patrick J. Bennett; Aging reduces surround suppression effects in a perceived speed task. Journal of Vision 2012;12(9):750. doi: 10.1167/12.9.750.
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In younger adults, direction discrimination for high-contrast patterns becomes more difficult as stimulus size increases (Tadin et al., Nature, 2003, 424, 312-5). Betts et al. (Neuron, 2005, 45, 361-6) found that this effect, known a spatial suppression, is reduced significantly in older adults, and hypothesized that this behavioural finding occurred as a result of decreased GABAergic inhibition in the aging visual system (Leventhal et al., Science, 2003, 300, 812-15). Recently, van der Smagt et al. (Vision Res., 2010, 50, 1900-4) found evidence for spatial suppression in younger adults using a task that measured the perceived speed, rather than the direction, of drifting gratings: perceived speed increased with stimulus size at low contrast, but decreased with increasing size at high contrast. The current experiment examined whether the effects of spatial suppression on speed judgments are reduced in older adults. Nine younger and 11 older subjects compared the speed of a drifting 1 cpd reference grating that varied in size (0.7 & 5 deg diameter) and contrast (2.8 & 92%) across conditions to the speed of a 1 cpd test grating that drifted at 2 deg/sec and whose size (0.7 deg) and contrast (38%) were fixed. Results from younger subjects replicated the main findings reported by van der Smagt et al., but the effect of stimulus size at high contrast was significantly smaller in older subjects. These results are consistent with the hypothesis that aging diminishes the effects of spatial suppression on motion tasks, although suppression may not change for tasks using static stimuli (Karas & McKendrick, J Vis, 2009, 9(5):11, 1-9; Farber et al., VSS 2010 & 2011) .
Meeting abstract presented at VSS 2012
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