June 2004
Volume 4, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2004
Evidence for reduced inhibition in the aging visual system revealed by a motion discrimination task
Author Affiliations
  • Lisa R. Betts
    McMaster University, Canada
Journal of Vision August 2004, Vol.4, 206. doi:10.1167/4.8.206
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      Lisa R. Betts, Christopher P. Taylor, Patrick J. Bennett, Allison B. Sekuler; Evidence for reduced inhibition in the aging visual system revealed by a motion discrimination task. Journal of Vision 2004;4(8):206. doi: 10.1167/4.8.206.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Elderly observers perform worse than their younger counterparts on many perceptual tasks, including contrast detection, orientation discrimination, and motion discrimination. These performance deficits may be linked to age-related changes in cortical perceptual mechanisms, such as the deterioration of inhibitory connections that help to fine-tune the selectivity of visual neurons (Leventhal et al., 2003). Recent psychophysical research with young observers suggests that such inhibitory processes impair motion discrimination for large, high-contrast stimuli (Tadin et al., 2003). We predicted that an age-related reduction in inhibitory processing would therefore benefit elderly observers in a discrimination task using large, high-contrast targets. Stimuli consisted of 1 cpd Gabor gratings drifting at a rate of 2 deg/s. The gratings were presented at two different sizes (0.7 and 2.7 deg) and at three different contrast levels (2.8%, 11% and 43%). A staircase procedure varied stimulus duration to obtain motion discrimination thresholds at 77% accuracy. Consistent with previous findings, duration thresholds for younger observers with low-contrast stimuli improved with increasing stimulus size, whereas thresholds in the high-contrast condition worsened with increasing stimulus size. Elderly observers showed the same pattern of results for low contrast gratings, with a greater improvement as a function of stimulus size compared to young observers. More importantly, as predicted, elderly duration thresholds for high-contrast gratings increased only marginally with increasing stimulus size. Furthermore, elderly thresholds were lower than young thresholds in the condition using the largest, high-contrast stimulus. Additional control experiments showed that the results were not due to age differences in retinal illuminance. The results are consistent with the hypothesis that intra-cortical inhibitory mechanisms, perhaps in area MT, are less potent in elderly observers.

Betts, L. R., Taylor, C. P., Bennett, P. J., Sekuler, A. B.(2004). Evidence for reduced inhibition in the aging visual system revealed by a motion discrimination task [Abstract]. Journal of Vision, 4( 8): 206, 206a, http://journalofvision.org/4/8/206/, doi:10.1167/4.8.206. [CrossRef]
Footnotes
 This research is supported by grants from NSERC and CIHR.
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