Contrast sensitivity in dyslexia

Karen Gross-Glenn, Bernt C. Skottun, William Glenn, Alex Kushch, Robert Lingua, Mark Dunbar, Bonnie Jallad, Herbert A. Lubs, Bonnie Levin, Mark Rabin, Lesley A. Parke, Ranjan Duara

Research output: Contribution to journalArticle

91 Scopus citations

Abstract

Contrast sensitivity was determined for dyslexic and normal readers. When testing with temporally ramped (i.e. stimuli with gradual temporal onsets and offsets) gratings of 0.6, 4.0, and 12.0 cycles/deg, we found no difference in contrast sensitivity between dyslexic readers and controls. Using 12.0 cycles/deg gratings with transient (i.e. abrupt) onsets and offsets, we found that dyslexic individuals had, compared to controls, markedly inferior contrast sensitivity at the shortest stimulus durations (i.e. 17, 34, and 102 ms). This deficit may reflect more sluggish temporal summation. There was no difference in sensitivity to 0.6 cycles/deg gratings with transient onsets and offsets. Under these conditions, the two groups showed a consistent and equal increase in sensitivity relative to the ramped baseline condition at 0.6 cycles/deg at the longer stimulus durations. This demonstrates that dyslexic readers have no deficit in their ability to detect stimulus transients, a finding which appears to be inconsistent with a transient system deficit. That detection of the low-frequency stimuli was mediated by the transient system is further indicated by the fact that these stimuli were more susceptible to forward masking than were the high-frequency stimuli. The effects of masking of both high and low spatial-frequency stimuli were about equal for dyslexic readers and controls. This is not in agreement with the transient system deficit theory, according to which one would expect there to be less masking of high spatial-frequency stimuli in the case of dyslexic readers.

Original languageEnglish (US)
Pages (from-to)153-163
Number of pages11
JournalVisual neuroscience
Volume12
Issue number1
DOIs
StatePublished - Jan 1 1995

Keywords

  • Contrast sensitivity
  • Dyslexia
  • Masking
  • Temporal summation
  • Transient system deficit

ASJC Scopus subject areas

  • Physiology
  • Sensory Systems

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    Gross-Glenn, K., Skottun, B. C., Glenn, W., Kushch, A., Lingua, R., Dunbar, M., Jallad, B., Lubs, H. A., Levin, B., Rabin, M., Parke, L. A., & Duara, R. (1995). Contrast sensitivity in dyslexia. Visual neuroscience, 12(1), 153-163. https://doi.org/10.1017/S0952523800007380