L/M speed-matching ratio predicts reading in children

Optom Vis Sci. 2007 Mar;84(3):229-36. doi: 10.1097/OPX.0b013e31803399df.


Purpose: Many behavioral studies have found impaired perception of dynamic visual stimuli in dyslexia and several neuroimaging studies have found reduced activation of the human motion area MT+ in dyslexia. These results are often interpreted as a magnocellular (MC) deficit in dyslexia. It has also been claimed that colored filters can help dyslexics to read. One defining feature of the MC-pathway is a greater weight for L-cone input than M-cone input, and at most very weak S-cone input. We measured the subjective speed matches between L-, M-, and S-cone isolating stimuli in good and poor readers.

Methods: Subjects performed a speed-matching task with drifting cone-isolating stimuli to find the point of subjective equality between two drifting patterns. Such a task is known to activate cortical area MT+, presumably via the MC-pathway.

Results: L- to M-cone speed-match ratios were negatively correlated with single-word (r=-0.46) and irregular-word reading (r=-0.56) but not with non-word reading.

Conclusions: Results suggest that relative L-cone sensitivity within the MC-pathway may limit orthographic reading performance.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Child
  • Color Perception / physiology
  • Contrast Sensitivity / physiology
  • Female
  • Humans
  • Male
  • Motion Perception / physiology*
  • Photic Stimulation
  • Psychophysics / methods
  • Reading*
  • Retinal Cone Photoreceptor Cells / physiology*
  • Task Performance and Analysis
  • Vision Tests
  • Visual Cortex / physiology*