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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.

Original publication

DOI

10.1097/OPX.0b013e31803399df

Type

Journal article

Journal

Optom Vis Sci

Publication Date

03/2007

Volume

84

Pages

229 - 236

Keywords

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