L/M Speed-Matching Ratio Predicts Reading in Children

Authors

CHASE, CHRIS PhD; DOUGHERTY, ROBERT F. PhD; RAY, NICOLA PhD; FOWLER, SUSAN DBO, PhD; STEIN, JOHN FRCP

L/M Speed-Matching Ratio Predicts Reading in Children

publication date

October 12, 2006

Abstract/Introduction

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.

Conclusion/Results

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

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