title: L/M speed-matching ratio predicts reading in children.
abstract: OBJECTIVE
  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.
authors: Department of Psychology, Claremont McKenna College, Claremont, California 91711, USA. chris.chase@claremontmckenna.edu
authors: Chris
authors: C
authors: Chase
authors: Robert F
authors: RF
authors: Dougherty
authors: Nicola
authors: N
authors: Ray
authors: Susan
authors: S
authors: Fowler
authors: John
authors: J
authors: Stein
mesh_terms: D000293:Adolescent; D002648:Child; D003118:Color Perception / Q000502:physiology; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation; D011601:Psychophysics / Q000379:methods; D011932:Reading; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D013647:Task Performance and Analysis; D014787:Vision Tests; D014793:Visual Cortex / Q000502:physiology*