Psychophysical evidence for a magnocellular pathway deficit in dyslexia

• Published in: Vision research (Oxford) Vol. 38; no. 11; pp. 1555 - 1559
• Main Authors: Demb, Jonathan B, Boynton, Geoffrey M, Best, Mary, Heeger, David J
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.1998; Elsevier Science
• Subjects: Adult; Adult and adolescent clinical studies; Biological and medical sciences; Contrast sensitivity; Contrast Sensitivity - physiology; Dyslexia - physiopathology; Female; Humans; Language and communication disorders; Magno; Male; Medical sciences; Motion discrimination; Motion Perception - physiology; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Psychophysics; Sensory Thresholds - physiology; Specific reading disability; Time Factors; Visual Pathways - physiopathology; Psychophysics; Contrast sensitivity; Motion discrimination; Magno; Specific reading disability; Human; Reading disorder; Perception threshold; Differential threshold; Exploration; Contrast; Language disorder; Spatial frequency; Temporal frequency; Visual stimulus; Visual pathway; Vision; Detection threshold; Stimulus velocity; Perception; Dyslexia
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(98)00075-3

The relationship between reading ability and psychophysical performance was examined to test the hypothesis that dyslexia is associated with a deficit in the magnocellular (M) pathway. Speed discrimination thresholds and contrast detection thresholds were measured under conditions (low mean luminance, low spatial frequency, high temporal frequency) for which psychophysical performance presumably depends on M pathway integrity. Dyslexic subjects had higher psychophysical thresholds than controls in both the speed discrimination and contrast detection tasks, but only the differences in speed thresholds were statistically significant. In addition, there was a strong correlation between individual differences in speed thresholds and reading rates. These results support the hypothesis for an M pathway abnormality in dyslexia, and suggest that motion discrimination may be a more sensitive psychophysical predictor of dyslexia than contrast sensitivity.