Abstract: Many behavioral and neurophysiological studies in recent years found that developmental dyslexia is related to deficits in basic perceptual processing. The magnocellular theory, proposed mostly by researchers working in the visual processing field, postulates that dyslexia is the result of a deficit in the magnocellular part of the visual system. This magnocellular system respondes to rapid changes in visual stimulation and a deficit here would lead the brain to confuse neural activities attributed to different fixations between saccades during text reading. A similar deficit also existes in the auditory domain, where dyslexics show difficulties in processing rapid, sequential, and transit sounds. It is believed that a general impairment in temporal processing underlies dyslexics poor performance in reading. Theories emphasizing the role of basic perceptual processing in reading impairment is in contrast with theories that focus on the deficits in the linguistic domain, reflecting the significant advancement in cognitive neuroscience and the decline of the modular approaches.

Key words: developmental dyslexia, perceptual processing, magnocellular deficit, temporal processing deficit