In France about 1 million children are thought to present learning disabilities for reading that in most cases correspond to developmental dyslexias. These are specific and constitutional deficits that prevent rapid and automatic reading abilities from developing, in spite of a normal intelligence and normal visual and auditory acuity. The most frequent form of dyslexia is called "phonological dyslexia" as it results from a deficit of perception and manipulation of phonemes (i.e. "phonological awareness"). Functional neuro-imaging has great potential for helping understand such functional deficits that are likely to be caused by microscopic abnormalities such as micro-polygyria localised in the perisylvian cortex. Tomographic methods have shown deficits of activation of these cortical areas. Electrophysiological methods revealed abnormalities of various events such as MMN or N400, and more recently, delayed latencies of earlier markers suggesting deficits of encoding short-lived features of speech signal.