ABSTRACT
Dyslexia is the most common and most carefully studied of the learning disabilities, affecting 80% of all individuals identified as learning disabled. Though brain imaging studies of dyslexia are relatively recent, neural systems influencing reading were first proposed over a century ago by Dejerine in studies of adults who suffered a stroke with subsequent acquired alexia, the sudden loss of the ability to read. Using functional magnetic resonance imaging (fMRI), converging evidence from many laboratories around the world has demonstrated a neural signature for dyslexia—that is, an inefficient functioning of posterior reading systems during reading real words and pseudowords. Connectivity analyses of fMRI data represent the most evolution in characterizing brain networks in dyslexia. In dyslexia, a deficit at the level of the phonologic module impairs the ability to segment the spoken word into its underlying phonologic elements and then link each letter(s) to its corresponding sound(s).
