Abstract

Background: Most children learn language effortlessly, but a minority struggle to master their native tongue for no obvious reason. This is known as specifi c language impairment. Affected chil-dren often have trouble learning to read and may also be diagnosed with developmental dyslexia. These language and literacy impairments are highly heritable, but their neurobiological basis is poorly understood. A popular notion is that the usual pattern of left-sided brain lateralization for language is disrupted in some children, which leads to problems with language and literacy. Until recently, it was diffi cult to test this idea, because we lacked easy methods to assess cerebral asym-metry directly in children. Advances: Functional transcranial Doppler ultrasound has been developed as a method for assess-ing relative blood fl ow to the left and right cerebral hemispheres during a language-activation task. This technique has made it much easier to assess cerebral asymmetry directly and has con-fi rmed the reduction of the usual left-sided language lateralization in specifi c language impair-ment and dyslexia. Studies performed with functional magnetic resonance imaging have pro-vided converging evidence. The challenge now is to understand the nature of this association. Individual differences in cerebral