"Language is a capacity specific to humans and thus biologically based. While our knowledge concerning the neural basis of language in the adult brain has increased considerably, little is known about the relation between language and brain during ontogeny. The present study will focus on the development of brain structure and language function in the domain of syntax. Behavioural and electrophysiological studies indicate that children's basic syntactic knowledge is well advanced at around 3 years of age. However, the ability to process complex hierarchically structured sentences only develops after the age of 5 and is still not adult-like by the age of 7. In adults, two different neural networks supporting syntax have been shown: one processing complex hierarchical syntactic structures and one processing local syntactic constraints. The latter consists of inferior frontal and anterior temporal regions connected via a fibre bundle called the extreme capsule fibre system, whereas the network supporting the processing of complex syntactic structures is based on inferior frontal and posterior temporal regions connected via the superior longitudinal fascile and arcuate fascile (SLF/AF). There is some neuroanatomical evidence that the latter fibre bundles develop relatively late in children. Here, we will investigate the hypothesis that the maturation of the SLF/AF is a prerequisite for the development of the human ability to process complex syntax. We will do so by correlating behavioural, functional and structural brain imaging data in children at different developmental stages. This research will provide fundamental knowledge about the codevelopment of language and the brain, and furthermore serve as a prerequisite for the diagnosis of atypical language development."