This lecture explores how the core and extended language networks of the brain are organized and what current research reveals about their function, structure, and development (Trettenbrein & Friederici, 2025). Against this general background, two key questions will be addressed: First, how can we investigate and test the function of specific brain regions, particularly in relation to the interface between linguistics and neuroscience (van der Burght et al., 2023)? Second, if language is fundamentally a mechanism for computing sentences, do sign languages rely on the same neural infrastructure as spoken languages and if so to what extent (Trettenbrein, Zaccarella, & Friederici, 2025)?