[The past and present status of "motor speech area": from classical modular "center" to nodal and supramodal component of multiple neuronal networks]

Abstract

In the classical, aphasiological (Wernicke-Lichtheim) model for neural basis of language, speech production was assigned to the "motor speech area" located in opercular and triangular part of the left inferior frontal gyrus (fronto-opercular cortex, Broca's area) and conceptualized as a classical "modular centre" within a simple, language-specific neural network. However, recent neuroimaging studies on healthy volunteers have demonstrated a far more complex connection between brain and language: the left fronto-opercular cortex is just one of many nodal points in multiple and partially overlapping neural networks subserving language. In addition, the fronto-opercular cortex is not a simple motor centre, but part of supramodal (executive) frontal system with a number of language and non-language functions. We review these novel roles of the left fronto-opercular cortex, with focus on its functions which extend far beyond the scope of classical Wernicke-Lichtheim model.