Rethinking the neurological basis of language

Functional neuroimaging, within 10 years, has produced evidence which leads us to question a number of the standard assumptions about the areas which are necessary and sufficient for language processing. Although neuroimaging evidence has corroborated much neuropsychological data, it forces a revision of a number of the standard interpretations of those data and some traditionally accepted notions must be totally discarded. We will provide an overview of some issues which have arisen in these years, giving examples from a number of laboratories and illustrating with experiments of our own. The circumstances under which the left posterior temporal lobe (Wernicke's area) and the left inferior frontal gyrus (Broca's area) are activated are reviewed, and several views of how they contribute to language processing are considered in the light of this evidence. Further evidence for the contribution of a number of other areas to language comprehension are reviewed, including the anterior temporal lobe, the cerebellum, the left superior median frontal lobe, the anterior insula and the left inferior temporal occipital junction. Further we discuss some of the conditions under which the right hemisphere contributes to language processing. We will conclude by discussing the implications of this research for the concept of modularity in the sense of Fodor [Modularity of Mind, MIT Press, Cambridge, 1983].