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The speaking brain
On October 16, 2009, Peter Hagoort and Willem Levelt, have published a perspective on neuroscience in Science. In this short publication, entitled 'The Speaking Brain', the director and emeritus director of the MPI for Psycholinguistics argue that human speech is a fine-tuned, step-wise neuronal process, in which Broca's area plays a crucial role.
Oct 16, 2009
How does intention to speak become the action of speaking? Human speech is generated in the brain through a series of steps in which a preverbal message is transformed into a linear sequence of speech sounds. However, the neural infrastructure that supports speech production is still little understood. There is no consensus among scientists about the temporal profile of the steps involved, or the role of feedback from later steps.
A study of Ned Sahin and Steven Pinker (et al.), published in the same Science volume, reports on local field potential data recorded from electrodes implanted in language-related brain regions of patients with epilepsy. The data show that the processing stages involved are not only temporally separated, but also spatially segregated in Broca's area, at a scale of only a few millimeters. The measured time course is consistent with the estimates in the literature, based on naming reaction time measurements. Broca's area seems to be recruited during both language production and comprehension. It is likely involved in unification operations at the word and sentence level, in connection with temporal regions that are crucial for memory retrieval.