THE SPEAKING BRAIN: A TUTORIAL INTRODUCTION TO fMRI EXPERIMENTS IN THE PRODUCTION OF SPEECH, PROSODY AND SYNTAX

In this study we will give an overview of the experimental work on the neuroanatomical correlates of language and speech production that we have done in recent years. First we will introduce the methodology of event-related functional magnetic neuro-imaging and the experimental paradigm that we employed. Then we will present and discuss the results of our experiments on (1) speech motor control, (2) articulatory complexity, (3) the neuroanatomical correlates of prosody, and (4) the neurocognitive substrates of syntactic processing. Experiments (1) and (2) show that the expected large motor speech network consisting of SMA, motor cortex and cerebellum is only active in planning and execution of simple articulatory movements. Increased articulatory complexity leads to more focused activation. Furthermore, we can show that only the execution of speech movements recruits the left anterior insula, while articulatory planning does not. The results of experiment (3) indicate that it is not the function of prosody (linguistic vs. affective) that controls lateralisation of prosodic processing, but that more general characteristics of the processing units like the size of the prosodic frame are responsible for the activation of different cortical regions. Finally, in experiment (4) we present first results on syntactic processing in speech production. Besides the expected activation of Broca’s area we found activations in Wernicke’s area and in the cerebellum. We have also found evidence for activations in other cortical areas, which are less often implicated in clinical studies on brain language correlations. The cognitive relevance of these areas and networks is still to be elucidated.