Nature Podcast 26 Apr 2007
This week the Nature Podcast looks at how lowering inhibition in the brain can lead to addiction, hears how a wind tunnel full of wings might help build more efficient aircraft, and explores how invasive species thrive on hard times.
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SPEECH PRODUCTION AND FUNCTIONAL MAGNETIC RESONANCE IMAGING
Sir - The study(1) that was described by Kerri Smith in the News article “Brain’s speech site is revisited and revised”(2) is interesting and is indeed in line with recent functional magnetic resonance imaging (fMRI) findings. In several studies, results were found that show activations for speech in larger areas than Broca’s area. However, it is important to stress that a practical issue has limited the application of fMRI in speech production studies so far. Producing speech during volume acquisition introduces motion-induced signal changes that confound the activation signals of interest(3). As a result, we still have an incomplete understanding of how the speech production process operates at a fundamental, neurobiological level.
A number of approaches, ranging from signal processing to using silent or covert speech have attempted to remove or prevent the effects of motion-induced artefacts. However, it has been shown in previous studies that brain activations during overt speech differ from activations during covert speech(4).
Speech localization in the brain can be improved, not only by using alternative imaging techniques, as was mentioned in the article by Kerri Smith(2), but also by using improved fMRI paradigms. Recently, new fMRI paradigms have been developed that use a clustered or sparse image acquisition technique, which make speech production studies in the MR-scanner possible(5, 6). The new fMRI paradigms make more accurate speech localization possible and will lead to a better understanding of the speech production process. Moreover, these new fMRI paradigms are particularly important for clinicians, for instance, for the preoperative localization of speech areas in brain tumor patients and patients with epilepsy.
Maurits van den Noort
Department of Biological and Medical Psychology
University of Bergen
Jonas Lies vei 91
N-5009 Bergen, Norway
1. Dronkers, N. F. et al. Brain (to appear).
2. Nature 446, 956-957 (2007).
3. Birn, R. M. et al. NeuroImage 23, 1046-1058 (2004).
4. Haller, S. et al. Neuropsychologia 43, 807-814 (2005).
5. Gracco, V. L. et al. NeuroImage 26, 294-301 (2005).
6. Van den Noort, M. et al. NeuroImage 31(S1), 35 (2006).
Posted by: Maurits van den Noort | May 3, 2007 12:42 PM
Good information, thaks.
Posted by: Kudry | October 28, 2007 11:57 AM