Complex brain landscape controls speech

September 21, 2010

Up to now, Broca's region in the brain has been thought to comprise two areas, since it was discovered in 1861, it has been regarded as one of the two regions in the cerebral cortex responsible for language. The conception of the neuroanatomical basis of our speech must be revised in its entirety according to researchers from Juelich, Aachen, Duesseldorf and Leipzig in the current edition of the journal PLoS Biology.

Broca's region is classically regarded as the motor centre for speech. Our ability to form phonemes and words is controlled here. According to the maps of the developed by Korbinian Brodmann, which are still in use today, Broca's region is composed of two areas. Over the last few years, however, researchers have begun to question this subdivision as a result of experience gained in clinical studies and the findings of analyses. " in Broca's region could result in a dozen different language problems," says Professor Katrin Amunts, brain researcher at Forschungszentrum Jülich and first author of the study. "For example, in articulation but also in comprehension or in grammar, as linguistic studies have shown. This tends to suggest a much more complexly structured centre of language than was previously believed."

The scientists therefore decided to take a closer look at the cytoarchitecture and distribution of different receptors in Broca's region. Receptor molecules are the key to signal transduction between - and can therefore help to further classify structurally similar regions. If the distribution of receptors is different in these regions, then the functions of the brain at these locations must also be different. "We discovered that Broca's region does not just comprise two areas, but rather several - all of which form a highly differentiated mosaic," says Professor Karl Zilles, co-author of this study. "It's a complex world that's dedicated to our faculty of speech."

The study shows, for example, a clear difference in the distribution of one receptor between the Broca areas of the two cerebral hemispheres and slight differences in the case of the other receptors. Further studies are required to determine whether this is the molecular basis for the different clinical findings in patients with lesions in Broca's region either exclusively in the left or right brain hemisphere. Patients with lesions in the left brain hemisphere completely lose their ability to speak, while those with lesions in the right-hand side can still articulate correctly but lose their speech melody.

"One of the tasks for the future is to conduct a detailed functional analysis of the new organization of Broca's region and to investigate the interaction of the previously unknown areas," says Amunts. A new project has already begun on the analysis of the second region in the brain responsible for the faculty of speech - Wernicke's area. Classically, this area is thought to be involved in the understanding of language.

The discovery in question of several molecularly and cellularly different cortical areas in Broca's language region and in neighbouring areas shows that our faculty of speech is actually embedded in a much more differentially developed landscape than we have believed for the past 150 years. The findings are not just important for language research and the diagnosis and treatment of strokes. They also alter the neurobiological basis for current discussions on the evolutionary development of language, speech training and language disorders.

More information: Amunts K, Lenzen M, Friederici AD, Schleicher A, Morosan P, et al. (2010) Broca's Region: Novel Organizational Principles and Multiple Receptor Mapping. PLoS Biol 8(9): e1000489. doi:10.1371/journal.pbio.1000489

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kevinrtrs
1 / 5 (4) Sep 22, 2010
The discovery in question of several molecularly and cellularly different cortical areas in Broca's language region and in neighbouring areas shows that our faculty of speech is actually embedded in a much more differentially developed brain landscape than we have believed for the past 150 years

This shows that such speech ability could not have developed via Darwinian evolutionary methods: the coordination between parts is simply staggeringly improbable to achieve with any kind of random process.
Skeptic_Heretic
5 / 5 (1) Sep 22, 2010
This shows that such speech ability could not have developed via Darwinian evolutionary methods: the coordination between parts is simply staggeringly improbable to achieve with any kind of random process.
Good thing Darwinian Evolution isn't a random process.
mabarker
1 / 5 (3) Sep 24, 2010
So, these findings *alter the neurobiological basis for current discussions on the evolutionary development of language* How exactly do they alter them, Skeptik Heretik? Please be specific. I'll just bet you'll say *natural selection* (whatever THAT is) & lucky, random mutations (even though you say above darwinism is directed).
Did you notice the authors of the original paper did not describe how this complex region might have evolved? It's because it didn't - it was created.
Skeptic_Heretic
5 / 5 (1) Sep 24, 2010
So, these findings *alter the neurobiological basis for current discussions on the evolutionary development of language* How exactly do they alter them, Skeptik Heretik?
I can't say, I'm not a neurobiologist. However, from the abstract above, the statement reads as "The speech centers of the brain are more complex than we previously thought, meaning anything we've based on that model isn't accurate.
I'll just bet you'll say *natural selection* (whatever THAT is) & lucky, random mutations (even though you say above darwinism is directed).
I didn't say Darwinian evolution was directed. I said darwinian evolution isn't a random process. It is a well defined process composed of multiple feedback loops including but not limited to predation, sexual selection, environmental selection, and primary heath reinforcers.
authors of the original paper did not describe how this complex region might have evolved?
No, they merely refuted Brodmann's map. Did you actually read it? Nope.
Skeptic_Heretic
5 / 5 (1) Sep 24, 2010
You two do realize that evolution isn't really questionable anymore. It is a well explored scientific theory that accurately describes all processes we've found in Nature regarding changees in populations of time thus far.

If you have questions, or actual arguments against it, publish a paper on it and turn the world of science on it's ear. You two spouting ignorant things on a Forum board for scientists will do nothing other than show us how ignorant you really are. Beyond that, what arrogance you display in taking hundreds of years of collaborative work involving some of the best minds among humankind and treating the knowledge as one would treat trash. Such arrogance and ignominity is considered a hallmark of evil within your faith. You may want to start practicing what you preach.

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