Probabilistic map of language regions: challenge and implication.

Sir, We have read the article entitled ‘Probabilistic map of critical functional regions of the human cerebral cortex: Broca’s area revisited’ by Tate et al. (2014) with great interest. In that article, the authors presented a bilateral probabilistic map for the essential functions by integrating the data from the ‘gold standard’ for mapping brain functions (direct cortical electrostimulation) in a large set of patients. In particular, the authors’ findings challenged two aspects of the classical theories of brain organization. First, their data added new and more direct evidence for the theory that the ventral premotor cortex (PMC), not the classical Broca’s area (Bizzi et al. , 2012), is the speech output region. Second, these authors reported that the crucial epicentres for speech output were not lateralized to the dominant hemispheres. A bilateral cortical requirement for speech output was demonstrated in this article. These results have major implications for brain surgery, and this conclusion has the potential to change neurosurgeons’ traditional surgical philosophy. Tate et al. (2014) observed that the region of interest-based probability of anarthria/arrest (speech output) in the ventral premotor cortex of the left hemisphere is 83%, whereas this probability is only 4% for the pars opercularis. Thus, the authors concluded that the bilateral ventral PMC served as the final common pathway for speech output and that Broca’s area was only involved in the higher-order aspects of language. This result is slightly different from our personal experience; therefore, we applied a similar method to perform a probability analysis for the ventral PMC and pars opercularis using our data from 69 Chinese-speaking patients. The only methodological distinction is that …