Reply: probabilistic map of language regions: challenge and implication.

Sir, We thank Dr Wu and colleagues for their interest in our recent probabilistic map of critical functional regions of the human cerebral cortex (Tate et al. , 2014). In particular, we are pleased to note that in their experience with 69 Chinese-speaking patients the authors confirmed a 79% probability of anarthria/speech arrest with stimulation of the left ventral premotor cortex (PMC), similar to our results (83%). These data support the crucial role of the ventral PMC for speech output, as suggested in previous reports (Duffau et al. , 2003; van Geemen et al. , 2014). Nonetheless, they also found a probability of ‘speech arrest’ in 32% of patients within the left pars opercularis (i.e. Broca’s area), which they stated is similar to the 26.7% rate observed by Sanai et al. (2008). However, if one looks at the primary data from the report by Sanai et al. (2008), which uses a relatively arbitrary 1 × 1 cm grid system, which does not specifically respect anatomic (sulci, gyri) or cytoarchitectural (Brodmann area) cortical features, there are three grids that include a portion of pars opercularis: for the two grids that are completely contained within pars opercularis, one has 0% speech arrest and another has 4.9%—these data are similar to our reported …