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 (ie 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 Â 1cm 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 4%. A third grid location has a reported 26.7% speech arrest rate (referred to in the letter by Wu and colleagues), but this region spans both pars opercularis and ventral PMC, so it is possible that many of the speech arrest sites are within the ventral PMC and not pars opercularis. In fact, in our study, there is a high density of speech arrest sites just posterior to the precentral sulcus, immediately behind the superior pars opercularis, but within ventral PMC (Tate et al., 2014). In addition, a recent study examining language deficits in glioma patients demonstrated that gliomas involving the ventral PMC were 5-fold more likely to cause aphasia compared to gliomas involving the inferior frontal gyrus (Bizzi et al., 2012), which also points to the ventral PMC as the primary speech output region. Another potential source for the discrepancy among studies evaluating speech arrest and anomias is related to the specifics of the chosen intraoperative tasks. For example, in our study, during the picture naming paradigm, patients are asked to proceed the object name with ‘This is a....’, enabling distinction of true anomia (where the patient will say ‘This is a.....’and cannot produce the object name) from speech arrest (patient is shown the picture and has zero verbal output). If one simply asked the patient to name pictures, it would be difficult to discern speech arrest from anomia. Thus, when reporting anomia, speech arrest, and articulation outcomes, it is important to precisely specify the intraoperative tasks employed to enable direct comparisons. Finally, as stated by Wu et al.(2014) doi: 10.1093/brain/awu253 Brain 2015: 138; 1–3| e338