Mapping language sites in cerebral cortex (Sanai et al., NEJM 2008) Stimulate brain regions in dominant hemisphere of conscious patients during surgery for brain tumor resection, before tumor resection, to minimize post- operative language deficits. Craniotomy over the tumor + 3cm max, with anesthesia. Apply lidocaine, open dura, withdraw anesthesia. Apply electrical stimulation to 1 sq cm areas while patient counts, reads, names objects. Determine which exposed brain regions in each patient are involved in speaking, reading, and naming. (Neurons can’t function normally while being stimulated electrically, so if the region is involved in a task, the patient will be unable to perform the task while that region is stimulated.)

Sanai N et al. N Engl J Med 2008;358:18-27 Frontal-Lobe Language Sites Red squares: total number of sites stimulated Blue squares: % of sites causing speech dysfunction when stimulated

Sanai N et al. N Engl J Med 2008;358:18-27 Temporal-Lobe Language Sites Red squares: total number of sites stimulated. Blue squares: % of sites causing speech dysfunction when stimulated. None of the temporal lobe sites tested caused complete speech arrest.

Sanai N et al. N Egl J Med 2008;358:18-27 Parietal-Lobe Language Sites Red squares: total number of sites stimulated. Blue squares: % of sites causing speech dysfunction when stimulated. None of the parietal lobe sites tested caused complete speech arrest.

Sanai N et al. N Engl J Med 2008;358:18-27 Negative Language Sites Upper value: total number of patients with no detectable language function at that site Lower value: % of patients with no detectable language function at that site

Authors’ Conclusions Language sites are highly variable in their location. “Current models of language localization in the dominant hemisphere insufficiently reflect the true diversity and in vivo patterns of cortical language organization.” (Sanai N et al. N Engl J Med 2008;358:18-27) Additional Conclusion Pictures of Broca’s area in anatomy textbooks may give a misleading impression that motor speech is produced by a relatively small and constant (from person to person) brain region.