A surgical approach to the anatomo-functional structure of language

Language is the most widely mapped cognitive function during brain surgery. Intraoperative language functional mapping using direct electrical stimulation under awake conditions is currently the gold standard technique for establishing the causal link between an area and a deficit that would be caused by its resection. It is also a powerful tool to investigate the anatomical correlates of current neuropsychological models of language.

The aim of this article is to reexamine the anatomo-functional structure of language that could be inferred from data obtained in direct electrical stimulation studies during awake surgery.

Concomitantly with the development of new neuropsychological models of language, major advances have been made in our understanding of error patterns elicited by language network stimulation, both cortically and axonally. Following the recognition of visual information, the language network of picture naming is organized in parallel into two main dorsal phonological and ventral semantic subsystems that are sustained anatomically by two systems (arcuate fasciculus and inferior fronto-occipital/inferior longitudinal/uncinate fasciculus respectively). Networks of articulatory and motor aspects of speech are now better depicted (aslant tract, third branch of longitudinal fasciculus). Finally, the links between the core language networks and the cognitive control networks are also emerging.

Mastering the language map and its dynamical properties should be a basic prerequisite for any neurosurgeon who wishes to operate on the brain with the aim of optimizing the extent of resection while preserving language abilities.