The electrophysiology of language perception and production
For over a century, an abundance of research has tried to elucidate the neurobiological basis of language processing in the human cortex. Neuroimaging and lesion studies have provided great insight into what functions different brain structures subserve. While these techniques provide a high spatial resolution they are limited in the temporal domain. Conversely, contributions from non-invasive electrophysiology provided a high temporal resolution with a limited ability to localize cortical sources. The combined spatial and temporal dynamics of cortical processing during language perception and production remains largely unknown. This dissertation addresses this issue by employing unique neuronal population recordings from neurosurgical patients performing linguistic tasks. The studies described here elucidate the timing, magnitude and spatial extent of cortical processing during perception and production of language. The results provide evidence on the level of single-trial that: 1) A rich network of independent and spatially distinct functional sub-regions of cortex subserve perception and production of language. 2) Neighboring sub-regions 4 mm apart can exhibit inverse functional specific responses to linguistic stimuli and self produced speech. 3) Broca's area is not involved in the actual act of articulation but rather in speech preparation and interfacing perception and production. Taken together, these results defy century old dogmas and suggest that language is supported by a complex network of independent sub-regions, with Broca's area acting as a mediator between perception and production rather than as the seat of articulation.