Using a rare procedure, researchers at the University of California, San Diego School of Medicine have revealed how language is processed in the brain.
The feat is a significant breakthrough in explaining gaps in scientists' understanding of human brain function.
"Two central mysteries of human brain function are addressed in this study: one, the way in which higher cognitive processes such as language are implemented in the brain and, two, the nature of what is perhaps the best-known region of the cerebral cortex, called Broca's area," said first author Dr. Ned T. Sahin.
The discoveries came after the researchers used a rare procedure in which electrodes were placed in the brains of patients.
The technique allowed surgeons to know which small region of the brain to remove to alleviate their seizures, while sparing the healthy regions necessary for language.
Recordings for research purposes were then made while the patients were awake and responsive.
The procedure, called Intra-Cranial Electrophysiology (ICE), allowed the researchers to resolve brain activity related to language with spatial accuracy down to the millimeter and temporal accuracy down to the millisecond.
This is the first experiment to use ICE to document how the human brain computes grammar and produces words.
For the study, the researchers recorded activity inside patients' brains while they repeated words verbatim or produced them in grammatical forms such as past tense or plural - a task that humans effortlessly compute every time they utter a sentence.
ICE enabled the authors to look at three components of language processing in real time, to determine whether related neuronal activities were implemented serially or in parallel, in local or distributed patterns.
"We showed that distinct linguistic processes are computed within small regions of Broca's area, separated in time and partially overlapping in space," said Sahin.
The study will be published in the latest issue of the journal Science.