Where and when in the brain are words distinguished from grammar?

When they are going to cut away a piece of brain near the speech centers that is causing seizures, they insert electrodes all around the area, so they can see what all the little areas really do in that particular brain, so they don't accidentally cut away somebody's ability to speak.

As long as they have the skull opened up and the brain wired, they might as well do some research, so the surgeons invite in some researchers to, for example, record what neurons fire when the brain receives various kinds of visual or auditory or tactile stimuli.

For this 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. Specifically, the researchers found patterns of neuronal activity indicating lexical, grammatical and articulatory computations at roughly 200, 320 and 450 milliseconds after the target word was presented. These patterns were identical across nouns and verbs and consistent across patients.

Lexical and grammatical I get. I don't know what an articulatory computation would be. Maybe how words string together? I googled it and got 12 hits, all of which were referencing the same study, using the same quote. I suspect this is where it started.