Abstract: Language is an immensely important human faculty that separates us from other animals. Knowledge of how the brain enacts language will have far-reaching consequences for society, from better treating language disorders to developing artificial intelligence and brain-machine interfaces. In this talk, I will review my past, current, and future contributions towards these endeavors. Although communicated language unfolds sequentially, one word at a time, comprehension of information embedded in sentences necessitates a tree of hierarchical nested phrases rather than linearly processing word sequences. My research shows that these theoretical structures are indeed created in the brain as we comprehend a sentence and shows how populations of neurons in language cortex enact this. Using intracranial recordings in surgical patient volunteers, I showed that in superior temporal and inferior frontal areas, high-gamma power increases with each successive word in a sentence, but decreases suddenly when a group words can be merged into a phrase. Each additional single word or multi-word merged phrase adds a similar amount of additional brain activity to these regions, providing evidence for a merge operation that applies equally to linguistic objects of arbitrary complexity. This pattern is consistent with a neural implementation of a stack machine parser creating a tree structure from the incoming language stream. Work I am currently conducting shows how manipulating neural activity at these same time points and brain areas by applying microstimulation can interrupt the brain’s merging of words and reproducibly alters a subject’s comprehension of a sentence, allowing for causal inferences to be made into these brain areas’ creation of syntactic structure. Altogether, this shows how we can interface with the brain on the grammatical level in sentences. I will discuss a future research direction of neural network research and applying computational theories to neurophysiological recordings to explore reading out word identity and semantic content from working memory in the brain, with a natural application of a cognitive language interface with the brain. Finally, I will complement this with presentation of some of my existing research advancing the theory of neural electrode design and discussing future research in the development of electrodes and implants for interfacing with the human brain.