Whole-brain dynamics of articulatory, acoustic and semantic speech representations

Speech production is a complex process that traverses several representations, from the meaning of spoken words (semantic), through the movement of articulatory muscles (articulatory) and, finally, to the produced audio waveform (acoustic). In our study, we aimed to identify how these different representations of speech are spatially and temporally distributed throughout the depth of the brain. By considering multiple representations from the same exact data, we can limit potential con-founders to better understand the different aspects of speech production and acquire crucial complementary information for speech brain-computer interfaces (BCIs). Intracranial speech production data was collected of 15 participants, recorded from 1647 electrode contacts, while they overtly spoke 100 unique words. The electrodes were distributed across the entire brain, including sulci and subcortical areas. We found a bilateral spatial distribution for all three representations, although there was a stronger tuning in the left hemisphere with a more widespread and temporally dynamic distribution than in the right hemisphere. The articulatory and acoustic representations share a similar spatial distribution surrounding the Sylvian fissure, while the semantic representation appears to be widely distributed across the brain in a mostly distinct network. These results highlight the distributed nature of the speech production process and the potential of non-motor representations for speech BCIs.