Neuronal-level representations of speech production in inferior frontal gyrus
Date:
The role of the inferior frontal gyrus (IFG) in speech production remains poorly understood. Although lesion studies consistently implicate IFG in speech production, brain–computer interfaces that decode speech from this region have historically performed substantially worse than those using speech motor cortex. This discrepancy raises the question of what information IFG encodes during speech production.
Prior neuroimaging and lesion studies suggest that IFG may be involved in phonological processing, supported by observations of phonemic paraphasias following damage to this region. To investigate this directly, we analyzed high-resolution intracortical recordings from a Utah array implanted in posterior IFG in a chronic human participant performing a speech production task.
We introduce a contrastive learning framework that maps neural activity into a low-dimensional latent space structured by phoneme sequence similarity. In this space, words with similar phonemic structure (e.g., part vs. past) cluster more closely than phonemically dissimilar words (e.g., part vs. dog). Using this approach, we find preliminary evidence for a phoneme-sequence representation in IFG that emerges after speech onset and performs significantly above chance.