Frequency-dependent effects of motor thalamus deep brain stimulation on speech and swallowing.

Speech and swallowing are complex motor sequences driven by cortico-bulbar communication between motor cortex and cranial muscles. Damage to these pathways impairs strength and control of orofacial muscles, causing chronic dysarthria and dysphagia that increase social isolation, aspiration risks, and mortality. We show that motor thalamus Deep Brain Stimulation (DBS) can improve these functions after traumatic brain injury (TBI). First, we demonstrated that low-frequency DBS (50-80 Hz) facilitates activation of cortico-bulbar fibers, immediately potentiating motor output in n = 8 participants with intact pathways. In a participant who sustained a TBI resulting in chronic moderate dysphagia and severe dysarthria, low-frequency DBS improved facial movement, swallowing efficiency, and speech intelligibility across respiratory, phonatory, and articulatory subsystems. Importantly, these improvements in facial articulator and speech subsystems control were specific to low-frequency (50-80 Hz) stimulation. These findings provide preliminary evidence that motor thalamus DBS can modulate corticobulbar circuitry to improve dysarthria and dysphagia following cerebral lesions.