People with Parkinson's Disease (PD) often suffer from speech difficulties, including low volume, monotone pitch, and slow articulation, collectively known as hypokinetic dysarthria. These issues worsen in the later stages of the disease. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a common treatment for advanced PD. While effective in treating motor symptoms, it often exacerbates hypokinetic dysarthria. The mechanism behind this worsening is still unknown, and understanding it might help reduce the side effects of STN-DBS and provide insights into the pathophysiology of hypokinetic dysarthria.

Recent evidence suggests a role for the subthalamic nucleus in speech production. Studies have confirmed the presence of a network involving the STN and the superior temporal lobe, an area crucial for voice articulation. We hypothesize that the STN-temporal network is integral to speech-related functions in PD and that DBS may impair this network. To test this hypothesis, we will study the STN-temporal network dynamics during a vocal modulation task, which has been shown to be sensitive to vocal deficits in PD.

We will record local field potentials from the STN and use EEG to monitor network dynamics during different task phases, both with and without DBS stimulation. Our study will address three questions: Is the STN-temporal network involved in speech? Does DBS affect network dynamics during speech production and modulation? Does this DBS interference directly impact task outcomes and, consequently, speech production?

By investigating the dynamics underlying the relationship between STN stimulation and speech, we aim to provide data that will help refine DBS parameters to avoid worsening speech.