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Investigating Subcortical Contributions to Speech Sequencing in Deep Brain Stimulator Recipients

This study will examine how two important brain circuits - one involving the subthalamic nucleus (STN) and one involving the ventral intermediate nucleus of the thalamus (VIM) - contribute to learning and producing speech sequences. Participants will include two groups: 1. individuals with Parkinson's disease who have deep brain stimulation (DBS) devices targeting the STN and 2. individuals with essential tremor who have DBS devices targeting the VIM. Participants will complete speech tasks involving the learning and repetition of novel sound sequences. During some parts of the study, DBS stimulation will be temporarily turned on or off in a controlled research setting. This will allow researchers to examine how stimulation affects both the learning of new speech sequences and the production of previously learned sequences. All STN participants and most VIM participants will also be equipped with a cutting-edge DBS system, the Percept PC, which will enable the recording of deep brain activity during the tasks. The results of this study will improve our understanding of how different brain circuits support speech learning and production. In particular, this study will help to differentiate the roles of the STN and VIM in learning the ordering of speech sounds within a syllable from learning of speech sequences containing multiple syllables. This knowledge may help guide future approaches to optimizing DBS settings to improve both movement and speech outcomes in individuals with neurological disorders, as well as provide greater general insight into how these brain structures contribute to speech production and learning.