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A Noninvasive Imaging Approach to Understanding Speech Changes Following Deep Brain Stimulation in Parkinson's Disease

Donald A. Robin
Research Imaging Center, The University of Texas Health Science Center, San Antonio, and Honors College, The University of Texas, San Antonio

Howard Poizner
Institute for Neural Computation, The University of California, San Diego

Wei Zhang
Crystal Franklin
Research Imaging Center, The University of Texas Health Science Center, San Antonio

Mario Liotti
Simon Fraser University, Burnaby, British Columbia, Canada

Deanie Vogel
Our Lady of the Lake University, San Antonio

Peter T. Fox
Research Imaging Center, The University of Texas Health Science Center, San Antonio, and South Texas Veterans Health Care Center, San Antonio

Contact author: Shalini Narayana, Research Imaging Center, The University of Texas Health Science Center, San Antonio, 7703 Floyd Curl Drive MSC 6240, San Antonio, TX 78229-3900. E-mail: narayana{at}uthscsa.edu.

Purpose: To explore the use of noninvasive functional imaging and "virtual" lesion techniques to study the neural mechanisms underlying motor speech disorders in Parkinson's disease. Here, we report the use of positron emission tomography (PET) and transcranial magnetic stimulation (TMS) to explain exacerbated speech impairment following subthalamic nucleus deep brain stimulation (STN-DBS) in a patient with Parkinson's disease.

Method: Perceptual and acoustic speech measures, as well as cerebral blood flow during speech as measured by PET, were obtained with STN-DBS on and off. TMS was applied to a region in the speech motor network found to be abnormally active during DBS. Speech disruption by TMS was compared both perceptually and acoustically with speech produced with DBS on.

Results: Speech production was perceptually inferior and acoustically less contrastive during left STN stimulation compared to no stimulation. Increased neural activity in left dorsal premotor cortex (PMd) was observed during DBS on. "Virtual" lesioning of this region resulted in speech characterized by decreased speech segment duration, increased pause duration, and decreased intelligibility.

Conclusions: This case report provides evidence that impaired speech production accompanying STN-DBS may result from unintended activation of PMd. Clinical application of functional imaging and TMS may lead to optimizing the delivery of STN-DBS to improve outcomes for speech production as well as general motor abilities.

Key Words: Parkinson's disease, neuroimaging, deep brain stimulation, transcranial magnetic stimulation

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