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Mapping typical and hypokinetic dysarthric speech production network using a connected speech paradigm in functional
Shalini Narayana1, Megan B Parsons2, Wei Zhang3
1Department of Pediatrics, Division of Pediatric Neurology, University of Tennessee Health Science Center, Memphis, TN 38103, USA; Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, TN 38103, USA; Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN 38103, USA.
This study introduces a new functional MRI (fMRI) method for mapping the speech production network (SPN) in individuals with and without hypokinetic dysarthria. The validated fMRI technique accurately identifies neural substrates involved in typical and disordered speech.
Area of Science:
- Neuroscience
- Speech Science
- Medical Imaging
Background:
- Motor speech disorders, such as hypokinetic dysarthria (HKD) associated with Parkinson disease, stem from central nervous system dysfunction.
- Understanding the neural circuitry of speech production is crucial for diagnosing and treating these disorders.
- Previous neuroimaging studies often faced limitations in capturing speech-related brain activity.
Purpose of the Study:
- To develop and validate a novel functional MRI (fMRI) task paradigm for overt continuous speech production with minimized head motion.
- To map the speech production network (SPN) in typical speakers and individuals with HKD using fMRI.
- To compare fMRI findings with established positron emission tomography (PET) data to ensure accuracy and reliability.
Main Methods:
- A new fMRI paradigm was developed, requiring participants to speak aloud while minimizing head movements.
- The speech production network (SPN) was mapped in 19 typical speakers and 21 individuals with HKD using fMRI.
- fMRI-derived SPN maps were compared with 15O-water PET data from typical speakers and a separate cohort of 10 HKD individuals.
Main Results:
- The fMRI overt connected speech paradigm proved feasible, showing no excessive motion artifacts.
- fMRI successfully identified brain areas consistent with PET studies, with significant spatial overlap (r=0.52 for typical speakers, r=0.43 for HKD).
- In individuals with HKD, fMRI revealed decreased activity in feedforward (premotor, motor cortices) and feedback (auditory, somatosensory) subsystems, consistent with PET findings.
Conclusions:
- The developed fMRI paradigm is a valid and accurate tool for localizing the neural substrates of typical and disordered speech production.
- This fMRI approach is suitable for studying various motor speech and voice disorders, including stuttering, apraxia of speech, dysarthria, and spasmodic dysphonia.
- The paradigm's ability to identify network dysfunction in HKD highlights its potential for clinical research and application.
