Decoding, Modulating, and Imaging Sensorimotor Pathways in the Brain
Willsey, Matthew
2020
Abstract
Many diseases and injuries irreparably harm the brain or spinal cord and result in motor paralysis, widespread sensory deficits, and pain. Often, there are no treatments for these injuries, and therapies revolve around rehabilitation and adapting to the acquired deficits. In this work, we investigate brain machine interfaces (BMIs) as a future therapy to restore sensorimotor function, use BMIs to understand sensorimotor circuits, and use novel imaging algorithms to assess structural damage of somatosensory inputs into the brain. Brain-controlled robotic arms have progressed rapidly from the first prototype devices in animals; however, these arms are often slow-moving compared to normal hand and arm function. In the first study, we attempt to restore higher-velocity movements during real-time control of virtual fingers using a novel feedforward neural network algorithm to decode the intended motor movement from the brain. In a non-human primate, the neural network decoder was compared with a linear decoder, the ReFIT Kalman filter (RFKF), that we believe represents the state-of-the-art in real-time finger decoding. The neural network decoder outperformed RFKF by acquiring more targets at faster velocities. This neural network architecture may also provide a blueprint for additional advances. Somatosensory feedback from robotic arms is important to achieve realistic function. The use of somatosensory thalamus was investigated as a site of implantation for a sensory prosthesis in subjects undergoing awake deep brain stimulation surgery (DBS). In this study, electrical stimulation of the thalamus was performed using different stimulation patterns and the evoked sensations were compared. We found that the sensations evoked by bursting (a burst of pulses followed by a rest period) and tonic (regularly repeating pulses) stimulation were often in different anatomic regions and often evoked differing sensory qualities. These techniques for controlling percept location and quality may be useful in not only in BMI applications but also in DBS therapies to better relieve symptoms and avoid unwanted side effects. Given the importance of sensory integration in motor functioning, the third study investigated the impact of a pharmacological perturbation on somatosensory content in primary motor cortex measured with Utah arrays implanted in two NHPs. Specifically, during continuous administration of nitrous oxide (N2O), somatosensory content was assessed by using the neural activity in primary motor cortex to classify finger brushings with a cotton-tip applicator. N2O degraded but did not eliminate somatosensory content in motor cortex. These findings provide insight into N2O mechanisms and may lead to further study of somatosensory afferents to motor cortex. A debilitating facial pain syndrome, called trigeminal neuralgia (TN), is thought to be caused by vascular compression of the sensory root that provides somatosensory feedback from the face. In this final study, magnetic resonance diffusion tensor imaging was used to assess the structural damage of this sensory root. In a retrospective manner, we developed and tested an algorithm that predicted the likelihood of pain relief after surgical treatment of TN. This algorithm could help select patients for surgery with the best chance for pain relief. Together, these studies advance BMI technologies that attempt to restore realistic function to those with irreparable damage to sensorimotor pathways. Furthermore, using BMIs and novel imaging, this work provides a better understanding of sensorimotor circuits and how sensory pathways can be damaged in disease states.Subjects
Neural Network, Brain-Machine Interface, Motor Decoding Thalamus, Deep Brain Stimulation, Movement Disorders, Burst, Perception Nitrous Oxide, NMDA antagonist, sensorimotor, consciousness, anesthesia Trigeminal neuralgia, Facial pain, Diffusion tensor imaging
Types
Thesis
Metadata
Show full item recordCollections
Remediation of Harmful Language
The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.
Accessibility
If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.