Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- All Subjects: Frequency-Domain Analysis
- All Subjects: Vibration--Therapeutic use.
Description
Neural interfacing applications have advanced in complexity, with needs for increasingly high degrees of freedom in prosthetic device control, sharper discrimination in sensory percepts in bidirectional interfaces, and more precise localization of functional connectivity in the brain. As such, there is a growing need for reliable neurophysiological recordings at a fine spatial scale matching that of cortical columnar processing. Penetrating microelectrodes provide localization sufficient to isolate action potential (AP) waveforms, but often suffer from recorded signal deterioration linked to foreign body response. Micro-Electrocorticography (μECoG) surface electrodes elicit lower foreign body response and show greater chronic stability of recorded signals, though they typically lack the signal localization necessary to isolate individual APs. This dissertation validates the recording capacity of a novel, flexible, large area μECoG array with bilayer routing in a feline implant, and explores the ability of conventional μECoG arrays to detect features of neuronal activity in a very high frequency band associated with AP waveforms.
Recordings from both layers of the flexible μECoG array showed frequency features typical of cortical local field potentials (LFP) and were shown to be stable in amplitude over time. Recordings from both layers also showed consistent, frequency-dependent modulation after induction of general anesthesia, with large increases in beta and gamma band and decreases in theta band observed over three experiments. Recordings from conventional μECoG arrays over human cortex showed robust modulation in a high frequency (250-2000 Hz) band upon production of spoken words. Modulation in this band was used to predict spoken words with over 90% accuracy. Basal Ganglia neuronal AP firing was also shown to significantly correlate with various cortical μECoG recordings in this frequency band. Results indicate that μECoG surface electrodes may detect high frequency neuronal activity potentially associated with AP firing, a source of information previously unutilized by these devices.
Recordings from both layers of the flexible μECoG array showed frequency features typical of cortical local field potentials (LFP) and were shown to be stable in amplitude over time. Recordings from both layers also showed consistent, frequency-dependent modulation after induction of general anesthesia, with large increases in beta and gamma band and decreases in theta band observed over three experiments. Recordings from conventional μECoG arrays over human cortex showed robust modulation in a high frequency (250-2000 Hz) band upon production of spoken words. Modulation in this band was used to predict spoken words with over 90% accuracy. Basal Ganglia neuronal AP firing was also shown to significantly correlate with various cortical μECoG recordings in this frequency band. Results indicate that μECoG surface electrodes may detect high frequency neuronal activity potentially associated with AP firing, a source of information previously unutilized by these devices.
ContributorsBarton, Cody David (Author) / Greger, Bradley (Thesis advisor, Committee member) / Santello, Marco (Committee member) / Buneo, Christopher (Committee member) / Graudejus, Oliver (Committee member) / Artemiadis, Panagiotis (Committee member) / Arizona State University (Publisher)
Created2018
Description
Humans constantly rely on a complex interaction of a variety of sensory modalities in order to complete even the simplest of daily tasks. For reaching and grasping to interact with objects, the visual, tactile, and proprioceptive senses provide the majority of the information used. While vision is often relied on for many tasks, most people are able to accomplish common daily rituals without constant visual attention, instead relying mainly on tactile and proprioceptive cues. However, amputees using prosthetic arms do not have access to these cues, making tasks impossible without vision. Even tasks with vision can be incredibly difficult as prosthesis users are unable to modify grip force using touch, and thus tend to grip objects excessively hard to make sure they don’t slip.
Methods such as vibratory sensory substitution have shown promise for providing prosthesis users with a sense of contact and have proved helpful in completing motor tasks. In this thesis, two experiments were conducted to determine whether vibratory cues could be useful in discriminating between sizes. In the first experiment, subjects were asked to grasp a series of hidden virtual blocks of varying sizes with vibrations on the fingertips as indication of contact and compare the size of consecutive boxes. Vibratory haptic feedback significantly increased the accuracy of size discrimination over objects with only visual indication of contact, though accuracy was not as great as for typical grasping tasks with physical blocks. In the second, subjects were asked to adjust their virtual finger position around a series of virtual boxes with vibratory feedback on the fingertips using either finger movement or EMG. It was found that EMG control allowed for significantly less accuracy in size discrimination, implying that, while proprioceptive feedback alone is not enough to determine size, direct kinesthetic information about finger position is still needed.
Methods such as vibratory sensory substitution have shown promise for providing prosthesis users with a sense of contact and have proved helpful in completing motor tasks. In this thesis, two experiments were conducted to determine whether vibratory cues could be useful in discriminating between sizes. In the first experiment, subjects were asked to grasp a series of hidden virtual blocks of varying sizes with vibrations on the fingertips as indication of contact and compare the size of consecutive boxes. Vibratory haptic feedback significantly increased the accuracy of size discrimination over objects with only visual indication of contact, though accuracy was not as great as for typical grasping tasks with physical blocks. In the second, subjects were asked to adjust their virtual finger position around a series of virtual boxes with vibratory feedback on the fingertips using either finger movement or EMG. It was found that EMG control allowed for significantly less accuracy in size discrimination, implying that, while proprioceptive feedback alone is not enough to determine size, direct kinesthetic information about finger position is still needed.
ContributorsOlson, Markey (Author) / Helms-Tillery, Stephen (Thesis advisor) / Buneo, Christopher (Committee member) / Santello, Marco (Committee member) / Arizona State University (Publisher)
Created2016