Hughes, Christopher L
(2021)
Biomimetic Intracortical Microstimulation of Human Somatosensory Cortex for a Bidirectional Brain-computer Interface.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Intracortical microstimulation (ICMS) of human somatosensory cortex can restore tactile sensations to people who have lost them. While ICMS can elicit tactile percepts that feel like they originate in the paralyzed hand and can improve brain-computer interface (BCI) control, the percepts can vary in terms of quality and naturalness. The goal of this work was to understand how modulating ICMS parameters can affect stimulation-induced tactile perception in humans. To this end, I asked how ICMS amplitude and frequency shape tactile perception. I found that ICMS amplitude consistently increased intensity. Surprisingly, increasing the ICMS frequency evoked more intense percepts on some electrodes but evoked less intense percepts on other electrodes. These different frequency-intensity relationships were divided into groups which also evoked distinct percept qualities at different stimulus frequencies. Further, changing the spacing between individual pulses without changing the overall charge or number of pulses changed the evoked percepts on half of the tested electrodes.
I then created ICMS pulses trains based on neural data from non-human primates that represented different features of the cortical response to mechanical tactile input. Using these biomimetic ICMS trains, I found that biomimetic trains that mimicked the spiking patterns of individual cortical neurons had electrode specific effects and did not generally improve naturalness. However, biomimetic trains that mimicked the recruitment of populations of neurons by varying stimulus amplitude were able to increase the perceived naturalness across many tested electrodes. These stimulus trains also increased the intuitiveness of stimulation, resulting in percepts that felt more like real mechanical input. Finally, we found that compared to fixed parameter stimulation, these biomimetic trains produced percepts that were more focal and were more likely to have the quality of “poke.”
Biomimetic modulation then might provide a superior way to encode sensory input by evoking more focal percepts and improving the naturalness and intuitiveness of evoked percepts. Future work will need to evaluate if biomimetic amplitude modulation can produce similar effects in other people with electrodes implanted in somatosensory cortex. This method then can improve upon sensory feedback algorithms for bidirectional BCIs, potentially improving the functionality in future clinical applications.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
13 July 2021 |
| Defense Date: |
1 July 2021 |
| Approval Date: |
3 September 2021 |
| Submission Date: |
16 July 2021 |
| Access Restriction: |
1 year -- Restrict access to University of Pittsburgh for a period of 1 year. |
| Number of Pages: |
196 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Bioengineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
microstimulation, somatosensory cortex, brain-computer interfaces, microelectrodes, sensory restoration |
| Date Deposited: |
03 Sep 2021 16:45 |
| Last Modified: |
03 Sep 2022 05:15 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/41432 |
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