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Cortical neuromodulations associated with local and global strategies used to improve performance in a novel brain machine interface task
Dissertation   Open access

Cortical neuromodulations associated with local and global strategies used to improve performance in a novel brain machine interface task

Nathaniel Reese Bridges
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2017
DOI:
https://doi.org/10.17918/etd-7453
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Abstract

Brain-computer interfaces Spinal cord--Wounds and injuries--Research Biomedical Engineering Neurons
It is becoming increasingly evident that neurons used to control an external device (i.e. direct neurons) in a Brain Machine Interface (BMI) task modulate their activity to enhance performance in the task. Research has also shown that neurons not directly linked to the BMI (i.e. indirect neurons) also modulate their activity but their role and the extent of modulation is unclear. Understanding the role of these indirect neurons is especially important when considering nervous system injuries such as spinal cord injury (SCI) in order to optimize performance in the injured state. In an effort to increase our understanding of indirect neurons, I developed a novel bilateral perturbation-based BMI tilt task that can be executed by rats with and without SCI. Within this task, I demonstrate that both hemispheres are equally engaged pre and post-SCI, starting performance begins well above chance and both animal types increase task performance with practice. Uniquely, animals can achieve performance improvements without traditional water rewards and be divided into distinct learning and non-learning groups. As animals learned, information changes suggest that learning animals use a combination of global (direct and indirect neuron modulations) and local strategies (direct-neuron specific modulations), whereas non-learning animals primarily used primarily global strategies. Interestingly in learning animals, only direct neurons increased information by increasing firing rate and timing differences between select tilt types, while indirect neurons only modulated firing rate differences. Additionally, only these direct neurons increased redundancy with practice. These results show that the cortex selectively modulates regions associated with BMI use but that neural effects can be seen in regions as far as the opposite hemisphere.

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