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Representation of Whole-body Navigation in the Primary Sensorimotor and Premotor Cortex

dc.contributor.advisor Nicolelis, Miguel A.L. Yin, Allen 2019-04-02T16:27:04Z 2019-04-02T16:27:04Z 2018
dc.description Dissertation
dc.description.abstract <p>Traditionally, brain-machine interfaces (BMI) recorded from neurons in cerebral</p><p>cortical regions associated with voluntary motor control including primary motor</p><p>(M1), primary somatosensory (S1), and dorsal premotor (PMd) cortices. Wheelchair</p><p>BMI where users’ desired velocity commands are decoded from these cortical neu-</p><p>rons can be used to restored mobility for the severely paralyzed. In addition,</p><p>spatial information in these areas during navigation can potentially can incorpo-</p><p>rated to bolster BMI performance. However, the study of spatial representation</p><p>and navigation in the brain has traditionally been centered on the hippocampal</p><p>structures and the parietal cortex, with the majority of the studies conducted in</p><p>rodents. Under this classical model, S1, M1, and PMd would not contain allocen-</p><p>tric spatial information. In this dissertation I show that a significant number of</p><p>neurons in these brain areras do indeed represent body position and orientation</p><p>in space during brain-controlled wheelchair navigation.</p><p>First, I describe the design and implementation of the first intracortical BMI</p><p>for continuous wheelchair navigation. Two rhesus monkeys were chronically im-</p><p>planted with multichannel microelectrode arrays that allowed wireless recordings</p><p>from ensembles of premotor and sensorimotor cortical neurons. While monkeys</p><p>remained seated in the robotic wheelchair, passive navigation was employed to</p><p>train a linear decoder to extract wheelchair velocity from cortical activity. Next,</p><p>monkeys employed the wireless BMI to translate their cortical activity into the</p><p>ivwheelchair’s translational and rotational velocities. Over time, monkeys improved</p><p>their ability to navigate the wheelchair toward the location of a grape reward. The</p><p>presence of a cortical representation of the distance to reward location was also</p><p>detected during the wheelchair BMI operation. These resutls demonstrate that</p><p>intracranial BMIs have the potential to restore whole-body mobility to paralyzed</p><p>patients.</p><p>Second, building upon the finding of cortical representation of the distance</p><p>to reward location, I found that during wheelchair BMI navigation the discharge</p><p>rates of M1, S1, and PMd neurons correlated with the two-dimensional (2D) room</p><p>position and the direction of the wheelchair and the monkey head. The activities</p><p>of these cells were phenomenologically similar to place cells and head direction</p><p>(HD) cells found in rat hippocampus and entorhinal cortices. I observed 44.6%</p><p>and 33.3% of neurons encoding room position in the two monkeys, respectively,</p><p>and the overlapping populations of 41.0% and 16.0% neurons encoding head di-</p><p>rection. These observations suggest that primary sensorimotor and premotor cor-</p><p>tical areas in primates are likely involved in allocentrically representing body po-</p><p>sition in space during whole-body navigation, which is an unexpected finding</p><p>given the classical model of spatial processing that attributes the representation of</p><p>allocentric space to the hippocampal formations.</p><p>Finally, I found that allocentric representation of body position in space was</p><p>not clear during passive wheelchair navigation. Two rhesus monkeys were pas-</p><p>sively transported in an experimental space with different reward locations while</p><p>neuronal ensemble activities from M1 and PMd were recorded wirelessly. The ac-</p><p>tivities of the recorded cells did not clearly represent the position and direction</p><p>of the wheelchair. These results suggest active navigation might be a prerequisite</p><p>for primary sensorimotor and PMd participation in the allocentric representation</p><p>of space.</p><p>In summary, dorsal premotor and primary sensorimotor cortical correlates of</p><p>body position and orientation in space were found in rhesus monkeys during</p><p>the operation of an intracortical wheelchair BMI for navigation. These findings</p><p>contradict the classical dichotomy of localized spatial processing, support a dis-</p><p>tributed model of spatial processing in the primate brain, and suggest both con-</p><p>text and species differences are important in neural processing. The incorporation</p><p>of the allocentric spatial information present in these cortical areas during brain-</p><p>controlled wheelchair navigation can potentially improve future BMI navigation</p><p>performance.</p>
dc.subject Neurosciences
dc.subject Biomedical engineering
dc.subject BMI
dc.subject Motor cortex
dc.subject Place cells
dc.subject Premotor cortex
dc.subject Primates
dc.subject Spatial navigation
dc.title Representation of Whole-body Navigation in the Primary Sensorimotor and Premotor Cortex
dc.type Dissertation
dc.department Biomedical Engineering

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