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Bidirectional Brain-Machine Interfaces for Modulating Stimulation and Neural Plasticity


Jo, HyeongChan (2022) Bidirectional Brain-Machine Interfaces for Modulating Stimulation and Neural Plasticity. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/df0t-1t79.


In prosthetics, tactile feedback can let us feel how we interact with the environment. Without this, it is extremely difficult to perform a motor task with fine control. The same idea can be applied in the brain-machine interface (BMI), which is an interface that directly connects external devices such as prosthetic limbs to the brain. Bidirectional BMI can deliver a stimulation to the brain as a sensory feedback, which can improve the performance of motor tasks. Such a bidirectional BMI can also serve a different role, if the stimulation encodes different information: if it encodes neural activity from another brain area, for example, then bidirectional BMI can provide a bypass for a damaged neural circuit. This may also affect the neural connectivity, strengthening or weakening the underlying neural connections. In this thesis, we present experiments that explore such applications of bidirectional BMI. First, we describe an experiment for characterizing neural connectivity between different brain areas. We found neural connectivity between supramarginal gyrus (SMG) and PMv (ventral premotor area), and also between anterior intraparietal (AIP) and Brodmann’s area 5 (BA5), characterized by field-field, spike-field, and partial spike-field coherence. Through partial spike-field coherence, we also revealed that the spikes in PMv may drive the activity in SMG, which is obscured in ordinary spike-field coherence. Next, we provide evidence of changes in neural connectivity caused by stimulation in S1. With spike-triggered stimulation, which delivers stimulation in S1 in response to spikes recorded in a selected channel in SMG, we could significantly increase the correlation between SMG and S1, measured by the spike time tilling coefficient (STTC) to avoid dependencies of the correlation on firing rates. Furthermore, we found that not only spike-triggered stimulations, but also random stimulations on multiple channels in S1, can vary partial spike-field coherence in theta and alpha bands within S1; such changes mostly occurred in channel pairs with zero phase difference in partial spike-field coherence. Finally, we demonstrate the possibility of volitional control on stimulation pattern in bidirectional BMI. It is shown that the participants could not only increase or decrease a single-channel firing rate, but also hold the firing rate in a given range, demonstrating a fine control over firing rate. These findings would begin to establish a framework for closed-loop modulation of neural activity with bidirectional BMI and could be used to develop new treatments for neurological damage, such as to promote plasticity in or bridge brain areas affected by stroke.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Brain-machine interface (BMI), bidirectional BMI, neural connectivity, coherence, brain stimulation
Degree Grantor:California Institute of Technology
Division:Biology and Biological Engineering
Major Option:Bioengineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Andersen, Richard A.
Thesis Committee:
  • Burdick, Joel Wakeman (chair)
  • Rutishauser, Ueli
  • Siapas, Athanassios G.
  • Andersen, Richard A.
Defense Date:29 July 2021
Record Number:CaltechTHESIS:08272021-174548241
Persistent URL:
Jo, HyeongChan0000-0002-1435-9124
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14345
Deposited By: HyeongChan Jo
Deposited On:03 Sep 2021 00:44
Last Modified:08 Nov 2023 00:08

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