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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2022)

Neuromodulation, targeting either the central nervous system or peripheral nervous system, is a viable therapy for many diseases, particularly for patients who are refractory to traditional treatments. The first part of this thesis aims to develop the non-invasive neuromodulation technique targeting the central nervous system, specifically the brain with transcranial direct current stimulation (tDCS). Compared to the conventional tDCS which uses two large pad electrodes, high-density tDCS has recently received more attention. With the high-density electrode system, it is able to achieve better stimulation performance in terms of stimulation intensity and focality. To further improve the performance of this promising technique, we characterize the performance with respect to the electrode factor for the high-density tDCS system. In addition, we have developed an optimization algorithm, Stimulation with Balanced Focality and Intensity (SBFI), to guide the high-density system, which provides effective and focal stimulation. The robustness of the computational model with standard tissue conductivity is also evaluated. The proposed technique can be applied to transcutaneous spinal cord stimulation (tSCS). The second part aims to develop the electrical modulation technique targeting the peripheral nervous system, specifically one of the second brain organs - colon. Electrical stimulation has been demonstrated as an alternative approach to alleviate intractable colonic motor disorders. However, knowledge of optimal electrical stimulation modalities and regional specific functional effects of colonic neuromodulation is lacking. We have investigated the regional colonic motility in response to different electrical stimulation modalities. In addition, we have developed a novel and efficient technique employing bio-impedance characterization to monitor colonic motor activity.

  • 1 supplemental ZIP
Cover page: Novel Techniques for Neuromodulation and Neural Signal Analysis
  • Article
  • Peer Reviewed
UCLA Previously Published Works (2022)
Electrical stimulation has been demonstrated as an alternative approach to alleviate intractable colonic motor disorders, whose effectiveness can be evaluated through colonic motility assessment. Various methods have been proposed to monitor the colonic motility and while each has contributed towards better understanding of colon motility, a significant limitation has been the spatial and temporal low-resolution colon motility data acquisition and analysis. This paper presents the study of employing bio-impedance characterization to monitor colonic motor activity. Direct distal colon stimulation was undertaken in anesthetized pigs to validate the bio-impedance scheme simultaneous with luminal manometry monitoring. The results indicated that the significant decreases of bio-impedance corresponded to strong colonic contraction in response to the electrical stimulation in the distal colon. The magnitude/power of the dominant frequencies of phasic colonic contractions identified at baseline (in the range 2-3 cycles per minute (cpm)) were increased after the stimulation. In addition, positive correlations have been found between bio-impedance and manometry. The proposed bio-impedance-based method can be a viable candidate for monitoring colonic motor pattern with high spatial and temporal resolution. The presented technique can be integrated into a closed-loop therapeutic device in order to optimize its stimulation protocol in real-time.
    Cover page: Bio-impedance method to monitor colon motility response to direct distal colon stimulation in anesthetized pigs
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2020)

    Background

    Knowledge on optimal electrical stimulation (ES) modalities and region-specific functional effects of colonic neuromodulation is lacking. We aimed to map the regional colonic motility in response to ES of (a) the colonic tissue and (b) celiac branch of the abdominal vagus nerve (CBVN) in an anesthetized porcine model.

    Methods

    In male Yucatan pigs, direct ES (10 Hz, 2 ms, 15 mA) of proximal (pC), transverse (tC), or distal (dC) colon was done using planar flexible multi-electrode array panels and CBVN ES (2 Hz, 0.3-4 ms, 5 mA) using pulse train (PT), continuous (10 min), or square-wave (SW) modalities, with or without afferent nerve block (200 Hz, 0.1 ms, 2 mA). The regional luminal manometric changes were quantified as area under the curve of contractions (AUC) and luminal pressure maps generated. Contractions frequency power spectral analysis was performed. Contraction propagation was assessed using video animation of motility changes.

    Key results

    Direct colon ES caused visible local circular (pC, tC) or longitudinal (dC) muscle contractions and increased luminal pressure AUC in pC, tC, and dC (143.0 ± 40.7%, 135.8 ± 59.7%, and 142.0 ± 62%, respectively). The colon displayed prominent phasic pressure frequencies ranging from 1 to 12 cpm. Direct pC and tC ES increased the dominant contraction frequency band (1-6 cpm) power locally. Pulse train CBVN ES (2 Hz, 4 ms, 5 mA) triggered pancolonic contractions, reduced by concurrent afferent block. Colon contractions propagated both orally and aborally in short distances.

    Conclusion and inferences

    In anesthetized pigs, the dominant contraction frequency band is 1-6 cpm. Direct colonic ES causes primarily local contractions. The CBVN ES-induced pancolonic contractions involve central neural network.
      Cover page: The effect of colonic tissue electrical stimulation and celiac branch of the abdominal vagus nerve neuromodulation on colonic motility in anesthetized pigs
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