Novel Techniques for Neuromodulation and Neural Signal Analysis

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