Non-invasive Brain Monitoring and Stimulation

Abstract

The ability to excite or block brain circuits at any desired location with focused neuromodulation techniques is critically important not only for understanding how the brain works, but also for the treatment of neural diseases. Currently neuromodulation has been applied to a broad area of diseases including: stroke, traumatic brain injury, pain, depression, bipolar disorder, anxiety, obsessive compulsive disorder, addiction, attention deficit, autism spectrum disorders, Alzheimer's disease and other dementias, schizophrenia, and epilepsy. Current neuromodulation methods are either FDA approved or under clinical trials. In this work, we develop a focused transcranial magnetic stimulator (TMS) for targeted brain stimulation. We also develop a electroencephalography (EEG) based brain monitoring technique and envision that eventually we can build a closed-loop neural modulation and monitoring system in the near future to flexibly adjust treatments according to measured responses. For the EEG monitoring, besides following the traditional brain electrical activity map, channel coherence, and correlation analysis methods, we also developed a 3-D signal tracking technique that could monitor brain activity and associate measured data with behaviors. Brain activities of delta, theta, alpha, and beta waves were traced in 3D when subjects were performing math calculations in mind or self-contemplating imagination. The technique allows us to accomplish recording and analysis without using event repeats as with the event related potential (ERP) measurement case. For the TMS work, we first developed both transient magnetic and electric vector field measurement probes with high spatial resolution and sensitivity. They were used for measurement and calibration of TMS generated 3-D vector field distribution and matched well with theoretical calculations. We also theoretically designed and experimentally implemented several different types of TMS systems that can produce a focused field, including a shield assistant field focusing system. A novel focused TMS system was developed, and we have used this system to induce reproducible unilateral movements on both mice and rats. The EMG signal was recorded and the focal spot of this TMS system was proved to be in the scale of only 2mm. Our future work will focus on both animal and human TMS coil development.