Bidirectional Neural Interface and Closed-Loop Control

Abstract

Bidirectional neural interface with closed-loop operation is important for both fundamental neuroscience research and the development of next-generation neuroprosthetics. However, the circuit and system design of bidirectional closed-loop brain–machine interfaces have not been well explored. This chapter discusses two of the most important issues, stimulation artifacts and closed-loop controllers. Stimulation artifacts are known issues in simultaneous neural stimulation and recording, which corrupt the neural recording. Even though a lot of studies have proposed methods to cancel or attenuate the stimulation artifacts, a comprehensive study considering different electrode configurations and circuit topologies is missing. This chapter presents the analysis, methods, experimental results, and design suggestions to reduce the effects of artifacts. The importance of a closed-loop methodology cannot be overemphasized in neural engineering. However, the design of closed-loop neural interface electronics has been a missing link in BMI systems. This chapter summarizes the mechanisms of different closed-loop neural interface systems, and presents the design of a general–purpose analog PID controller. The PID controller is integrated in a bidirectional neural interface system-on-chip (SoC). Experimental results are presented.