title: Autonomous control for mechanically stable navigation of microscale implants in brain tissue to record neural activity.
abstract: Emerging neural prosthetics require precise positional tuning and stable interfaces with single neurons for optimal function over a lifetime. In this study, we report an autonomous control to precisely navigate microscale electrodes in soft, viscoelastic brain tissue without visual feedback. The autonomous control optimizes signal-to-noise ratio (SNR) of single neuronal recordings in viscoelastic brain tissue while maintaining quasi-static mechanical stress conditions to improve stability of the implant-tissue interface. Force-displacement curves from microelectrodes in in vivo rodent experiments are used to estimate viscoelastic parameters of the brain. Using a combination of computational models and experiments, we determined an optimal movement for the microelectrodes with bidirectional displacements of 3:2 ratio between forward and backward displacements and a inter-movement interval of 40 s for minimizing mechanical stress in the surrounding brain tissue. A regulator with the above optimal bidirectional motion for the microelectrodes in in vivo experiments resulted in significant reduction in the number of microelectrode movements (0.23 movements/min) and longer periods of stable SNR (53 % of the time) compared to a regulator using a conventional linear, unidirectional microelectrode movement (with 1.48 movements/min and stable SNR 23 % of the time).
authors.affiliation: Biomedical Engineering, School of Biological and Health Systems Engineering, Arizona State University, ECG 334, P. O. Box 879709, Tempe, AZ, 85287-9709, USA.
authors.forename: Sindhu
authors.initials: S
authors.lastname: Anand
authors.affiliation: Biomedical Engineering, School of Biological and Health Systems Engineering, Arizona State University, ECG 334, P. O. Box 879709, Tempe, AZ, 85287-9709, USA.
authors.forename: Swathy Sampath
authors.initials: SS
authors.lastname: Kumar
authors.affiliation: Biomedical Engineering, School of Biological and Health Systems Engineering, Arizona State University, ECG 334, P. O. Box 879709, Tempe, AZ, 85287-9709, USA. jit@asu.edu.
authors.forename: Jit
authors.initials: J
authors.lastname: Muthuswamy
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D004567:Electrodes, Implanted; D004867:Equipment Design; D008297:Male; D055595:Mechanical Phenomena; D008839:Microelectrodes; D009038:Motion; D009474:Neurons / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D059629:Signal-To-Noise Ratio; D013314:Stress, Mechanical
keywords: Microdrive; Neural implants; Neural interfaces; Probes; Prostheses; Robot; Soft tissue