A Miniature Low-Power Multi-Biomarker-Based Brain Sensor for Closed-Loop DBS

Abstract

Thus far only a few closed-loop deep brain stimulation (DBS) devices have been developed. These devices measure one biomarker for closing the stimulation loop. However, there are many types of neurological disorders requiring different biomarkers to be monitored. Therefore, a multiple-biomarker-based neural sensing device is needed to achieve closed-loop DBS for multiple disorders. This paper presents the design, fabrication, and in vitro evaluation of a miniature multi-biomarker-based neural sensor for closed-loop DBS. The developed device is capable of concurrent sensing and processing of action potentials (APs) and local field potentials (LFPs) from within the brain. A signal conditioning circuit involving the following stages is incorporated into the device: pre-amplification through an instrumentation amplifier, noise and artifact rejection via active filters, and post-amplification by means of micro-power operational amplifiers. It is a portable and miniature device allowing for use in closed-loop DBS of small laboratory animals. The device benefits from a gain of 100 dB in both the biomarker paths. The frequency specifications of the AP and LFP sensing circuits are 300 Hz–10 kHz and 2 Hz–40 Hz, respectively. It requires only $965~\mu \text{A}$ to operate on both channels from a 3-V coin battery. The device has been validated via a bench-test by using both sinusoidal signals and pre-recorded human neural signals. In addition, in vitro validation using saline solution has been carried out on the device confirming its accurate operation. The experimental results are presented and discussed.