Abstract
The application of a neural stimulator to small animals is highly desired for the investigation of electrophysiological studies and development of neuroprosthetic devices. For this purpose, it is essential for the device to be implemented with the capabilities of full implantation and wireless control. Here, we present a fully implantable stimulator with remote controllability, compact size, and minimal power consumption. Our stimulator consists of modular units of (1) a surface-type cortical array for inducing directional change of a rat, (2) a depth-type array for providing rewards, and (3) a package for accommodating the stimulating electronics, a battery and ZigBee telemetry, all of which are assembled after independent fabrication and implantation using customized flat cables and connectors. All three modules were packaged using liquid crystal polymer (LCP) to avoid any chemical reaction after implantation. After bench-top evaluation of device functionality, the stimulator was implanted into rats to train the animals to turn to the left (or right) following a directional cue applied to the barrel cortex. Functionality of the device was also demonstrated in a three-dimensional (3D) maze structure, by guiding the rats to better navigate in the maze. The movement of the rat could be wirelessly controlled by a combination of artificial sensation evoked by the surface electrode array and reward stimulation. We could induce rats to turn left or right in free space and help their navigation through the maze. The polymeric packaging and modular design could encapsulate the devices with strict size limitations, which made it possible to fully implant the device into rats. Power consumption was minimized by a dual-mode power-saving scheme with duty cycling. The present study demonstrated feasibility of the proposed neural stimulator to be applied to neuroprosthesis research.
Highlights
Brain–computer interface technology has shown a wide range of potential applications in clinical areas and scientific studies by means of the sophisticated recording or stimulating of corticalElectronics 2019, 8, 706; doi:10.3390/electronics8060706 www.mdpi.com/journal/electronicsElectronics 2019, 8, 706 neurons [1,2,3]
Such devices can contribute to the field of general neural prosthetics as they are largely based on the same key technological components, including electrode arrays, circuit designs, wireless power and communications circuits, miniaturization, and hermetic packaging
5.9gg weight) weight) encasing encasing the the wireless wireless stimulating stimulating circuit circuit board board package was assembled with independently fabricated surface and depth electrode arrays via a feedthrough, was assembled with independently fabricated surface and depth electrode arrays via a feedthrough, connectors and and cables
Summary
Brain–computer interface technology has shown a wide range of potential applications in clinical areas and scientific studies by means of the sophisticated recording or stimulating of corticalElectronics 2019, 8, 706; doi:10.3390/electronics8060706 www.mdpi.com/journal/electronicsElectronics 2019, 8, 706 neurons [1,2,3]. Electrical stimulation of the cortex in animal models can be useful for preclinical evaluations of safety and efficacy of implantable neural prostheses as well as for basic research when studying neural functions and behaviors. One of these approaches is the control of animal motion by electrically modulating particular locations of the animal cortex based on knowledge of animal brain functions and device technology related to implantable electrodes and stimulating systems. The electrical stimulation of the primary sensory cortex (S1) is known to induce virtual touching sensation of the contralateral whisker [6,7,8,9]
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