Wireless Brain-machine Interface Systems Research Articles

Multichannel neural recording with a 128 Mbps UWB wireless transmitter for implantable brain-machine interfaces.

To realize a low-invasive and high accuracy BMI (Brain-machine interface) system, we have already developed a fully-implantable wireless BMI system which consists of ECoG neural electrode arrays, neural recording ASICs, a Wi-Fi based wireless data transmitter and a wireless power receiver with a rechargeable battery. For accurate estimation of movement intentions, it is important for a BMI system to have a large number of recording channels. In this paper, we report a new multi-channel BMI system which is able to record up to 4096-ch ECoG data by multiple connections of 64-ch ASICs and time division multiplexing of recorded data. This system has an ultra-wide-band (UWB) wireless unit for transmitting the recorded neural signals to outside the body. By preliminary experiments with a human body equivalent liquid phantom, we confirmed 4096-ch UWB wireless data transmission at 128 Mbps mode below 20 mm distance.

Backscattering Neural Tags for Wireless Brain-Machine Interface Systems

Brain-machine interface (BMI) technology has tremendous potential to revolutionize healthcare by greatly improving the quality of life of millions of people suffering from a wide variety of neurological conditions. Radio-frequency identification (RFID)-inspired backscattering is a promising approach for wireless powering of miniature neural sensors required in BMI interfaces. We analyze the functionality of millimeter-size loop antennas in the wireless powering of miniature cortical implants through measurements in a human head equivalent liquid phantom and in the head of a postmortem pig. For the first time, we present the design and measurement of a miniature 1×1×1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> backscattering device based on a cubic loop connected with an RFID integrated circuit (IC). Our measurement results show that this very small loop receives sufficient electromagnetic power to activate the IC when the device is implanted in a pig's head. This demonstrates the feasibility of extremely small implant antennas in challenging wireless biomedical systems.

Noninvasive detection of brain order-disorder transitions using functional EEG

Systems capable of real-time monitoring have several potential health-related applications, particularly for individuals who desire to age in place as well as those living with acute health conditions. An electrical response exists near the scalp from ionic transmission within neurons (brain cells) and may be measured noninvasively by electroencephalography (EEG). Use of EEG for detecting convulsive1, 2 and nonconvulsive3 epilepsy is well developed and documented in the literature with sensitivities between 80 and 90%. Real-time EEG monitoring during sleep may provide valuable information on alterations in sleep patterns, which has been shown to be effective in detecting and predicting anxiety, depression, and early dementia in the elderly.4, 5 Anxiety and depression in turn have been directly correlated to numerous deleterious chronic health conditions such as cardiovascular disease, stroke, sleep disorders, and diabetes. Having a mechanism to detect and predict onset of anxiety and depression would be a powerful out-of-clinic tool. A potential application for at-home EEGmonitoring is assessment of head injuries and post-concussion syndrome. As these conditions affect the alertness of individuals, there is evidence that head injuries affect the alpha wave patterns of the EEG in the range of 8–12Hz.6 While many previous studies have shown the potential for EEG to detect and assess cognitive impairments, most have been conducted under controlled research conditions in the clinic. Extension of these findings to the home requires further investigation as environmental conditions are likely to affect the EEG data collected. Wang and colleagues7 showed the efficacy of an untethered, wireless brain-machine interface system using 20 dry electrodes embedded into a head cap. This wireless ‘functional’ EEG Figure 1. (a) User-friendly smartphone interface to the functional electroencephalography (f-EEG) head mount. (b) 1D Peano-Hilberttype space-filling curve replaces the 3D layout of the electrodes. (c) High-density wired conventional EEG is replaced by a wireless hat. (d) Right-hemisphere brain f-EEG response stimulated by the visual input for a left eye dominator: before (left) and after compressive sensing (middle), as well as the difference errors (right). (e) Singlet electrode-averaged EEG (left) vs. pair-electrode fluctuation f-EEG (right) reflecting the subject’s intention to point a computer screen cursor to the left as opposed to the right: 121 electrodes (1 node to 82 points), 250Hz (averaged over 1/16 second).

Miniature implantable and wearable on-body antennas: towards the new era of wireless body-centric systems [antenna applications corner

Wireless body-centric sensing systems have an important role in the fields of biomedicine, personal healthcare, safety, and security. Body-centric radio-frequency identification (RFID) technology provides a wireless and maintenance-free communication link between the human body and the surroundings through wearable and implanted antennas. This enables real-time monitoring of human vital signs everywhere. Seamlessly integrated wearable and implanted miniaturized antennas thus have the potential to revolutionize the everyday life of people, and to contribute to independent living. Low-cost and low-power system solutions will make widespread use of such technology become reality. The primary target applications for this research are body-centric sensing systems and the relatively new interdisciplinary field of wireless brain-machine interface (BMI) systems. Providing a direct wireless pathway between the brain and an external device, a wireless brain-machine interface holds an enormous potential for helping people suffering from severely disabling neurological conditions to communicate and manage their everyday life more independently. In this paper, we discuss RFID-inspired wireless brain-machine interface systems. We demonstrate that mm-size loop implanted antennas are capable of efficiently coupling to an external transmitting loop antenna through an inductive link. In addition, we focus on wearable antennas based on electrically conductive textiles and threads, and present design guidelines for their use as wearable-antenna conductive elements. Overall, our results constitute an important milestone in the development of wireless brain-machine interface systems, and a new era of wireless body-centric systems.

A Fully Implantable, Programmable and Multimodal Neuroprocessor for Wireless, Cortically Controlled Brain-Machine Interface Applications

Reliability, scalability and clinical viability are of utmost importance in the design of wireless Brain Machine Interface systems (BMIs). This paper reports on the design and implementation of a neuroprocessor for conditioning raw extracellular neural signals recorded through microelectrode arrays chronically implanted in the brain of awake behaving rats. The neuroprocessor design exploits a sparse representation of the neural signals to combat the limited wireless telemetry bandwidth. We demonstrate a multimodal processing capability (monitoring, compression, and spike sorting) inherent in the neuroprocessor to support a wide range of scenarios in real experimental conditions. A wireless transmission link with rate-dependent compression strategy is shown to preserve information fidelity in the neural data. At 32 channels, the neuroprocessor has been fully implemented on a 5mm×5mm nano-FPGA, and the prototyping resulted in 5.19 mW power consumption, bringing its performance within the power-size constraints for clinical use. The optimal design for compression and sorting performance was evaluated for multiple sampling frequencies, wavelet basis choice and power consumption.

Design of Wireless Links to Implanted Brain–Machine Interface Microelectronic Systems

This letter presents a monolithic integration of an antenna with an array of neural recording electrodes on a flexible thin film. The structure was designed for long-term neural recording in a wireless brain-machine interface system. The implant-on-body antenna pair is optimized for maximal link power efficiency to maximize the battery life of a portable outside-body control unit. We provide guidelines for the design of the sub-skin-depth implant antenna and validate the antenna simulation model with wireless link measurements in air. We propose a new computational analysis of both the power and voltage delivery to the battery-free implant under design variations to guarantee efficient on-chip RF-to-dc conversion.