Vol. 24, Issue 1: Fall 2016

Pixie Dust for your Nerves: A wireless sensor changing the game of neural modulation and therapy

Chelsey Campillo

In today’s medical age, many diseases are treated with pharmaceutical drugs, such as packaged painkillers and hormones; however such treatments can be very taxing on the body. One solution to this problem may be bioelectronic medicine – a new form of treatment that originated in 1998 by Dr. Kevin Tracey, the President, Director, and CEO of The Feinstein Institute for Medical Research.

As described by the Feinstein Institute, bioelectronic medicine is an interdisciplinary field that incorporates the work of clinicians, molecular biologists, neuroscientists, and engineers in order to create devices that can target specific molecular pathways in the nervous system. Products from the bioelectronic medicine field include the neural tourniquet (a device that uses nerve stimulation to slow blood loss) and other nerve stimulators that are currently undergoing human clinical trials.

Dr. Jose Carmena and Dr. Michel Maharbiz, researchers at the University of California, Berkeley and Helen Wills Neuroscience Institute, are currently working to further develop bioelectronic technologies. One such device, which was described in the August 3, 2016 issue of Neuron, is a wireless, ultrasound-based recording device, otherwise known as “neural dust.”

The lower prevalence of obesity in the male Costa Rican population suggests healthier lifestyles. However, this trend is less common in Costa Rican women, who have a higher risk of high blood pressure and diabetes, which could be a result of the high fertility levels. It is important to analyze these relationships because “from a life expectancy standpoint, it is thus better to live in Costa Rica for low-SES individuals” (Dow). Other research on the correlation between SES and health has also found that “adults with incomes four times or more above the poverty level were more than two times as likely as the adults below poverty level to engage in rigorous physical activity three to four times per week” (Center for Disease Control). A possible confounding variable that is leading to the differences in mortality rates and life expectancy between Costa Rica and the United States is the great amount of diversity in the United States.

Neural dust is a wireless, millimeter-scale sensor that is implanted alongside a nerve, muscle, or any organ of interest. The sensor, which is just the size of a grain of sand, includes a flexible printed circuit board, two recording electrodes, transistor, and piezoelectric crystal. In addition to the wireless mote, an external transceiver board plays a crucial role in powering and receiving data from the sensor. More specifically, the external board emits ultrasonic waves to the piezoelectric crystal on the mote, which converts the waves into usable energy. In addition, the crystal will reflect ultrasonic waves back to the external transceiver board. This form of signaling is otherwise known as “backscatter.” In the event that a voltage spike arises from a nearby cell, the spike will alter the wave vibrations and electric circuit between the two electrodes. Thus, the signal recorded from the backscatter will also change.

The wireless trait of neural dust is a great advantage in monitoring neural signaling. Current methods of recording the peripheral nervous system, including fMRI, EEG, and MEGs, rely heavily on the use of wires and cannot record the activity of individual cells. Although these methods of recording are non-invasive, they fail to provide high resolution in recording physiological processes at the cellular level. Neural dust, on the other hand, allows for stable, wireless recordings with high resolution of specific neural pathways and signaling. Since a single nerve bundle conducts countless signals to and from multiple organ sites, it is necessary to be able to record from specific sites along a single nerve - at the cellular level. With this technology, researchers can collect unprecedented data on cognitive processes such as perception, memory, language, and movement control. Neural dust even shows great potential to be able to record from a distinguished site within a nerve.

In comparison, some neural recording methods use radio waves instead of ultrasonic waves. The use of electromagnetic energy –including radio waves– can be problematic, since they are deemed to be more harmful in the human body than ultrasound. Meanwhile, neural dust introduces a much less invasive way of treating neurological diseases, especially because ultrasound is found to be safer than electromagnetic energy. In 2008, the FDA determined that a higher power of ultrasound can be used in the body in comparison to radio waves.

Ultimately, the functions of neural dust include scanning and stimulating nerve cells, and clinical studies show that neurostimulating devices like neural dust can help with epilepsy, bladder control, and appetite suppression. Due to the device’s millimeter-scale and precise recording capability, it can help treat neurological disorders with a higher likelihood of avoiding infections and other major side effects during treatment. Already, Maharbiz and Carmena are developing a version of neural dust that is smaller than 1 mm3, which can better avoid irritations in the body. Moreover, new technologies such as neural dust can help further advance neuromodulation therapies - treatments that involve direct electrical stimulation to the central and peripheral nervous system.

Many challenges lie ahead for this line of therapeutic technology, and it will take several years before it can be applied in humans. However, many scientists around the globe are working diligently in this emerging field of study, and there are already ongoing experiments using a similar electrode as neural dust in paralyzed monkeys. On November 9, 2016, neuro-engineers at Brown University published results in Nature that showed a wireless device’s capability of giving paralyzed primates the ability to walk again. However, the device they used in order to promote movement in the leg was slightly larger than 1 mm3 – and this is where neural dust can be of aid.

About the Author

Chelsey Campillo is a third-year undergraduate student from Maryland. She is majoring in Molecular and Cell Biology, with an emphasis in Neurobiology. She loves learning about anything related to the human brain, and hopes to get her PhD in neuroscience in the future.