Researchers win grant from the National Science Foundation to target tinnitus

June 2011

A team of Wayne State University researchers was awarded $330,000 from the National Science Foundation to develop a 3-D neural probe. Their aim is to develop an implantable device that will suppress tinnitus, a neurological disorder that affects more than 250 million people worldwide.

With the ever-expanding knowledge in the fields of neuroscience and neurosurgery, there is an increasing need for devices and tools that enable neuroscientists to delve deeper into the physiological and pathological function of neural tissue at the level of groups of neurons. A variety of neural probes have significantly contributed to important discoveries within the neuroscience community. Despite this steady progress over the past two decades, there is a strong demand for improved probes with new functionality. The Wayne State team will address this need by developing a 3-D neural probe that simplifies the fabrication and assembly process of high-density 3-D arrays of electrodes.

Yong Xu, Ph.D., associate professor of Electrical and Computer Engineering, and Jinsheng Zhang, Ph.D., associate professor and associate research director of Otolaryngology and associate professor of Communication Sciences and Disorders, said the project, "A novel 3-dimensional neural probe technology combining electrical and chemical interfaces," is based on a flexible skin structure and simple folding procedure. The technology will enable the integration of micro-channels for neurotransmitter-based chemical stimulation and local delivery of drugs for biocompatibility improvement.

The team aims to develop next generation 3-D neural probes that can electrically and chemically stimulate neurons with greater efficacy and can monitor neural activity from deeper regions of the brain.

"One highly desirable feature is 3-D array of electrodes to monitor or modulate neural activities with 3-D spatial resolution," Dr. Xu said. "In addition, it is very advantageous to integrate micro-channels that enable neurotransmitter-based chemical stimulation and local drug delivery to reduce or suppress tissue response, one of the major obstacles for successful chronic implantation. Currently there is no good method of making 3-D array of electrodes, let alone the integration of micro-channels with 3-D arrays of electrodes."

Naturalistic chemical stimulation using integrated micro-channels could address some of the issues concerning pure electrical stimulation of neural probes, such as poor spatial resolution, degradation of metal electrodes and water hydrolysis due to the large stimulation currents and charges required to depolarize the neuron cells. In addition, the fabrication process is post-complementary metal-oxide-semiconductor compatible, allowing the monolithic integration of CMOS circuits with neural probes using an economical post-CMOS process.

"These important features will help us become the leader in the new round of worldwide races to develop the next generation neural probes," Dr. Xu said. "The successful development of the implantable device will be useful for treating a variety of neurological disorders, such as refractory paralysis, epilepsy, Parkinson's disease, Alzheimer's disease, blindness and tinnitus."

The doctors will target tinnitus suppression with the implantable neural probe they are developing. Tinnitus affects 50 million Americans and more than 250 million people worldwide. In the United States alone, between 3 million and 4 million people are debilitated by the condition, often described as a persistent ringing or hissing in the ears.

There is no reliable treatment for tinnitus. Pharmacologic treatment and rehabilitation can improve the emotional and psychological reaction to tinnitus, but this therapy has been unreliable and requires long periods of time and a considerable amount of patient compliance. Recent clinical studies have shown that stimulation of the auditory cortex through transcranial magnetic stimulation or direct electrical stimulation has acute or longer-lasting suppressive effects, providing new hope in finding an effective and reliable therapy.

"Our recent work has shown that electrical stimulation is a promising method to suppress tinnitus," Dr. Zhang said. "Once we better understand the mechanisms underlying electrical and chemical stimulation-induced suppression, we will be fully focused on advancing the engineering fabrication to create a minimally- or even non-invasive medical device for diagnosis and treatment."