Easing tinnitus with specially timed signals
Millions of Americans hear ringing in their ears — a condition called tinnitus — and new research shows an experimental device could help quiet the phantom sounds by targeting unruly nerve activity in the brain.
In a new study in Science Translational Medicine, a team from the University of Michigan (UM) reported the results of the first animal tests and clinical trial of the approach, including data from 20 human tinnitus patients, sciencedaily.com wrote.
Based on years of scientific research into the root causes of the condition, the device uses precisely timed sounds and weak electrical pulses that activate touch-sensitive nerves, both aimed at steering damaged nerve cells back to normal activity.
Human participants reported that after four weeks of daily use of the device, the loudness of phantom sounds decreased, and their tinnitus-related quality of life improved. A sham ‘treatment’ using just sounds did not produce such effects.
Results from tests in guinea pigs and a double-blind human study funded by the Coulter Foundation validate years of preclinical research funded by the National Institutes of Health, including previous tests in guinea pigs.
The UM team has new National Institutes of Health (NIH) funding for an additional clinical trial to further refine the approach. UM holds a patent on the concept behind the device and is developing it for potential commercialization.
Susan Shore, the UM Medical School professor who leads the research team, said, “The brain, and specifically the region of the brainstem called the dorsal cochlear nucleus, is the root of tinnitus.
“When the main neurons in this region, called fusiform cells, become hyperactive and synchronize with one another, the phantom signal is transmitted into other centers where perception occurs.
“If we can stop these signals, we can stop tinnitus. That is what our approach attempts to do, and we’re encouraged by these initial parallel results in animals and humans.”
A dual-stimulus approach to treating tinnitus
The approach, called targeted bimodal auditory-somatosensory stimulation, involves two senses. The device plays a sound into the ears, alternating it with precisely timed, mild electrical pulses delivered to the cheek or neck.
This sets off a process called stimulus-timing dependent plasticity, or STDP, which was first explored in animals and led to long-term changes in the rate at which the nerves fire.
The approach aims to reset the activity of fusiform cells, which normally help our brains receive and process both sounds and sensations such as touch or vibration — what scientists call somatosensory inputs.
Under normal conditions, fusiform cells help our brains focus on where sounds are coming from, and help us tune out sensations that result from the movement of our own head and neck.
But the UM team’s previous work in animals showed that loud noise can trigger a change in the nerve cells’ activity — altering its timing so that they fire off synchronized signals spontaneously instead of waiting for an actual sound in the environment.