Tinnitus is a condition in which individuals perceive sound or buzz without external sources and can affect a large part of the global population. Many patients report sleep disruptions, but the exact link between tinnitus and sleep remains elusive. A major study led by Dr. Linus Milinski and Dr. Victoria M. Bajo of Oxford University provide new insights into this link. Their work, published in the peer-reviewed journal PLOS One, proposes important findings about brain activity related to tinnitus, which refers to controlling electrical signals in the brain such as hearing and perception, influenced by animal studies using ferrets.
The researchers used a small group of adult ferrets exposed to mild noise trauma to induce tinnitus-like symptoms. They used a variety of behavioral tinnitus tests to assess the animal’s ability to detect silence, lacking strong indicators of tinnitus. The team obtained tinnitus indicators after noise exposure and up to six months later. In addition, records of healthy hearing pathways from the ear to the brain were performed to check the integrity of the auditory system. The results show that persistence in auditory processing, frequency-specific deficits (describing how the brain analyzes sound signals in the ears) and persistent signs of tinnitus, indicating persistent hearing impairment and tinnitus.
Crucially, this study explores how sleep changes when animals develop tinnitus and how patterns of brain activity associated with tinnitus are regulated throughout sleep and awakening. Behavioral and brain activity data suggest that ferrets experiencing tinnitus also exhibit disrupted sleep patterns, increased wake-up episodes and changes in sleep patterns during deep sleep phases, thus supporting the possibility of tinnitus disrupting sleep. However, neural markers of tinnitus appear to be significantly reduced during sleep, suggesting that sleep may temporarily inhibit the perception of phantom hearing. “Although tinnitus may interfere with sleep, our findings suggest that sleep-dependent brain activity may also regulate neural patterns associated with tinnitus, which may have implications for the development of sleep-based interventions,” explains Dr. Milinski.
The study’s brain wave record tracks the brain’s electrical activity to assess sleep and arousal status and brain responses to stimuli, highlighting that the neural responses to sounds vary at different stages of awakening and sleep. During awake and REM sleep, hearing-induced potential is most pronounced and decreases during non-bibi eye movement sleep. This increases the likelihood of tinnitus-related ADHD that promotes responsiveness to stimuli may not be uniform, and sleep may provide natural, albeit temporarily relieve symptoms. In fact, once ferrets develop tinnitus, the indicators of ADHD will be extensive during awakening, but are less obvious or even non-existent during sleep. “During sleep, the nerve features of tinnitus appear less, suggesting possible gating mechanisms, a process that controls the brain that controls signals to reach consciousness and may play a role in mitigating the perception of phantoms,” Dr. Bajo notes.
The discovery of Dr. Milinski, Dr. Bajo and colleagues opens up new potential treatments. If sleep reduces brain activity related to tinnitus, interventions designed to improve sleep quality may be beneficial to individuals with chronic tinnitus. Future research could explore pharmacological or behavioral strategies that exploit the natural regulation of tinnitus-related brain activity by sleep. The researchers stressed that further research is needed to determine whether similar mechanisms exist in humans and how they can be used for therapeutic purposes.
However, by demonstrating the dynamic interaction between tinnitus and sleep states, this study has provided interesting insights into the neurophysiological basis of tinnitus. Since sleep appears to play a role in reducing the severity of brain activity associated with tinnitus, these findings offer promising directions for future research in auditory neuroscience.
Journal Reference
Milinski L., Nodal FR, Emmerson MKJ, King AJ, Vyazovskiy VV, Bajo VM “Cortical-induced activity is regulated by sleep state in ferret model of tinnitus. A cross-case study.” Plos One, 2024; 19(12):E0304306. doi: https://doi.org/10.1371/journal.pone.0304306
About the Author
Linus Milinski From George-Night School University in Göttingen, Germany, he received a bachelor’s degree in biology and neuroscience, studying how sounds are processed during sleep. He received his PhD from Oxford University, investigating pathological and spontaneous brain activity, especially tinnitus, interacting with natural sleep processes and sleep regulation. Now based in the Department of Physics, Anatomy and Genetics at Oxford University, Sir Jules Tonn’s Sleep and Circadian Neuroscience Institute (SCNI) and the Cavlin Institute for Nanoscience Discovery, his research focuses on how to control the cerebral cortex to control the establishment of sleep-related brain activity and sleep stress.
Victoria M. Bajo He is an associate professor of neuroscience at Oxford University, and studies neural circuits involving auditory attention, sensory processing, and plasticity. Her research focuses on reducing the cortical pathways that shape auditory perception. She showed that removing specific cortical hyperplasia neurons disrupted tone perception, while silent cortical neurons impaired adaptation to auditory changes. She also studied cross-pattern interactions, revealing how whisker stimulation inhibits inducing activity in the auditory cortex. Another major focus of her work is tinnitus, a phantom auditory perception that affects 1-3% of the population. Her team examined its effects on speech clarity and how sleep and tinnitus interact. Her work promotes understanding of auditory plasticity, sensory processing, and potential treatments for tinnitus and hearing-related diseases.
Fernando R. Nodal He then earned his PhD in Neuroscience from the University of Salamanca in Spain, and he moved to Oxford as a fellow at the European Union Marie Curie to develop the space representative of Senior Cocirus in collaboration with Professor AJ King. Since then, he has been studying different aspects of auditory perception by combining behavior, electrophysiology, and anatomical techniques. One of his main interests is the neuroplasticity that relies on experience. Sensory neuroplasticity lays the foundation for our stable perceptions in changing situations or after changing sensory inputs (such as unilateral hearing loss), although poor adaptation processes may lead to phantom perception, such as tinnitus.
Matthew KJ Emmerson A medical student at Oxford University, he conducted research in the auditory lab in the Department of Physiology, Anatomy and Genetics, and his ultimate honors program research project works on tinnitus and sleep. He is now a doctor at the Royal Berkshire Hospital in Reading, England.
Andrew King He is the principal investigator of Wellcome, professor of neurophysiology, and director of the Center for Integrated Neuroscience, Department of Physics, Anatomy and Genetics at Oxford University. He studied physiology at King’s College London and received his PhD from the MRC National Institute of Medicine. In addition to the mantra of a visiting scientist at the Boston Institute of Ophthalmology, he has since worked at Oxford, where his research has been supported by scholarships from the Science and Engineering Research Council, the Lister Institute of Preventive Medicine and Wellcome Trust. Andrew’s research combines a combination of experimental and computational methods to study how the auditory brain adapts to rapidly changing statistics that characterize real-life sounds, integrate other sensory and movement-related signals, and learn to compensate for the changing inputs caused by hearing impairment. He is a scholarship to the Wellcome Award for Physiology, the Royal Society, the School of Medical Sciences and the Society of Physiology, and is a senior editor at Elife.
Vladyslav Vyazovskiy He graduated from Kharkif State University in Ukraine in 1997 and received his Ph.D. from the University of Zurich in 2004. After postdoctoral and lecturer positions at the University of Wisconsin-Madison and University of Surrey, he joined the Department of Physiology, Anatomy, and Genetics (DPAG) at Oxford in 2013, becoming a senior fellow, professor of neuroscience in 2015 and member of the Islamic College and Medical College since 2020 and since 2020. Sir Jules Thorne’s Institute of Sleep and Circadian Neuroscience (SCNI) and the Cafflin Institute of Nanoscience. Vladyslav Vyazovskiy is Vice President of the European Society for Sleep Research and Director of Postgraduate Research at DPAG. His research interests include the neurobiology of sleep and torpor, aging, behavior, neuropharmacology, and mechanisms of brain oscillation during waking and sleep.
