Tinnitus, i.e. the perception of phantom sounds in the absence of an acoustic stimulus, can be caused by hearing loss. Under which circumstances does this occur? Which mechanisms are involved? Roland Schaette and Richard Kempter from the Bernstein Center for Computational Neuroscience and the Humboldt University in Berlin found answers to these questions using computer simulations.
Tinnitus arises in the auditory pathway of the central nervous system. In animal studies, tinnitus-like activity of neurons - so-called hyperactivity - has been found in the dorsal cochlear nucleus (DCN), the first processing stage for acoustic information in the brain. Neurons of the DCN receive input directly from the auditory nerve and react to it with neuronal discharges - one says, they "fire".
Even without any acoustic signals, however, cells of the auditory nerve and the auditory pathway are still active and fire spontaneously at a certain rate, the "spontaneous firing rate" - comparable to the background noise produced by electrical devices. Various studies suggest that hearing loss can increase the spontaneous firing rate of nerve cells in the DCN and that animals perceive this as a kind of tinnitus. In a theoretical model, Schaette and Kempter explain the link between tinnitus and hearing loss for the first time.
After hearing loss, auditory nerve fibers and neurons along the auditory pathway only react to loud sounds. For soft sounds below the increased hearing threshold, the neurons fire spontaneously. Many neurons thus show an overall reduced activity. This could trigger a mechanism called "homeostatic plasticity", which ensures that neuronal activity is neither too high nor too low. If the average activity of the neurons is too low, homeostasis enhances their sensitivity. As the scientists could show in their model, neurons then react more strongly to the activity of the auditory nerve; in particular the spontaneous firing rate increases.
Moreover, Schaette and Kempter also demonstrated in their model that this mechanism only applies to certain types of neurons - for example to type III neurons of the DCN. These neurons are primarily activated by sound. Therefore, their average activity initially drops after hearing loss and the mechanism described above is initiated: homeostasis has to counteract this loss in activity and elevate firing rates, which then also leads to an increased spontaneous firing rate.
In contrast, type IV neurons are either activated or inhibited by sound, depending on sound intensity. Hearing loss only has a minor effect on their average activity. Accordingly, these neurons are less susceptible to hyperactivity. This prediction of the Berlin scientists' model corresponds with experimental findings: In rodents type III neurons dominate in the DCN. Here, tinnitus-like hyperactivity has been observed. In contrast, such an activity has not yet been found in cats, whose DCN mainly holds type IV neurons.
"Our studies have corroborated the association between hearing loss and tinnitus, which could provide a foundation for new treatment strategies," Kempter states. "Our hope would be that a tailored exposure to acoustic signals over an appropriate frequency range could help to drive back the hyperactivity caused by hearing loss".Original publication:
Schaette R, Kempter R: Development of hyperactivity after hearing loss in a computational model of the dorsal cochlear nucleus depends on neuron response type. Hear Res 240:57-72 (2008). doi:10.1016/j.heares.2008.02.006Contact:
A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
18.08.2017 | Life Sciences
18.08.2017 | Physics and Astronomy
18.08.2017 | Materials Sciences