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Dr. Ing . Tobias Balkenhol

Consequences of Hearing Impairment and Auditory Rehabilitation on Brain Function

Hearing loss is common, and it is on the rise. It narrows communication and is probably associated with a tendency for depression and cognitive decline. Our research is concerned with the consequences of hearing impairment and auditory rehabilitation on brain function with special focus on adaptive plasticity associated with electrical hearing via a cochlear implant (CI) and on maladaptive plasticity associated with tinnitus. To investigate these processes we use psychophysical methods and electroencephalography (EEG). Better insight into adaptive and maladaptive auditory plasticity is expected to improve steering plasticity towards desired adaptions in the auditory brain centers.

Our research focusses on:

Electrical Hearing with Cochlear Implants

CIs provide an opportunity for the severely hearing-impaired or deaf to perceive sound by bypassing the damaged sensory cells in the cochlea and by directly stimulating fibers in the auditory nerve electrically. A CI consists of an external part with microphone, speech processor and transmitter and a surgically implanted internal part with a receiver and an electrode in the cochlea. Due to limited transmission of the frequency components and temporal characteristics of acoustic sounds, CI users have to learn to associate the signals from the implant with sounds in their auditory memory.

We are interested in how the auditory and language areas in the brain adapt to electrical hearing. With psychophysical testing and auditory evoked potentials (AEP) we investigate whether intense auditory training, improved speech processing strategies, and better communication between the listening devices used by an individual lead to improved and less effortful speech comprehension. In addition, we are working on the optimization of algorithms for automated removal of artifacts, which are for instance generated by the CI and are recorded during the EEG measurement. These artifacts have to be removed before analysis of brain activity. 

Tinnitus

Tinnitus is a noise that seems to originate in the ear or head rather than from an external source. Most tinnitus sensations are of subjective nature which means that they are not generated by a sound source but by activity within the auditory system. Subjective tinnitus is heard only by the affected person, therefore, its loudness is hard to determine. In addition tinnitus may lead to distress. If tinnitus is very disturbing as experienced by some of those affected life quality may be compromised.

Mechanisms leading to tinnitus sensations are still a controversial issue, but tinnitus appears to be an indirect consequence of hearing impairments. We investigate brain oscillations in tinnitus patients with particular on the auditory cortex and on cortical areas concerned with attention, emotion and consciousness. Aims are to differentiate the heterogenous group of tinnitus patients into therapeutically relevant subgroups, the investigation of cortical reorganization in tinnitus patients, and the development of tinnitus therapies.

A: Auditory evoked potentials (AEP) before and after automated removal of CI artifacts. B: Cluster analysis result for group comparison of hearing conditions monaural (CI) vs. bimodal/bimodal (CI at one ear and hearing aid at the other ear) for the time interval of the N100. C: For hearing conditions from B source localization with eLORETA shows differences in the auditory cortex for N100.

Selection of relevant publications

  1. Wallhäusser-Franke E, Delb W, Balkenhol T, Hiller W, Hörmann K. Tinnitus-Related Distress and the Personality Characteristic Resilience. Neural Plasticity 2014:370307.
  2. Balkenhol T, Wallhäusser-Franke E, Delb W. Psychoacoustic Tinnitus Loudness and Tinnitus-Related Distress Show Different Associations with Oscillatory Brain Activity. PLoS One 2013; 8:e53180.
  3. Wallhäusser-Franke E, Brade J, Balkenhol T, D’Amelio R, Seegmüller A, Delb W. Tinnitus: Distinguishing between Subjectively Perceived Loudness and Tinnitus-Related Distress. PLoS One 2012; 7:e34583.

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