Exploiting the Potential of Neural Attentional Control to Overcome Hearing Impairment

This study will improve the understanding of the cerebral mechanisms that underlie the control of auditory selective attention and evaluate the potential of neuromodulation to enhance neural attention control as a possible way to overcome hearing impairment.

First, electroencephalography (EEG) will be applied to identify neural marker of auditory attention in individuals with hearing loss (HL), tinnitus (TI) and normal hearing (NH). Afterwards, the importance of the identified markers for attention control will be tested using non-invasive transcranial alternating current stimulation (tACS) and neurofeedback (NF).

Hearing loss and associated conditions such as tinnitus are the fourth highest cause of disability worldwide, with estimated annual cost of over 750 billion dollars. Due to the rise and ageing of the global population, the number of people with hearing impairment is growing at a rapid pace. Besides, the incidence of noise induced hearing impairment is also increasing in younger populations. A common complaint of hearing impaired individuals is the significant decline of speech comprehension under challenging listening conditions. These situations typically include reverberations, background noise or multiple speakers and they require the listener to direct attention selectively to a target sound source (e.g. the interlocutor) and to suppress distracting sounds in the background (e.g. from not attended speakers).

Auditory prostheses with pinna-imitating microphones can improve the localization of a target sound source through the sensory enhancement of spatial cues in the acoustic signal. However, the benefit of additional sensory information is limited due of the missing implementation of attention control that would permit the selective amplification of the target sound source and the suppression of irrelevant distracting noise.

The question of how the brain instantiates attentional filter mechanisms that control target amplification and distractor suppression has drawn a lot of interest in the field of cognitive neuroscience. Neural markers of auditory attention such as lateralized oscillatory brain activity in the alpha frequency band (\~8-12Hz) and the enhanced neural tracking of attended of attended speech have been linked to the top-down control of attention. However, the interrelationship between these neural markers is still underexplored. Further, the functional role of alpha band oscillations in auditory attention is underspecified as they could potentially implement target enhancement and distractor suppression. Together, this limits the understanding of the neuro-cognitive basis of attention.

The proposed project aims to address this problem by improving the investigators understanding of the cerebral mechanisms that underlie the control of auditory selective attention. The outlined research project will test the hypothesis that individuals with hearing impairment have deficits in auditory distractor inhibition that are reflected by ineffective neural suppression of irrelevant information. This hypothesis will be examined in three different lines of research. In research line 1, I will test a new framework in individuals who suffer from sensorineural hearing loss or tinnitus that allows to dissociate target selection and distractor suppression at the neural level based on electroencephalography (EEG) recordings. In research lines 2-3, I will then evaluate the potential of electric brain stimulation and neurofeedback to enhance auditory distractor suppression.The results of this project will have theoretical implications for current models of auditory attention and speech comprehension by specifying the functional role of oscillatory brain activity in normal hearing individual and hearing impaired populations. Beyond, this research will contribute new insights how the control of auditory selective attention could be implemented in a brain-computer interface.

Eligibility Criteria:
Inclusion Criteria:

* Age: 18-35 / 55-75
* German as first language
* Normal or corrected to normal vision
* Right-handed
* Normal hearing, hearing impairment or tinnitus (see specified inclusion)
* Normal hearing: ≤20 decibel (dB) hearing level (HL) at frequencies from 250 Hz to 8,000 Hz for both ears.

Specified inclusion for Experiment 1, 2, 3 \& 4:

* Hearing loss:
* bilateral symmetrical sensorineural hearing loss
* pure tone thresholds of ≥25 dB HL at one or more frequencies between 250 Hz and 8,000 Hz and differences in thresholds across the two ears of ≤20 dB at every frequency.
* Tinnitus:
* Persistent chronic tinnitus with duration of more than 3 months
* Tinnitus with a Tinnitus Handicap Inventory Grade 2 to 4 (18-76 points)

Exclusion Criteria:

* Non-symmetrical hearing loss
* Raised bi- or multilingually (second language acquired earlier than 6 years of age)
* Women who are currently pregnant or breastfeeding
* History of brain injury or any neurological disorder (y/n)

  • For example, stroke, traumatic brain injury, brain surgery, epilepsy etc.
* Dyslexia
* History of psychiatric disorder
* Recent recreational drug consumption
* Known or suspected drug or alcohol abuse
* Medication with cognitive side effects (e.g., psychoactive medications or sleeping pills)
* Metallic implants in the head region (excluding fixed braces and tooth fillings)
* Any implanted medical device (e.g., cardiac pacemakers)
* Previous enrolment in one of the experiments comprising the main investigational plan