HeRRI
Hearing Rehabilitation Research Infrastructure
The infrastructure will facilitate a wide range of hearing research in animal models and human subjects. Fitted for translational research, similar electrophysiological measurements are performed in animals and humans: auditory evoked potentials including electrocochleography, electrically evoked compound action potentials, auditory brainstem responses, and cortical potentials. In animals these measurements can be related to histological and molecular analyses of the cochlear and neural structures. In humans these measurements can be related to and combined with psychophysical measures as speech perception, spectral discrimination and sound localization in various acoustic environments.
Infrastructure and User Services
The infrastructure consists of laboratories that share features (sound-proof, Faraday shield) that enable similar measurements in animals and humans.
We envision four rooms for in vivo experiments with small animals (guinea pigs, mice), each with a surgical microscope, equipment for gas anaesthesia, and a system for monitoring physiological parameters. There will be equipment for both acoustical (up to 100 kHz for ultrasonic hearing of small animals) and electrical stimulation (as in cochlear implants), and equipment to record evoked potentials. Two rooms will have multi-channel recording equipment to record single-cell responses from auditory nerve to auditory cortex. A lab will be added for processing cochlear and neural samples for microscopy and molecular analyses.
For human studies we envision an anechoic chamber for spatial-hearing experiments, a room with adaptive reverberation allowing simulation of real-life acoustic environments, a sound-proof room for neurophysiological experiments, and two sound-proof rooms for psychophysical experiments.
The anechoic chamber contains a sound localization setup with speakers and lights in full field (left-right, front-rear, top-down) with high resolution (5 degrees), and a head tracking device. A room with varying reverberation times allows measurements in daily-life hearing conditions. The third room contains EEG recording equipment for auditory evoked potentials to acoustical, and in case of cochlear implant users, electrical stimulation. Two sound-proof rooms contain equipment for psychophysical experiments using free-field speakers or head phones. Silent computers are used (<10 dBA). Audio recording and calibration equipment consist of sound level meter, in-ear microphones, artificial ear, artificial mastoid, and head and torso simulator.
Examples/description of the type of research
The main purpose of the infrastructure is measuring hearing performance outcomes. This can be achieved using psychophysical methods, and by objective measures , i.e., electrophysiological recordings and functional near-infrared spectroscopy (fNIRS). Alongside, other outcomes can be measured such as listening effort using pupillometry. Animal experiments are accompanied by histological assessment of cochlear structures and characterization of cellular expression patterns.
The animal chambers will facilitate longitudinal measurements in animals chronically implanted with electrodes over several months in which interventions and treatments can be tested. Examples of these measurements are electrically evoked compound action potentials, cochlear microphonics, auditory brainstem responses, cortical auditory evoked potentials (CAEPs). Examples of treatments are neurotrophic factors to promote neural survival, corticosteroids to reduce detrimental tissue growth, novel drugs that counter ototoxic effects of chemotherapy, and medium that promotes regeneration of sensory cells.
The chambers for human experiments will facilitate psychophysical and electrophysiological measurements, and combinations thereof. Experiments will involve healthy human subjects and hearing-impaired patients including cochlear implant users and patients with other (implantable) hearing devices. Examples of psychophysical measurements are speech perception, spectral shape discrimination, and sound localization; acoustic conditions and positions of the listener can be varied. Examples of electrophysiological measurements are apart above-mentioned, in particular the ones that appear to be predictive of perceptive outcomes CAEPs to acoustic changes and EEG to speech sounds. Interventions and treatments can be tested. Examples of interventions are music training and multisensory training, and examples of treatments are as above-mentioned for the animal experiments.
How to access the infrastructure?
The facility consists of physical rooms for measuring hearing outcomes in animals and humans. Investigators will be provided access to run their experiments.