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Alejandro Lopez

Research Engineer

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mail@eriksholm.com

This outreach project is working on a clear characterisation of auditory responses in Ear-EEG setups.

Recording electrophysiological signals with electrodes inside the ear is possible. However, there are many challenges posed by the complex anatomy of the ear cavity. This project, carried out by PhD Christian Bech Christensen and Associate Professor Preben Kidmose at Aarhus University, aims at providing a clear characterisation of auditory response in Ear-EEG setups. The project is funded by the Oticon Foundation, and Eriksholm serves as a stakeholder, consultant and facilitator with a genuine interest in the scientific knowledge that can be achieved through the external collaboration.

eeg-setup_960x450

With the use of high-density scalp and Ear-EEG setups this study aims at investigating:

1. Spatial distribution of Auditory Steady-State Responses (ASSR) in Ear-EEG configurations: ASSR responses occur when the auditory neurons synchronise their action potentials in phase with a sound feature such as a modulation. When we measure these responses with EEG electrodes on the scalp, we can identify a spatial distribution of the electric potential with respect to where we placed the electrodes (2nd figure on the left). By placing a dense array of electrodes inside the ear, we can also derive a similar spatial distribution of the electric potential within the ear (2nd figure on the right).


spatial-distribution-of-assr_960x450

2. Source mapping of EEG responses into the ear: Auditory evoked responses such as the ASSR are generated by contribution of different sources along the central nervous system. By looking at how these responses are captured by many electrodes placed in different locations, we can derive backward models to get statistical inferences as to where the signal was most likely generated.

3. Ear-EEG multichannel signal processing: High density setups, like the one used in this project, allow us to evaluate if the use of more available information is a benefit for faster and more efficient ways to measure these types of responses.

4. Temporal dynamics of steady-state responses

From these investigations we hope to better understand the practicalities of using electrophysiological responses like the ASSR to evaluate the auditory processing of a given user. We also expect to better understand how to harvest these responses to have an effect on the signal processing of hearing devices.

 


Further reading

Bech Christensen, C., Hietkamp, R. K., Harte, J. M., Lunner, T., & Kidmose, P. (2018). Toward EEG-Assisted Hearing Aids: Objective Threshold Estimation Based on Ear-EEG in Subjects With Sensorineural Hearing Loss. Trends in Hearing, 22, 2331216518816203. doi:10.1177/2331216518816203

Christensen CB, Harte JM, Lunner T, Kidmose P (2018). Ear-EEG-Based Objective Hearing Threshold Estimation Evaluated on Normal Hearing Subjects. IEEE Trans Biomed Eng. doi: 10.1109/TBME.2017.2737700