Description

Below, you can find quick answers to frequently asked questions on the Eclipse Aided Cortical module.

For more detailed information, please refer to the Interacoustics Academy complete guide or the Aided Cortical quick guide.

Table of contents

What is the difference between the speech sounds?

The Aided Cortical module comes with three sets of speech-like stimuli:

ManU-IRU stimuli
HD-Sounds
Ling sounds

ManU-IRU stimuli

The ManU-IRU stimuli have been developed by the Interacoustics Research Unit (IRU) and Manchester University. The ManU-IRU stimuli are aligned with the International Speech Test Signal (ISTS) and are excellent in their frequency specificity.

HD-Sounds

The HD-Sounds are updated versions of the natural speech sounds created by Dr. Harvey Dillion, Ph.D. where the updated stimuli are made more frequency specific.

Ling sounds

The Ling sounds: /m/, /u/, /a/, /i/, /sh/, /s/ are shortened versions of the original Ling-6 (HL) sounds. The Ling sounds have been shortened to 100 ms to make them better suited for cortical responses.

Can the Aided Cortical module be used in conjunction with eABR?

The Aided Cortical module can be used as a supplement to the eABR test to evaluate a patient's audibility using their hearing implant.

However, aided cortical testing should not be performed during CI surgery instead of eABR, and eABR should still be used as a way of measuring CI-electrode function and auditory nerve integrity.

What intensity should I test at?

This is a decision which needs to be made on a case-by-case basis depending on the hearing loss and expected audibility for each individual patient, as well as what the clinical question is.

As this is a free field test, how are responses recorded?

Cortical responses are generated bilaterally and are not limited to one side only because neural pathways cross. For this reason, cortical responses are recorded between the right channel and the vertex electrode, and contralateral responses are recorded from the left channel and the vertex electrode.

Is there an age limit on patients who can undergo aided cortical testing?

No, there are no age limitations. However, it is worth noting that the waveform morphology will look very different on infants when compared to waveforms from adults.

Why is the vertex electrode not placed on the true vertex?

When dealing with infants, having the vertex electrode on the top of the head is difficult because of the skull not being fused. Having to shave the patient's head to improve impedances is also another challenge.

Furthermore, Visram et al. (2023) mention that placing the vertex electrode on the true vertex versus high forehead yields no significant response differences [1].

What impedances do I need?

Balanced impedances for all electrodes at or below 5 kiloohms are optimal.

Why is there an 'i' after Fmp?

This is because the Aided Cortical module uses a detector specifically designed to detect aided cortical responses.

Why is the FmpiTM not shown instantly?

The Fmpi value will show after 10 sweeps.

Why is there no Fmpi value, only a percentage?

The Fmpi detector calculates the individual's response to the stimuli, so the response confidence is given in percentage to show the individual patient's response to the stimuli.

How do I connect the free field speaker?

To use the free field speaker, you must connect the jack plug to the 'Bone Outp.' socket. The Aided Cortical module uses the Bone Outp. plug in the setup as well.

What does SpRefl mean?

SpRefL is an abbreviation for Speech Reference Level and is used in the Aided Cortical module because the speech sounds are presented with reference to the ISTS.

Which intensities are available?

By default, three intensities are available for use:

55 dB SpRefL (soft speech)
65 dB SpRefL (normal speech)
75 dB SpRefL (loud speech)

It is still possible to add intensities in the system setup.

Can I perform aided cortical testing on cochlear-implant patients?

You can perform aided cortical testing on both cochlear-implant candidates and cochlear-implant users. However, you may see artifacts on the waveform with cochlear implants.

In these cases, it is important to review the morphology of the waveform alongside the Fmpi value when making an interpretation to assess whether the Fmpi value could be related to the presence of artifacts or a genuine cortical response.

The Fmpi cannot distinguish an artifact generated by a cochlear implant from a cortical response. To allow for easier identification of an artifact, setting the low pass display filter to none may assist in this.

Changing the low pass recording filter in the system setup to 100 Hz may help the recording if you consistently see large artifacts.

What is the Sound Field Analysis button?

The Sound Field Analysis opens the Sound Field Analyzer, which you can use to compensate for any acoustic changes in the test room. For example, if you move the patient further away from the initial calibration, the Sound Field Analysis compensates for this increase in distance.

By using and placing the provided ambient microphone at the place of testing, all stimuli will be measured and will display deviations from the calibrated values. If this is the case, press 'adjust to target', which will compensate for the new test conditions. This only takes a few seconds.

Is the Sound Field Analysis a calibration of the system?

No, the Sound Field Analysis is not a calibration. The Sound Field Analysis is a compensation that is referenced to a calibrated target.

How often should I calibrate my system?

A yearly calibration of the Eclipse should still be performed.

How do I turn the intensity of the Sound Field Analyzer down?

In the EP calibration software, it is possible to reduce the intensity of the Sound Field Analyzer.

When I press the Sound Field Analysis, I get a pop up saying no target available. What do I do?

If this happens, it is because the system is not calibrated. The system must be calibrated before use, and this must be done at the test location.

What are the stop criteria for the test?

For response present, the Fmpi detector will aid as a stop criterion, as will the waveforms displayed. You can split waveforms in A and B buffers as known from ABR and display both channels separately. The waveform reproducibility feature known from ABR is also available.

For response absent, the system has a built-in residual noise calculator. Noise targets will be different than those used in ABR because cortical responses contain more noise.

Are BC protocols affected by the fact that the BC output is used in the Eclipse for the loudspeaker?

No, the Aided Cortical module uses its own calibration, making it work independently of other modules. So, you can plug in the bone conductor after you have done your aided cortical testing and do testing with a BC protocol.

Why are the residual noise targets set at a higher value than ABR?

In aided cortical testing, the patient is awake and is supposed to be engaged in some sort of activity. This makes it difficult to reach the same residual noise values in aided cortical testing as in ABR.

What sort of task should I give my patient during the test?

The patient should be engaged in a silent activity. For example, silent toys or silent movies. Toys or movies with sound could mask the stimuli presented from the speaker.

If I right click, I can see something called 'Stimulus color'. What is that?

Stimulus color is another way of visualizing your waveforms. By default, the color of each waveform depends on what ear state you have chosen. For example, your waveform will be blue if you have chosen the state Aided Left (AL).

By choosing stimulus color, the color of your waveforms is based on the stimulus and not by the ear. Stimulus colors are set by default.

How do I change the color of my waveforms?

You can do this in the calibration software under 'Aided Cortical general setup'.

References

[1] Visram, A. S., Stone, M. A., Purdy, S. C., Bell, S. L., Brooks, J., Bruce, I. A., Chesnaye, M. A., Dillon, H., Harte, J. M., Hudson, C. L., Laugesen, S., Morgan, R. E., O'Driscoll, M., Roberts, S. A., Roughley, A. J., Simpson, D., & Munro, K. J. (2023). Aided Cortical Auditory Evoked Potentials in Infants With Frequency-Specific Synthetic Speech Stimuli: Sensitivity, Repeatability, and Feasibility. Ear and hearing, 44(5), 1157-1172.

Presenter

Rasmus Skipper, MSc Audiology