A non-comercial educational resource for the Audiology profession
Downloadable files / videos on Cortical ERA
The following files may be viewed or downloaded.
Please read the notes on this page relating to the file in question. Some of the video files are quite large.
We performed a study on the performance of CERA in volunteer adults in order to assess the speed of our current system and to investigate the effects of certain stimulus presentation features. We presented some results at the IERASG symposium in Havana, Cuba, in June 2005 and the paper appeared in Ear & Hearing in 2006.
You may download a PDF version here.
A paper on the objective detection of the cortical N1-P2 response using signal to noise ratio was presented at the XXI Biennial Symposium of the IERASG, Rio de Janeiro, Brazil, June 2009.
An interesting paper by Van Maanen & Stapells comparing CERA and two rates of steady-state threshold estimation is available here.
Run an "optimised" Cortical ERA test yourself! Scroll down for the latest videos.
The following video clips are examples of patients being tested using the author's system in Liverpool, UK.
They are a little jerky since they were recorded at 8 or 10 frames per second.
The first video (5.79MB) is a 3 kHz bone conduction Cortical ERA test, with masking, lasting 4.37 minutes. Intensities used are 40, 20, 0 and 10 dBHL and yield a threshold of 5 dBHL. The lower panel is the incoming EEG (note how at the end of each sweep, the waveform becomes smoother - this is the 15 Hz low-pass digital filtering of individual sweeps). The upper panel is the averaging area. A repetition rate of 0.7Hz with 30% variability is used. Three sub-averages are acquired in a cyclical fashion and at the end of 15 sweeps a grand average (in red - this is a right ear test) is automatically created. Cursors are placed automatically, though the operator may reposition them, and a correlation coefficient calculated (lower left of the panel). At 40 & 20 dBHL only 15 sweeps are needed but at the lower intensities, closer to threshold, further averaging is undertaken. However, before this occurs, a 10 second stimulus-free period is provided to allow the response to recover and so minimise the effects of adaptation. An intensity series is displayed, allowing the operator to assess the responses and so establish the hearing threshold or the need for further testing.
The second video (6.4MB) is a segment of tests at 1kHz by air conduction using the simultaneous right & left Cortical ERA technique (3.22 minutes), this time shown on a computer running Windows XP. Again, the video starts just after completion of testing at 60dBHL and demonstrates the acquisition of tests at 40 and 20dBHL. The quality of this patient's responses are less than ideal, but this example is included here to demonstrate that even so, the technique is viable. Clearly, in such cases the precision of the threshold estimate will be modest.
Now here's something you wouldn't be able to do using ABR.
The third video clip (19.1MB) shows a 250Hz air conduction test on both ears (5.23 minutes). Right & left ear intensities of 50/50, 30/30 and 20/40dBHL are employed, and suggest CERA thresholds that were within 5dB of the patient's behavioural thresholds. Using ABR, issues of neural synchrony make responses to low frequency stimuli at low sensation levels almost impossible to record. In contrast, CERA responses at low frequencies are just as well defined, accurate and frequency specific as those at higher frequencies.
Take home message?
The author designed and developed this system for his own clinical and medico-legal use with hardware and software from Cambridge Electronic Design (the assistance of their software engineer Dr Geoff Horseman is gratefully acknowledged). Although this system is commercially available, it is a pity that such software has not been incorporated into existing ERA systems.
This is because there in no demand.
There is no demand because the possibilities and potential of this test have not been fully recognised.
That was a primary reason for the creation of this web site!
If you are impressed with this technique then please give the manufacturer of your ERA system a hard time - point them at this site and tell them to make one available!