Information Needed - corticals (proceedure, use etc)

[gemma]

I am trying to find information regarding corticals (proceedure, use etc) wondering if anyone could help

[incus]

Guy is clearly too modest to plug his own website (excellent it is)
http://www.corticalera.com/

[gemma]

thats brilliant i had trouble finding good sites thank you

[Guy]

Not too modest, just hadn't logged on for half a day.

Whenever people refer to "corticals" I'm not sure what they mean.
The N1-P2 response can be used in adults & older children as a threshold estimation tool for objective audiometry and that's what my web site deals with.
However there has been recent interest in an earlier (P1) response in neonates which, it is claimed, can give certain supra-threshold information useful to the habilitation process. Researchers include Suzanne Purdy & Harvey Dillon in NW/Austrailia but in the UK the person to ask is Kevin Munro (Manchester). Kevin is also interested in using cortical responses to assess neural plasticity in adults.

[incus]

I would also add Anu Sharma in Dallas. Her group's approach to using corticals in HI infants is different in that they are using P1 latency as a marker of auditory cortical maturation, showing late and non-developing P1 response without input but rapid reduction after aiding or implantation. But there is a time window for plasticity. Hope is this may be useful in clinic to ensure aids are doing job and baby is progressing before we can tell behaviourally or through speech/lang/communication development

http://www.colorado.edu/slhs/eeglab/personnel.html

[Guy]

Absolutely right, incus.
Anu has shown that the plasticity time window extends to 3.5 years at least but is less than 7 years of age. Good work, supporting the general notion of early identification and management of hearing impairment.
However these tests (especially those on infants) take a long time and require specialist equipment / knowledge so are probably not ready for widespread clinical application.

[gemma]

you'll have to excuse my ignorance because i dont know much about this area but could corticals be used to detect lesion formation?

[Guy]

A perfectly reasonable question.
Quick answer: No
Long answer: although the visual equivalent of the N1-P2 response is sensitive to neuropathy affecting cortical structures such as MS or certain space-occupying lesions, the auditory N1-P2 is not sensitive to the vast majority of neurological problems except in severe cases such as cortical deafness (normal ABR & OAE but absent cortical).
So, used in combination with other tests it can occasionally be helpful.

[rasheda.begum]

I'm going to be doing my dissertation (next year) on comparing the amplitudes, latencies and wave morphology of 3 different speech stimuli in CERA testing. But I’m not really sure why you’d use speech stimuli instead of your frequency specific tone bursts. Could anyone shed any light on this?

Rasheda

[incus]

I'm going to be doing my dissertation (next year) on comparing the amplitudes, latencies and wave morphology of 3 different speech stimuli in CERA testing. But I’m not really sure why you’d use speech stimuli instead of your frequency specific tone bursts. Could anyone shed any light on this?

Rasheda

I guess the reasoning for using speech stimuli is these are 'real world' and more 'relevant' However I am far from convinced this makes sense. When you get different morphology /latencies I would say this may be entirely explicable by the different spectrum and time signature of the speech tokens. I think we need more info about responses to well controlled stimuli.
If people want to use speech tokens we need to ensure they are the same in different labs as otherwise there is no way to properly compare results . Why not use synthesised stimuli?

[rasheda.begum]

Thank you for your reply.

I agree with your comment about the morphology and latencies being different due to the spectrum of the speech token itself. I know that I will be comparing 3 different synthesised speech tokens, however, I am unsure what I should expect (especially as I will comparing it to a tone burst) and base my hypothesis on?

Rasheda

[Guy]

Without wishing to be unkind, this sounds a bit like "let's play with this and see what happens". We've all been guilty of that but its bad science.
I think you need to speak to your supervisor and between you, develop a really clear idea of the question you want to answer. Keep it simple!
Only then should you start to develop your experimental design.

[rasheda.begum]

That’s a fair comment to make as that's how I feel about it right now- I don’t really know why I’m looking at the differences in morphology, amplitude and latency

[rasheda.begum]

Without wishing to be unkind, this sounds a bit like "let's play with this and see what happens". We've all been guilty of that but its bad science.
I think you need to speak to your supervisor and between you, develop a really clear idea of the question you want to answer. Keep it simple!
Only then should you start to develop your experimental design.

I've spoken to my tutor and now have a better idea of what I will be doing with my dissertation. I will be comparing waveforms from CERA responses using tone bursts versus speech tokens (which will have the same centre frequency to the tone burst); to see if there is a statistical difference in responses between the two stimuli. I’ll be using three different sets of speech tokens and respective tone bursts.

However, I am having a tough time trying to complete a literature review and find relevant journal articles. I’ve been on corticalera.com and found the website very useful, but is there anywhere I’d be able to get some information about studies or journal articles on Cortical ERA testing?

[Guy]

Yes, there is quite a literature on this. One good reference is:
Tremblay KL, Kalstein L, Billings CJ, Souza PE. (2006). The neural representation of consonant-vowel transitions in adults who wear hearing aids. Trends Amplif. 10, 155-162.
Another is:
Martin BA, Tremblay KL, Korczak P. (2008 ). Speech Evoked Potentials: From the Laboratory to the Clinic. Ear Hear. 29, 285-313.

The big mistake to avoid is to use different stimuli (e.g. tone bursts, speech tokens etc) and then attribute differences in the cortical responses as representation of discrimination of the stimuli. This is because the fine temporal, intensity and spectral differences of the stimuli are likely to lead to slightly different responses even if the listener fails to discriminate any difference.
So, be very careful with your experimental design and don't over-interpret the significance of your results.