ABR / ERP simultaneous recording

[Emz]

We are attempting to collect both ABRs and ERPs simultaneously, by recording raw data then offline filtering and post-processing.

We started using the ABR mode and got fairly good results, although our ERPs appeared attenuated and we suppose this was due to the 100Hz high pass filter.

Some colleagues helped us to set up a standard mode recording using the external ports for our 1 data electrode and 2 reference electrodes. We used speedmode7 (though to be honest I'm not entirely sure what the implications of that are). We are still fiddling with our data, but it looks rather noisy.

Is it possible to collect good data for both ABRs and ERPs simultaneously, and if so, what parameters/set up would you recommend?

Emz

[Coen]

We did not foresee that customers would want to perform simultaneous ABR and ERP. Therefore, the current firmware and acquisition software does not support simultaneous ABR and ERP.

The possibilities with your current system are:

- Speedmode 9: record ABR only from the special ABR electrodes with the special ABR acquisition software (ActiABR-101)
- Speedmodes 4-7: record with standard active electrodes according to http://www.biosemi.com/faq/adjust_samplerate.htm with standard ActiView.

In speedmode 7, you can acquire channels 1-32 and the 8 EX channels and the sensor channels on 16 kHz. In speedmode 7, the special ABR channels are disabled. It is possible to use 2 standard EX electrodes to record ABR in this speedmode, see http://www.biosemi.com/abr.htm. However, with stadnard EX electrodes the (high frequency) signal-to-noise ratio may be worse than with the special ABR electrodes (because the standard EX electrodes and channels are optimized for lower EEG frequencies, whereas the ABR electrodes and channels are optimized for high frequencies).

Recording the special ABR electrodes together with a number of standard electrodes is technically possible, but would require custom made firmware and acquisition software. Please contact BioSemi directly to discuss the requirements and possibilities.

Best regards, Coen (BioSemi)

[tom_campbell75]

Hi,

I hope that this article is of interest:

http://sccn.ucsd.edu/eeglab/refs/Campbell11.pdf

Best regards,

Tom.

[Alexandre]

Thank you for this fresh paper. So if I understand well you actually used mode 7 with conventional Biosemi electrodes ? Did you carry out your analyses with EEGLAB ? What about introducing a random jitter between two stimuli to avoid responses from previous trials ?

Best

Alexandre

[tom_campbell75]

Hi Alexandre, Yes Mode 7 with the conventional pin electrodes. Sure, I analysed it in MATLAB. Jittering and Adjarring is in the pipeline. T.

[sarahah]

Is there a global value of CFM & ERP? I have found methods to override global erp & cfm values in constraints, but I'd rather like to set the global ones. The problem is I can't find where to set them.