Delivering electric shocks while recording EEG
Posted: Fri May 24, 2019 5:58 pm
Hi,
We have a new experiment that involves delivering electric shocks (using Biopac stimulator) while recording EEG with BioSemi. We have noticed that while the stimulator is on, the EEG data looks clean, same as when the stimulator is turned off. However, when we attach the two electrodes from the stimulator to the subject’s arm (without even delivering a shock), there is a very robust high-frequency noise. We have a few questions with regard to that:
1. The lowpass filter in the ActiView “monopolar display” screen is set to 100 Hz. If we change this to 20 Hz, the signal looks much better. Just to make sure that we understand correctly – Does that mean that the raw data is digitized using an online lowpass filter?
2. It is possible to change the cutoff value during the experiment? Meaning, to use 20 Hz in blocks were subjects are connected to the stimulator, but to return to the 100 Hz in blocks where they are not.
3. Do you have any other suggestions of how to rearrange the setup, in order to minimize this electric noise?
Any help would be highly appreciated.
Thanks in advance!
We have a new experiment that involves delivering electric shocks (using Biopac stimulator) while recording EEG with BioSemi. We have noticed that while the stimulator is on, the EEG data looks clean, same as when the stimulator is turned off. However, when we attach the two electrodes from the stimulator to the subject’s arm (without even delivering a shock), there is a very robust high-frequency noise. We have a few questions with regard to that:
1. The lowpass filter in the ActiView “monopolar display” screen is set to 100 Hz. If we change this to 20 Hz, the signal looks much better. Just to make sure that we understand correctly – Does that mean that the raw data is digitized using an online lowpass filter?
2. It is possible to change the cutoff value during the experiment? Meaning, to use 20 Hz in blocks were subjects are connected to the stimulator, but to return to the 100 Hz in blocks where they are not.
3. Do you have any other suggestions of how to rearrange the setup, in order to minimize this electric noise?
Any help would be highly appreciated.
Thanks in advance!