2 questions about reference
Posted: Mon Dec 01, 2008 11:41 pm
Hi
Our lab recently started working with ActiveTwo system.
I have 2 questions about reference to which I couldn't find direct answers so far.
1. While I recorded signals from some subjects, I noticed that whenever I choose to display the data with the reference option set on "none" (CMS and DRL), I got a flickering purple light from the reference panel on the left side. From the reading I've made I understood that the data are saved in any case in a non referenced format and that the panel I'm talking about is for display only. However, as it looks to me like a warning signal I wonder what it means and whether I'm doing something wrong.
2. When uploading the BDF files to eeglab (version 6.01b) I am asked for a BioSemi ref channel number (with the option of non=average ref). Two issues are not clear to me here - If I use EX1 channel as a nose ref, how do I choose it? In addition, I get a message saying that if I do not choose a ref channel I loose 40dB of SNR. Why would that be the case with average ref, which is the default option when importing the data to eeglab?
Thanks for any advice!
B.S
Our lab recently started working with ActiveTwo system.
I have 2 questions about reference to which I couldn't find direct answers so far.
1. While I recorded signals from some subjects, I noticed that whenever I choose to display the data with the reference option set on "none" (CMS and DRL), I got a flickering purple light from the reference panel on the left side. From the reading I've made I understood that the data are saved in any case in a non referenced format and that the panel I'm talking about is for display only. However, as it looks to me like a warning signal I wonder what it means and whether I'm doing something wrong.
2. When uploading the BDF files to eeglab (version 6.01b) I am asked for a BioSemi ref channel number (with the option of non=average ref). Two issues are not clear to me here - If I use EX1 channel as a nose ref, how do I choose it? In addition, I get a message saying that if I do not choose a ref channel I loose 40dB of SNR. Why would that be the case with average ref, which is the default option when importing the data to eeglab?
Thanks for any advice!
B.S