Hello, my name is Sujin, a student in the Department of Brain and Cognitive Science at Seoul National University, South Korea. I am trying to use the sLoreta program to try source analyze, but there is no explanation in other thesis or tutorial on how to use sLoreta to source analyze ERP data, so I post my question.
The following are the steps I analyzed and related questions. 1. I have completed Auditory P300 data analysis with eeglab. So, in eeglab, erp data were stored separately for each stimulus. (target/standard) 2. I converted the data stored for each stimulus into loreta format through eeglab. But I have a question here. ERP data has tasks, unlike resting, and when these tasks are cognitively processed, activation appears to be maximal between 250-450ms. Therefore, this time window is also important for analysis in loreta, and I am not sure how to import data among the following methods to obtain activation according to this time window. 1) Do I have to leave only this time window (250-450ms) using eeglab before putting it in loreta, convert it to loreta format in eeglab and put data into the loreta program? 2) Can I input the desired time window in the option to select the time window in the loreta program? 3) Is there another way to subtract only the desired time window after completing the entire time window conversion in the loreta program?
I searched several papers, but couldn't find a specific analysis method, so I sent an email.
I'd really appreciate it if anyone who know how to analysis erp data using sLoreta could reply.
Best,
Sujin
Dear Sujin,
the question you asked is a bit wobbly, what I can deduce is you wish to create an epoch for each event.
For that, you need to take into consideration the onset i.e. the moment at which the stimulus is given.
Also, generally, a single event epoch is considered pre-stimuli and extends to post the desired potential, which in the case of your study is p300.
During my masters, we measured an epoch that lasted from -200ms to 1000ms.
this implies 200ms before stimuli are presented and post that, 1000ms. this takes into consideration of delayed onset of p300 and other potentials. although this was all in regard to the study.
Also, this further brings me to a query, If you have EEGlab and you have done pre-processing of data on the same, why do you intend to do post-processing on sloreta?
Sankalp Sharma Thank you for answer the question.
the point that i wonder,
How I transform erp data before importing to sLoreta?
After completing the data preprocessing with eeglab, I want to check the source activation between 300-400ms using sloreta. 1) For each subject, after averaging all trials, should the time window be specified in the loreta program? 2) Whether each epcoh should put consecutive files, and whether the time window should be specified in the loreta program.
Sujin An Please Go through the following link for the transformation of ERP data to sloreta:
https://sccn.ucsd.edu/pipermail/eeglablist/2012/005185.html
1. For each subject you only need to specify once. the time frame, it will consider it for all the events in question for that subject. But, yes, for each participant/subject you need to specify the time frame for the epoch separately while post-processing.
2. epoch has to be created on an event basis, i.e. if your study has multiple input stimuli, you need to have a separate file for each stimulus which comprises all the events of that particular subject, also, not to mention, including their specific time frames. and as mentioned above, for each subject you need to specify the time frame for analysis for that particular event/stimulus.
- Badges
- Science topic
- Similar topics
- Analytical Chemistry
- Column