Which level of EEG is better to get clear information?
Yes.
ECoG / intracranial-EEG may miss large scale synchronous activity (such as some alpha band activity) that scalp EEG can record because volume conduction effects tend to average electrocortical activity over widespread cortical regions, improving signal-to-noise ratios of widespread synchronous activity. However scalp-EEG will miss much beta/gamma band activity because this activity tends to be less synchronous over large regions of cortex (and scalp-EEG also records broadband muscle artifact in this range). Intracranial-EEG also tends to be recorded from a small region of cortex while scalp-EEG records from the majority of the cortical surface.
There exists much theoretical and some empirical work supporting this (see the attached article and its references). I cannot find a simple spectra plot of scalp-EEG versus ECoG in the same subject however (although there may be a confound in this comparison because ECoG is typically only recorded in patient populations).
Nunez, P. L., & Srinivasan, R. (2010). Scale and frequency chauvinism in brain dynamics: too much emphasis on gamma band oscillations. Brain Structure and Function, 215(2), 67-71.
https://link.springer.com/article/10.1007%2Fs00429-010-0277-6
Intracranial EEG will pretty much always provide a more direct measure of activity, since you don't have the extra levels of skin, skull, and CSF sitting between the source and the electrode. On the other hand, intracranial EEG has the obvious drawback that it requires removing the skull, whereas scalp EEG is entirely non-invasive. Which one to use depends on the nature of your research question (for some research questions, precise source localization is just not that important) and availability of participants (if your study sample is going to be limited to, e.g., volunteers from university psychology classes, then you are not going to be able to ask students to volunteer to come into the lab for the afternoon and have their skulls removed).
Hello Stephen
Thank you for the brief reply. what about the information i can get ? In that case which one is better and precise (Scalp or Intracranial)?. I will be glad if you can explain me with an article. Thank you.
Like I suggested above, intracranial EEG will of course provide more precise localization, but it is subject to other drawbacks. For more information, if you search online for e.g. "comparison of EEG and ECoG" or similar search queries, you will find plenty of papers.
Yes.
ECoG / intracranial-EEG may miss large scale synchronous activity (such as some alpha band activity) that scalp EEG can record because volume conduction effects tend to average electrocortical activity over widespread cortical regions, improving signal-to-noise ratios of widespread synchronous activity. However scalp-EEG will miss much beta/gamma band activity because this activity tends to be less synchronous over large regions of cortex (and scalp-EEG also records broadband muscle artifact in this range). Intracranial-EEG also tends to be recorded from a small region of cortex while scalp-EEG records from the majority of the cortical surface.
There exists much theoretical and some empirical work supporting this (see the attached article and its references). I cannot find a simple spectra plot of scalp-EEG versus ECoG in the same subject however (although there may be a confound in this comparison because ECoG is typically only recorded in patient populations).
Nunez, P. L., & Srinivasan, R. (2010). Scale and frequency chauvinism in brain dynamics: too much emphasis on gamma band oscillations. Brain Structure and Function, 215(2), 67-71.
https://link.springer.com/article/10.1007%2Fs00429-010-0277-6
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