What you can see is that from the raw signal at the bottom, the b version here,
you can that there are several fluctuations across all the channels here.
What we often can see, some people do, some researchers are doing, and
some commercial companies are doing is using what we,
what is called the event potent event related potentials or evoke potentials.
What that means is that, we have a highly systematized way of showing stimuli.
So we present an image at one particular time we repeat the same image or
a similar image several times to generate a,
an average response profile from that signal, from that stimulus.
So, as you can see, in the orange here in the b this is the time points where we
are showing let's say a particular, a particular image.
And, what you can see then is that you have eight or
nine different time points where you have shown that.
What you then do is to make the average signal over time the first second or so.
And you get a, what we could call, a response profile.
And this profile you can see on the top right corner in the,
in the c, str, figure here.
What this allows us to do is to look at the responses of different peaks and
valleys in terms of the, the changes in the discharges.
And there are several there's a whole literature on showing what those
typically mean.
We know that at approximately 400 milliseconds after the onset of
the stimulus, there is typically some kind of semantic and
understanding of the stimulus itself.
So changes in words or misplaced words
might actually lead to a deflection of the, what's called the, the N400 signal.
And finally, a,
another way of doing EEG is to look at different changes in frequency.
As you can see at the bottom right, there are ways in which you
can look at the high frequency or the low frequency, or the middle frequency.
The low frequency being the delta, for example, is the slow wave.
You typically see the delta activation very,
really high when people are in deep sleep.
As opposed to that you see that the beta and
the gamma tends to be this the they are always the high frequency bands.
And they tend to be related to high engagement of of brain activation.
And also, you know co,
communication across different areas of the brain as well.
So integrative activation we could call it.
This is a a, a 2D map put on the scalp o, of a of a, kind of a,
a template scal, scalp showing the spatial distribution of the signal as well.
And today there are even ways that you can reconstruct the EEG;
signal relatively well so you can, you can pinpoint where in the brain,
especially in the cortical mantle, but also some deeper regions.
You can reconstruct the signal to find out not only grossly where you are, but
also pinpoint certain structures where the activation has been has been most active.