[Eeglablist] Correlation with N400 mean amplitude values

[sujata sinha]

Hi Veronica,

I agree with Arild's reply to your first question.
The same applies for your second question as well.

For example, you want to test the correlation between the mean amplitude of
the N400 in response to negative stimuli and the EQi test score.
Case 1:
Suppose, you have used the real N400 mean values (not the absolute ones),
and you found a positive correlation.
This means that higher the EQi score, more positive is the mean N400 value.
And, as the N400 is a negative deflection, we would conclude that people
who have larger EQi scores tend to show smaller N400s than those with
smaller EQi values.

Case 2:
You have taken the absolute values instead, and you found a positive
correlation. This would again mean that  higher the EQi score, more
positive is the |mean N400 value|, where |value| == absolute value.
As N400 is a negative going deflection, so you would say that higher the EQ
score, smaller is the N400 (less negative value).

Following the same approach, you would decipher the correlation if it is a
negative one.


Best,
Sujata


Thanks and regards
Sujata Sinha



On Sat, Apr 20, 2024 at 10:05 PM Veronica Debora TORO via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Thank you very much for your reply! What if I don't want to make the
> difference between two conditions instead? What if I wanted to investigate
> separately the correlation between the mean amplitude of the N400 in
> response to negative (and subsequently positive) stimuli and the EQi test
> score?
>
> Inviato da Outlook per Android<
> https://urldefense.com/v3/__https://aka.ms/AAb9ysg__;!!Mih3wA!BQhySUDHm095hk6uBVBDmesPW1-tus3wOWSdgN2ohfyDRP0yg3Hn7Ic83WK2CNMSOdyEM90haJ5WO2cr1JfNSYGa8DNblhNU4mR4B5ssjg$
> >
> ________________________________
> From: Arild Hestvik <ahestvik at gmail.com>
> Sent: Friday, April 19, 2024 3:14:50 AM
> To: Veronica Debora TORO <veronicadebora.toro at studenti.unipr.it>
> Cc: Veronica Debora TORO via eeglablist <eeglablist at sccn.ucsd.edu>
> Subject: Re: [Eeglablist] Correlation with N400 mean amplitude values
>
> If you think of N400 as an experimental effect (the difference between two
> conditions), then it makes no difference whether you use the absolute value
> or a signed value, it is just the expression of a difference between two
> conditions. The sign is a result of the direction of the subtraction. Note
> that the if the baseline is high, the peak of the N400 difference wave does
> not have to be a negative voltage value, it could be greater than zero,
> even if you subtract control from test.
>
> On Wed, Apr 17, 2024 at 9:37 PM Veronica Debora TORO via eeglablist <
> eeglablist at sccn.ucsd.edu<mailto:eeglablist at sccn.ucsd.edu>> wrote:
> Dear EEGLAB users,
> I have a specific question about n400 mean amplitude values.
> I would like to correlate n400 mean amplitude values extracted from
> specific electodes and some scores (for example EQi test score).
> Among the studies published in the literature, I found that some studies
> use raw values of n400 mean amplitude (with positive or negative sign) for
> correlation analyses, while others use Absolute values. In which cases Is
> One methodology used rather than the other? Are there advantages or
> disadvantages?
> Thank you in Advance
>
> Best
>
> Debora
>
> Inviato da Outlook per Android<
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> >
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