[Eeglablist] Correlation with N400 mean amplitude values

[Ryan Hubbard]

The problem with not using any sort of difference is that some individuals
will just have higher amplitude responses, but this variance may just be
due to some more basic physiological differences that are unrelated to the
individual differences you're interested in. So, isolating the "signal" or
"effect" of interest is the argument for using a conditional difference.

Note however that there are some arguments against using the "ERP
difference" approach for measuring individual differences, and instead
using a residualization approach (where one signal predicts the amplitude
of the other in a regression model). That paper is here:
https://urldefense.com/v3/__https://doi.org/10.1111/psyp.12664__;!!Mih3wA!DVWJU9TRGz2kD3uTJBaBRcbijeC0C5JSSmS9fytN3CcAJflaXkKwAxBsEKm7JIfxqv32677X7PwzoTrylWZLIz0S84U$ 

On Sat, Apr 20, 2024 at 8:47 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<
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> >
> ________________________________
> 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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-- 
Ryan Hubbard
Postdoctoral Research Associate
Cognition and Brain Laboratory (CABLAB)
Department of Psychology
University of Illinois at Urbana-Champaign