# [Eeglablist] ERPS vs Time-Freq

Sun Mar 2 00:58:43 PST 2014

```Hi,

It is informative site which discusses about Evoked vs Induced ERP.

http://personalpages.manchester.ac.uk/staff/Wael.El-deredy/erbd/

-Iman

From: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Makoto Miyakoshi
Sent: Thursday, February 27, 2014 10:48 PM
Cc: EEGLAB List
Subject: Re: [Eeglablist] ERPS vs Time-Freq

Dear Iman,

I'm not sure if there is any difference... I was not aware of it.

You may want to check dftfilt3() for the EEGLAB default wavelet (and let us
know what you find).

> And what is the difference btw evoked and induced potential.

Evoked is phase-reset to stimulus onset and induced is not. I thought
Galambos proposed this distinction, but I could be wrong.

Makoto

Hi ,

What is the difference btw the traditional time-freq representation of an
ERP and ERPS? Are they the same? Since Suppose,  we have two epochs x1 and
x2 with zero means , then

1-      In traditional  way :  we make an average out of them x_avg and then
make the Fourier transform of them F(x_avg)=F([x1+x2]/2 ) = F(x1/2)+F(x2/2)=
[F(x1) + F(X2)] / 2

2-      In ERPS we calculate time-freq for each epoch F(x1) and F(x2) and
then make the average ERPS=[ Fx(1) + F(x2)] / 2

And what is the difference btw evoked and induced potential. My questions
are mostly from Chp 3 of the Oxford Handbook of Event Related Potential
Components pg 77-78

Best

Iman

--

Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego

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