[Eeglablist] RE : ERSP comparisons

[Andre Achim]

To test whether paired data differ across channels at a given time, across
time at a given channel or across both channels and time, you may use the
attached function that implements the PC1 test that I developed. The
reference is in the function's comments.
I packaged the function extractPC1 that I use to extract only the first
principal component within this PC1 function for simplicity of transmitting.
It coiuld be extracted if needed. You need the statistical toolbox;
otherwise, remove parameter p and the call to TCDF.

This is essentially a signal detection test and it may be, for instance, on
the individual sweeps form a given channel (or set of channels) in a given
condition in a given subject to decide whether that channel contains signal
for that condition in that subject or whether these data behave as
consisting of noise only.

I use another function based on the first two princial components to
compared two independent sets of data (two groups of subjects or single
sweeps from two conditions within a single subject).

Andre Achim
Universite du Quebec a Montreal (UQAM)


-----Message d'origine-----
De : eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] De la part de Dott. Stefania Costa
Neurofisiologia
Envoyé : 18 octobre 2007 08:05
À : eeglablist at sccn.ucsd.edu
Objet : [Eeglablist] ERSP comparisons


dear all user,

i need an help!when i compute ERSP comparisons between two conditions, i 
obtain 3 plots: ERSP on condition 1, ERSP on condition 2 and ERSP 
difference.
sometime, it seems that, for a specific time point and estimate of 
linear-spaced frequency, there are marked differences; indeed, that 
differences are not correctly detected.
i don't understand very well the bootstrap method for significance, and 
i think that some bias can derive from "common baseline computing". i wish
ask EEGLab user an alternative method to detect that differences, thank you,

Stefania Costa, PhD student
Department oh Human Physiology and Pharmachology,
Rome,ITALY
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