[Eeglablist] Variables from ERSP analysis

Alejandro Wainselboim awainselboim at yahoo.com.ar
Thu Jul 22 07:19:23 PDT 2010





Dear all, 

             
I have recently performed an ERSP analysis with EEGLAB of a study composed with
data from 24 participants that underwent 2 different experimental conditions
with a 19 channel eeg recording system. Epoch time limits were -200ms to +2500
ms. The newtimef parameters that I used were: 





 'cycles',
[0.5 0.1], 'padratio', [1],  'alpha', [NaN],  'freqscale',
['linear]', 'scale', ['abs'], 'nfreqs', [100], 'freqs', [1.1 20]

 

According to this I would have 100
frequencies and 200 time points analyzed.

 

I see that the *.DATERSP files that are
generated after running the analysis for each participant include a chan_ersp
and a chan_erspbase variable for each channel. The  chan_ersp
variables are matrices composed of 100 rows and 200 columns, which I
understand represent the values in that channel  for each of the 100
frequencies  (rows) at each of the analyzed time points (columns). I would
like to know ¿in what scale should I interpret these values? 

 

On the other hand, the chan_erspbase variables
are matrices composed of 1 row and 100 columns. I understand that the values
obtained in this case represent the mean  power  for each frequency
(column) calculated along the entire baseline period (from -200 to 0 ms in this
case). ¿Is this interpretation correct? ¿In what scale should I  read the
obtained values of the chan_erspbase matrices?

 

Thank you in advance for your help, 

           
                     
                 Alejandro
Wainselboim

           
                     
                   Behavioral
Biology  

                                                    
IBYME-CONICET

                                                  
Vuelta de Obligado 2490

                                                  
Buenos Aires, Argentina




      
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