[Eeglablist] .datersp file contents question

[Makoto Miyakoshi]

Dear Steven,

I'm not sure what you mean by 'branches' but I guess these are either ICs
or conditions?

Makoto


2014-02-26 4:42 GMT-08:00 Mikołaj Magnuski <imponderabilion at gmail.com>:

> Hi Steven,
>
> by default spectra and ersps computed in EEGlab are transformed to dB (10
> * log10( power ) ).
> erspbase should represent baseline (in dB too) that was subtracted from
> each time step of your ersp. The baseline is mean spectrum in time range
> that you defined when precomputing (by default it is everything before time
> zero).
> This means that ersp fields contain baseline-corrected time-freq
> representation in dB.
> (if I am not correct about ersp or erspbase fields, please correct me,
> eeglablist).
> 25 lut 2014 22:18 "Steven Pillen" <stevendpillen at gmail.com> napisał(a):
>
>>  Hello, EEGLAB list.
>>
>> We were running an ERSP study, and we had some questions about the output
>> files.
>>
>> When we load the contents of a .datersp file with the function, "m =
>> importdata('filename.datersp'), the m struct contains two elements for each
>> channel:
>>
>>  chan1_ersp: [100x200 single]
>>  chan1_erspbase: [1x100 single]
>>
>> I figure that the two dimensions of the plain "ersp" correspond to
>> frequency and time respectively, because they are the same size as the
>> m.freqs and the m.times branches.  What I am unsure of is what exactly I am
>> looking at in the contents of these files.  Can anyone tell me what the
>> numbers in those branches represent?
>>
>> I was hoping, for instance, that the values in the "ersp" branch would
>> contain a table of the spectrum values for each cross-section of frequency
>> and time, but it looks like maybe they've had some kind of normalization
>> applied to them, like maybe a logarithmic function or something.  I want to
>> be sure what I'm looking at before I attempt any statistical analysis.
>>
>> Also, what is the relationship between the "ersp" and the "erspbase"?
>>
>> Thank you,
>> Steven Pillen
>>
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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