[Eeglablist] Time Frequency Statistics
arno at salk.edu
Fri Aug 27 17:36:26 PDT 2004
David and Joe,
you may also use the function tftopo to find significant time-frequency
regions across subjects.
See this section of the EEGLAB manual
The example above computes significance across channels but the same
strategy may be used to compute significance across subjects.
The function tftopo accepts time-frequency decompositions and bootstrap
arrays from several electrodes and subjects. It uses binomial statistic
on the bootstrap array of all subjects to mask non-significant
time-frequency regions (for instance, the function will plot significant
time-frequency regions in at least 7 out of 10 subjects).
Joseph Brooks wrote:
> The time-frequency analysis is done using a function called timef. One
> of the outputs of timef is a 2D matrix (time x frequency). This
> contains the data that is used to generate the time-frequency map that
> you see.
> In order to do a statistical analysis I do the following:
> (1) Write a script that will run the timef function on data from each
> subject and each condition.
> (2) The script saves the outputs of each run of timef into a matlab
> variable (I save things into structure variables....e.g. the structure
> may contain fields for each condition and then the subjects within that).
> (3) You can then save the output variables (a structure in my case) to
> (4) Now, the time-frequency maps can be accessed and you can select
> any portion of the matrix that you choose.
> (5) run your statistical analysis of choice on some sub-matrix of
> interest of the time-frequency maps.
> (6) to take the mean across subjects, just stack the matrices from all
> the individual subjects into a 3D matrix and take the mean (using the
> mean function in matlab) over the subject dimension.
> Time and frequency are outputs of the timef function and will serve as
> axes for the time-frequency matrix.
> Type "help timef" at the matlab command line for full information
> about the use of timef.
*Arnaud Delorme, Ph.D.*
Computational Neurobiology Lab, Salk Institute
10010 North Torrey Pines Road
La Jolla, CA 92037 USA
*Tel* : /(+1)-858-458-1927 ext 15/
*Fax* : /(+1)-858-458-1847/
*Web page *: www.sccn.ucsd.edu/~arno <http://www.sccn.ucsd.edu/%7Earno>
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