Investigating Fieldtrip

Christian Hesse c.hesse at FCDONDERS.RU.NL
Tue Mar 6 08:59:57 CET 2007

```Hi Grant,

> Basically, we need to:
> 1) Open time series data that is in ASCII format.  The data is just
> one
> or two channels of potentials from one or two electrodes sampled at
> 200Hz.

Assuming that the data format can be read using standard Matlab file
I/O functions (fread or dlmread) all that is required is then to
convert the data into an appropriate FieldTrip (FT) data structure.
This will work best if your data naturally divides into "trials" or
epochs, but in principle you can also define intervals of arbitrary
length with arbitrary overlap (which may be useful for subsequent
spectral / time-frequency analysis).

> 2) Identify regions in the data that have 'high voltage/low frequency'
> or 'low voltage/high frequency'.  (Perhaps this could be determined
> based on average in data region vs average potential of whole data
> set).

There are several ways in which this could be accomplished in FT.

> 3) Calculate power spectra for the data regions.
>
> 4) Calculate spectral edge frequencies for the data regions
>
> 5) Do some simple statistics comparing data regions (eg, spectral edge
> frequency of controls vs experimental group).

All easy.

> 6) Creating m files to automate as much as possible.

That's the essence of FT philosophy :-)

> So my questions are:
>
> 1) Is this straight forward to do in Fieldtrip?

Mostly, yes. However, you may need to write the odd small function
yourself, which is then passed to and called by FT: at the end of the
day, FT is merely a "box of tools" :-)

> 2) Do we need anything more than the MATLAB program itself (ie, do we
> need any other MATLAB toolboxes)?

FT has been written to be as "stand alone" as possible, so you should
be OK. I could imagine that the only other Matlab Toolboxes you might
need are the Statistics Toolbox (to do paramteric tests, FT can do
non-parametric permutation tests using any statistic/measure derived
from your data) based on permutation) and perhaps the Signal
Processing Toolbox (although I am pretty sure that FT is now self-
sufficient there).

> 3) Is there another (free) library that might be better for this
> kind of
> a problem?

Not sure about free ones ... you could always write your own stuff in
Matlab, I guess.

Hope this helps,
Regards,
Christian

----------------------------------------------------------------------
Christian Hesse, PhD, MIEEE

F.C. Donders Centre for Cognitive Neuroimaging
P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Tel.: +31 (0)24 36 68293
Fax: +31 (0)24 36 10989

Email: c.hesse at fcdonders.ru.nl
Web: www.fcdonders.ru.nl
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