Eric Maris maris at NICI.RU.NL
Mon Nov 14 17:13:01 CET 2005

Hi Christopher,

> I have two questions concerning clusterrandanalysis:
> First, I performed a frequency analysis with Brain Vision Analyzer and
> exported these data into an Excel and SPSS file. How can I import these
> data into Matlab in order to obtain a format on which I can perform a
> Cluster-level Randomization Test for a Within Subjects experiment?

This is not a question about clusterrandanalysis but about how to import
preprocessed data from another package such that it is compatible with
Fieldtrip functions.

Although I am not an expert in these issues (Robert Oostenveld is our
expert), I think it is complicated and intellectually not very satisfying
(because of all the bookkeeping that is probably involved). I advise you to
import your non-preprocessed BVA data files into Fieldtrip (we have import
routines for this) and do you frequency analysis in Fieldtrip. Besides sound
statistics, Fieldtrip also offers state-of-the art spectral density
estimation. Learning the Fieldtrip function freqanalysis will probably take
less time than importing your BVA power spectra.

> Second, I want to compare three conditions, two drug conditions and a
> placebo condition. In all conditions, a baseline measurement was made
> before drug intake. I want to take in account these baseline measurements.
> In a parametric test like MANOVA this is usually done with a covariate or
> the introduction of an extra factor (time). How can I perform this in
> clusterrandanalysis?

1. Divide the activation power by the baseline power (and, optionally, take
the log of this ratio) and submit this to clusterrandanalysis.

2. Compare each of the drug conditions with the placebo condition (using a
T-statistic) with respect to this baseline-normalized dependent variable.


Eric Maris

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