Time frequency statistics - comparing 3 conditions

Helen Morgan h.morgan at BANGOR.AC.UK
Wed Nov 28 11:29:39 CET 2007

I wonder if anyone can give me some advice about the appropriate type of
analysis for my data set.
I am currently analysing data from a repeated-measures design, in which
there are three conditions: two are single tasks, and the third is a dual
task consisting of both single tasks. I have obtained TFRs (using the
multitaper method) for each condition, showing relative increase/decrease in
power. However, I am uncertain which type of statistical analysis to use for
this data. The single tasks seem to produce a different pattern of activity,
and I have compared them with a cluster-based permutation test using a
t-statistic (using 'freqstatistics' with the 'montecarlo' method). However,
the dual task is expected to consist of a combination of the activity
patterns for both single tasks (and possibly some kind of additional
integration process). so comparing this to each of the two single tasks
using a t-statistic may not be suitable. An F test does not provide enough
information and would need to be followed by t-tests anyway. The other
alternative seems to be using a statistic based on linear regression; that
is, to evaluate whether the dual task activity is a mix of both single tasks.
Can anyone recommend an unbiased way to analyse this kind of data using the
functions implemented in fieldtrip? I would be very grateful for any ideas.

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