Dear spm experts,
thanks for your help for our previous query; the results we achieved
look promising.
You suggested that we may be experiencing difficulties in examining the
main effects of mood because these may be associated with very low frequency
signal changes , which may have been obscured by our selection of filters.
You suggested we provide further details of the experiment.
the aim of the experiment is to examine the effects of experimental mood
induction on verbal fluency activations, in bipolar patients and normal
controls.
Each subject undergoes 3 mood induction tasks each lasting approx 6.5 mins.
Each mood induction task is followed by verbal fluency tasks during which an
fmri time series is obtained. Each verbal fluency task consists of 30 sec
epochs of each of three conditions Repition (A), Generation (B) and Rest(C),
ordered as follows:
C A B C C B A A B C C B A
The first rest epoch is discarded prior to analysis.
In analysing the data so far, to examine verbal fluency effects, and
modulation of these by mood, we have used two cut off filters as follows:
haemodynamic response function ( HRF)
high frequency cut-off: 180 180 180
the high frequency we presume is optimised depending on previous input data
we would be grateful for your help in the determination of the
appropriate filter and contrasts to allow us to best examine the main
effects of mood.
thanks again for your help
alan mcbride & David Barbenel
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