Hi Sören
This might be due to low frequency components in the signal that happen to correlate with your task regressors in your designmatrix. Long block durations (i.e. over a minute, roughly) are not very beneficial either, since they are more likely to correlate with low-frequency components that are very likely to be present in fMRI data. I have never noticed ventricle activation in an event related model, for example.
The problem could also have been caused by movement related variance. I have seen ventricle "activation" before in a block-design language dataset of a colleage, most likely due to movement related variance. Especially in tasks, such as language, where head movement is likely to be correlated with your model, this might occur, since the task related regressors will explain the movement signal quite well in that case.
To check this you could calculate the correlation between the movement parameters (as obtained from realigment) with your task regressors in your design matrix.
I think there is little one can do about this, other than changing the design...
Good luck,
Bas
-----Oorspronkelijk bericht-----
Van: SPM (Statistical Parametric Mapping)
[mailto:[log in to unmask]]Namens Sören Krach
Verzonden: donderdag 7 juli 2005 9:49
Aan: [log in to unmask]
Onderwerp: [SPM] Activation of ventricle
Dear list,
in our study, 33 subjects performed a language task. After a random-effect group analysis we got nice activation in the expected language area and additionally, much less nice, in the ventricle system. No ventricular activation was found in the individual subjects. Any idea why that can be?
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