Could I ask the SPM community to comment on a study design that I have
been asked to replicate.
The design has 3 tasks:
1) Implicit social exclusion (where the subject is knowingly excluded
from a task, a game of catch)
2) Inclusion (the subject is included in the game of catch)
3) Explicit social exclusion (the subject is unknowingly excluded from
the game of catch)
The original design did not use a traditional A-B-A-B design but simply
a 2 min session of task 1 followed by a 2 min session of task 2 followed
by a 2 min session of task 3.
Contrasts were then made between session 1 and session 2 for example.
My initial thoughts were that the main reason for using A-B-A-B etc was
to allow filtering of low (scanner drift etc) and high (physiological)
frequency noise inherent in any fMRI exam.
There are good behavioural reasons for using the above design but does
this type of experiment not increase variance by including the low and
high frequency noise in the fitting.
Thanks in advance for the help,
Gordon
--
Dr. Gordon D. Waiter
MRI Physicist
Department of Radiology
University of Aberdeen
Research MRI Centre
Lilian Sutton Building
Foresterhill
Aberdeen
AB25 2ZD
Tel: +44 (0)1224 559725
Fax: +44 (0)1224 559718
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www.abdn.ac.uk/radiology
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