On Tue, 23 Feb 2010 14:19:18 +0000, Marco Sperduti
<[log in to unmask]> wrote:
>Dear SPM's users,
>
>I'm setting up an fMRI experiment, I would like to know if there is a
theoretical maximum lenght for a block.
>
>thank's a lot,
>
>Marco
There's no theoretical limit. Rather, the problem with really long blocks is that
the longer the block, the greater the chance that the signal will be
confounded with low-frequency noise. That's an "empirical" limit, insofar as it
depends on the noise.
Other people here would be better able to give you precise advise on how long
a block can be without losing power due to this problem. My impression is
that anything over a minute is pretty long, and even a minute is longer than
usual in published studies.
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