Hi - this sounds reasonable, yes.
Cheers, Steve.
On Sat, 4 Sep 2004, Francois Lalonde wrote:
> Hello Everyone,
>
> My question is similar to the one that Jack Grinband asked a few days ago
> but with an added condition.
>
> I have a block design with three conditions and rest periods between trials.
> This is a visual memory task in which subjects memorize a pattern and,
> after a short delay, have to decide whether a second pattern is either the
> same or different as the first. The first pattern is preceeded by an
> instruction to study and the second pattern is preceeded by an instruction
> to recall. For this analysis the entire sequence of study, pattern, recall,
> pattern is considered as a single trial. The conditions are as follows:
>
> The first condition called "easy memory" follows the sequence decribed above
> with an easily memorized pattern.
>
> The second condition called "hard memory" follows the same sequence but with
> a more complex pattern.
>
> The third condition called "no memory" follows the same sequence but the
> instructions have changed. Instead of studying the pattern subjects are
> instructed to "look" at the pattern and instead of the word "recall"
> subjects are given the correct answer to the following pattern. Subjects
> are familiarized with the task prior to scanning and reaction times support
> the assumption that they are, in fact, not making the effort to remember
> during the "no memory" trials.
>
> If we consider the order of the conditions as no memory, easy memory, and
> hard memory then, following Christian Beckman's recommendation, there should
> be one regressor equal to 1 whenever a pattern or instruction is present
> (1,1,1). Another regressor whenever subjects have to memorize (0,1,1) and
> finally a contrast to differentiate between the 2 memory conditions (0,-1,1).
>
> Any feedback would be greatly appreciated.
>
> Francois
>
Stephen M. Smith DPhil
Associate Director, FMRIB and Analysis Research Coordinator
Oxford University Centre for Functional MRI of the Brain
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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