Back to PLS HelpPosted on 11/17/13 12:03:42
Number of posts: 13
Dear PLS experts,
Is it possible to apply task/behavioral PLS on contrast maps instead of the raw data?
My second question is about jittering for E.R. fMRI and an appropriate size of temporal window for task PLS analysis. If I choose 8 TR (TR=2.5) for the temporal window, as it is suggested in most of the PLS publications, then more than 2 stimuli fall into this temporal window which makes the temporal brain score bouncy. However, if I choose a shorter temporal window, it is likely that the specified time may not to be sufficient for HRF to be elicited. So how should I chosse the correct size of the temporal window?
Many thanks!
Kambiz
Replies:
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Posted on 11/17/13 15:48:58
Number of posts: 229
Hi Kambiz
1) Using PLS on contrast maps: not a good idea - the variance structure in those maps is not what is expected by the PLS approach
2) jitter - your events should be "properly" jittered with respect to the TR, regardless of analysis method. If you have too many events in a given temporal window, you will likely run into similar challenges, for example, if you convolve a HRF against the data and enter it into a univariate analysis.. You can probably get by with a shorter temporal window of 6-7 TRs (15 - 17.5s), but that may or may not deal with your concerns.
cheers
Nancy
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