 |
 |
Hi Peter, Thanks for your guidance. It worked! But one thing I want to ask is, when I plot beta against time bin, should I add a data point for time bin=0? Because my stimulus is ON at first 2 time bins, and I don't want to create a false impression that beta is already max right at the beginning of each trial, which doesn't look like the classical HRF curve. Second question is, if I have 2 sessions for each subject, is it okay just to average both sessions to create 1 plot? Thanks a lot for your advice! Andy On Fri, Apr 25, 2014 at 9:46 PM, Andy Yeung <[log in to unmask]> wrote: > Hi Peter, > Thanks very much for your clarification. I think what you said is correct. > Let me try it out and come back here to report my progress. Thanks! > > Best, > Andy > > > On Fri, Apr 25, 2014 at 7:52 PM, Zeidman, Peter < > [log in to unmask]> wrote: > >> Hi Andy, >> >> I think the confusion here is due to terminology. >> >> >> >> When you say you had two stimuli, I think you mean you had two >> conditions, let’s call them A and B. Some blocks were of condition A and >> some blocks were of condition B. The blocks were then randomly intermixed, >> e.g. ABBABAA. Is that correct? >> >> >> >> If that’s correct, your condition A blocks and condition B blocks should >> be entered as separate conditions when you specify the GLM. Then each will >> be given a set of FIR columns. >> >> >> >> Please forgive me if I’ve not understood your question! >> >> >> >> Best, >> >> Peter. >> >> >> >> *From:* Andy Yeung [mailto:[log in to unmask]] >> *Sent:* 25 April 2014 10:57 >> *To:* Zeidman, Peter >> *Cc:* [log in to unmask] >> *Subject:* Re: [SPM] How to use FIR for multiple contrasts in single >> session >> >> >> >> Thank you Peter and To all, >> >> >> >> Yes I had 2 stimuli in a session, they were in pseudo-randomized blocks >> of 6 seconds separated with 15 seconds of baseline conditions. TR was 3 >> seconds. >> >> So, (6+15)/3 = 7 time bins. >> >> Design Matrix gave me 7 columns corresponding to 7 time bins. But 2 >> stimuli are mixed in these 7 columns, I suppose. Can you help? >> >> >> >> Best, >> >> Andy >> >> >> >> On Fri, Apr 25, 2014 at 3:58 PM, Zeidman, Peter < >> [log in to unmask]> wrote: >> >> Dear Andy, >> >> First, can I confirm you really mean 2 stimuli in a session? Are these >> blocks or events? >> >> >> >> The FIR model will create a series of columns for each of your >> conditions. So if one condition (as defined in your onsets) is stimulus1, >> and the other condition is stimulus2, then you’ll get what I think you want. >> >> >> >> Best, >> >> Peter. >> >> >> >> >> >> *From:* SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] *On >> Behalf Of *Andy Yeung >> *Sent:* 25 April 2014 04:54 >> *To:* [log in to unmask] >> *Subject:* [SPM] How to use FIR for multiple contrasts in single session >> >> >> >> Dear all, >> >> >> >> I would like to investigate the change in beta at different time bins, >> for 2 stimuli in a session. >> >> To Specify 1st level, the FIR model allows me to input contrasts scan >> images and define IOI according to TR. >> >> >> >> But I don't know how to separate 2 stimuli at defining contrast in >> Results. In design matrix, each column is for each time bin. So, eg time >> bin 1 contains con images from both stimuli 1 and 2. >> >> >> >> Can anyone help me on separating the stimuli into separate series of time >> bins? >> >> >> >> Yours, >> >> Andy >> >> >> > >