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,AndyOn 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