On 19 October 2011 13:23, Liam Nestor <
[log in to unmask]> wrote:
> Hi Eugene
>
> I have a monetary incentive delay (MID) task. I want to try and employ a
> temporal difference reinforcement learning (TDRL) model.
>
> The MID has a prepare period, 3 cue conditions and 6 outcome conditions
> (EV=10).
>
> The contrasts generated for each subject, for each run (n=3) from the first
> level analysis are:
> Cope 1 = Loss Cue (EV 1)
> Cope 2 = Win Cue (EV 2)
> Cope 3 = Neutral Cue (EV 3)
> Cope 4 = Lost Outcome (EV 4)
> Cope 5 = Saved Outcome (EV 5)
> Cope 6 = Lost+Saved (EV 1+EV 2)
> Cope 7 = Won Outcome (EV 6)
> Cope 8 = Missed Outcome (EV 7)
> Cope 9 = Won+Missed (EV 6+EV 7)
> Cope 10 = Neutral Lost Outcome (EV 8)
> Cope 11 = Neutral Won Outcome (EV 9)
> Cope 12 = Prepare (EV 10)
>
> The TDRL model concerned involves the Win Cue period X probability (0.44) -
> the "expected value". The "expected value" is calculated as the sum of all
> possible outcomes (4.5) X probability (0.44).
>
> Therefore, I want to run the formula - Win cue X 0.44 - sum of all possible
> outcomes (4.5) X probability (0.44) to generate a new image file. I have
> tried the following:
>
> fslmaths cope2.nii.gz -mul 0.44 -sub 4.5 -mul 0.44 cope13.nii.gz
>
> It generates cope13.nii.gz, but it won't threshold on this file when I run a
> Fixed Effects level analysis averaging across the 3 runs.
>
> I have no knowledge of being able to use this formula when setting up the
> contrasts in the FSL GLM GUI, which is why I'm attempting to do this in the
> "stats" directory afterwards.
>
> Thanks,
>
> Liam.
>
>
> On 19 October 2011 12:31, Eugene Duff <
[log in to unmask]> wrote:
>>
>> Hi Liam -
>>
>> On 19 October 2011 12:14, Liam Nestor <
[log in to unmask]> wrote:
>>>
>>> Dear FSL users
>>>
>>> Using fslmaths, I want run a formula, using files that go into the
>>> "stats" directory, which are generated from a first level analysis. The
>>> files that end up in this directory are cope; neff; pe; tstat; varcope and
>>> zstat. The formula is very simple - merely multiplying one of the contrasts
>>> by a number and subtracting another number.
>>>
>>
>> The cope and varcope files are the primary images used in higher level
>> analyses. Both will be affected by multiplication of the contrasts. You
>> might want to describe want you are trying to do to - I can't really think
>> of a reason why you would want to do what you are saying.
>> Cheers,
>> Eugene
>>
>>
>>
>>>
>>> What I'm not sure about is which contrast files will go into the formula?
>>> The cope; neff; pe; tstat; varcope or zstat files? All of them? I have tried
>>> using the cope, tstat and zstat files in the formula, but when I run a Fixed
>>> Effects analysis (averaging across runs), it will not create thresholded
>>> zstat files for the new files that I have created using fslmaths.
>>>
>>> I'm not able to set this formula up using the FSL GUI when doing the
>>> first level analyses, which is why I am having to resort to this formula
>>> subsequently.
>>>
>>> Thanks,
>>>
>>> Liam.
>>>
>>>
>>> --
>>> Liam J Nestor PhD
>>>
>>
>
>
>
> --
> Liam J Nestor PhD
>
>