Hi,
1) It doesn't matter whether you call this block or event-related -
the timings are the timings - just set them up with either of the
"custom" options and the result will be identical.
2) Ah, no, I hadn't realised that your scanning was not continuous.
In this case, no, things get a lot more complicated as you will have
nasty T1 saturation effects to model.....see previous postings on the
list by people like Andreas Bartsch and Joe Devlin on these issues.
Cheers, Steve.
On 26 Oct 2007, at 06:04, Xu Chen wrote:
> Thanks, Steve.
>
> I am bringing up two more questions based on your answer .
>
> 1) are you suggesting me to analyze this data as block design
> instead of event-related? I'd rather treat it as event-related,
> but how?
>
> 2) As you may have noticed that the data collection is not
> continuous in the sequence diagram. Only in steps 2, 5, 8,
> 11......the data were collected. How can I deal with this in FSL?
>
> Thanks again
>
> Chen
>
> Steve Smith wrote:
>> Hi - sounds like you have 3 conditions, including stim1=rest.
>>
>> Hence you should model this with just two EVs, one for when stim2
>> is on and one for when stim3 is on. You can use either custom1 or
>> custom3 to generate these.
>>
>> Cheers, Steve.
>>
>>
>> On 25 Oct 2007, at 04:01, Xu Chen wrote:
>>
>>> Dear FSLers
>>>
>>> I am trying to analyze a fMRI dataset collected using the
>>> following sequence diagram,
>>> 1, 'stim1' ( on for 8 seconds)
>>> 2, collect 4 scans (S11, S12, S13, S14) with 'stim1' off but
>>> 'stim2' on (TR=2s) 3, rest for 8 seconds
>>>
>>> 4, 'stim3' ( on for 8 seconds)
>>>
>>> 5, collect 4 scans (S21, S22, S23, S24) with 'stim3' off but
>>> 'stim2' on (TR=2s)
>>> 6, rest for 8 seconds 7, 'stim1' ( on for 8 seconds)
>>>
>>> 8, collect 4 scans (S31, S32, S33, S34) with 'stim1' off but
>>> 'stim2'on (TR=2s)
>>>
>>> 9, rest for 8 seconds
>>>
>>> 10, 'stim3' ( on for 8 seconds)
>>>
>>> 11, collect 4 scans (S41, S42, S43, S44) with 'stim3' off but
>>> 'stim2'on (TR=2s)
>>> 12, rest for 8 seconds .......................
>>>
>>> It is essentially an modified event-related experimental design.
>>> 'stim2' ( actually 'the gradient noise') is always on in data
>>> collection
>>> steps only (step 2 , 5, 8, 11 ..... in above). And I want to apply
>>> paired-t test on this data to get the contrast between 'stim1' and
>>> 'stim3', namely, compare the pairs of (S11,S21) (S12, S22) (S13,
>>> S23)
>>> (S14, S24) (S31, S41) (S32, S42) (S33, S43) (S34, S44)..........
>>>
>>> I am not sure whether FEAT is capable to do this kind of
>>> analysis. If
>>> positive, how?
>>>
>>> Thanks
>>>
>>> Chen
>>
>>
>> ---------------------------------------------------------------------
>> ------
>> Stephen M. Smith, Professor of Biomedical Engineering
>> Associate Director, Oxford University FMRIB Centre
>>
>> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
>> +44 (0) 1865 222726 (fax 222717)
>> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
>> ---------------------------------------------------------------------
>> ------
>>
>>
------------------------------------------------------------------------
---
Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR 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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