hi list,

 

I am new to FSL and have just joined the list.

I am working on a fMRI project where the model consists of blocks as rest, angry,rest, neutral, rest, happy,rest, fearful, rest. This block is repeated for 5 times.

here rest represents showing a fixation cross and the other stimuli are showing pictures representing them.

 

I modeled the task in FSL using choose Custom (3 column format).

When i looked at the timeplots for contrast of angry (or happy or fearful or neutral) versus rest I am getting a distinct negative peak in the intial time period for data as well as the model.

Where as for  the timeplots for contrasts of angry (or happy or fearful) versus neutral, the same model doesnt show the peak. 

 

I unable to understand the difference seen in the two cases. Also since the first block is of rest, we do not expect to see any such peaks. Also the same peak is not seen in the data or model parts for the other rest periods. Since the rest block is same for the entire task one would expect for all the rest sections in the time plots to be similar.

 

I am attaching tsplots for contrast fear v/s neutral and one for fear v/s rest.

 

Is it something to do in the way FSL models? Also convolution is done using a double gamma hrf.

 

Thanks,

 

Mayuresh K.

Biomedical Engineering Dept.

SUNY at Stony Brook