Hello everyone,
I used FsFast to do retinotopy analysis as described at https://surfer.nmr.mgh.harvard.edu/fswiki/FsFastIndividualRetinotopyAnalysis
I have data for both a clockwise and a counter-clockwise rotating wedge, and when I do retinotopy on these separately, it seems to work fine, but when I put both runs in one retinotopy analysis (as 001 and 002), they seem to cancel each other out and the results looks rubbish; sliceview-sess shows very little activation and the surf-sess polar maps don't make sense.
Do you have any idea what might be the problem here? Of course I defined opposite directions for both runs in the rtopy.par files.
Some 'problems' with my data which might give you a clue as to what's going on: - I don't have eccentricity runs, so I copied polar data in a 'fake' eccentricity run. Doesn't seem to be the problem, since retinotopy works fine for the clockwise and counterclockwise runs separately. - My wedge starts at the top right of the screen, so I need to state an angle offset when watching the results in tksurfer (-0.125) in order for the colour coding to make sense (blue = horizontal meridian, right?) - Although the movement of the wedge fits perfectly with the scans in the clockwise run (each wedge lasts one TR and starts exactly at the start of a scan), there is a slight offset for the counterclockwise run; wedges still last exactly one TR but the first wedge doesn't start exactly at the start of a scan. This doesn't seem to cause problems when I analyse the runs separately, but could it explain why the activations seem to cancel each other out when I combine them in one analysis?
I would appreciate any suggestions.
Thanks, Peter Kok