Hi all,
Thank you very much! I did 2 runs of each of the stimuli I described in one session (I previously got some pretty decent maps from these data using the mrVista package from Stanford). I followed the retinotopy instructions from the FS wiki ( http://surfer.nmr.mgh.harvard.edu/fswiki/FsFastIndividualRetinotopyAnalysis) but the results did not make much sense. I guess I need to use some other commands or change some parameters in order to view reasonable eccentricity and polar angle maps. I have not managed to find any other documentation on how to do this. This is what my "raw angle" looks like: http://dl.dropbox.com/u/6981172/raw_angle.tif Best, Anders 2011/7/7 Jonathan Polimeni <j...@nmr.mgh.harvard.edu> > > hi anders, > > the optimal set of stimulus parameters will depend somewhat on what > cortical area(s) you are trying to map and on the details of your > acquisition. in general, stimulating with both clockwise- and > counterclockwise-rotating wedges for polar angle mapping and with both > expanding and contracting rings for eccentricity mapping improves the > accuracy of the maps, and the proper analysis of this data is implemented > fsfast. the width of the wedge or the ring will depend on the cortical > area you are trying to stimulate, but you may want to consider a thinner > wedge. also, 8 Hz flickering has been shown to activate area V1 more > strongly than other frequencies, and smoothly moving stimuli can also > help. then, depending on your voxel size, field strength, coil array, > etc., you could include more cycles and may need to average together > multiple runs. > > marty, roger et al. have a few nice papers that i'd recommend that discuss > some of these details relating to phase-encoded retinotopic stimuli. > > Sereno & Tootell. Curr Opin Neurobiol. 2005;15(2):135-44. > Tootell et al. J Neurosci. 1997;17(18):7060-78. > Sereno et al. Science. 1995;268(5212):889-93. > > (the '97 paper discusses the ring/wedge thickness, the '95 paper discusses > the advantages of using both expanding + contracting stimuli, and the '05 > paper discusses the use of smoothly varying stimuli.) > > hope this helps. were you able to get reasonable looking maps with the > stimuli you described below? > > > -jon > > > > > On Thu, 7 Jul 2011, Anders Hougaard wrote: > > > Dear freesurfers, > > > > > > Which stimuli do you think provide the best retinotopic maps? > > > > I have done a retinotopy analysis using the following stimuli: > > > > Polar angle: > > > > - 45 deg counter-clockwise rotating wedge > > - 8 unique positions > > - flickering at 2 Hz > > - stimulation period: 36 sec > > - no. of cycles: 6 > > - TR = 3 > > > > Eccentricity: > > > > - expanding ring > > - 8 unique positions > > - flickering at 2 Hz > > - stimulation period: 36 sec > > - no. of cycles: 6 > > - TR = 3 > > > > Any suggestions on how to optimize this stimulation? > > E.g. different period length, more runs, bi-directional, different TR > > > > Thank you! > > > > Best regards, > > > > Anders > > > > > The information in this e-mail is intended only for the person to whom it > is > addressed. If you believe this e-mail was sent to you in error and the > e-mail > contains patient information, please contact the Partners Compliance > HelpLine at > http://www.partners.org/complianceline . If the e-mail was sent to you in > error > but does not contain patient information, please contact the sender and > properly > dispose of the e-mail. > >
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