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Hi - this is more of a design-decision question than a software one; one approach to modelling intensity nonlinearities is to "linearise" the effects by creating extra EVs that model the various nonlinearities when combined with each other by the GLM. Probably a good start point is to read the literature on the Balloon model (Buxton etc) and Volterra kernels (Friston etc) - that may give you enough pointers to make it straightforward for you to create the necessary EVs (e.g. in matlab) to feed into FEAT. Cheers. On 3 Sep 2010, at 09:46, Roman M wrote: > In case my message was 'lost' in the daily inflow.. > > > Date: Tue, 31 Aug 2010 13:46:55 +0000 > From: [log in to unmask] > Subject: [FSL] BOLD non-linearities in fast ER designs > To: [log in to unmask] > > Hi, I am thinking about a new experiment I'm planning. One possibility is to have a very rapid ER design (with ISI much smaller than 4 seconds) which would give me plenty of trials, but I understand at that speed of presentation the bold response has significant non-linearities. Is there a way to account for these effects in FSL? Do you think this is a big problem? > > thank you > > Roman --------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------