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Hi - in order to interpret the absolute size of estimated PE values, you need to first multiply them by the peak-to-peak height in the model (i.e., look inside design.mat) - after doing this, regardless of the convolution type, you know the fitted peak-to-peak height. In none of this, at this point, are things normalised into percentages (etc.). Cheers, Steve On Wed, 8 Dec 2004, Ramapriyan Pratiwadi wrote: > Hi, > > We recently ran an analysis using the FIR basis set, rather than the the > double-gamma HRF. To our surpise, the range of values for the pe images > were much much lower than expected; in fact, they look like percent > signal change. And when the betas for the basis set were graphed, they > indeed looked like a typical HRF. > > Do the pe images need to be scaled in some way, or are they already in > percent deviation from baseline. > > Thanks, > > Ram > > > > ------------------------------------ > Ram Pratiwadi > Research Assistant > University of Pennsylvania, Brain Behavior Laboratory > > -- > This message has been scanned for viruses and > dangerous content by MailScanner, and is > believed to be clean. > MailScanner thanks transtec Computers for their support. > -- Stephen M. Smith DPhil Associate Director, FMRIB and Analysis Research Coordinator Oxford University Centre for Functional MRI of the Brain John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK +44 (0) 1865 222726 (fax 222717) [log in to unmask] http://www.fmrib.ox.ac.uk/~steve