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Hi, This doesn't sound like too small an ROI; FEAT doesn't implement the 'official' small-volume correction, but in general it doesn't make much difference anyway. I would go ahead and use this as a pre- thresholding mask in FEAT. The problem with using randomise in FEAT is that it doesn't correctly deal with autocorrelations (if this is a first-level analysis) or full mixed-effects modelling (if this is a higher-level analysis). Cheers. On 15 Feb 2008, at 20:59, Soohyun Cho wrote: > Hello experts, > > I am trying to do small volume correction limiting my search for > activations within the frontal cortex. > I made a mask by combining all of the frontal cortex of the Harvard > Oxford atlas (frontal pole + MFG + IFGtri + IFGop). > > If I use this frontal mask as a prethresholding mask within feat, > would there be any problems? e.g. perhaps this volume is too small > for Random Field Theory to work properly? > > Is it better to use this mask with Randomise for small volume > correction? > > Thank you for your response. > > Soohyun. > --------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------