<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear all<div class=""><br class=""></div><div class="">We are sorry to report that with merging the recent <a href="https://github.com/fieldtrip/fieldtrip/pull/1377" class="">pull request #1377</a> about a month ago, we introduced a bug in the FieldTrip release that might have affected your computations.<br class=""><br class="">Specifically, the handling of the defaults for cfg.reducerank and the cfg.backproject changed a bit, which had an unforeseen sideeffect in ft_prepare_leadfield, if (and only if) you used this function for the computation of MEG-based leadfields, using the singleshell method. Specifically, ft_prepare_leadfield would by default compute MEG singleshell leadfields with reducerank=2 (this is how it always has been), but it would wrongly backproject (i.e. the intended projection of the rank-reduced 2-column leadfield back into 3D space with a column for the x, y, and z dipole moment in Cartesian space) the rank-reduced leadfield. Rather, ft_prepare_leadfield would on <a href="https://github.com/fieldtrip/fieldtrip/blob/af5f9822413d11e66f3821943e945e98ab766da6/ft_prepare_leadfield.m#L292" class="">line 292</a> discard the last column. The error was due to MATLAB interpreting if [] as false, causing on line 295 only the first two columns to be copied to the output. Consequently, the leadfield for the z-direction was discarded.<br class=""><br class="">Are you affected? If you used the master branch from GitHub (which is the development version), or a release version between 20200529 and 20200607, and if you have used ft_prepare_leadfield for MEG with singleshell models, then you are likely affected. You can check yourself: your precomputed leadfields should have three columns; if they only have two columns and you did not explicityly specify reducerank and backproject in your configuration, your leadfields are wrong. Other models than MEG singleshell are not affected.<br class=""><br class="">To resolve the problem, please update to the latest 20200623 release version from the <a href="ftp://ftp.fieldtriptoolbox.org/pub/fieldtrip/" class="">FTP server</a> or from the <a href="https://github.com/fieldtrip/fieldtrip/releases" class="">GitHub release page</a> and recompute your leadfields, source estimates, etcetera.</div><div class=""><br class=""></div><div class="">best regards,</div><div class="">Robert</div><div class=""><br class=""></div></body></html>