Hi Benjamin, The participants were asked to perform a sequence (10 in a row) of ‘rhythmic’ taps, cued by the visual flashes. My suspicion is that occasionally the subjects were anticipating the cue a bit too eagerly, getting ahead of the pacing stimulus now and then.
Best wishes, Jan-Mathijs > On 25 May 2018, at 17:09, Benjamin Chiêm <[email protected] > <mailto:[email protected]>> wrote: > > Dear HCP experts, > > When looking to tmegpreproc data, during motor task and with trials locked on > the onset of the flashing cross (TFLA files), I am quite surprised to observe > that the EMG signal sometimes triggers before the onset of the flashing cross > in some trials. > > To be more specific, let us consider the right hand trials of subject 104012 > in the first run. In attachment you will find the EMG signal of trial 4 > (KO.png) and 8 (OK.png), after high-pass Butterworth filtering at 10Hz, and > taken in absolute value. On the X-axis, time step 611 (i.e. the center of the > time window) corresponds to the onset of the flashing cross. However, we > observe on the KO.png figure that the EMG triggers before this time step, > although it should follow the stimulus, not precede it… I have been able to > observe this in many trials, as well as in data related to other subjects. > Where does this come from? Or am I missing something? > > Besides, it seems that the TEMG alignment is more reliable. > > Thank you in advance for your help ! > > Benjamin > > > _______________________________________________ > HCP-Users mailing list > [email protected] <mailto:[email protected]> > http://lists.humanconnectome.org/mailman/listinfo/hcp-users > <http://lists.humanconnectome.org/mailman/listinfo/hcp-users><KO.png><OK.png> _______________________________________________ HCP-Users mailing list [email protected] http://lists.humanconnectome.org/mailman/listinfo/hcp-users
