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
>  
>  
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