Dear PsychoPy community,
I am setting up my task on PsychoPy for a TMS experiment.
We have an image presented for 1 s and we use LTP pulse trains to control the TMS stimulation starting at
t=0 , onset of the image presentation, 10 pulses spaced by 50 ms, in one block of the experiment
t = 500 ms, in the middle of the image presentation, 10 pulses spaced by 50 ms, in another block of the experiment
We set t = 0 the time of the image onset.
We tested the time precision of LTP pulses sent by the psychoPy builder with respect to image onset (t=0) with a photodiode capturing the onset of the image.
We have 2 problems:
First, we have the delay between the image onset ( time 0 in the builder) and the desired LTP pulse time in both cases ( 0 ms and 500 ms), with the pulse jittering in a range of 10 ms around the desired time across trials.
To be crystal clear, if the pulse is set to be delivered at t =0 ), the actual pulse is recorded to between -5 and +5 ms around the image presentation.
If the pulse is set to be delivered at t = 500 ms, the actual pulse is recorded to between 495 and 505 ms around the image presentation.
We tried to use static components to preload the image, but we ended up masking TMS pulses.
Can you suggest a way to improve these jitters?
- The time interval between 2 consecutive pulses is set to be 50ms.
We observe that for 80% of the cases the inter-pulses interval falls between 49 and 51 ms, but for the remaining 20% is around 45 ms.
Can you suggest a way to avoid this arbitrary inter pulse interval?
Attached the Builder file for your reference.
Thank you in advance.