Bonsai/Bonvision question: how to use a function to control the movement of a stimulus

[rjs360]

Dear all, I am interested in presenting a grating stimulus whose x-axis motion is governed by a sine function. My current basic workflow is attached below, which is a slight modification of one of the online tutorials for orthographic presentation of grating stimuli:

I found issue #2241 here on the discussion board, in which an ExpressionTransform was suggested to move a stimulus, which seemed an appropriate option. I am able to apply such an ExpressionTransform to the Location(x) of the DrawGratings, but this is not quite desirable, as the result appears to be that one specific grating stimulus frame is just moving back and forth (e.g., in the case of using a simple sine function) on the grey background canvas (if that makes sense). I can also apply the sine function to TemporalFrequency parameter of the DrawGratings as in the attached workflow screenshot.

Is there a better/different way of doing this? In a non-Bonsai based paradigm we use, I generate an grating image of desired spatial frequency, apply a function that shifts the position of that image over time, and it is then presented as a frame-by-frame movie to the subject. I like the idea of implementing closed-loop control over these stimuli, so I am looking into Bonsai for this reason currently. However, it is not straightforward to me yet how in the current workflow applying the function to the TemporalFrequency exactly translates into changes in stimulus amplitude and frequency, even though it seems to work in qualitative sense (i.e. the grating moves in a sinusoidal fashion).

Thanks for any insight/tips/comments

[banchan86]

Hi @rjs360! Hmm sounds like temporal frequency is the right property to manipulate. Are you looking for something different or just trying to understand more how it works? There is an online demo of temporal frequency and drifting gratings at link.

[rjs360]

Hi @banchan86, thanks for the reply and the link! I am actually finding that manipulating the movement of the stimuli x-axis ('LocationX' property of the 'DrawGratings' node) by using a sine-based expression transform, works better than manipulating the temporal frequency property. I just needed to make sure to use appropriate dimensions of the grating, so it stays within the confines of my display (if that makes sense). And yes, I am mainly trying to understand how in Bonsai/Bonvision one would (best practice) manipulate the movement of a grating presentation (i.e., one golden standard in assessing responsiveness to gratings in the area I am active is to present complex (e.g., sum of sines) sinusoidal movement patterns). Learning a lot!