Optic flow field stimulus

Support
1

Hi Chris,

Does mworks support generating optic flow field stimulus? I know it does RDK but what about optic flow (the kind that gives a 3D appearance like this)?

It would be great if I could use a module to create a patch of optic flow stimulus of a desired size, centered at a desired location on the screen, with a desired % of dot motion coherence and a desired half-life of each dot presentation.

Thanks!
Sujay

4

Hi Sujay,

The first version of the optic flow field stimulus is now in the MWorks nightly build. I’ve attached an example experiment that demonstrates how it works. The experiment live queues the stimulus, so you can change its parameters while it runs to get a feel for how they work.

When you have a chance, please test this out, and let me know if it meets your needs.

Cheers,
Chris
off_demo.mwel.zip (1.3 KB)

5

Thanks, Chris. Looks great. Works well. Could we make the patch circular as opposed to square or have such an option? Also, the tiny dots in the background of the parametrically controlled dots seem to enhance motion perception with an added ‘direction-contrast’. I wasn’t thinking of the opposing dots as background and haven’t really seen it being used in the literature, but it’s an interesting stimulus to test. Can we have this as an option instead of always being present?

6

Hi Sujay,

Could we make the patch circular as opposed to square or have such an option?

You can do that by adding a layer and mask. Please see the attached example.

Also, the tiny dots in the background of the parametrically controlled dots seem to enhance motion perception with an added ‘direction-contrast’.

I don’t know what you’re describing. MWorks doesn’t draw any “tiny dots in the background”. All the dots are the same size, regardless of their “depth” (z coordinate). They differ only in their 3D direction of motion: Coherent dots move in the specified direction, while non-coherent ones move in random directions.

My best guess is that you’re describing a visual artifact, not something that’s actually on screen. A quick way to test this is to pause the experiment with MWClient’s pause button. If the “tiny dots” disappear, then they were a product of your brain, not anything MWorks was doing. If they don’t disappear, then please take a screen shot and send it to me.

Thanks,
Chris

off_with_mask.mwel.zip (1.4 KB)

7

Hi Sujay,

Here is a screenshot with tiny dots in the background. Their size doesn’t change when I change the ‘foreground’ dot size.

Screen Shot 2023-06-22 at 11.05.29 AM
Screen Shot 2023-06-22 at 11.05.29 AM1920×848 72.4 KB

Thanks, I see the issue now. That definitely is not intentional, and I don’t see it on my Mac. However, I think I know the source of the problem. Let me make a fix and get an updated build to you.

Chris

8

Hi Sujay,

There’s a new nightly build with a change that (hopefully) fixes the issue you encountered. Can you try it out and see if the tiny dots are gone?

Thanks,
Chris

9

Hi Sujay,

Have you had a chance to try the updated optic flow field stimulus? I’m just wondering if the change I made eliminates the tiny background dots you were seeing.

Thanks,
Chris

10

Hi Chris, sorry for the delay. I just tried it, and the tiny background dots are gone. Thanks for fixing it!