MWorks behavior when eyetracking is lost

Support
1

Hi Chris,

Is there a way to prevent mworks from issuing rewards when eyetracking has been lost? What seems to happen is that when the monkey turns his head and eyelink no longer has a signal, the fixation location is placed somewhere near the center of the screen–sometimes this falls within the fixation window which means that rewards will be issued even when there is no fixation.

Is there a way to prevent this from happening or to change where the eye coordinates are placed when eyetracking is lost?

Thanks,
Darren

2

Hi Darren,

What seems to happen is that when the monkey turns his head and eyelink no longer has a signal, the fixation location is placed somewhere near the center of the screen

I don’t know why this is happening. If any data is missing in a message received from the EyeLink, then MWorks sets the corresponding variables to -32768, so that’s what you should see in your “raw” x/y eye positions. Instead, it sounds like the raw positions are being set to zero, which leads to the calibrated position lying near the center of the screen.

Can you check whether that’s correct (either by looking at the raw positions in your event file, or by watching on the EyeLink computer to see what happens when the monkey turns his head)? If it’s true that the EyeLink sends zeros when the monkey is looking away, then you could use that fact to prevent rewards from being issued in that case. For example, you could attach an action to your raw y position variable that checks if x and y are both exactly zero. If they are, you could set a “no rewards” variable to one, and then check that before dispensing a reward.

Chris

3

Hi Darren,

Just following up on this issue. Were you able to resolve the problem, or do you need more assistance?

Thanks,
Chris

4

Hi Chris,

Thanks for following up. The issue basically went away on its own so I
never got around to implementing your suggestions. (We’ve moved the
eyetracker and adjusted various other settings for unrelated reasons and
the default location it places the fixation point now when tracking is lost
is no longer near the center of the screen)