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Eye-tracker

For details on how to set-up Eye-tracker consult the User manual which is also available in the locker behind the MSR-cabinet.

Equipment required

  • The screen
  • Eye-tracker

You will also need some lines of code in your Presentation scripts to initiate the eye-tracker, start calibration procedure and start recording.

Before measurement

  1. Put screen in correct position (see Screen and projector)
  2. Start eye-tracker software by pressing the letter t on the keyboard, then press enter

! If you do not see a terminal on the eye-tracking PC when you turn on the screen - Check that the screen setting of the Stimulation PC is not set in dual screen mode and that the correct input channel is selected - Check that the eye-tracking computer is turned on. The computer is found at the bottom of the stimulation cabinet

! To start eye-tracker in simulation mode type t -x and press enter

  1. Make sure you have the right configuration for your needs and that the corneal reflection (CR) and pupil thresholds are set.
  2. Adjust eye-tracker by moving the arm or by tilting the screen a bit.
  3. Make sure MISC-channels 1-6 are activated in Acquisition settings. This is where ET-data is stored.

Calibration and validation

When participant is seated in the MSR, calibrate the system then validate your calibration.

During measurement

  1. Monitor eye-positions

! As participants tend to sink down a bit during recordings eye-tracking may be lost if not chair is raised properly
! If using the table, make sure pads or participant's hands are not blocking the eye-tracker

  1. Check calibration

After measurement

  1. Turn off eye-tracking software
  2. Remove eye-tracker and put back in box

Eye-tracking data is saved accordingly: * MISC001 = X Left * MISC002 = Y Left * MISC003 = Pupil Left * MISC004 = X Right * MISC005 = Y Right * MISC006 = Pupil Right

Specifications

For eye tracking we use an EyeLink 1000 binocular tracker from SR Research. The current installation runs at a maximum of 1000 Hz, tracking both eyes binocular.

The eye tracker is typically controlled via Neurobs Presentation,
Via Presentation you can access the eye tracker output in realtime.

The X, Y and pupil diameter of each eye is also output into the MEG system analog channels and sampled side by side with the MEG data. The calibration space of the Eye-tracker is 1920x1080, with 0,0 in the top left corner.

The Eye tracker settings are aligned to the projector, so that the projector ini-file uses the pixel space (1920x1080), standard visual size (72x44 cm) and distance (100 cm) of the projector.

  • Further technical specifications for the equipment is found in the manual here.

Issues

The eye-tracking program is beeping and blinking

The eye-tracker has been disconnected from the cables in the MSR. Reconnect the eye-tracker or close the eye-tracking program.

Eyes look blurry and the pupils are not detected.

Check that the participant's hands or paddings are not blocking the camera.