Eye-tracker
Eye-tracker installation in the MEG
I/ Before the experiment
First, select MISC001 and MISC002 channnels in the Acquisition control software and then you need to adapt your matlab script to acquire eye-tracking data. The code you need to insert in your script are :
- In config : calibration parameters
- In main script:
o Eyelink( 'Message', 'Isaywhatwantinhere' )
o exp_get_gazedata( screen, cfg.verbose)
o Eyelink( 'StopRecording')
- In the saving script : download the eye-tracker file
Here is an example of config stoping etc in one mat file : Attach:script_gazenew (all the functions are one after the other in the script, check the entire file)
Or another example Attach:exp_gazetrack_drift_correct to get saccade)
II/ When you run an experiment
1/ Installation of the eye-tracking system in the MEG
You'll need : - the camera - the objective - the Eyelink-box (the one with tape) and its power supply
Here are the steps:
- install the camera in the machine : take the golden screws and put the camera on its holder on the screen : to know if the camera is not upside-down check that the cables that connect the camera are on the right side and the text on its back is not inverted - screw the objective to the camera - connect the camera and the IR lighter to the cables (orange optic fibber and two black ones) - go plug the power supply for the camera in the back of the stimulus cabinet on the bottom raw - go tape in Eyelink box to the left of the eye link computer - screw the plug of the stim o the eyelink box - plug the power supply to the eyelink box - turn on the eyelink computer - launch the elcl.exe script
2/ Find the eye of your subject
When you've plugged everything, that eyelink software is on and that the screen position is properly adjusted, you should check that the camera finds the eye of your subject. Go next to your subject and check the screen of the eyelink computer. Be careful that the image is not upside-down, if yes inverse the camera. Move the foot of the camera and the lighter to set it to the eye of your subject. Be careful : the image is not in the good direction : the right is on the left and the inverse. So if you look for the right eye of your subject, ask him or she to close his/her eye to check that you found the good eye. Adjust the focus of the camera until it finds the pupil of your subject.
3/Calibration details
All the calibration instructions are written on the command window of matlab Press c to start calibration Subject has to fixate the points one after the other If the programm doesn't continue by itself, press the space bar to validate the eye position when fixation is ok (stable position is written in green on the eyelink computer) After that, press v to do the validation of the calibration : post-test Redo the calibration at the beginning of each block
4/ Trouble shooting
Pb if the subject is wearing mascara If the position of the head is somehow oblic compare to the position of the IR projector, then it will have trouble finding the pupil when the point is very low