SpinozaWiki:Eyelink+Presentation+MRI Help Guide

Eyelink + Presentation + MRI Help Guide

6 Feb2011

Olympia Colizoli
Tomas Knapen
Renee Visser

University of Amsterdam

Help Guide for Preslink

Windows PC-> Start -> Programs -> SR research -> EyeLink -> Programming -> Runtime AP -> PresLink -> PresLink User’s Guide

Configuration

Installation and initial configuration is already done at the Spinoza center.

Configuration guidelines in PresLink manual.

Also, see internet configuration (back of manual)

Setup Eyelink

1 Turn on Presentation computer with the option “Meting met EyeLink”

2 Turn on and check the level of the battery in the scanning room.

• If less than 2-3 hours, replace it with the new battery and plug in the old one to charge

3 Take off the lens cap

4 Turn on EyeLink computer & monitor

5 Choose EyeLink mode (not Windows mode)

If Eyelink doesn’t start: elcl.exe in DOS on Eyelink computer

To get old EDF files, start in Windows mode Look in the elcl folder the data

Test EyeLink Connection

Initially, the connection will be closed between the PC and EyeLink computers, even if the IP address is configured properly.

EyeLink says ‘Link Closed’

To Open the Link.....

Test configuration without Presentation

It is not always convenient to check the connection or to do a calibration through Presentation.

Start -> Programs -> SR Research -> EyeLink-> TRACK

File:Picture2.png

This will open a screen connected to EyeLink without Presentation.

You can do a calibration or adjust the camera/focus this way.

Commands

Most of the keyboard commands work from both the EyeLink and Presentation computers.You can also use the mouse on the EyeLink computer.

ENTER - show eye on monitor
Left/Right - zoom in on eye

C - calibration
SPACE - start calibration
ENTER - accept calibration

V - validation
SPACE - start validation
ENTER - accept validation

Within Presentation:
F4 ->either back to eye screen, or start of experiment
ENTER -> accept drift check (when you see fixation point in center of screen)
F4 -> start experiment

D - Drift check (correct for eye movement on one central fixation point)
Enter - accept drift correction

Camera Setup/Calibration

Check your sample rate
At the MRI scanner, lowering the sample rate to less than 2K can help with the stability of the eyetracker.

9-pt calibration is standard, but more difficult subjects can be given a 6-pt or 3-pt calibration

Turn off ‘Manual Accept Fixation’ if you want the fixation point to move automatically once the position is registered.

Calibration improves when:
1. Tell the subjects to look at the middle of the cross in the fixation square
2. Tell the subjects not move your eyes until the fixation square moves.

Validation should show that all points are under 1.00

NOTE:

EDF file names cannot exceed 8 characters,
Which means that your SUBJECT NAME cannot exceed 8 characters!
If it does, you will get an error when the EDF file is transferred to the Presentation computer

Clean-up

Remember to take care of the equipment:

1. “Exit EyeLink” -> DOS Mode -> Power button OFF
2. Lens cap -> back on
3. Turn off battery and recharge if needed
4. Turn off EyeLink monitor

Converting EDF files to ASC

The EDF files are not in a readable format. In order to use them, you must convert them to ASC. This must be done from the command line on a computer with EyeLink installed.

The code for this conversion is in the Examples folder of the EDF Access API folder.
c:\Program Files\SR Research\EyeLink\edf_Access_API\example

Start-> RUN -> CMD -> set CD to EDF Acces API folder, which contains edf2asc.exe.

To get a list of all arguments for this function, just type edf2asc
edf2asc –s locationofedffile\nameoffile.edf (-s gives all samples)
edf2asc –e locationofedffile\nameoffile.edf (-e gives all events)
In between these two command lines make sure to rename the .asc file (eg. nameoffile_s.asc for sample file and nameoffile_e.asc for event file) before converting the next one, otherwise the .asc file will be overwritten.

Programming in Presentation with EyeLink Scenario Files with EyeLink code

Check out the example file “track.sce” for an example of using Presentation scripts with EyeLink.

A copy of this code is in the PresLink user guide.

Most of the code can remain, but you must make sure to specify when you want to send a message to the eyetracker EDF file. For example, at the start and end of a trial.

tracker.send_message(“some string”);

Note: EDF file names cannot exceed 8 characters.