1、13T Scan Room ASL Long Range Eye-Tracker Set-up1) Turn on the black box power supply, white ASL control unit, eye-tracker monitor/TV (all are in the control room): a) black box power supply = in the bottom left compartment of the 3T computer desk, b) white ASL control unit = on top of the eye-tracke
2、r monitor/TV2) Turn on the Eye-Tracker apparatus and the eye-tracker mini monitor (in scan room)3) Attach the eye-tracker and stimulus mirror assembly to the head coil (in scan room):a) The mirror assembly is strapped onto the head coil at three different sites: 1 strap on the side opposite the eye-
3、track mirror and 2 straps on the same side as the eye-track mirrorb) When strapping the assembly down onto the head coil, make sure the white markings on both sides of the mirror assembly line up with the green eyebrow lines on the headcoilc) The stimulus mirror should be at an angle so that the bla
4、ck frame of the stimulus mirror lines up with the thin blue line of tape on both inner sides. If it isnt, you can adjust the angle of the stimulus mirror by adjusting the bottom knobs (found on both sides of the assembly)d) The angle of the eye-tracker mirror should be positioned already to capture
5、the participants left pupil and corneal reflections. If not, you can adjust it with the top set of knobs (described in subsequent steps) once the participant is settled on the scanner bed.24) Back in the control room, start the EyeTrac6000 (double click on the “Shortcut to EyeTrac600.” that appears
6、on the ASL computer desktop). 5) In the “Upload to ASL Eye Tracker Control Unit” window, click “Upload” (on the lower left corner). 6) Double click on the “ASLVidCap” icon (upper right corner on desktop). In the “ASLVidCap” window, click “Options” and select “Preview” to see what the participant is
7、looking at. Also, you can select the “Eye/Scene Video” button on the menu bar of the “ASL Eye-Trac 6” window.7) On the Presentation computer, open the eye calibration screen. In Eye-Track window on the ASL computer, click on “Calibrate” and then on “Check Set Points”. Make sure all 9 points line up
8、correctly with the 9 points on the ASLVidCap window.a) If not, edit the points with “Modify Set Points”.8) Get the participant settled onto the scanner bed and then landmark the participant, but keep the bed at this position for the subsequent steps (until step 13).9) Ask the participant to close hi
9、s/her eyes, go to the eye-tracker apparatus, remove the IR filter (has golden face on one side), and use the filter that reduces the intensity of visible light. The participant should keep his/her eyes closed for step 10 and 11.10) Go back to the participant, and look for a red box around the partic
10、ipants eye. This box should be square-shaped, with the sides being 2-3cm. If this red box is too narrow (i.e. looking more rectangular than square), it means the eye-tracker mirror is not at an optimal position and needs to be rotated down towards the participants eye. 11) Adjust the angle by rotati
11、ng the top knobs until the bottom edge of this red box sits a little bit below the participants eye-lashes (when his/her eyes are closed)*You are rotating the mirror in the right direction if you notice the mirror reflecting light (this reflection is square-shaped) down the bore. If the light reflec
12、tion is moving towards you, youre rotating the mirror the wrong way. *This eye-track mirror should be at a 45 angle, with the golden side facing the eye-track apparatus. *Also, one of the edge has blue tape on it. This edge should be at the bottom.12) Once this red box is on the participants eye, go
13、 back to the eye-tracker apparatus and put the IR filter back in place.13) Then ask the participant to open his/her eyes. Even when the bed is still at the landmark position, you should see at least a portion (if not the whole) pupil reflection near the top right corner of the mini monitor. You may
14、have to adjust the contrast to see the reflection. 314) Send your participant all the way into the bore and go back to the eye-tracker apparatus. You need to adjust the contrast to see the reflections clearly. The pupil/corneal reflection should have move down and to the left of the mini-monitor. If
15、 part of the participants pupil reflection is cut off, ask the participant to move his/her head a little to the right or left (the direction of movement depends on what part of the pupil reflection is being cut off).15) You can also center the pupil and corneal reflections (on the monitor) by adjust
16、ing the two knobs located behind the mirror on the far right (Aiming Mirror) to center the pupil reflection. a) But if you can avoid doing this, its probably best since the system is already aligned in a way so that you can see the pupil reflection when the participant is outside of the bore and whe
17、n they are all the way in.b) DO NOT move the Illuminator Mirror or IR Beam Splitter. The Camera and light source would then be completely out of alignment.16) Once the brightness and contrast of the pupil and corneal reflections look good (i.e. the pupil reflection is bright, but not so bright that
18、the corneal reflection cannot be seen distinctly from the pupil reflection), go to the control room and look at the reflections shown in the eye-tracker TV monitor. a) In the “Eye Discrimination” window, you can select “Auto Discrimination” and ASL will automatically find threshold at which the pupi
19、l and corneal reflections can be discriminated. To do so, check the “Auto” box.4b) If the small circles and cross-hairs (white = pupil reflection, black = corneal reflection) are stable and not blinking, then the set-up is complete and data collection can start.c) If the circles and cross-hairs blin
20、k or disappear intermittently, then adjust the brightness and contrast (back in the scan room) until they are stable. OR-d) You can also turn off auto discrimination and manually set the pupil and corneal threshold until the cross-hairs are stable (and the circles have a clear, defined shaped) 17) T
21、urn off the mini-monitor in the scan room and go back to the control room to start the experiment. If not turned off, the monitor will interfere with the scans.18) In the control room, display the calibration screen on the Presentation computer. 19) At the eye-track computer, select the “Calibrate”
22、option in the EyeTrac6000 window (now called “ASL Eye-Trac 6 Net Usr”). Then, select “Standard Calibration”20) Ask the participant if he/she can see all 9 letters on the screen. If he/she cannot, press the “up,” “down,” “left,” or “right,” arrows on the black projector until he/she can see all 9 let
23、ters.21) Have the participant look at the calibration screen, one letter at a time, from “A” to “I”. To calibrate, have the participant look at “A” for a few seconds. Check to make sure he/she is looking at “A” using the ASLVidCap preview feature. Make sure that the circles and cross-hairs for the r
24、eflections (on the monitor) are stable before locking in the coordinates. Hit the space bar (or click on the “Save Current Point” button) so the software can lock this position in as “A.” Then, ask the participant to look at “B”22) Use the ASL TV monitor to make sure that the participants corneal an
25、d pupil reflections are moving to different locations as he/she looks at different letters. For instance, if he/she looks at “A”, his/her reflections should be in a different location on the monitor then when he/she is looking at B. This change in reflection location is pretty subtle. 23) Repeat for
26、 “B” to “I.” Once all calibration points are set, test out the calibration by having the participant look at the points.24) If calibration for a few points is bad, just select “Calibrate,” “Standard Calibration,” scroll down to the desired point(s) in the calibration pop-up window, and re-calibrate
27、only the bad point(s). Then select “Calibrate and exit.”25) To start recoding eye-track data, select “File” from the “ASL Eye-Trac 6”window and select “New Data File” 26) In the pop-up window, type in the file name (e.g ID_Task_run#) and select the directory (DesktopEye Tracker Data Files) where the
28、 file will be saved. Click “Save” and the “Enter File Description” window will appear. The following should appear: “ASL Eye 5Tracker data file.” Hit “OK.” This data file is now created and should be loaded onto the “ASL Eye-Trac 6” window.27) Load the task onto the Presentation computer and do the
29、adjustments for this functional scan. Before hitting the “Continue” button that starts the functional scan, remind the participant to look at the “+” fixation sign when it appears in the middle of the presentation screen. This will allow you to see if the calibration is incorrect. Then, click on the
30、 green triangle/arrow record button on the “ASL Eye-Trac6” menu to start recording the eye-track data file. Then, start the scan.28) Sometimes, the calibration can be “off” during the run (for instance, if the participant has slightly moved after calibration). To correct for this, select “Calibrate”
31、 (in the “ASL Eye-Trac 6” menu), then “Eye Position Offset.” If the participants eye is not on the “+” when he/she is fixating, hit “Set Point 5” in the “Eye Offset” window. The location where the participants eye was looking is now the fixation point. *The eye-tracking can be “off” during fixation
32、due to noise or the participant blinking, so do not excessively click on the “Set Point 5” button. Use this button if the eye-tracking is consistently “off” during several instances of fixation. TO UNDO THE “SET POINT 5” OPTION, JUST CLICK ON THE “RESET” BUTTON.29) On the “ASL Eye-Track” window, you
33、 will see if an XDAT files is being recorded during your functional scans. If not, then presentation is not hooked up correctly to the ASL control unit. Make sure the parallel port (port 1) is connected from the presentation computer to the white ASL control unit.30) Once the scan is done, stop reco
34、rding data for this run by clicking the red stop button in the “ASL Eye-Trac 6” menu. Then go to “File” and “Close Data File”31) To record eye-track data for different runs, repeat steps 25-28.32) Once you have run all the scans, you will need to obtain the measurements described below in order to a
35、nalyze the eye-track data. a) The average distance for the screen to the participants eye is 87.6 inches.b) After the participant leaves, display the calibration screen on the Presentation computer, move the bed into the bore so that the region above the 2nd button on the side of the bed is free, an
36、d then move the projection screen to this spot. Then get the following measurements:i. Horizontal distance from the middle of point D to the middle of point Eii. Vertical distance from the middle of point H to the middle of point E*You can get these measurements when the participant is still in the
37、bore (before step b above), but that will mean that your participant will be in the bore for a minute or two longer than he/she would like.Summary: Measurements Needed for analysisHorizontal Distance D E6Vertical Distance H EDistance from participant eye to center of scene plane33) Turn off the eye-
38、track apparatus in the scan room.34) Put the eye-tracking mirror assembly into the green container.35) Hang the plastic cover over the eye-tracker assembly. 36) Then turn off the black box power supply, white ASL control unit, and ASL TV/monitor in the control room.37) Close the EyeTrac6000 program.
