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biac:experimentalcontrol:eyetracker [2014/12/11 14:46] cmp12 [Starting the eyetracker software] |
biac:experimentalcontrol:eyetracker [2023/02/23 18:43] |
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- | ====== Eyetracking in MRI ====== | ||
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- | BIAC currently has eyetracking capabilities available on its 3T MRI scanner.\\ | ||
- | The eyetracking system involves 3 components: | ||
- | * Eyetracking camera -- Mounted inside scanner with view of pupil | ||
- | * Viewpoint software -- Calculates eye position and pupil diameter | ||
- | * Data collection and synchronization with behavioral paradigm software | ||
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- | The eyetracking camera is an MR compatible miniature analog video camera manufactured by [[http:// | ||
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- | Typical applications of the eyetracking camera in fMRI are: | ||
- | * Using the camera to monitor subject alertness (no tracking) | ||
- | * Eyetracking to verify correct eye position (e.g. fixation) | ||
- | * Eyetracking to follow eye position within a scene | ||
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- | Note: The eyetracking hardware available inside the scanner has limited spatial and temporal resolution compared to high-precision devices that are not MR-compatible ([[biac: | ||
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- | ====== Connecting the camera ====== | ||
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- | Set up of the eyetracker hardware inside the magnet room will be done entirely by the MR technician. | ||
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- | The magnet room eyetracker hardware ([[biac: | ||
- | consists of: | ||
- | * Power supply | ||
- | * Connector box | ||
- | * Video cable from penetration panel to connector box | ||
- | * Camera with cable to connector box | ||
- | * Camera mounting hardware (different mounts for goggles and projector viewing) | ||
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- | **Set-up steps:**\\ | ||
- | 1) Plug the power supply into the wall outlet at the back of the magnet room, nearest the video projector. (The power supply is usually found on the floor at the back of the magnet room, near the penetration panel.)\\ | ||
- | 2) Connect the power supply to the connector box (see Figure).\\ | ||
- | 3) Make sure the video cable is connected between the connector box and BNC port J64 on the penetration panel.\\ | ||
- | 4) Connect the camera cable to the connector box.\\ | ||
- | 5) Turn ON the eyetracker switch on the connector box. | ||
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- | Note: The scanner magnetic field can affect the power supply; to minimize problems, keep the power supply as far away from the scanner as possible, and unplug the power supply after you are finished using it. | ||
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- | ====== Starting the eyetracker software ====== | ||
- | You must start the " | ||
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- | In the [[biac: | ||
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- | Once you have a video image, use the brightness and contrast sliders in the middle at the top of the Viewpoint display to adjust the camera image until you get a reasonable picture. | ||
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- | ====== Mounting the camera for use with the video projector ====== | ||
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- | To use the head-coil camera mount, the camera is attached to a plastic rod (via a single nylon screw), which is inserted into a mounting bracket that clamps onto the outside of the 8-channel head coil above the subject' | ||
- | **Take care to rotate the camera up outside of the head coil before attempting to slide the coil over the subject' | ||
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- | Camera position can be adjusted by sliding the bracket along the arm of the coil, and by tilting and rotating the plastic rod to get an optimal view of the eye. Once in position, lock the rod in place using the nylon screw. | ||
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- | ====== Calibrating the eyetracker software ====== | ||
- | Once the eye is centered and the brightness and contrast have been adjusted to lock onto the iris, the eyetracker needs to be calibrated. | ||
- | To do so, warn the subject to pay attention and focus on the boxes and dot that will appear on the screen. Then select the **Calibration-> | ||
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- | ====== Integrating eyetracking into a behavioral paradigm ====== | ||
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- | ===== Integration with Presentation ===== | ||
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- | Using Presentation, | ||
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- | [[biac: | ||
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- | ===== Integration with CIGAL ===== | ||
- | The Showplay fMRI software in CIGAL can use the eyetracker in two different ways. The easiest is to initialize it to read streaming eye-position data from the ViewPoint eyetracking program in real-time; in this mode, synchronization and generation of eye-position output files is performed automatically for any Showplay paradigm. CIGAL can also be used to send commands to the Viewpoint program to help synchronize the timing of data files generated by Viewpoint | ||
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- | [[biac: | ||
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- | ====== Analyzing eyetracker output ====== | ||
- | Typical uses of the eyetracker: | ||
- | * Watch subject' | ||
- | * Plot eye position to check for errors in fixation\\ | ||
- | * Plot eye position as gaze path on stimulus images\\ | ||
- | * Correlate eye position with stimulus timing\\ | ||
- | * Use eye position as regressor variables in fMRI analysis | ||
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- | ====== ====== | ||
- | **See also**\\ | ||
- | {{: | ||
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- | **[[biac: | ||