Eye Tracking and its Application in MRI and EEG Settings
32
Eye Tracking and its Application in MRI and EEG Settings Marcus Johnson, Ph.D SR Research Ltd. Toronto - Ottawa, Canada
description
Eye Tracking and its Application in MRI and EEG Settings. Marcus Johnson, Ph.D SR Research Ltd. Toronto - Ottawa, Canada. Agenda. Discussion of eye tracking hardware components System cabling and integration for noise/artifact minimization Synchronization options - PowerPoint PPT Presentation
Transcript of Eye Tracking and its Application in MRI and EEG Settings
Eye Tracking and its Application in MRI and EEG Settings
Marcus Johnson, Ph.DSR Research Ltd.
Toronto - Ottawa, Canada
AgendaAgenda
• Discussion of eye tracking hardware components
• System cabling and integration for noise/artifact minimization
• Synchronization options
• Discussion of Recording/Messaging Options
System HardwareSystem Hardware
Desktop MountDesktop Mount
• Useful in EEG Environment• Remote Mode with Sticker on EEG Cap• Chinrest Mode for More Precise Recording – One concern is Chinrest
Long Range MountLong Range Mount
Camera Head Infrared Illuminator with Focusing Lens
Camera Lens
Different Lenses (75mm,50mm,35mm) forDifferent Distances (overall range: 60-150cm)Required for MRI, Potentially Useful with EEG
Typical MRI ConfigurationTypical MRI Configuration
MRI Mounting Options - MRI Mounting Options - TripodTripod
Difficult to find tripods with no ferromagnetic metals in them
(Picture from MEG setup)
MRI Mounting Options – Screen MountMRI Mounting Options – Screen Mount
No ferromagneticmetals
Flexible positioning
Flexible positioning
Works with most MRIs
No ferromagneticmetals
MRI Mounting Options – Screen MountMRI Mounting Options – Screen Mount
No ferromagneticMetals
Rests on Trio’sbed rails
MRI Mounting Options – Trio Tray MRI Mounting Options – Trio Tray MountMount
Optional built-in screen
Works with Siemens 3T Trio
MRI Head Coil MirrorsMRI Head Coil Mirrors
Allows subject to see screen and for eye tracker to see subject
Best to use front-surfacedmirrors to prevent ghostingand secondary reflections
Long Range System Long Range System CablingCabling
Long Range System CablingLong Range System Cabling
Patch Panel Connection Options (DB9 or BNC) Battery Option
Power Options
Camera Base Box on Side of Host PCFiber Optic Data Cable
Lemo Connectors (to Camera/Illum.)
Long Range System CablingLong Range System Cabling
Long Range System CablingLong Range System Cabling
No detectable interference with proper cabling (Graph from system use in MEG)
System System SynchronizationSynchronization
System SynchronizationSystem Synchronization
•Pre-Experiment activities•Check Tracker Settings (via Set Options Screen and sending commands from Display PC)•Participant setup•Calibration•Validation
MRI/Eye Tracker MRI/Eye Tracker SynchronizationSynchronization
•Running the experiment•Blocks •Trials
•MRI sends synchronization pulse (TTL) to Display PC – Display PC in turn sends Message to Host PC•Pulse triggers Display screen onset – on screen onset Display PC sends Message to Host PC•Pulse typically sent from MRI to Parallel Port or USB Device•Can optionally be split and sent to Host PC Parallel Port
•Parallel Port status on Host recorded on every sample
•Optional drift correction/drift checking•Usually between Blocks•Can also enable online drift correction with mouse click
MRI/Eye Tracker MRI/Eye Tracker SynchronizationSynchronization TTLPulse
MessageWhenPulse
Received
Display PCUpdates Screen
MessageWhen
ScreenUpdated
Time
EEG/Eye Tracker EEG/Eye Tracker SynchronizationSynchronization
•Running the experiment•Blocks •Trials
•Display PC draws to screen – at same time sends Message to Host PC and sync pulse (TTL) to EEG•Message/Pulse occur at screen retrace event•Pulse typically sent from Parallel Port or USB Device of Display PC to EEG – can also be sent from Parallel Port of Host PC •Event types can be coded (32 different pulse values)
•Optional drift correction/drift checking•Usually between Trials•Can also enable online drift correction with mouse click
Analog CardAnalog Card•Option for Host PC – usually used for devices like EEG•Converts Digital Data to Analog Voltages
•Output to BNC connectors•Voltage range configurable
•Three Channels per eye being tracked•Horizontal Position•Vertical Position•Pupil Size
•Also allows for extra Digital In/Out (in addition to Parallel Port)•Quick –
•Data can be inserted into empty EEG channels•Allows for easy alignment with EEG data
•Dirty – •Noise is added by D/A and A/D conversion•Saccade/Fixation information is lost
EEG/Eye Tracker EEG/Eye Tracker SynchronizationSynchronization
Display PCUpdates Screen
MessageWhen
ScreenUpdated
Time
TTLWhenScreenUpdated
Within1 msec
OptionalConstantAnalog
Out to EEG
EEG/Eye Tracker EEG/Eye Tracker SynchronizationSynchronization
Display PCUpdates Screen
MessageWhen
ScreenUpdated
Time
ORTTLfrom
Host PCto
EEG
About1 msec
OptionalConstantAnalog
Out to EEG
Recording and Recording and MessagingMessaging
Recording and TrialsRecording and Trials•Messages are Not Just For Marking Stimulus Events•Data Viewer Format:
•Trial Onset MessagesTRIALID 1 (TRIALID2, etc.)
•Trial Event MessagesDISPLAY_1_ONBUTTON_RECEIVEDDISPLAY_2_ON
•Trial Variable Messages!V TRIAL_VAR trial_condition condition_1!V TRIAL_VAR reaction_time 2364
•Trial Interest Area Messages!V IAREA RECTANGLE 1 100 200 200 300 square
•Target Position Messages (for moving targets)!V TARGET_POS Targ1 (512, 384) 1 0!V TARGET_POS Targ1 (512, 364) 1 0
•Trial Offset MessagesTRIAL_RESULT 0
Recording and TrialsRecording and Trials•Messages are Not Just For Marking Stimulus Events•Data Viewer Format:
For full description of Data Viewer format see:
Data Viewer User Manual (Help -> Contents) “Protocol for EyeLink Data to Viewer Integration”
Recording and TrialsRecording and Trials•EyeLink Recording and Analysis Messages are Independent•Scenario 1:
•Start Recording•Start Trial Loop•For Each Trial:
•Trial Onset Message•Stimulus Event Messages
•Mark Every Event of Trials•Trial Condition Messages
•Independent Variables•Behavioral (non eye-based) Dependent Measures
•Trial Interest Area Messages•Trial Offset Message
•End Trial Loop•Stop Recording
Recording and TrialsRecording and Trials•EyeLink Recording and Analysis Messages are Independent•Scenario 2 (Like Experiment Builder):
•Start Trial Loop•For Each Trial:
•Start Recording•Trial Onset Message•Stimulus Event Messages
•Mark Every Event of Trials•Stop Recording•Trial Condition Messages
•Independent Variables•Behavioral (non eye-based) Dependent Measures
•Trial Interest Area Messages•Trial Offset Message
•End Trial Loop
Recording and TrialsRecording and Trials•EyeLink Recording and Analysis Messages are Independent
• Can Use Scenario 1 or 2 for Most Programming Environments
e.g., Psychtoolbox (Matlab), E-Prime, Presentation, C, Python
• If using Experiment Builder, Must Stick to Scenario 2 •Many Messages Sent Automatically with Experiment Builder
Thank you!Thank you!
• Documents•EyeLink 1000 User Manual•EyeLink 1000 Installation Guide•SR Research Experiment Builder•Windows Programmers Guide •EyeLink Data Viewer
• Contact Information•E-mail: [email protected]•Phone: 1-613-271-8686/ 1-866-821-0731•Web: http://www.sr-support.com
EyeLink SupportEyeLink Support
EyeLinkEyeLink SupportSupport
