Presentation on theme: "Psychophysics in the Magnet Sean Marrett Functional MRI Facility, NIMH/NIH/DHHS, Bethesda, MD, USA."— Presentation transcript:
Psychophysics in the Magnet Sean Marrett Functional MRI Facility, NIMH/NIH/DHHS, Bethesda, MD, USA
Imagine you are starting up your own FMRI lab Goal is to maximize the range of possible fMRI experiments and ease with which they can be set up. Exercise in this seminar is to consider range of essential equipment and pros and cons of different configurations Bare bones and build up from there
What is needed Experiment control and stimulus generation software (sometimes the same, sometimes very different) Interface with scanner to allow synchronization Visual display Device to allow subject feedback Auditory stimulus delivery Physiological monitoring setup with scanner synchronization Method for recording eye-movement Force measurement Pain stimulation Digression on head motion – Prospective head movement correction
Hostile magnet Strong static magnetic field can disrupt operation of many devices Projectors Projectiles RF emitted by coil(s) can interfere with operation and damage some equipment and can also cause heating in devices / objects that can make them a hazard Rapidly changing magnetic field (gradient) can induce current in devices which can interfere or damage electronic devices Gradients also responsible for high levels of acoustic noise which make MR very loud (up to 120dB) which can damage hearing and also make it hard to communicate with subjects. Significant ear protection required Cables bringing electronic signals in and out of magnet room can bring in small signals that cause artifacts, especially because RF signals detected in FMRI are so tiny tat very low levels of spurious signals brought in from outside can produce prominent or subtle artifacts in reconstructed images.
fORP FIU932 Interface box for button presses Connects to user’s laptop via USB Connects to trigger box via BNC Connects to button box via proprietary 12-pin fiber connector. Compatible with legacy button boxes. Current Designs FIU932 System Synchronization Devices
Stimulus presentation software (Experimental control) What is needed Commercial packages – E-prime – Presentation Open source alternatives – PsychoPy – VisionEgg – Psychophysics Toolbox (+ Matlab($$)) – Pygame
Visual stimulus Simplest setup includes external projector Wave guide/ Long throw lens Good mirror system & screen (DaLite)
Visual stimulus (cont) Projector sited inside magnet room (Faraday cage) Projector <> Projectile Some video signals are right around NMR resonance frequencies Optical mux/demux
Video system practicalities Rear projection vs front projection (Easy set-up and more uniform field of view for diverse body types) Optics and long-throw lens (Buhl/Navitar is your friend) Some modern DLP projectors very hard to modify Inside magnet / Faraday cage Outside magnet / wave guide / operation (turning it on and off) Timing and synchronization / video memory buffer E.g. unreliable timing can make backward masking problematic!
Delivering auditory stimulus in the magnet Very loud ambient noise Headphones with transducers outside magnet Headphones with electrostatics inside magnet – Confon system Opto-acoustic systems Noise cancellation features Gradients also responsible for high levels of acoustic noise which make MR very loud (up to 120dB) which can damage hearing and also make it hard to communicate with subjects. Significant ear protection required Close fitting head coils complicate ear protection and audio delivery
Recording subject feedback/response (basic) Classic button box Must be synchronized with scanner Best if well-integrated with experimental control software Several vendors including CurrentDesign, Psychology Software Tools, Cedrus Range from classic button box to foot response, VAS etc Examples
Biopac Display The 1st trace is from the respiration sensor / belt. The 2nd trace shows data from the pulse oximeter. The 3rd trace is the scanner’s TR trigger. The 4th trace is the filtered respiration data (similar to #1). The 5th trace is the filtered pulse oximeter data (similar to #2).
Touch, taste Ingeholm touch simulator Taste – gustatory Other specialized devices (shout out to George Dold and Section on Instrumentation)
John E. Ingeholm, George R. Dold, Lawerence E. Pfeffer, David Ide, Seth R. Goldstein, Kenneth O. Johnson, Ro... The Helix: A multi-modal tactile stimulator for human functional neuroimaging
Gustatory stimulus delivery John Ingeholm and George Dold and Tom Talbot and others
Other essential devices from Section on Instrumentation
Starting your own lab – FMRI device budget Scanner sync interface + basic button box ~ $2K and up Projector/visual display system - $4K and up (including mirror fabrication) Audio system - $5K and up Eye tracking - $10K and up External physiological monitor $5K and up