Visual stimulation systems

All visual stimulation for subjects during fMRI experiments is provided from the researcher's own laptop computer. The facility does not provide a computer for this purpose. However, we do employ two different visual stimulation delivery systems at the CBS Neuroimaging Facility.

The first, and most commonly used, is a standard video-projection technique. The video display from the user's laptop is sent via VGA cable to a conventional video projector, positioned behind the scanner room. It projects the display into the scanner room through a large feed-through tube, where it is projected onto a white plastic screen that bolts into the bore of the magnet. Subjects see the screen via mirrors attached to the head coils while in the magnet. This video delivery method is completely compatible with the EyeLink Eyetracking system. The video feed from the laptop is split so the researchers can also view it on a second monitor in the control room at the same time the subject in the magnet views it. Additionally, this video signal can also be viewed on the large-screen in the control room for teaching purposes.

For more advanced video requirements, the NordicNeuroLab VisualSystem is available.

 

The VisualSystem allows the researcher to easily present high-quality graphics or text to the subject. It has separate channels for each eye, and using frame sequential presentation, true 3D and stereo stimuli can be displayed. The VisualSystem has been designed with an adjustable arm that allows for fast positioning into the preferred angle of view for each subject, and easy securing the Siemens 12-channel head coil. It will not, however, attach to the 32-channel head coil, due to the design of the 32-channel coil. All studies using the VisualSystem must be conducted with the 12-channel coil at this time.

Because the VisualSystem completely covers the eyes, rendering it incompatible with remote eyetrackers like our EyeLink system, an integrated EyeTracking Camera is included with the VisualSystem. The core piece is an MR-compatible camera, which, thanks to a built-in infra-red light source, also works in darkness. The obtained composite video signal can be used to simply monitor, or, with the help of eye tracking software, to record and analyze eye movements. Our set-up provides a single camera solution for the monitoring of either the left or the right eye. NNL can provide, on request, binocular setups capturing the movements of both eyes.