A dichoptic projection system for visual psychophysics in fMRI scanners

Here we describe a projection system based on the combination of linear polarizing filters, designed to allow dichoptic presentation of visual stimuli during fMRI experiments. Currently available MRI compatible dichoptic presentation systems are either highly expensive, require degradation of the projected stimulus such as the removal of all but one color or are difficult to deploy in a range of scanner environments. The system described here is relatively low in cost, requires no change in stimulus properties and could be used in many types of scanner facilities. We provide a verification of the system demonstrating minimal cross-talk between the images presented to the two eyes.