Development of a method to present wide-view visual stimuli in MRI for peripheral visual studies.

We developed a novel wide-view visual presentation system for fMRI studies. Computer-generated images were projected onto a hemispheric, translucent screen inside the MRI bore and were then back-projected onto a 52mm diameter screen. To achieve a wide field view, a spherical screen with a curvature radius of 30mm was placed 30mm away from the subjects' eyes. The subjects wore contact lenses that enabled them to focus on the screen, and the resulting visual field reached 120°. To evaluate the clarity and quality of the MRI images, a signal-to-noise ratio valuation experiment was performed. In addition, we successfully applied this visual presentation system to studies of visual retinotopic mapping and object perception neural function in the peripheral visual field. Our study demonstrated that the system is compatible with the MRI environment. Based on the wide-field mapping results, this system was more effective at mapping a checkerboard stimuli in V1-V3 from the central to peripheral visual fields. In higher-level visual areas, we successfully located several classical category-selective areas, including the face-selective area (FFA), occipital face area (OFA), house-selective area (PPA), transverse occipital sulcus (TOS), lateral occipital complex (LOC) and posterior fusiform area (pFs). In these areas, we found that the response amplitudes exhibited different decreasing trends with increasing eccentricity. In conclusion, we developed a simple, effective method for presenting wide-view visual stimuli within the MRI environment that can be applied to many kinds of fMRI studies of peripheral vision.