Development of a new binocular visual stimulation device using image guides for functional MRI

Functional magnetic resonance imaging ( fMRI) makes it possible to detect r egions of neuronal activity in the brain. Moreover, this examination is qui te non-invasive. Although fMRI is popularly employed in ophthalmology, it i s sometimes impossible to give optimal visual stimulation to the subject be cause the space inside the MRI equipment is very small and has a strong mag netic field. Thus, there are strict limitations on visual stimulation devic es. In order to resolve these problems, we developed a new binocular visual stimulation device for fMRI using image guides. This device consists of a pair of image guides, LCD projectors, C-mounted objective lenses, and eyepi eces. The image guides and the eyepieces are diamagnetic. They can be attac hed to the surface or head coil unit of the MRI equipment without any magne tic influence on the fMRI signals. Since the images in both eyepieces are c ompletely separated, binocular parallax stimulation can easily be given to a subject. This makes it possible to investigate stereopsis with fMRI. This device will be very useful for the fMRI investigation of the brain region related to visual function.