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

Abstract

Functional magnetic resonance imaging (fMRI) makes it possible to detect regions of neuronal activity in the brain. Moreover, this examination is quite non-invasive. Although fMRI is popularly employed in ophthalmology, it is sometimes impossible to give optimal visual stimulation to the subject because the space inside the MRI equipment is very small and has a strong magnetic field. Thus, there are strict limitations on visual stimulation devices. 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 eyepieces. The image guides and the eyepieces are diamagnetic. They can be attached to the surface or head coil unit of the MRI equipment without any magnetic influence on the fMRI signals. Since the images in both eyepieces are completely 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.