Objective visual field testing with functional magnetic resonance imaging

Abstract

Purpose : To detect cortical retinotopy using the functional magnetic resonance imaging technique at clinical circumstances. Methods : Four normal volunteers were examined. Four experiments were performed on each subject: a ‘central-peripheral’ visual field stimulation and an ‘upper-lower’ visual field stimulation, both for right and left visual hemifields. The checkerboard stimuli, presented on a front projection screen, subtended 3 degrees of visual angle in height and 5 degrees in width. Sequential paradigms alternated rest phases with no checkerboard stimulation and stimulation phases. For the ‘central-peripheral’ visual field stimulation, the checkerboard was presented to either the central or peripheral visual field. During the ‘upper-lower’ visual field stimulation, the checkerboard was presented to either the upper or lower visual field. Results : The central visual field stimulation revealed a broad activated area in the contralateral occipital pole, whereas the peripheral visual field stimulation displayed a more anterior and narrower activated area. The ‘upper-lower’ visual field stimulation revealed broad activated areas covering the contralateral occipital pole. The upper visual field stimulation revealed the center of the cortical activation located inferiorly to lower visual field stimulation. Conclusion : Retinotopical eccentricity in the primary visual cortex is accurately detected using simple visual stimulations partially presented to the central-peripheral visual field. Upper visual field stimulation bordering the horizontal meridian could be differentiated from lower visual field stimulation in the associated visual cortex. This technique may help to evaluate the visual field.