Gracile Bundle

GRACILE BUNDLE (Gratiolet), visual radiation, radiatio optica, belongs to the visual system, serves to connect primary visual centers with the visual cortex. The G. b. is the direct continuation of Wernicke's field, the fibers of which originate in the corpus geniculatum laterale, pulvinar and corpora quadrigemina anteriora, and is located in the white matter of the brain surrounding the posterior horn of the lateral ventricle, occupying the stratum sagittate externum and partly internum and mixing with association and commissural fibers. According to some authors, a special arrangement of fibers is observed in this bundle depending on their origin from the retina; according to others, all fibers are mixed and have no special arrangement. The G. b. ends in the visual centers located on the inner surface of the occipital lobe (see illustration in Visual pathways, centers). When this bundle is affected, homonymous hemianopsia is observed with preservation of pupillary reaction (see Hemianopsia).