Lateral view of the optic radiations. The optic radiations originate from the lateral geniculate nucleus LGN) of the thalamus.  The latter nucleus is not visible in this dissection and is located medial to the posterior limb of the internal capsule.   The fan-shaped optic radiations project laterally and posteriorly, around the temporal horn and atrium of the lateral ventricle, to terminate in the primary visual cortex on the medial surface of the occipital lobe.  Note that the proximal portion of the optic radiations fuses with the posterior limb of the internal capsule, thus, lesions in this region produce combined contralateral hemiparesis and hemianopsia.  Fibers in the inferior part of the optic radiation project initially for a short distance into the temporal lobe as “Meyers loop.”  The latter fibers convey information from the contralateral superior visual field; thus, a lesion of Meyer's loop produces a contralateral superior quadrantanopia, or a "pie-in-the-sky" visual field deficit.  The substantia innominata is a part of the basal forebrain and lies on the ventral surface of the cerebrum, lateral to the hypothalamus and medial to the amygdala.  (Image courtesy of AL Rhoton, Jr.)