Retinogeniculate projections following early cerebral hemispherectomy in the vervet monkey

The effects of early, unilateral cerebral hemispherectomy on retinogenicula te projections were studied in the vervet monkey (Cercopithecus aethiops sa beus). Hemispherectomy eliminates all geniculocortical pathways and thus re moves cortical factors involved in the survival of retinogeniculate project ions. Complete removal of the left cerebral cortex was performed in two mon keys at 6 months and 8 months of age. After a postsurgical survival period of 50 months (SHG3) and 45 months (SHG4), both animals and a normal adult m onkey received intraocular injections of [H-3]proline (5 mCi) in the left e ye and WGA-HRP (100 mul, 5%) in the right eye. The dorsal lateral geniculat e nucleuseuron (LGNd) ipsilateral to the hemispherectomy was on average 73% smaller than the contralateral LGNd. The magno- and parvocellular layers i psilateral to the cortical ablation in both hemispherectomized subjects rec eived a layered, eye-specific pattern of retinal input. This suggests that retinogeniculate projections could be sustained in the absence of geniculat e relay cells.