Retinogeniculate projections following early cerebral hemispherectomy in the vervet monkey.

The effects of early, unilateral cerebral hemispherectomy on retinogeniculate projections were studied in the vervet monkey (Cercopithecus aethiops sabeus). Hemispherectomy eliminates all geniculocortical pathways and thus removes cortical factors involved in the survival of retinogeniculate projections. Complete removal of the left cerebral cortex was performed in two monkeys at 6 months and 8 months of age. After a post-surgical survival period of 50 months (SHG3) and 45 months (SHG4), both animals and a normal adult monkey received intraocular injections of [3H]proline (5 mCi) in the left eye and WGA-HRP (100 microliters, 5%) in the right eye. The dorsal lateral geniculate nucleuseuron (LGNd) ipsilateral to the hemispherectomy was on average 73% smaller than the contralateral LGNd. The magno- and parvocellular layers ipsilateral to the cortical ablation in both hemispherectomized subjects received a layered, eye-specific pattern of retinal input. This suggests that retinogeniculate projections could be sustained in the absence of geniculate relay cells.