EFFECT OF EARLY MONOCULAR ENUCLEATION UPON OCULAR DOMINANCE COLUMNS AND CYTOCHROME-OXIDASE ACTIVITY IN MONKEY AND HUMAN VISUAL-CORTEX

We examined cytochrome oxidase (GO) activity in striate cortex of four macaque monkeys after monocular enucleation at ages 1, 1, 5, and 12 w eeks. These animal experiments were performed to guide our interpretat ion of CO patterns in occipital lobe specimens obtained from two child ren who died several years after monocular enucleation during infancy for tumor. In the macaques, the ocular dominance columns were labelled by injecting [H-3]proline into the remaining eye. After enucleation a t age 1 week, ocular dominance columns were eliminated in layer IVc be ta, resulting in a uniform pattern of autoradiographic label and CO st ;lining. However, columns could still be seen in wet, unstained sectio ns and with the Liesegang silver stain. Autoradiographs through layers IVc alpha and IVa showed residual, shrunken columns belonging to the missing eye, indicating that enucleation has less drastic effects in t hese layers. In the two human cases, enucleation at age 1 week also re sulted in uniform CO staining in layer IVc. In the macaque after enucl eation at age 5 weeks, ocular dominance columns belonging to the missi ng eye were severely narrowed, but still occupied 20% of layer IVc bet a. CO revealed wide, dark columns alternating with thin, pale columns in layer IVc beta. The CO pattern and the columns labelled by autoradi ography matched perfectly. After enucleation at age 12 weeks, only mil d shrinkage of ocular dominance columns occurred. Enucleation at ages 1, 5, and 12 weeks did not alter the pattern of thin-pale-thick-Dale s tripes in V2. The main findings from this study were that (1) CO histo chemistry accurately labels the boundaries of columns in layer IVc bet a of macaque striate cortex after early monocular enucleation, making it a suitable technique for defining the critical period for plasticit y of ocular dominance columns in human striate cortex; (2) enucleation causes more severe shrinkage of ocular dominance columns than eyelid suture; (3) early monocular enucleation obliterates ocular dominance c olumns in layer IVc beta, but their pattern remains visible in wet sec tions and with the Liesegang stain; and (4) enucleation does not affec t CO staining in V2.