Hypercolumns in primate visual cortex can develop in the absence of cues from photoreceptors

The visual cortex in primates consists of an array of anatomically and chemically identifiable cellular modules (hypercolumns) with distinct physiological properties. For example, layers II/III in the macaque monkey contain a regular array of cytochrome oxidase-rich blobs. Furthermore, the surrounding cytochrome oxidase-poor interblob regions have a higher density of neuropeptide Y-positive aspiny stellate cells. Neurons in the blobs are thought to mediate predominantly low spatial frequencies and color vision, while those in the interblobs appear to be engaged in pattern vision and high spatial frequency analysis. In this study we examined the role of the retina in the development of hypercolumns. A bilateral retinal ablation was performed in embryos at midgestation, before any photoreceptors had established contacts with other retinal neurons and before layers II/III of the cortex--or their synaptic connection--had been generated. We found that the cortex in operated animals had cytochrome oxidase blobs and that their size and spacing were normal. In addition, neuropeptide Y-containing neurons were preferentially distributed in the interblob region as in control animals. Our findings indicate that some basic aspects of the cyto- and chemoarchitectonic organization of the cerebral cortex, which presumably evolved for the analysis of form and color, can emerge in the absence of cues from the retinal photoreceptors that mediate these attributes of vision.