Background and stimulus-induced patterns of high metabolic activity in the visual cortex (area 17) of the squirrel and macaque monkey

We have used 2-deoxy-D-14Cglucose (2-DG) autoradiography and cytochrome oxidase histochemistry to examine background and stimulus-induced patterns of metabolic activity in monkey striate cortex. In squirrel monkeys (Saimiri sciureus) that binocularly or monocularly viewed diffuse white light or binocularly viewed bars of many orientations and spatial frequencies, 2-DG consumption was not uniform across the cortex but consisted of regularly spaced radial zones of high uptake. The zones extended through all laminae except IVc beta and, when viewed tangentially, formed separate patches 500 microns apart. The cytochrome oxidase stain in these animals also revealed patches of high metabolism which coincided with the 2-DG patches. Squirrel monkeys binocularly viewing vertical stripes showed parallel bands of increased 2-DG uptake in the cortex, while the cytochrome label in these animals remained patchy. When monkeys were kept in the dark during 2-DG exposure, 2-DG-labeled patches were not seen but cytochrome oxidase-positive patches remained. In macaque (Macaca nemestrina) monkeys, binocular stimulation with many orientations and spatial frequencies produced radial zones of high 2-DG uptake in layers I to IVa and VI. When viewed tangentially, these zones formed a dots-in-rows pattern with a spacing of 350 X 500 microns; cytochrome oxidase staining produced an identical pattern. Macaca differed from Saimiri in that monocular stimulation labeled alternate rows. These results indicate that there are radial zones of high background metabolism across squirrel and macaque monkey striate cortex. In Saimiri these zones do not appear to be related to an eye dominance system, while in Macaca they do. The presence of these zones of high metabolism may complicate the interpretation of 2-DG autoradiographs that result from specific visual stimuli.