Cytochrome-oxidase blobs are central to two of the most influential ideas in contemporary visual neuroscience--cortical modularity and parallel processing pathways. In particular, the regular 2D array of cytochrome-oxidase-rich blobs in primate visual cortex is arguably the most compelling evidence for cortical modularity and has been hypothesized to mark a separate processing stream through the visual cortex. Although previously a variety of mammals have been studied, blobs have only been demonstrated in the visual cortex of primates, which has led to the conclusion that blobs represent a primate-specific feature of visual cortical organization. Here we demonstrate the presence of cytochrome-oxidase blobs in a nonprimate species. Throughout the full tangential extent of layers II-III in cat visual cortex the cytochrome-oxidase staining pattern is distinctly patchy, with the darkly stained blobs forming a regular 2D array. In addition, the blobs in cat visual cortex are functionally related to the underlying ocular dominance columns. The presence of cytochrome-oxidase blobs in the cat clearly demonstrates that they no longer can be considered a primate-specific feature of visual cortical organization.

In layer IV of the primary visual cortex, in both the macaque monkey and the cat, geniculocortical terminals representing the two eyes are segregated into alternating zones known as ocular dominance bands. Viewed tangentially, in the monkey these bands take the form of a series of branching parallel stripes that run roughly perpendicular to the border of striate cortex. In the cat, the overall ocular dominance pattern consists of irregularly branching, beaded bands that exhibit no predominant orientation. If the striking differences in the appearance of these two patterns reflect important differences in the basic rules governing cortical ocular dominance, then this poses a problem for attempts to formulate general principles of visual cortical organization. However, it has been suggested that the differences in the appearance of the ocular dominance patterns in these two species could result simply from known differences in the boundary conditions of their geniculocortical pathways. This article describes the formulation and testing of a single computational model that accurately predicts the quite dissimilar ocular dominance patterns in cats and monkeys. This model also generalizes to predict the different ocular dominance patterns observed in young and old three-eyed frogs, supporting the notion that the overall pattern of ocular dominance is governed by a common set of rules. The significance of these results is discussed in terms of previous models, which have focused largely on local processes underlying the development of ocular dominance segregation. Although the present model is not a developmental one, it does shed some light on potential mechanisms for establishing retinotopy in striate cortex and on possible developmental relationships between the geniculostriate pathway and intrinsic modularity of the striate cortex.

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To evaluate the role of carotid endarterectomy (CE) in patients 80 years and older an 8-year study of 172 nonrandomized cases of octogenarians with cerebrovascular disease was done. Ninety octogenarians underwent CE whereas 82 octogenarians, with arteriographically established carotid artery disease, were not operated on and served as a control series. The stroke rate after CE was 6%. In follow-up extending to 8 years the late stroke rate was only 2%, whereas the cumulative long-term stroke rate in the nonoperated group was 16%. These late strokes were appropriate to the side of the arteriographically demonstrated disease. In 1008 nonoctogenarians who underwent CE during this same time interval, the stroke rate after CE was 2% and the mortality rate was 0.6%. In the octogenarian population, however, the mortality rate after stroke was an alarming 40% in the operated group and 62% in the nonoperated control group. Arteriographic flow-limiting (greater than 75% stenosis) intracranial occlusive disease was identified in 53% of the octogenarians undergoing operation and in all patients who suffered a postoperative neurologic deficit. This incidence of severe intracranial disease was nearly five times that of the nonoctogenarian patients undergoing CE. Although the stroke rate after CE in the octogenarian patient was 6%, the late stroke rate was only 2% compared with the cumulative stroke rate of 16% in the nonoperated octogenarian patients. Severe intracranial occlusive disease and, therefore, flow deprivation may play a more significant role as a cause of postoperative deficits than in younger patients, but CE is appropriate for selected octogenarians on the basis of physiologic rather than chronologic age.

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