Fig. 7.

Monkey 2 (adult monocular suture vs laser).A, CO montage showing the cortical scotoma coinciding with the retinal lesion illustrated in Figure 6. Within the scotoma, dark ocular dominance columns (sutured right eye) alternate with pale ocular dominance columns (lesioned left eye). The scotoma includes the edge of the right eye’s optic disk representation (asterisk). It has the size and location that one would expect from the retinal lesion, suggesting that no fill-in occurred after a survival time of 9 weeks. Surrounding the scotoma, there is a faint pattern of thin dark columns (open left eye’s core zones) alternating with wide pale columns (sutured right eye’s ocular dominance columns plus the left eye’s border strips). Between both patterns, there is a variable transition zone of ambiguous staining (bracket). Inset, Diagram summarizing the pattern in layer IVc, with numbers inparentheses referring to optical density. The high-contrast CO pattern (bottom right) corresponds to ocular dominance columns within the cortical scotoma. The low-contrast CO suture pattern (top left) outside the scotoma is not equivalent to the ocular dominance columns. It consists of thin dark columns (core zones of the open left eye) alternating with wide pale columns. Note that there are three densities of CO activity in the cortex: open left eye (0.547), sutured right eye (0.507–0.508), and lasered left eye (0.388). This experiment establishes (1) that suture has less drastic effects on CO activity than enucleation, and (2) that suture reduces CO activity within the border strips of the open eye’s ocular dominance columns (explaining why the left eye’s dark columns are so thin outside the scotoma).B, Single section through the supragranular layers, showing alternating rows of dark (open left eye) and light (sutured right eye) patches outside the scotoma. Inside the scotoma (dotted line), this alternating pattern was lost. The boundaries of the ocular dominance columns in A were projected onto B to identify patches belonging to either the left or right eye. A sample of 50 left eye and 50 right eye patches yielded nearly the same mean optical density (0.383 and 0.384, respectively), indicating that enucleation (actually, focal retinal destruction) and suture have equal effects on metabolic activity in the upper layers of striate cortex, although they have quite different effects in layer IVc, as evinced by the striking pattern of ocular dominance columns in A.