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EYE BRAIN AND VISION - PART 6

Cột hạn được đặt ra bởi Mountcastie, nên mọi người có lẽ có thể giả định rằng, ông đã có một cấu trúc pillarlike trong tâm trí. Bây giờ chúng ta biết rằng phiến từ sẽ phù hợp hơn cho vỏ não thị giác. Thuật ngữ là khó thay đổi, tuy nhiên, và có vẻ như tốt nhất để dính vào các thuật ngữ nổi tiếng, mặc dù thiếu sót của nó. | ocean-and-islands pattern is still not clear. The term column was coined by Mountcastie so one can probably assume that he had a pillarlike structure in mind. We now know that the word slab would be more suitable for the visual cortex. Terminology is hard to change however and it seems best to stick to the well-known term despite its shortcomings. Today we speak of columnar subdivisions when some cell attribute remains constant from surface to white matter and varies in records taken parallel to the surface. For reasons that will become clear in the next chapter we usually restrict the concept to exclude the topographic representation that is position of receptive fields on the retina or position on the body. Two experiments using radioactive deoxyglucose. Top A cross section of the two hemispheres through the occipital lobes in a control animal that had its visual field stim ulated with both eyes open following the intravenous injection. Bottom After injec tion an animal viewed the stimulus with one eye open and the other closed. This experiment was done by C. Kennedy M. H. Des Rosiers 0. Sakurada M. Shinohara M. Reivich J. W. Jehle and L. Sokoloff. 19 In this experiment by Roger Tootell the target-shaped stimulus with radial lines was centered on an anesthetized macaque mon-key s right visual field for 45 minutes after injection with radioactive 2-deoxyglucose. One eye was held closed. The lower picture shows the labeling in the striate cortex of the left hemisphere. This autoradiograph shows a section parallel to the surface the cortex was flattened and frozen before sectioning. The roughly vertical lines of label represent the semi circular stimulus lines the horizontal lines of label represent the radial lines in the right visual field. The hatching within each line of label is caused by only one eye having been stimulated and represents oculardominance columns. ORIENTATION COLUMNS In the earliest recordings from the striate cortex it was noticed that whenever