Cerebral achromatopsia
From Psy3242
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Overview
Cerebral achromatopsia is a category of color-blindness (achromatopsia), distinguished by its etiology: damage to the ventro-medial occipital lobe, as opposed to an abnormal retinal structure. Nearly all known accounts of cerebral achromatopsia stem from illness/neurological damage to the ventro-medial occipital lobe. Visual processing areas of both hemispheres must sustain severe damage for this rare form of colorblindness to occur. In addition to the severity of damage necessary to produce the condition, the location involved (including the area known as V8) is also small and difficult to injure. Those who develop cerebral achromatopsia lose the ability to identify individual colors, and even to imagine and remember them (as seen in the Sacks story, "Case of the Colorblind Painter"). This is due, according to Ogden, to a "loss of color memory" (150). It is not certain, however, whether the loss is because of "deficient color perception", or an "independent memory deficit" (150). On another note, affected persons do remain able to detect differences between colors. For example, while a man with cerebral achromatopsia would not be able to see a painted wall and understand it to be "blue", if the wall were painted with alternating blue and yellow stripes, he would easily discern a difference in the stripes. Cerebral achromatopsia sometimes exhibits comorbidity with other neurological dysfunctions, including visual agnosias (for example, in the case of Michael, discussed in Ogden, prosopagnosia, or the "inability to recognize faces on sight" (140)).
Cases
- Michael (from Ogden): After a motorcycle incident, which put him into a temporary coma, Michael was revealed to have lost the ability to recognize objects and faces by sight. In addition, he reported being unable to see or imagine colors. Brain scans revealed significant damage (to both the grey and white matter) to the medial area of his occipital lobes.
- "Jonathan" (from Sacks): A painter whose world was irrevocably changed after he was injured in a car accident. Jonathan was at first discouraged by this loss of not only the ability to see color, but to visualize and remember it. Food, he notes, is difficult to eat because it looks so unappetizing without any color. Not only this--he cannot even close his eyes to make eating easier, because the image in his head is just as bland and grey. He knows the word "blue", but it is an empty word, like all mentions of color. Eventually, however, he came to find the beauty and fascination in his new way of seeing the world, and went on to transform his artistic style, and to create new and interesting works of art.
Sources
Ogden, Jenni. Fractured Minds: A Case-Study Approach to Clinical Neuropsychology. New York: Oxford University Press, 2005.
Sacks, Oliver. The Case of the Colorblind Painter.
