Cerebral achromatopsia

From Psy3242

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. 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)).

Sources used: Ogden, Jenni. Fractured Minds: A Case-Study Approach to Clinical Neuropsychology. New York: Oxford University Press, 2005.