Heywood C A, Kentridge R W, Cowey A
Department of Psychology, Science Laboratories, South Road, Durham, DH1 3LE, UK.
Conscious Cogn. 1998 Sep;7(3):410-23. doi: 10.1006/ccog.1998.0364.
Cortical color blindness, or cerebral achromatopsia, has been likened by some authors to "blindsight" for color or an instance of "covert" processing of color. Recently, it has been shown that, although such patients are unable to identify or discriminate hue differences, they nevertheless show a striking ability to process wavelength differences, which can result in preserved sensitivity to chromatic contrast and motion in equiluminant displays. Moreover, visually evoked cortical potentials can still be elicited in response to chromatic stimuli. We suggest that these demonstrations reveal intact residual processes rather than the operation of covert processes, where proficient performance is accompanied by a denial of phenomenal awareness. We sought evidence for such covert processes by conducting appropriate tests on achromatopsic subject M.S. An "indirect" test entailing measurement of reaction times for letter identification failed to reveal covert color processes. In contrast, in a forced choice oddity task for color, M.S. was unable to verbally indicate the position of the different color, but was surprisingly adept at making an appropriate eye movement to its location. This "direct" test thus revealed the possible covert use of chromatic differences.
皮质性色盲，或称为大脑性全色盲，一些作者将其比作颜色方面的“盲视”或颜色“隐蔽”加工的一个实例。最近有研究表明，尽管这类患者无法识别或区分色调差异，但他们仍表现出显著的处理波长差异的能力，这可能导致在等亮度显示中对色彩对比度和运动的敏感性得以保留。此外，对色彩刺激仍可诱发视觉诱发电位。我们认为，这些证据揭示的是完整的残留加工过程，而非隐蔽加工过程的运作，隐蔽加工过程中熟练的表现伴随着对现象意识的否认。我们通过对色盲患者M.S.进行适当测试来寻找此类隐蔽加工过程的证据。一项“间接”测试要求测量字母识别的反应时间，但未能揭示隐蔽的颜色加工过程。相比之下，在一项颜色的强制选择异常任务中，M.S.无法口头指出不同颜色的位置，但令人惊讶的是，他很擅长做出适当的眼球运动指向其位置。因此，这项“直接”测试揭示了可能存在的对色彩差异的隐蔽利用。
