Sagiv Noam, Heer Jeffrey, Robertson Lynn
Department of Psychology, University of California, Berkeley, CA, USA.
Cortex. 2006 Feb;42(2):232-42. doi: 10.1016/s0010-9452(08)70348-4.
The neural mechanisms involved in binding features such as shape and color are a matter of some debate. Does accurate binding rely on spatial attention functions of the parietal lobe or can it occur without attentional input? One extraordinary phenomenon that may shed light on this question is that of chromatic-graphemic synesthesia, a rare condition in which letter shapes evoke color perceptions. A popular suggestion is that synesthesia results from cross-activation between different functional regions (e.g., between shape and color areas of the ventral pathway). Under such conditions binding may not require parietal involvement and could occur preattentively. We tested this hypothesis in two synesthetes who perceived grayscale letters and digits in color. We found no evidence for preattentive binding using a visual search paradigm in which the target was a synesthetic inducer. In another experiment involving color judgments, we show that the congruency of target color and the synesthetic color of irrelevant digits modulates performance more when the digits are included within the attended region of space. We propose that the mechanisms giving rise to this type of synesthesia appear to follow at least some principles of normal binding, and even synesthetic binding seems to require attention.
参与整合形状和颜色等特征的神经机制存在一定争议。准确的整合是依赖于顶叶的空间注意功能，还是在没有注意输入的情况下也能发生？一种可能为这个问题提供线索的特殊现象是色-字联觉，这是一种罕见的情况，即字母形状会引发颜色感知。一个普遍的观点是，联觉是由不同功能区域之间的交叉激活引起的（例如，腹侧通路的形状和颜色区域之间）。在这种情况下，整合可能不需要顶叶的参与，并且可能在注意前就发生。我们对两名将灰度字母和数字感知为彩色的联觉者进行了测试。我们使用视觉搜索范式（其中目标是联觉诱导物），没有发现注意前整合的证据。在另一项涉及颜色判断的实验中，我们表明，当数字包含在空间的注意区域内时，目标颜色与无关数字的联觉颜色的一致性对表现的调节作用更大。我们提出，产生这种类型联觉的机制似乎至少遵循一些正常整合的原则，甚至联觉整合似乎也需要注意。
